1
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Wong SH, Liou YM, Yang JJ, Lee IC. KCNQ2 mutations cause unique neonatal behavior arrests without motor seizures: Functional characterization. Epilepsy Behav 2024; 156:109798. [PMID: 38788659 DOI: 10.1016/j.yebeh.2024.109798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 03/15/2024] [Accepted: 04/14/2024] [Indexed: 05/26/2024]
Abstract
OBJECTIVE KCNQ2 gene mutation usually manifests as neonatal seizures in the first week of life. Nonsense mutations cause a unique self-limited familial neonatal epilepsy (SLFNE), which is radically different from developmental epileptic encephalopathy (DEE). However, the exact underlying mechanisms remain unclear. METHODS The proband, along with their mother and grandmother, carried the c.1342C > T (p.Arg448Ter) mutation in the KCNQ2 gene. The clinical phenotypes, electroencephalography (EEG) findings, and neurodevelopmental outcomes were comprehensively surveyed. The mutant variants were transfected into HEK293 cells to investigate functional changes. RESULTS The proband exhibited behavior arrests, autonomic and non-motor neonatal seizures with changes in heart rate and respiration. EEG exhibited focal sharp waves. Seizures were remitted after three months of age. The neurodevelopmental outcomes at three years of age were unremarkable. A functional study demonstrated that the currents of p.Arg448Ter were non-functional in homomeric p.Arg448Ter compared with that of the KCNQ2 wild type. However, the current density and V1/2 exhibited significant improvement and close to that of the wild-type after transfection with heteromeric KCNQ2 + p.Arg448Ter and KCNQ2 + KCNQ3 + p.Arg448Ter respectively. Channel expression on the cell membrane was not visible after homomeric transfection, but not after heteromeric transfection. Retigabine did not affect homomeric p.Arg448Ter but improved heteromeric p. Arg448Ter + KCNQ2 and heteromeric KCNQ2 + Arg448Ter + KCNQ3. CONCLUSIONS The newborn carrying the p. Arg448Ter mutation presented frequent behavioral arrests, autonomic, and non-motor neonatal seizures. This unique pattern differs from KCNQ2 seizures, which typically manifest as motor seizures. Although p.Arg448Ter is a non-sense decay, the functional study demonstrated an almost-full compensation mechanism after transfection of heteromeric KCNQ2 and KCNQ3.
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Affiliation(s)
- Swee-Hee Wong
- Division of Pediatric Neurology, Department of Pediatrics, Chung Shan Medical University Hospital, Taichung, Taiwan; Institute of Medicine, School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Ying-Ming Liou
- Department of Life Sciences, National Chung-Hsing University, Taichung, Taiwan; The iEGG and Animal Biotechnology Center, Rong Hsing Research Center for Translational Medicine, Natinal Chung Hsing University, Taichung 40227, Taiwan
| | - Jiann-Jou Yang
- Genetics Laboratory and Department of Biomedical Sciences, Chung Shan Medical University, Taichung, Taiwan
| | - Inn-Chi Lee
- Division of Pediatric Neurology, Department of Pediatrics, Chung Shan Medical University Hospital, Taichung, Taiwan; Institute of Medicine, School of Medicine, Chung Shan Medical University, Taichung, Taiwan.
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2
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Muhammad A, Calandranis ME, Li B, Yang T, Blackwell DJ, Harvey ML, Smith JE, Daniel ZA, Chew AE, Capra JA, Matreyek KA, Fowler DM, Roden DM, Glazer AM. High-throughput functional mapping of variants in an arrhythmia gene, KCNE1, reveals novel biology. Genome Med 2024; 16:73. [PMID: 38816749 PMCID: PMC11138074 DOI: 10.1186/s13073-024-01340-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 04/26/2024] [Indexed: 06/01/2024] Open
Abstract
BACKGROUND KCNE1 encodes a 129-residue cardiac potassium channel (IKs) subunit. KCNE1 variants are associated with long QT syndrome and atrial fibrillation. However, most variants have insufficient evidence of clinical consequences and thus limited clinical utility. METHODS In this study, we leveraged the power of variant effect mapping, which couples saturation mutagenesis with high-throughput sequencing, to ascertain the function of thousands of protein-coding KCNE1 variants. RESULTS We comprehensively assayed KCNE1 variant cell surface expression (2554/2709 possible single-amino-acid variants) and function (2534 variants). Our study identified 470 loss- or partial loss-of-surface expression and 574 loss- or partial loss-of-function variants. Of the 574 loss- or partial loss-of-function variants, 152 (26.5%) had reduced cell surface expression, indicating that most functionally deleterious variants affect channel gating. Nonsense variants at residues 56-104 generally had WT-like trafficking scores but decreased functional scores, indicating that the latter half of the protein is dispensable for protein trafficking but essential for channel function. 22 of the 30 KCNE1 residues (73%) highly intolerant of variation (with > 70% loss-of-function variants) were in predicted close contact with binding partners KCNQ1 or calmodulin. Our functional assay data were consistent with gold standard electrophysiological data (ρ = - 0.64), population and patient cohorts (32/38 presumed benign or pathogenic variants with consistent scores), and computational predictors (ρ = - 0.62). Our data provide moderate-strength evidence for the American College of Medical Genetics/Association of Molecular Pathology functional criteria for benign and pathogenic variants. CONCLUSIONS Comprehensive variant effect maps of KCNE1 can both provide insight into I Ks channel biology and help reclassify variants of uncertain significance.
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Affiliation(s)
- Ayesha Muhammad
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, 1235 Medical Research Building IV, 2215B Garland Avenue, Nashville, TN, 37232, USA
- Medical Scientist Training Program, Vanderbilt University, Nashville, TN, 37232, USA
| | - Maria E Calandranis
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Bian Li
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
- Regeneron Pharmaceuticals Inc., Tarrytown, NY, USA
| | - Tao Yang
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Daniel J Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - M Lorena Harvey
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Jeremy E Smith
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Zerubabell A Daniel
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Ashli E Chew
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - John A Capra
- Bakar Computational Health Sciences Institute and Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, 94143, USA
| | - Kenneth A Matreyek
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Douglas M Fowler
- Department of Genome Sciences, University of Washington, Seattle, WA, 98195, USA
| | - Dan M Roden
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, 1235 Medical Research Building IV, 2215B Garland Avenue, Nashville, TN, 37232, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Andrew M Glazer
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, 1235 Medical Research Building IV, 2215B Garland Avenue, Nashville, TN, 37232, USA.
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232, USA.
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3
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Archer C. Isothermal Titration Calorimetry for Fragment-Based Analysis of Ion Channel Interactions. Methods Mol Biol 2024; 2796:271-289. [PMID: 38856907 DOI: 10.1007/978-1-0716-3818-7_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Ion channels are membrane proteins that may also have intracellular and extracellular domains that interact with other ligands. In many cases, these interaction sites are highly mobile and may undergo changes in the configuration upon binding with regulatory signaling molecules. Isothermal titration calorimetry (ITC) is a powerful technique to quantify protein-ligand interactions of purified samples in solution. This chapter describes a fragment-based analysis method using ITC to quantify the interactions between a domain of the voltage-gated Kv7 channel and the calcium-regulated protein calmodulin. This example can be used to quantify the interactions between specific domains of other ion channels and their regulatory signaling proteins.
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Affiliation(s)
- Crystal Archer
- University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
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4
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Huang Y, Ma D, Yang Z, Zhao Y, Guo J. Voltage-gated potassium channels KCNQs: Structures, mechanisms, and modulations. Biochem Biophys Res Commun 2023; 689:149218. [PMID: 37976835 DOI: 10.1016/j.bbrc.2023.149218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/19/2023] [Accepted: 11/03/2023] [Indexed: 11/19/2023]
Abstract
KCNQ (Kv7) channels are voltage-gated, phosphatidylinositol 4,5-bisphosphate- (PIP2-) modulated potassium channels that play essential roles in regulating the activity of neurons and cardiac myocytes. Hundreds of mutations in KCNQ channels are closely related to various cardiac and neurological disorders, such as long QT syndrome, epilepsy, and deafness, which makes KCNQ channels important drug targets. During the past several years, the application of single-particle cryo-electron microscopy (cryo-EM) technique in the structure determination of KCNQ channels has greatly advanced our understanding of their molecular mechanisms. In this review, we summarize the currently available structures of KCNQ channels, analyze their special voltage gating mechanism, and discuss their activation mechanisms by both the endogenous membrane lipid and the exogenous synthetic ligands. These structural studies of KCNQ channels will guide the development of drugs targeting KCNQ channels.
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Affiliation(s)
- Yuan Huang
- Department of Cardiology, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Demin Ma
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Zhenni Yang
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Yiwen Zhao
- The Key Laboratory of Neural and Vascular Biology, The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Ministry of Education, Hebei Medical University, Shijiazhuang, 050011, China
| | - Jiangtao Guo
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China.
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5
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Novelli V, Faultless T, Cerrone M, Care M, Manzoni M, Bober SL, Adler A, De-Giorgio F, Spears D, Gollob MH. Enhancing the interpretation of genetic observations in KCNQ1 in unselected populations: relevance to secondary findings. Europace 2023; 25:euad317. [PMID: 37897496 PMCID: PMC10637310 DOI: 10.1093/europace/euad317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 10/11/2023] [Indexed: 10/30/2023] Open
Abstract
AIMS Rare variants in the KCNQ1 gene are found in the healthy population to a much greater extent than the prevalence of Long QT Syndrome type 1 (LQTS1). This observation creates challenges in the interpretation of KCNQ1 rare variants that may be identified as secondary findings in whole exome sequencing.This study sought to identify missense variants within sub-domains of the KCNQ1-encoded Kv7.1 potassium channel that would be highly predictive of disease in the context of secondary findings. METHODS AND RESULTS We established a set of KCNQ1 variants reported in over 3700 patients with diagnosed or suspected LQTS sent for clinical genetic testing and compared the domain-specific location of identified variants to those observed in an unselected population of 140 000 individuals. We identified three regions that showed a significant enrichment of KCNQ1 variants associated with LQTS at an odds ratio (OR) >2: the pore region, and the adjacent 5th (S5) and 6th (S6) transmembrane (TM) regions. An additional segment within the carboxyl terminus of Kv7.1, conserved region 2 (CR2), also showed an increased OR of disease association. Furthermore, the TM spanning S5-Pore-S6 region correlated with a significant increase in cardiac events. CONCLUSION Rare missense variants with a clear phenotype of LQTS have a high likelihood to be present within the pore and adjacent TM segments (S5-Pore-S6) and a greater tendency to be present within CR2. This data will enhance interpretation of secondary findings within the KCNQ1 gene. Further, our data support a more severe phenotype in LQTS patients with variants within the S5-Pore-S6 region.
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Affiliation(s)
- Valeria Novelli
- Centro Cardiologico Monzino, IRCCS, Via C. Parea 4, Milano, 20138, Italy
| | - Trent Faultless
- Toronto General Hospital Research Institute, University of Toronto, Toronto, Canada
| | - Marina Cerrone
- Inherited Arrhythmia Clinic and Heart Rhythm Center, ‘Leon Charney’ Division of Cardiology NYU Grossman School of Medicine, NewYork, NY, USA
| | - Melanie Care
- Inherited Arrhythmia and Cardiomyopathy Program, Division of Cardiology, University of Toronto, 200 Elizabeth St.Rm 3GW-360, Toronto M5G 2C4, Ontario, Canada
| | - Martina Manzoni
- Centro Cardiologico Monzino, IRCCS, Via C. Parea 4, Milano, 20138, Italy
| | - Sara L Bober
- Toronto General Hospital Research Institute, University of Toronto, Toronto, Canada
| | - Arnon Adler
- Toronto General Hospital Research Institute, University of Toronto, Toronto, Canada
| | - Fabio De-Giorgio
- Department of Health Care Surveillance and Bioethics, Section of Legal Medicine, Fondazione Policlinico A.Gemelli IRCCS,Università Cattolica del Sacro Cuore, 00168, Rome, Italy
| | - Danna Spears
- Inherited Arrhythmia and Cardiomyopathy Program, Division of Cardiology, University of Toronto, 200 Elizabeth St.Rm 3GW-360, Toronto M5G 2C4, Ontario, Canada
| | - Michael H Gollob
- Toronto General Hospital Research Institute, University of Toronto, Toronto, Canada
- Inherited Arrhythmia and Cardiomyopathy Program, Division of Cardiology, University of Toronto, 200 Elizabeth St.Rm 3GW-360, Toronto M5G 2C4, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Canada
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McCormick L, Wadmore K, Milburn A, Gupta N, Morris R, Held M, Prakash O, Carr J, Barrett‐Jolley R, Dart C, Helassa N. Long QT syndrome-associated calmodulin variants disrupt the activity of the slowly activating delayed rectifier potassium channel. J Physiol 2023; 601:3739-3764. [PMID: 37428651 PMCID: PMC10952621 DOI: 10.1113/jp284994] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 06/21/2023] [Indexed: 07/12/2023] Open
Abstract
Calmodulin (CaM) is a highly conserved mediator of calcium (Ca2+ )-dependent signalling and modulates various cardiac ion channels. Genotyping has revealed several CaM mutations associated with long QT syndrome (LQTS). LQTS patients display prolonged ventricular recovery times (QT interval), increasing their risk of incurring life-threatening arrhythmic events. Loss-of-function mutations to Kv7.1 (which drives the slow delayed rectifier potassium current, IKs, a key ventricular repolarising current) are the largest contributor to congenital LQTS (>50% of cases). CaM modulates Kv7.1 to produce a Ca2+ -sensitive IKs, but little is known about the consequences of LQTS-associated CaM mutations on Kv7.1 function. Here, we present novel data characterising the biophysical and modulatory properties of three LQTS-associated CaM variants (D95V, N97I and D131H). We showed that mutations induced structural alterations in CaM and reduced affinity for Kv7.1, when compared with wild-type (WT). Using HEK293T cells expressing Kv7.1 channel subunits (KCNQ1/KCNE1) and patch-clamp electrophysiology, we demonstrated that LQTS-associated CaM variants reduced current density at systolic Ca2+ concentrations (1 μm), revealing a direct QT-prolonging modulatory effect. Our data highlight for the first time that LQTS-associated perturbations to CaM's structure impede complex formation with Kv7.1 and subsequently result in reduced IKs. This provides a novel mechanistic insight into how the perturbed structure-function relationship of CaM variants contributes to the LQTS phenotype. KEY POINTS: Calmodulin (CaM) is a ubiquitous, highly conserved calcium (Ca2+ ) sensor playing a key role in cardiac muscle contraction. Genotyping has revealed several CaM mutations associated with long QT syndrome (LQTS), a life-threatening cardiac arrhythmia syndrome. LQTS-associated CaM variants (D95V, N97I and D131H) induced structural alterations, altered binding to Kv7.1 and reduced IKs. Our data provide a novel mechanistic insight into how the perturbed structure-function relationship of CaM variants contributes to the LQTS phenotype.
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Affiliation(s)
- Liam McCormick
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
- Manchester Centre for Genomic Medicine, North West Genomic Laboratory HubSaint Mary's HospitalManchesterUK
| | - Kirsty Wadmore
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Amy Milburn
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Nitika Gupta
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Rachael Morris
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Marie Held
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Ohm Prakash
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Joseph Carr
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Richard Barrett‐Jolley
- Department of Musculoskeletal and Ageing Science, Institute of Life Course and Medical Sciences, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Caroline Dart
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
| | - Nordine Helassa
- Department of Biochemistry, Cell and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life SciencesUniversity of LiverpoolLiverpoolUK
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Paul A, Chumbale SS, Lakra A, Kumar V, Alhat DS, Singh S. Insights into Leishmania donovani potassium channel family and their biological functions. 3 Biotech 2023; 13:266. [PMID: 37425093 PMCID: PMC10326225 DOI: 10.1007/s13205-023-03692-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 06/26/2023] [Indexed: 07/11/2023] Open
Abstract
Leishmania donovani is the causative organism for visceral leishmaniasis. Although this parasite was discovered over a century ago, nothing is known about role of potassium channels in L. donovani. Potassium channels are known for their crucial roles in cellular functions in other organisms. Recently the presence of a calcium-activated potassium channel in L. donovani was reported which prompted us to look for other proteins which could be potassium channels and to investigate their possible physiological roles. Twenty sequences were identified in L. donovani genome and subjected to estimation of physio-chemical properties, motif analysis, localization prediction and transmembrane domain analysis. Structural predictions were also done. The channels were majorly α-helical and predominantly localized in cell membrane and lysosomes. The signature selectivity filter of potassium channel was present in all the sequences. In addition to the conventional potassium channel activity, they were associated with gene ontology terms for mitotic cell cycle, cell death, modulation by virus of host process, cell motility etc. The entire study indicates the presence of potassium channel families in L. donovani which may have involvement in several cellular pathways. Further investigations on these putative potassium channels are needed to elucidate their roles in Leishmania. Supplementary Information The online version contains supplementary material available at 10.1007/s13205-023-03692-y.
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Affiliation(s)
- Anindita Paul
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Mohali, 160062 Punjab India
| | - Shubham Sunil Chumbale
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Mohali, 160062 Punjab India
| | - Anjana Lakra
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Mohali, 160062 Punjab India
| | - Vijay Kumar
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Mohali, 160062 Punjab India
| | - Dhanashri Sudam Alhat
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Mohali, 160062 Punjab India
| | - Sushma Singh
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, SAS Nagar, Mohali, 160062 Punjab India
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8
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Muhammad A, Calandranis ME, Li B, Yang T, Blackwell DJ, Harvey ML, Smith JE, Chew AE, Capra JA, Matreyek KA, Fowler DM, Roden DM, Glazer AM. High-throughput functional mapping of variants in an arrhythmia gene, KCNE1, reveals novel biology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.28.538612. [PMID: 37162834 PMCID: PMC10168370 DOI: 10.1101/2023.04.28.538612] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Background KCNE1 encodes a 129-residue cardiac potassium channel (IKs) subunit. KCNE1 variants are associated with long QT syndrome and atrial fibrillation. However, most variants have insufficient evidence of clinical consequences and thus limited clinical utility. Results Here, we demonstrate the power of variant effect mapping, which couples saturation mutagenesis with high-throughput sequencing, to ascertain the function of thousands of protein coding KCNE1 variants. We comprehensively assayed KCNE1 variant cell surface expression (2,554/2,709 possible single amino acid variants) and function (2,539 variants). We identified 470 loss-of-surface expression and 588 loss-of-function variants. Out of the 588 loss-of-function variants, only 155 had low cell surface expression. The latter half of the protein is dispensable for protein trafficking but essential for channel function. 22 of the 30 KCNE1 residues (73%) highly intolerant of variation were in predicted close contact with binding partners KCNQ1 or calmodulin. Our data were highly concordant with gold standard electrophysiological data (ρ = -0.65), population and patient cohorts (32/38 concordant variants), and computational metrics (ρ = -0.55). Our data provide moderate-strength evidence for the ACMG/AMP functional criteria for benign and pathogenic variants. Conclusions Comprehensive variant effect maps of KCNE1 can both provide insight into IKs channel biology and help reclassify variants of uncertain significance.
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Affiliation(s)
- Ayesha Muhammad
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Medical Scientist Training Program, Vanderbilt University, Nashville, TN 37232, USA
| | - Maria E. Calandranis
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Bian Li
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Tao Yang
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Daniel J. Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - M. Lorena Harvey
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jeremy E. Smith
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Ashli E. Chew
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - John A. Capra
- Bakar Computational Health Sciences Institute and Department of Epidemiology and Biostatistics, University of California, San Francisco, CA 94143, USA
| | - Kenneth A. Matreyek
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Douglas M. Fowler
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Dan M. Roden
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Andrew M. Glazer
- Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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9
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Nuñez E, Jones F, Muguruza-Montero A, Urrutia J, Aguado A, Malo C, Bernardo-Seisdedos G, Domene C, Millet O, Gamper N, Villarroel A. Redox regulation of K V7 channels through EF3 hand of calmodulin. eLife 2023; 12:e81961. [PMID: 36803414 PMCID: PMC9988260 DOI: 10.7554/elife.81961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 02/10/2023] [Indexed: 02/22/2023] Open
Abstract
Neuronal KV7 channels, important regulators of cell excitability, are among the most sensitive proteins to reactive oxygen species. The S2S3 linker of the voltage sensor was reported as a site-mediating redox modulation of the channels. Recent structural insights reveal potential interactions between this linker and the Ca2+-binding loop of the third EF-hand of calmodulin (CaM), which embraces an antiparallel fork formed by the C-terminal helices A and B, constituting the calcium responsive domain (CRD). We found that precluding Ca2+ binding to the EF3 hand, but not to EF1, EF2, or EF4 hands, abolishes oxidation-induced enhancement of KV7.4 currents. Monitoring FRET (Fluorescence Resonance Energy Transfer) between helices A and B using purified CRDs tagged with fluorescent proteins, we observed that S2S3 peptides cause a reversal of the signal in the presence of Ca2+ but have no effect in the absence of this cation or if the peptide is oxidized. The capacity of loading EF3 with Ca2+ is essential for this reversal of the FRET signal, whereas the consequences of obliterating Ca2+ binding to EF1, EF2, or EF4 are negligible. Furthermore, we show that EF3 is critical for translating Ca2+ signals to reorient the AB fork. Our data are consistent with the proposal that oxidation of cysteine residues in the S2S3 loop relieves KV7 channels from a constitutive inhibition imposed by interactions between the EF3 hand of CaM which is crucial for this signaling.
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Affiliation(s)
| | - Frederick Jones
- School of Biomedical Sciences, Faculty of Biological Sciences, University of LeedsLeedsUnited Kingdom
| | | | | | | | | | | | - Carmen Domene
- Department of Chemistry, University of BathBathUnited Kingdom
- Department of Chemistry, University of OxfordOxfordUnited Kingdom
| | - Oscar Millet
- Protein Stability and Inherited Disease Laboratory, CIC bioGUNEDerioSpain
| | - Nikita Gamper
- School of Biomedical Sciences, Faculty of Biological Sciences, University of LeedsLeedsUnited Kingdom
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10
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Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic intervention. Biochem Pharmacol 2023; 208:115413. [PMID: 36646291 DOI: 10.1016/j.bcp.2023.115413] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023]
Abstract
A number of mutations to members of several CNS potassium (K) channel families have been identified which result in rare forms of neonatal onset epilepsy, or syndromes of which one prominent characteristic is a form of epilepsy. Benign Familial Neonatal Convulsions or Seizures (BFNC or BFNS), also referred to as Self-Limited Familial Neonatal Epilepsy (SeLNE), results from mutations in 2 members of the KV7 family (KCNQ) of K channels; while generally self-resolving by about 15 weeks of age, these mutations significantly increase the probability of generalized seizure disorders in the adult, in some cases they result in more severe developmental syndromes. Epilepsy of Infancy with Migrating Focal Seizures (EIMSF), or Migrating Partial Seizures of Infancy (MMPSI), is a rare severe form of epilepsy linked primarily to gain of function mutations in a member of the sodium-dependent K channel family, KCNT1 or SLACK. Finally, KCNMA1 channelopathies, including Liang-Wang syndrome (LIWAS), are rare combinations of neurological symptoms including seizure, movement abnormalities, delayed development and intellectual disabilities, with Liang-Wang syndrome an extremely serious polymalformative syndrome with a number of neurological sequelae including epilepsy. These are caused by mutations in the pore-forming subunit of the large-conductance calcium-activated K channel (BK channel) KCNMA1. The identification of these rare but significant channelopathies has resulted in a resurgence of interest in their treatment by direct pharmacological or genetic modulation. We will briefly review the genetics, biophysics and pharmacology of these K channels, their linkage with the 3 syndromes described above, and efforts to more effectively target these syndromes.
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11
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Emerging mechanisms involving brain Kv7 channel in the pathogenesis of hypertension. Biochem Pharmacol 2022; 206:115318. [PMID: 36283445 DOI: 10.1016/j.bcp.2022.115318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/15/2022] [Accepted: 10/17/2022] [Indexed: 12/14/2022]
Abstract
Hypertension is a prevalent health problem inducing many organ damages. The pathogenesis of hypertension involves a complex integration of different organ systems including the brain. The elevated sympathetic nerve activity is closely related to the etiology of hypertension. Ion channels are critical regulators of neuronal excitability. Several mechanisms have been proposed to contribute to hypothalamic-driven elevated sympathetic activity, including altered ion channel function. Recent findings indicate one of the voltage-gated potassium channels, Kv7 channels (M channels), plays a vital role in regulating cardiovascular-related neurons activity, and the expression of Kv7 channels is downregulated in hypertension. This review highlights recent findings that the Kv7 channels in the brain, blood vessels, and kidneys are emerging targets involved in the pathogenesis of hypertension, suggesting new therapeutic targets for treating drug-resistant, neurogenic hypertension.
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12
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Bauer CK, Holling T, Horn D, Laço MN, Abdalla E, Omar OM, Alawi M, Kutsche K. Clinically Relevant KCNQ1 Variants Causing KCNQ1-KCNE2 Gain-of-Function Affect the Ca2+ Sensitivity of the Channel. Int J Mol Sci 2022; 23:ijms23179690. [PMID: 36077086 PMCID: PMC9456291 DOI: 10.3390/ijms23179690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 08/18/2022] [Accepted: 08/22/2022] [Indexed: 11/16/2022] Open
Abstract
Dominant KCNQ1 variants are well-known for underlying cardiac arrhythmia syndromes. The two heterozygous KCNQ1 missense variants, R116L and P369L, cause an allelic disorder characterized by pituitary hormone deficiency and maternally inherited gingival fibromatosis. Increased K+ conductance upon co-expression of KCNQ1 mutant channels with the beta subunit KCNE2 is suggested to underlie the phenotype; however, the reason for KCNQ1-KCNE2 (Q1E2) channel gain-of-function is unknown. We aimed to discover the genetic defect in a single individual and three family members with gingival overgrowth and identified the KCNQ1 variants P369L and V185M, respectively. Patch-clamp experiments demonstrated increased constitutive K+ conductance of V185M-Q1E2 channels, confirming the pathogenicity of the novel variant. To gain insight into the pathomechanism, we examined all three disease-causing KCNQ1 mutants. Manipulation of the intracellular Ca2+ concentration prior to and during whole-cell recordings identified an impaired Ca2+ sensitivity of the mutant KCNQ1 channels. With low Ca2+, wild-type KCNQ1 currents were efficiently reduced and exhibited a pre-pulse-dependent cross-over of current traces and a high-voltage-activated component. These features were absent in mutant KCNQ1 channels and in wild-type channels co-expressed with calmodulin and exposed to high intracellular Ca2+. Moreover, co-expression of calmodulin with wild-type Q1E2 channels and loading the cells with high Ca2+ drastically increased Q1E2 current amplitudes, suggesting that KCNE2 normally limits the resting Q1E2 conductance by an increased demand for calcified calmodulin to achieve effective channel opening. Our data link impaired Ca2+ sensitivity of the KCNQ1 mutants R116L, V185M and P369L to Q1E2 gain-of-function that is associated with a particular KCNQ1 channelopathy.
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Affiliation(s)
- Christiane K. Bauer
- Department of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
- Correspondence:
| | - Tess Holling
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Denise Horn
- Department of Medical Genetics and Human Genetics, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt Universität zu Berlin and Berlin Institute of Health, 13353 Berlin, Germany
| | - Mário Nôro Laço
- Medical Genetics Unit, Hospital Pediátrico, Centro Hospitalar e Universitário de Coimbra, 3004-561 Coimbra, Portugal
| | - Ebtesam Abdalla
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria 5422031, Egypt
- Genetics Department, Armed Forces College of Medicine (AFCM), Cairo 4460015, Egypt
| | - Omneya Magdy Omar
- Department of Pediatrics, Faculty of Medicine, Alexandria University, Alexandria 5422031, Egypt
| | - Malik Alawi
- Bioinformatics Core, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
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13
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Wei AD, Wakenight P, Zwingman TA, Bard AM, Sahai N, Willemsen MH, Schelhaas HJ, Stegmann APA, Verhoeven JS, de Man SA, Wessels MW, Kleefstra T, Shinde DN, Helbig KL, Basinger A, Wagner VF, Rodriguez-Buritica D, Bryant E, Millichap JJ, Millen KJ, Dobyns WB, Ramirez JM, Kalume FK. Human KCNQ5 de novo mutations underlie epilepsy and intellectual disability. J Neurophysiol 2022; 128:40-61. [PMID: 35583973 PMCID: PMC9236882 DOI: 10.1152/jn.00509.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We identified six novel de novo human KCNQ5 variants in children with motor/language delay, intellectual disability (ID), and/or epilepsy by whole exome sequencing. These variants, comprising two nonsense and four missense alterations, were functionally characterized by electrophysiology in HEK293/CHO cells, together with four previously reported KCNQ5 missense variants (Lehman A, Thouta S, Mancini GM, Naidu S, van Slegtenhorst M, McWalter K, Person R, Mwenifumbo J, Salvarinova R; CAUSES Study; EPGEN Study; Guella I, McKenzie MB, Datta A, Connolly MB, Kalkhoran SM, Poburko D, Friedman JM, Farrer MJ, Demos M, Desai S, Claydon T. Am J Hum Genet 101: 65-74, 2017). Surprisingly, all eight missense variants resulted in gain of function (GOF) due to hyperpolarized voltage dependence of activation or slowed deactivation kinetics, whereas the two nonsense variants were confirmed to be loss of function (LOF). One severe GOF allele (P369T) was tested and found to extend a dominant GOF effect to heteromeric KCNQ5/3 channels. Clinical presentations were associated with altered KCNQ5 channel gating: milder presentations with LOF or smaller GOF shifts in voltage dependence [change in voltage at half-maximal conduction (ΔV50) = ∼-15 mV] and severe presentations with larger GOF shifts in voltage dependence (ΔV50 = ∼-30 mV). To examine LOF pathogenicity, two Kcnq5 LOF mouse lines were created with CRISPR/Cas9. Both lines exhibited handling- and thermal-induced seizures and abnormal cortical EEGs consistent with epileptiform activity. Our study thus provides evidence for in vivo KCNQ5 LOF pathogenicity and strengthens the contribution of both LOF and GOF mutations to global pediatric neurological impairment, including ID/epilepsy.NEW & NOTEWORTHY Six novel de novo human KCNQ5 variants were identified from children with neurodevelopmental delay, intellectual disability, and/or epilepsy. Expression of these variants along with four previously reported KCNQ5 variants from a similar cohort revealed GOF potassium channels, negatively shifted in V50 of activation and/or delayed deactivation kinetics. GOF is extended to KCNQ5/3 heteromeric channels, making these the predominant channels affected in heterozygous de novo patients. Kcnq5 LOF mice exhibited seizures, consistent with in vivo pathogenicity.
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Affiliation(s)
- Aguan D Wei
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Paul Wakenight
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Theresa A Zwingman
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Angela M Bard
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Nikhil Sahai
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington
| | - Marjolein H Willemsen
- Department of Human Genetics and Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Helenius J Schelhaas
- Department of Neurology, Academic Centre for Epileptology Kempenhaeghe, Heeze, The Netherlands
| | - Alexander P A Stegmann
- Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Judith S Verhoeven
- Department of Neurology, Academic Centre for Epileptology Kempenhaeghe, Heeze, The Netherlands
| | - Stella A de Man
- Department of Pediatrics, Amphia Hospital, Breda, The Netherlands.,Department of Human Genetics, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - Marja W Wessels
- Department of Human Genetics, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - Tjitske Kleefstra
- Department of Human Genetics and Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | - Katherine L Helbig
- Ambry Genetics, Aliso Viejo, California.,Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Alice Basinger
- Medical Genetics, Cook Children's Hospital, Fort Worth, Texas
| | - Victoria F Wagner
- Department of Pediatrics, University of Texas Health Science Center, Houston, Texas
| | | | - Emily Bryant
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - John J Millichap
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois.,Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois.,Epilepsy Center, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - Kathleen J Millen
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington.,Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington
| | - William B Dobyns
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington.,Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington.,Department of Neurology, University of Washington School of Medicine, Seattle, Washington
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington.,Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington
| | - Franck K Kalume
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington.,Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington
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14
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Mosca I, Rivolta I, Labalme A, Ambrosino P, Castellotti B, Gellera C, Granata T, Freri E, Binda A, Lesca G, DiFrancesco JC, Soldovieri MV, Taglialatela M. Functional Characterization of Two Variants at the Intron 6—Exon 7 Boundary of the KCNQ2 Potassium Channel Gene Causing Distinct Epileptic Phenotypes. Front Pharmacol 2022; 13:872645. [PMID: 35770094 PMCID: PMC9234691 DOI: 10.3389/fphar.2022.872645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Pathogenic variants in KCNQ2 encoding for Kv7.2 potassium channel subunits have been found in patients affected by widely diverging epileptic phenotypes, ranging from Self-Limiting Familial Neonatal Epilepsy (SLFNE) to severe Developmental and Epileptic Encephalopathy (DEE). Thus, understanding the pathogenic molecular mechanisms of KCNQ2 variants and their correlation with clinical phenotypes has a relevant impact on the clinical management of these patients. In the present study, the genetic, biochemical, and functional effects prompted by two variants, each found in a non-familial SLNE or a DEE patient but both affecting nucleotides at the KCNQ2 intron 6-exon 7 boundary, have been investigated to test whether and how they affected the splicing process and to clarify whether such mechanism might play a pathogenetic role in these patients. Analysis of KCNQ2 mRNA splicing in patient-derived lymphoblasts revealed that the SLNE-causing intronic variant (c.928-1G > C) impeded the use of the natural splice site, but lead to a 10-aa Kv7.2 in frame deletion (Kv7.2 p.G310Δ10); by contrast, the DEE-causing exonic variant (c.928G > A) only had subtle effects on the splicing process at this site, thus leading to the synthesis of a full-length subunit carrying the G310S missense variant (Kv7.2 p.G310S). Patch-clamp recordings in transiently-transfected CHO cells and primary neurons revealed that both variants fully impeded Kv7.2 channel function, and exerted strong dominant-negative effects when co-expressed with Kv7.2 and/or Kv7.3 subunits. Notably, Kv7.2 p.G310S, but not Kv7.2 p.G310Δ10, currents were recovered upon overexpression of the PIP2-synthesizing enzyme PIP5K, and/or CaM; moreover, currents from heteromeric Kv7.2/Kv7.3 channels incorporating either Kv7.2 mutant subunits were differentially regulated by changes in PIP2 availability, with Kv7.2/Kv7.2 G310S/Kv7.3 currents showing a greater sensitivity to PIP2 depletion when compared to those from Kv7.2/Kv7.2 G310Δ10/Kv7.3 channels. Altogether, these results suggest that the two variants investigated differentially affected the splicing process at the intron 6-exon 7 boundary, and led to the synthesis of Kv7.2 subunits showing a differential sensitivity to PIP2 and CaM regulation; more studies are needed to clarify how such different functional properties contribute to the widely-divergent clinical phenotypes.
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Affiliation(s)
- Ilaria Mosca
- Department of Medicine and Health Science “V. Tiberio”, University of Molise, Campobasso, Italy
| | - Ilaria Rivolta
- School of Medicine and Surgery, University of Milano-Bicocca, Monza-Center for Neuroscience (NeuroMI), Milan, Italy
| | - Audrey Labalme
- Department of Medical Genetics, Hospices Civils de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Paolo Ambrosino
- Department of Science and Technology (DST), University of Sannio, Benevento, Italy
| | - Barbara Castellotti
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Cinzia Gellera
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elena Freri
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Monza-Center for Neuroscience (NeuroMI), Milan, Italy
| | - Gaetan Lesca
- Department of Medical Genetics, Hospices Civils de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Jacopo C. DiFrancesco
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
- Department of Neurology, ASST “San Gerardo” Hospital, University of Milano-Bicocca, Monza, Italy
| | - Maria Virginia Soldovieri
- Department of Medicine and Health Science “V. Tiberio”, University of Molise, Campobasso, Italy
- *Correspondence: Maria Virginia Soldovieri, ; Maurizio Taglialatela,
| | - Maurizio Taglialatela
- Department of Neuroscience, University of Naples “Federico II”, Naples, Italy
- *Correspondence: Maria Virginia Soldovieri, ; Maurizio Taglialatela,
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15
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Zheng Y, Liu H, Chen Y, Dong S, Wang F, Wang S, Li GL, Shu Y, Xu F. Structural insights into the lipid and ligand regulation of a human neuronal KCNQ channel. Neuron 2021; 110:237-247.e4. [PMID: 34767770 DOI: 10.1016/j.neuron.2021.10.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 09/20/2021] [Accepted: 10/19/2021] [Indexed: 01/10/2023]
Abstract
The KCNQ family (KCNQ1-KCNQ5) of voltage-gated potassium channels plays critical roles in many physiological and pathological processes. It is known that the channel opening of all KCNQs relies on the signaling lipid molecule phosphatidylinositol 4,5-bisphosphate (PIP2). However, the molecular mechanism of PIP2 in modulating the opening of the four neuronal KCNQ channels (KCNQ2-KCNQ5), which are essential for regulating neuronal excitability, remains largely elusive. Here, we report the cryoelectron microscopy (cryo-EM) structures of human KCNQ4 determined in complex with the activator ML213 in the absence or presence of PIP2. Two PIP2 molecules are identified in the open-state structure of KCNQ4, which act as a bridge to couple the voltage-sensing domain (VSD) and pore domain (PD) of KCNQ4 leading to the channel opening. Our findings reveal the binding sites and activation mechanisms of ML213 and PIP2 for neuronal KCNQ channels, providing a framework for therapeutic intervention targeting on these important channels.
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Affiliation(s)
- You Zheng
- iHuman Institute, ShanghaiTech University, Shanghai, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Heng Liu
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yuxin Chen
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Shaowei Dong
- iHuman Institute, ShanghaiTech University, Shanghai, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Fang Wang
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Shengyi Wang
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Geng-Lin Li
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Yilai Shu
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Fudan University, Shanghai, 200031, China; Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China; NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China.
| | - Fei Xu
- iHuman Institute, ShanghaiTech University, Shanghai, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, China; Center for Excellence in Molecular Cell Science, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China.
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16
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Chen X, Zhang Y, Ren X, Su Q, Liu Y, Dang X, Qin Y, Yang X, Xing Z, Shen Y, Wang Y, Bai Z, Yeh ETH, Wu H, Qi Y. The SUMO-specific protease SENP2 plays an essential role in the regulation of Kv7.2 and Kv7.3 potassium channels. J Biol Chem 2021; 297:101183. [PMID: 34509475 PMCID: PMC8488601 DOI: 10.1016/j.jbc.2021.101183] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 08/28/2021] [Accepted: 09/08/2021] [Indexed: 11/04/2022] Open
Abstract
Sentrin/small ubiquitin-like modifier (SUMO)-specific protease 2 (SENP2)-deficient mice develop spontaneous seizures in early life because of a marked reduction in M currents, which regulate neuronal membrane excitability. We have previously shown that hyper-SUMOylation of the Kv7.2 and Kv7.3 channels is critically involved in the regulation of the M currents conducted by these potassium voltage-gated channels. Here, we show that hyper-SUMOylation of the Kv7.2 and Kv7.3 proteins reduced binding to the lipid secondary messenger PIP2. CaM1 has been shown to be tethered to the Kv7 subunits via hydrophobic motifs in its C termini and implicated in the channel assembly. Mutation of the SUMOylation sites on Kv7.2 and Kv7.3 specifically resulted in decreased binding to CaM1 and enhanced CaM1-mediated assembly of Kv7.2 and Kv7.3, whereas hyper-SUMOylation of Kv7.2 and Kv7.3 inhibited channel assembly. SENP2-deficient mice exhibited increased acetylcholine levels in the brain and the heart tissue because of increases in the vagal tone induced by recurrent seizures. The SENP2-deficient mice develop seizures followed by a period of sinus pauses or atrioventricular conduction blocks. Chronic administration of the parasympathetic blocker atropine or unilateral vagotomy significantly prolonged the life of the SENP2-deficient mice. Furthermore, we showed that retigabine, an M-current opener, reduced the transcription of SUMO-activating enzyme SAE1 and inhibited SUMOylation of the Kv7.2 and Kv7.3 channels, and also prolonged the life of SENP2-deficient mice. Taken together, the previously demonstrated roles of PIP2, CaM1, and retigabine on the regulation of Kv7.2 and Kv7.3 channel function can be explained by their roles in regulating SUMOylation of this critical potassium channel.
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Affiliation(s)
- Xu Chen
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yuhong Zhang
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Xiang Ren
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Qi Su
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yan Liu
- School of Life Sciences & Research Center for Peptide Drugs, Yan'an University, Yan'an, Shaanxi, China
| | - Xing Dang
- College of Chemistry and Chemical Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi, China
| | - Yuanyuan Qin
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Xinyi Yang
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Zhengcao Xing
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yajie Shen
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yaya Wang
- College of Chemistry and Chemical Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi, China
| | - Zhantao Bai
- School of Life Sciences & Research Center for Peptide Drugs, Yan'an University, Yan'an, Shaanxi, China
| | - Edward T H Yeh
- Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Hongmei Wu
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China.
| | - Yitao Qi
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China.
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17
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Urrutia J, Aguado A, Gomis-Perez C, Muguruza-Montero A, Ballesteros OR, Zhang J, Nuñez E, Malo C, Chung HJ, Leonardo A, Bergara A, Villarroel A. An epilepsy-causing mutation leads to co-translational misfolding of the Kv7.2 channel. BMC Biol 2021; 19:109. [PMID: 34020651 PMCID: PMC8138981 DOI: 10.1186/s12915-021-01040-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 04/29/2021] [Indexed: 12/21/2022] Open
Abstract
Background The amino acid sequence of proteins generally carries all the necessary information for acquisition of native conformations, but the vectorial nature of translation can additionally determine the folding outcome. Such consideration is particularly relevant in human diseases associated to inherited mutations leading to structural instability, aggregation, and degradation. Mutations in the KCNQ2 gene associated with human epilepsy have been suggested to cause misfolding of the encoded Kv7.2 channel. Although the effect on folding of mutations in some domains has been studied, little is known of the way pathogenic variants located in the calcium responsive domain (CRD) affect folding. Here, we explore how a Kv7.2 mutation (W344R) located in helix A of the CRD and associated with hereditary epilepsy interferes with channel function. Results We report that the epilepsy W344R mutation within the IQ motif of CRD decreases channel function, but contrary to other mutations at this site, it does not impair the interaction with Calmodulin (CaM) in vitro, as monitored by multiple in vitro binding assays. We find negligible impact of the mutation on the structure of the complex by molecular dynamic computations. In silico studies revealed two orientations of the side chain, which are differentially populated by WT and W344R variants. Binding to CaM is impaired when the mutated protein is produced in cellulo but not in vitro, suggesting that this mutation impedes proper folding during translation within the cell by forcing the nascent chain to follow a folding route that leads to a non-native configuration, and thereby generating non-functional ion channels that fail to traffic to proper neuronal compartments. Conclusions Our data suggest that the key pathogenic mechanism of Kv7.2 W344R mutation involves the failure to adopt a configuration that can be recognized by CaM in vivo but not in vitro. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01040-1.
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Affiliation(s)
- Janire Urrutia
- Instituto Biofisika, CSIC-UPV/EHU, 48940, Leioa, Spain.,Present address: Department of Physiology, Faculty of Medicine and Nursery, UPV/EHU, 48940, Leioa, Spain
| | | | - Carolina Gomis-Perez
- Instituto Biofisika, CSIC-UPV/EHU, 48940, Leioa, Spain.,Present address: Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
| | | | | | - Jiaren Zhang
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Eider Nuñez
- Instituto Biofisika, CSIC-UPV/EHU, 48940, Leioa, Spain
| | | | - Hee Jung Chung
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Aritz Leonardo
- Departamento de Física Aplicada II, Universidad del País Vasco, UPV/EHU, 48940, Leioa, Spain.,Donostia International Physics Center, 20018, Donostia, Spain
| | - Aitor Bergara
- Centro de Física de Materiales CFM, CSIC-UPV/EHU, 20018, Donostia, Spain.,Donostia International Physics Center, 20018, Donostia, Spain.,Departmento de Materia Condensada, Universidad del País Vasco, UPV/EHU, 48940, Leioa, Spain
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18
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González-Garrido A, Domínguez-Pérez M, Jacobo-Albavera L, López-Ramírez O, Guevara-Chávez JG, Zepeda-García O, Iturralde P, Carnevale A, Villarreal-Molina T. Compound Heterozygous KCNQ1 Mutations Causing Recessive Romano-Ward Syndrome: Functional Characterization by Mutant Co-expression. Front Cardiovasc Med 2021; 8:625449. [PMID: 33693037 PMCID: PMC7937651 DOI: 10.3389/fcvm.2021.625449] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 01/11/2021] [Indexed: 11/13/2022] Open
Abstract
Next Generation Sequencing has identified many KCNQ1 genetic variants associated with type 1 long QT or Romano-Ward syndrome, most frequently inherited in an autosomal dominant fashion, although recessive forms have been reported. Particularly in the case of missense variants, functional studies of mutants are of aid to establish variant pathogenicity and to understand the mechanistic basis of disease. Two compound heterozygous KCNQ1 mutations (p.A300T and p.P535T) were previously found in a child who suffered sudden death. To provide further insight into the clinical significance and basis for pathogenicity of these variants, different combinations of wildtype, A300T and P535T alleles were co-expressed with the accessory β-subunit minK in HEK293 cells, to analyze colocalization with the plasma membrane and some biophysical phenotypes of homo and heterotetrameric channels using the patch-clamp technique. A300T homotetrameric channels showed left-shifted activation V1/2 as previously observed in Xenopus oocytes, decreased maximum conductance density, slow rise-time300ms, and a characteristic use-dependent response. A300T slow rise-time300ms and use-dependent response behaved as dominant biophysical traits for all allele combinations. The P535T variant significantly decreased maximum conductance density and Kv7.1-minK-plasma membrane colocalization. P535T/A300T heterotetrameric channels showed decreased colocalization with plasma membrane, slow rise-time300ms and the A300T characteristic use-dependent response. While A300T left shifted activation voltage dependence behaved as a recessive trait when co-expressed with WT alleles, it was dominant when co-expressed with P535T alleles. Conclusions: The combination of P535T/A300T channel biophysical properties is compatible with recessive Romano Ward syndrome. Further analysis of other biophysical traits may identify other mechanisms involved in the pathophysiology of this disease.
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Affiliation(s)
- Antonia González-Garrido
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico City, Mexico.,Cátedras CONACyT, Consejo Nacional de Ciencia y Tecnología, Mexico City, Mexico
| | - Mayra Domínguez-Pérez
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico City, Mexico
| | - Leonor Jacobo-Albavera
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico City, Mexico
| | - Omar López-Ramírez
- Department of Neurobiology, University of Chicago, Chicago, IL, United States
| | - José Guadalupe Guevara-Chávez
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico City, Mexico
| | - Oscar Zepeda-García
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico City, Mexico
| | - Pedro Iturralde
- Departamento de Electrofisiología, Instituto Nacional de Cardiología "Ignacio Chávez", Mexico, Mexico
| | - Alessandra Carnevale
- Laboratorio de Enfermedades Mendelianas, Instituto Nacional de Medicina Genómica, Mexico, Mexico
| | - Teresa Villarreal-Molina
- Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico City, Mexico
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19
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Zhuang W, Yan Z. The S2-S3 Loop of Kv7.4 Channels Is Essential for Calmodulin Regulation of Channel Activation. Front Physiol 2021; 11:604134. [PMID: 33551832 PMCID: PMC7854705 DOI: 10.3389/fphys.2020.604134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 12/23/2020] [Indexed: 11/16/2022] Open
Abstract
Kv7.4 (KCNQ4) voltage-gated potassium channels control excitability in the inner ear and the central auditory pathway. Mutations in Kv7.4 channels result in inherited progressive deafness in humans. Calmodulin (CaM) is crucial for regulating Kv7 channels, but how CaM affects Kv7 activity has remained unclear. Here, based on electrophysiological recordings, we report that the third EF hand (EF3) of CaM controls the calcium-dependent regulation of Kv7.4 activation and that the S2–S3 loop of Kv7.4 is essential for the regulation mediated by CaM. Overexpression of the mutant CaM1234, which loses the calcium binding ability of all four EF hands, facilitates Kv7.4 activation by accelerating activation kinetics and shifting the voltage dependence of activation leftwards. The single mutant CaM3, which loses the calcium binding ability of the EF3, phenocopies facilitating effects of CaM1234 on Kv7.4 activation. Kv7.4 channels co-expressed with wild-type (WT) CaM show inhibited activation when intracellular calcium levels increase, while Kv7.4 channels co-expressed with CaM1234 or CaM3 are insensitive to calcium. Mutations C156A, C157A, C158V, R159, and R161A, which are located within the Kv7.4 S2–S3 loop, dramatically facilitate activation of Kv7.4 channels co-expressed with WT CaM but have no effect on activation of Kv7.4 channels co-expressed with CaM3, indicating that these five mutations decrease the inhibitory effect of Ca2+/CaM. The double mutation C156A/R159A decreases Ca2+/CaM binding and completely abolishes CaM-mediated calcium-dependent regulation of Kv7.4 activation. Taken together, our results provide mechanistic insights into CaM regulation of Kv7.4 activation and highlight the crucial role of the Kv7.4 S2–S3 loop in CaM regulation.
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Affiliation(s)
- Wenhui Zhuang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Physiology and Biophysics, School of Life Sciences, Human Phenome Institute, Fudan University, Shanghai, China
| | - Zhiqiang Yan
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Physiology and Biophysics, School of Life Sciences, Human Phenome Institute, Fudan University, Shanghai, China.,Shenzhen Bay Laboratory, Institute of Molecular Physiology, Shenzhen, China
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20
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Li T, Wu K, Yue Z, Wang Y, Zhang F, Shen H. Structural Basis for the Modulation of Human KCNQ4 by Small-Molecule Drugs. Mol Cell 2020; 81:25-37.e4. [PMID: 33238160 DOI: 10.1016/j.molcel.2020.10.037] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 09/28/2020] [Accepted: 10/28/2020] [Indexed: 12/17/2022]
Abstract
Among the five KCNQ channels, also known as the Kv7 voltage-gated potassium (Kv) channels, KCNQ2-KCNQ5 control neuronal excitability. Dysfunctions of KCNQ2-KCNQ5 are associated with neurological disorders such as epilepsy, deafness, and neuropathic pain. Here, we report the cryoelectron microscopy (cryo-EM) structures of human KCNQ4 and its complexes with the opener retigabine or the blocker linopirdine at overall resolutions of 2.5, 3.1, and 3.3 Å, respectively. In all structures, a phosphatidylinositol 4,5-bisphosphate (PIP2) molecule inserts its head group into a cavity within each voltage-sensing domain (VSD), revealing an unobserved binding mode for PIP2. Retigabine nestles in each fenestration, inducing local shifts. Instead of staying within the central pore, linopirdine resides in a cytosolic cavity underneath the inner gate. Electrophysiological analyses of various mutants corroborated the structural observations. Our studies reveal the molecular basis for the modulatory mechanism of neuronal KCNQ channels and provide a framework for structure-facilitated drug discovery targeting these important channels.
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Affiliation(s)
- Tian Li
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Kun Wu
- Emergency Medicine Clinical Research Center, Beijing Key Laboratory of Cardiopulmonary Cerebral Resuscitation, Medical Research Center, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Zhenlei Yue
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Yifei Wang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Fan Zhang
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China
| | - Huaizong Shen
- Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang 310024, China; Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang 310024, China.
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21
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Tran B, Ji ZG, Xu M, Tsuchida TN, Cooper EC. Two KCNQ2 Encephalopathy Variants in the Calmodulin-Binding Helix A Exhibit Dominant-Negative Effects and Altered PIP 2 Interaction. Front Physiol 2020; 11:1144. [PMID: 33041849 PMCID: PMC7518097 DOI: 10.3389/fphys.2020.571813] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 08/18/2020] [Indexed: 11/13/2022] Open
Abstract
Heterozygous missense variants in KCNQ2, which encodes the potassium channel subunit Kv7.2, are among the most common genetic causes of severe neonatal-onset epileptic encephalopathy. Because about 20% of known severe Kv7.2 missense changes lie within the intracellular C-terminal region, improving understanding of the underlying pathogenic mechanisms is important. We analyzed the basis for the severe phenotypes of Kv7.2 A337T and A337G, variants in the C-terminal’s calmodulin (CaM)-binding Helix A. When expressed heterologously in mammalian cells, alone or in combination with wild type Kv7.2 or with wild type Kv7.2 and Kv7.3, both variants strongly suppressed channel currents. A337T channels expressed alone exhibited significantly reduced protein half-life and surface trafficking and co-immunoprecipitated less CaM. For both variants, increasing cellular phosphatidylinositol 4,5-bisphosphate (PIP2) by overexpression of PI(4)P5-kinase restored current densities. For both variants, the fraction of current suppressed by activation of M1 muscarinic receptors with 10 μM oxotremorine methiodide, which depletes PIP2, was less than for controls. During voltage-sensitive phosphatase-induced transient PIP2 depletion and resynthesize, potassium current inhibition and recovery kinetics were both markedly slowed. These results suggest that these variants may reduce currents by a mechanism not previously described: slowing of PIP2 migration between the bulk membrane and binding sites mediating channel electromechanical coupling. A novel Kv7.2/3-selective opener, SF0034, rescued current amplitudes. Our findings show that these two Helix A variants suppress channel current density strongly, consistent with their severe heterozygous phenotypes, implicate impairment of CaM and PIP2 regulation in KCNQ2 encephalopathy pathogenesis, and highlight the potential usefulness of selective Kv7 openers for this distinctive pathogenic mechanism and patient subgroup.
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Affiliation(s)
- Baouyen Tran
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Zhi-Gang Ji
- Department of Neurology, Baylor College of Medicine, Houston, TX, United States
| | - Mingxuan Xu
- Department of Neurology, Baylor College of Medicine, Houston, TX, United States
| | - Tammy N Tsuchida
- Departments of Pediatrics and Neurology, Children's National Medical Center, Washington, DC, United States
| | - Edward C Cooper
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States.,Department of Neurology, Baylor College of Medicine, Houston, TX, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
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22
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Heteromeric Kv7.2 current changes caused by loss-of-function of KCNQ2 mutations are correlated with long-term neurodevelopmental outcomes. Sci Rep 2020; 10:13375. [PMID: 32770121 PMCID: PMC7415140 DOI: 10.1038/s41598-020-70212-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 07/22/2020] [Indexed: 12/19/2022] Open
Abstract
Pediatric epilepsy caused by KCNQ2 mutations can manifest benign familial neonatal convulsions (BFNC) to neonatal-onset epileptic encephalopathy (EE). Patients might manifest mild to profound neurodevelopmental disabilities. We analysed c.853C > A (P285T) and three mutations that cause KCNQ2 protein changes in the 247 position: c.740C > T (S247L), c.740C > A (S247X), and c.740C > G (S247W). S247L, S247W, and P285T cause neonatal-onset EE and poor neurodevelopmental outcomes; S247X cause BFNC and normal outcome. We investigated the phenotypes correlated with human embryonic kidney 293 (HEK293) cell functional current changes. More cell-current changes and a worse conductance curve were present in the homomeric transfected S247X than in S247L, S247W, and P285T. But in the heteromeric channel, S247L, S247W and P285T had more current impairments than did S247X. The protein expressions of S247X were nonfunctional. The outcomes were most severe in S247L and S247W, and severity was correlated with heteromeric current. Current changes were more significant in cells with homomeric S247X, but currents were “rescued” after heteromeric transfection of KCNQ2 and KCNQ3. This was not the case in cells with S247L, S247W. Our findings support that homomeric current changes are common in KCNQ2 neonatal-onset EE and KCNQ2 BFNC; however, heteromeric functional current changes are correlated with long-term neurodevelopmental outcomes.
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23
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Lazo PA, García JL, Gómez-Puertas P, Marcos-Alcalde Í, Arjona C, Villarroel A, González-Sarmiento R, Fons C. Novel Dominant KCNQ2 Exon 7 Partial In-Frame Duplication in a Complex Epileptic and Neurodevelopmental Delay Syndrome. Int J Mol Sci 2020; 21:ijms21124447. [PMID: 32585800 PMCID: PMC7352878 DOI: 10.3390/ijms21124447] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 12/23/2022] Open
Abstract
Complex neurodevelopmental syndromes frequently have an unknown etiology, in which genetic factors play a pathogenic role. This study utilizes whole-exome sequencing (WES) to examine four members of a family with a son presenting, since birth, with epileptic-like crises, combined with cerebral palsy, severe neuromotor and developmental delay, dystonic tetraparexia, axonal motor affectation, and hyper-excitability of unknown origin. The WES study detected within the patient a de novo heterozygous in-frame duplication of thirty-six nucleotides within exon 7 of the human KCNQ2 gene. This insertion duplicates the first twelve amino acids of the calmodulin binding site I. Molecular dynamics simulations of this KCNQ2 peptide duplication, modelled on the 3D structure of the KCNQ2 protein, suggest that the duplication may lead to the dysregulation of calcium inhibition of this protein function.
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Affiliation(s)
- Pedro A. Lazo
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, 30007 Salamanca, Spain; (J.L.G.); (R.G.-S.)
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, 30007 Salamanca, Spain
- Correspondence:
| | - Juan L. García
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, 30007 Salamanca, Spain; (J.L.G.); (R.G.-S.)
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, 30007 Salamanca, Spain
| | - Paulino Gómez-Puertas
- Centro de Biología Molecular Severo Ochoa, CSIC-Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain; (P.G.-P.); (Í.M.-A.)
| | - Íñigo Marcos-Alcalde
- Centro de Biología Molecular Severo Ochoa, CSIC-Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain; (P.G.-P.); (Í.M.-A.)
- Biosciences Research Institute, School of Experimental Sciences, Universidad Francisco de Vitoria, 28223 Madrid, Spain
| | - Cesar Arjona
- Institut de Recerca Sant Joan de Déu, Esplugues de Llobregat, 08950 Barcelona, Spain; (C.A.); (C.F.)
- Instituto Pediátrico de Enfermedades Raras (IPER), Hospital Sant Joan de Déu, 08950 Barcelona, Spain
| | - Alvaro Villarroel
- Instituto de Biofísica, Consejo Superior de Investigaciones Científicas (CSIC), Universidad del País Vasco, 48940 Bilbao, Spain;
| | - Rogelio González-Sarmiento
- Molecular Mechanisms of Cancer Program, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas (CSIC), Universidad de Salamanca, 30007 Salamanca, Spain; (J.L.G.); (R.G.-S.)
- Instituto de Investigación Biomédica de Salamanca (IBSAL), Hospital Universitario de Salamanca, 30007 Salamanca, Spain
- Unidad de Genética Molecular, Departamento de Medicina, Universidad de Salamanca, 37008 Salamanca, Spain
| | - Carmen Fons
- Institut de Recerca Sant Joan de Déu, Esplugues de Llobregat, 08950 Barcelona, Spain; (C.A.); (C.F.)
- Neurology Department, Hospital Sant Joan de Déu, Sant Joan de Déu Research Institute and CIBERER, Instituto de Salud Carlos III, 08950 Barcelona, Spain
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24
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Vigil FA, Carver CM, Shapiro MS. Pharmacological Manipulation of K v 7 Channels as a New Therapeutic Tool for Multiple Brain Disorders. Front Physiol 2020; 11:688. [PMID: 32636759 PMCID: PMC7317068 DOI: 10.3389/fphys.2020.00688] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 05/27/2020] [Indexed: 12/12/2022] Open
Abstract
K v 7 ("M-type," KCNQ) K+ currents, play dominant roles in controlling neuronal excitability. They act as a "brake" against hyperexcitable states in the central and peripheral nervous systems. Pharmacological augmentation of M current has been developed for controlling epileptic seizures, although current pharmacological tools are uneven in practical usefulness. Lately, however, M-current "opener" compounds have been suggested to be efficacious in preventing brain damage after multiple types of insults/diseases, such as stroke, traumatic brain injury, drug addiction and mood disorders. In this review, we will discuss what is known to date on these efforts and identify gaps in our knowledge regarding the link between M current and therapeutic potential for these disorders. We will outline the preclinical experiments that are yet to be performed to demonstrate the likelihood of success of this approach in human trials. Finally, we also address multiple pharmacological tools available to manipulate different K v 7 subunits and the relevant evidence for translational application in the clinical use for disorders of the central nervous system and multiple types of brain insults. We feel there to be great potential for manipulation of K v 7 channels as a novel therapeutic mode of intervention in the clinic, and that the paucity of existing therapies obligates us to perform further research, so that patients can soon benefit from such therapeutic approaches.
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Affiliation(s)
- Fabio A Vigil
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Chase M Carver
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, United States
| | - Mark S Shapiro
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX, United States
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25
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Nappi P, Miceli F, Soldovieri MV, Ambrosino P, Barrese V, Taglialatela M. Epileptic channelopathies caused by neuronal Kv7 (KCNQ) channel dysfunction. Pflugers Arch 2020; 472:881-898. [PMID: 32506321 DOI: 10.1007/s00424-020-02404-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 05/12/2020] [Accepted: 05/18/2020] [Indexed: 11/28/2022]
Abstract
Seizures are the most common neurological manifestation in the newborn period, with an estimated incidence of 1.8-3.5 per 1000 live births. Prolonged or intractable seizures have a detrimental effect on cognition and brain function in experimental animals and are associated with adverse long-term neurodevelopmental sequelae and an increased risk of post-neonatal epilepsy in humans. The developing brain is particularly susceptible to the potentially severe effects of epilepsy, and epilepsy, especially when refractory to medications, often results in a developmental and epileptic encephalopathy (DEE) with developmental arrest or regression. DEEs can be primarily attributed to genetic causes. Given the critical role of potassium (K+) currents with distinct subcellular localization, biophysical properties, modulation, and pharmacological profile in regulating intrinsic electrical properties of neurons and their responsiveness to synaptic inputs, it is not too surprising that genetic research in the past two decades has identified several K+ channel genes as responsible for a large fraction of DEE. In the present article, we review the genetically determined epileptic channelopathies affecting three members of the Kv7 family, namely Kv7.2 (KCNQ2), Kv7.3 (KCNQ3), and Kv7.5 (KCNQ5); we review the phenotypic spectrum of Kv7-related epileptic channelopathies, the different genetic and pathogenetic mechanisms, and the emerging genotype-phenotype correlations which may prove crucial for prognostic predictions, disease management, parental counseling, and individually tailored therapeutic attempts.
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Affiliation(s)
- Piera Nappi
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy
| | - Francesco Miceli
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy
| | | | - Paolo Ambrosino
- Department of Science and Technology (DST), University of Sannio, Benevento, Italy
| | - Vincenzo Barrese
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy
| | - Maurizio Taglialatela
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy.
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26
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Hoshi N. M-Current Suppression, Seizures and Lipid Metabolism: A Potential Link Between Neuronal Kv7 Channel Regulation and Dietary Therapies for Epilepsy. Front Physiol 2020; 11:513. [PMID: 32523549 PMCID: PMC7261926 DOI: 10.3389/fphys.2020.00513] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 04/27/2020] [Indexed: 12/28/2022] Open
Abstract
Neuronal Kv7 channel generates a low voltage-activated potassium current known as the M-current. The M-current can be suppressed by various neurotransmitters that activate Gq-coupled receptors. Because the M-current stabilizes membrane potential at the resting membrane potential, its suppression transiently increase neuronal excitability. However, its physiological and pathological roles in vivo is not well understood to date. This review summarizes the molecular mechanism underlying M-current suppression, and why it remained elusive for many years. I also summarize how regulation of neuronal Kv7 channel contributes to anti-seizure action of valproic acid through inhibition of palmitoylation of a Kv7 channel binding protein, and discuss about a potential link with anti-seizure mechanisms of medium chain triglyceride ketogenic diet.
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Affiliation(s)
- Naoto Hoshi
- Department of Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States.,Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA, United States
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27
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Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
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Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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28
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Núñez E, Muguruza-Montero A, Villarroel A. Atomistic Insights of Calmodulin Gating of Complete Ion Channels. Int J Mol Sci 2020; 21:ijms21041285. [PMID: 32075037 PMCID: PMC7072864 DOI: 10.3390/ijms21041285] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/07/2020] [Accepted: 02/12/2020] [Indexed: 12/13/2022] Open
Abstract
Intracellular calcium is essential for many physiological processes, from neuronal signaling and exocytosis to muscle contraction and bone formation. Ca2+ signaling from the extracellular medium depends both on membrane potential, especially controlled by ion channels selective to K+, and direct permeation of this cation through specialized channels. Calmodulin (CaM), through direct binding to these proteins, participates in setting the membrane potential and the overall permeability to Ca2+. Over the past years many structures of complete channels in complex with CaM at near atomic resolution have been resolved. In combination with mutagenesis-function, structural information of individual domains and functional studies, different mechanisms employed by CaM to control channel gating are starting to be understood at atomic detail. Here, new insights regarding four types of tetrameric channels with six transmembrane (6TM) architecture, Eag1, SK2/SK4, TRPV5/TRPV6 and KCNQ1–5, and its regulation by CaM are described structurally. Different CaM regions, N-lobe, C-lobe and EF3/EF4-linker play prominent signaling roles in different complexes, emerging the realization of crucial non-canonical interactions between CaM and its target that are only evidenced in the full-channel structure. Different mechanisms to control gating are used, including direct and indirect mechanical actuation over the pore, allosteric control, indirect effect through lipid binding, as well as direct plugging of the pore. Although each CaM lobe engages through apparently similar alpha-helices, they do so using different docking strategies. We discuss how this allows selective action of drugs with great therapeutic potential.
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29
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Hefting LL, D'Este E, Arvedsen E, Benned-Jensen T, Rasmussen HB. Multiple Domains in the Kv7.3 C-Terminus Can Regulate Localization to the Axon Initial Segment. Front Cell Neurosci 2020; 14:10. [PMID: 32116557 PMCID: PMC7010958 DOI: 10.3389/fncel.2020.00010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 01/14/2020] [Indexed: 11/13/2022] Open
Abstract
The voltage-gated Kv7.2/Kv7.3 potassium channel is a critical regulator of neuronal excitability. It is strategically positioned at the axon initial segment (AIS) of neurons, where it effectively inhibits repetitive action potential firing. While the selective accumulation of Kv7.2/Kv7.3 channels at the AIS requires binding to the adaptor protein ankyrin G, it is currently unknown if additional molecular mechanisms contribute to the localization and fine-tuning of channel numbers at the AIS. Here, we utilized a chimeric approach to pinpoint regions within the Kv7.3 C-terminal tail with an impact upon AIS localization. This strategy identified two domains with opposing effects upon the AIS localization of Kv7.3 chimeras expressed in cultured hippocampal neurons. While a membrane proximal domain reduced AIS localization of Kv7.3 chimeras, helix D increased and stabilized chimera AIS localization. None of the identified domains were required for AIS localization. However, the domains modulated the relative efficiency of the localization raising the possibility that the two domains contribute to the regulation of Kv7 channel numbers and nanoscale organization at the AIS.
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Affiliation(s)
- Louise Leth Hefting
- Membrane Trafficking Group, Department of Biomedical Sciences, The Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Elisa D'Este
- Optical Microscopy Facility, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Emil Arvedsen
- Membrane Trafficking Group, Department of Biomedical Sciences, The Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Tau Benned-Jensen
- Membrane Trafficking Group, Department of Biomedical Sciences, The Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hanne Borger Rasmussen
- Membrane Trafficking Group, Department of Biomedical Sciences, The Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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30
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Ambrosino P, Soldovieri MV, Di Zazzo E, Paventi G, Iannotti FA, Mosca I, Miceli F, Franco C, Canzoniero LMT, Taglialatela M. Activation of Kv7 Potassium Channels Inhibits Intracellular Ca 2+ Increases Triggered By TRPV1-Mediated Pain-Inducing Stimuli in F11 Immortalized Sensory Neurons. Int J Mol Sci 2019; 20:ijms20184322. [PMID: 31487785 PMCID: PMC6769798 DOI: 10.3390/ijms20184322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 09/01/2019] [Accepted: 09/02/2019] [Indexed: 12/11/2022] Open
Abstract
Kv7.2-Kv7.5 channels mediate the M-current (IKM), a K+-selective current regulating neuronal excitability and representing an attractive target for pharmacological therapy against hyperexcitability diseases such as pain. Kv7 channels interact functionally with transient receptor potential vanilloid 1 (TRPV1) channels activated by endogenous and/or exogenous pain-inducing substances, such as bradykinin (BK) or capsaicin (CAP), respectively; however, whether Kv7 channels of specific molecular composition provide a dominant contribution in BK- or CAP-evoked responses is yet unknown. To this aim, Kv7 transcripts expression and function were assessed in F11 immortalized sensorial neurons, a cellular model widely used to assess nociceptive molecular mechanisms. In these cells, the effects of the pan-Kv7 activator retigabine were investigated, as well as the effects of ICA-27243 and (S)-1, two Kv7 activators acting preferentially on Kv7.2/Kv7.3 and Kv7.4/Kv7.5 channels, respectively, on BK- and CAP-induced changes in intracellular Ca2+ concentrations ([Ca2+]i). The results obtained revealed the expression of transcripts of all Kv7 genes, leading to an IKM-like current. Moreover, all tested Kv7 openers inhibited BK- and CAP-induced responses by a similar extent (~60%); at least for BK-induced Ca2+ responses, the potency of retigabine (IC50~1 µM) was higher than that of ICA-27243 (IC50~5 µM) and (S)-1 (IC50~7 µM). Altogether, these results suggest that IKM activation effectively counteracts the cellular processes triggered by TRPV1-mediated pain-inducing stimuli, and highlight a possible critical contribution of Kv7.4 subunits.
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Affiliation(s)
- Paolo Ambrosino
- Department of Science and Technology, University of Sannio, 82100 Benevento, Italy
| | - Maria Virginia Soldovieri
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, 86100 Campobasso, Italy
| | - Erika Di Zazzo
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, 86100 Campobasso, Italy
| | - Gianluca Paventi
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, 86100 Campobasso, Italy
| | - Fabio Arturo Iannotti
- Institute of Biomolecular Chemistry, National Research Council, Pozzuoli, 80121 Naples, Italy
| | - Ilaria Mosca
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, 86100 Campobasso, Italy
| | - Francesco Miceli
- Division of Pharmacology, Department of Neuroscience, University of Naples "Federico II", 80131 Naples, Italy
| | - Cristina Franco
- Department of Science and Technology, University of Sannio, 82100 Benevento, Italy
| | | | - Maurizio Taglialatela
- Division of Pharmacology, Department of Neuroscience, University of Naples "Federico II", 80131 Naples, Italy.
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31
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Meisel E, Tobelaim W, Dvir M, Haitin Y, Peretz A, Attali B. Inactivation gating of Kv7.1 channels does not involve concerted cooperative subunit interactions. Channels (Austin) 2019; 12:89-99. [PMID: 29451064 PMCID: PMC5972808 DOI: 10.1080/19336950.2018.1441649] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Inactivation is an intrinsic property of numerous voltage-gated K+ (Kv) channels and can occur by N-type or/and C-type mechanisms. N-type inactivation is a fast, voltage independent process, coupled to activation, with each inactivation particle of a tetrameric channel acting independently. In N-type inactivation, a single inactivation particle is necessary and sufficient to occlude the pore. C-type inactivation is a slower process, involving the outermost region of the pore and is mediated by a concerted, highly cooperative interaction between all four subunits. Inactivation of Kv7.1 channels does not exhibit the hallmarks of N- and C-type inactivation. Inactivation of WT Kv7.1 channels can be revealed by hooked tail currents that reflects the recovery from a fast and voltage-independent inactivation process. However, several Kv7.1 mutants such as the pore mutant L273F generate an additional voltage-dependent slow inactivation. The subunit interactions during this slow inactivation gating remain unexplored. The goal of the present study was to study the nature of subunit interactions along Kv7.1 inactivation gating, using concatenated tetrameric Kv7.1 channel and introducing sequentially into each of the four subunits the slow inactivating pore mutation L273F. Incorporating an incremental number of inactivating mutant subunits did not affect the inactivation kinetics but slowed down the recovery kinetics from inactivation. Results indicate that Kv7.1 inactivation gating is not compatible with a concerted cooperative process. Instead, adding an inactivating subunit L273F into the Kv7.1 tetramer incrementally stabilizes the inactivated state, which suggests that like for activation gating, Kv7.1 slow inactivation gating is not a concerted process.
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Affiliation(s)
- Eshcar Meisel
- a Department of Physiology & Pharmacology , the Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel
| | - William Tobelaim
- a Department of Physiology & Pharmacology , the Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel
| | - Meidan Dvir
- a Department of Physiology & Pharmacology , the Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel
| | - Yoni Haitin
- a Department of Physiology & Pharmacology , the Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel
| | - Asher Peretz
- a Department of Physiology & Pharmacology , the Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel
| | - Bernard Attali
- a Department of Physiology & Pharmacology , the Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University , Tel Aviv , Israel
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32
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Alaimo A, Etxeberria A, Gómez-Posada JC, Gomis-Perez C, Fernández-Orth J, Malo C, Villarroel A. Lack of correlation between surface expression and currents in epileptogenic AB-calmodulin binding domain Kv7.2 potassium channel mutants. Channels (Austin) 2019; 12:299-310. [PMID: 30126342 PMCID: PMC6161613 DOI: 10.1080/19336950.2018.1511512] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Heteromers of Kv7.2/Kv7.3 subunits constitute the main substrate of the neuronal M-current that limits neuronal hyper-excitability and firing frequency. Calmodulin (CaM) binding is essential for surface expression of Kv7 channels, and disruption of this interaction leads to diseases ranging from mild epilepsy to early onset encephalopathy. In this study, we addressed the impact of a charge neutralizing mutation located at the periphery of helix B (K526N). We found that, CaM binding and surface expression was impaired, although current amplitude was not altered. Currents were reduced at a faster rate after activation of a voltage-dependent phosphatase, suggesting that phosphatidylinositol-4,5-bisphosphate (PIP2) binding was weaker. In contrast, a charge neutralizing mutation located at the periphery of helix A (R333Q) did not affect CaM binding, but impaired trafficking and led to a reduction in current amplitude. Taken together, these results suggest that disruption of CaM-dependent or CaM-independent trafficking of Kv7.2/Kv7.3 channels can lead to pathology regardless of the consequences on the macroscopic ionic flow through the channel.
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Affiliation(s)
- Alessandro Alaimo
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Ainhoa Etxeberria
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Juan Camilo Gómez-Posada
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Carolina Gomis-Perez
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Juncal Fernández-Orth
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Covadonga Malo
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Alvaro Villarroel
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
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33
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Epileptic Encephalopathy In A Patient With A Novel Variant In The Kv7.2 S2 Transmembrane Segment: Clinical, Genetic, and Functional Features. Int J Mol Sci 2019; 20:ijms20143382. [PMID: 31295832 PMCID: PMC6678645 DOI: 10.3390/ijms20143382] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/04/2019] [Accepted: 07/05/2019] [Indexed: 11/18/2022] Open
Abstract
Kv7.2 subunits encoded by the KCNQ2 gene provide a major contribution to the M-current (IKM), a voltage-gated K+ current crucially involved in the regulation of neuronal excitability. Heterozygous missense variants in Kv7.2 are responsible for epileptic diseases characterized by highly heterogeneous genetic transmission and clinical severity, ranging from autosomal-dominant Benign Familial Neonatal Seizures (BFNS) to sporadic cases of severe epileptic and developmental encephalopathy (DEE). Here, we describe a patient with neonatal onset DEE, carrying a previously undescribed heterozygous KCNQ2 c.418G > C, p.Glu140Gln (E140Q) variant. Patch-clamp recordings in CHO cells expressing the E140Q mutation reveal dramatic loss of function (LoF) effects. Multistate structural modelling suggested that the E140Q substitution impeded an intrasubunit electrostatic interaction occurring between the E140 side chain in S2 and the arginine at position 210 in S4 (R210); this interaction is critically involved in stabilizing the activated configuration of the voltage-sensing domain (VSD) of Kv7.2. Functional results from coupled charge reversal or disulfide trapping experiments supported such a hypothesis. Finally, retigabine restored mutation-induced functional changes, reinforcing the rationale for the clinical use of Kv7 activators as personalized therapy for DEE-affected patients carrying Kv7.2 LoF mutations.
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34
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Archer CR, Enslow BT, Taylor AB, De la Rosa V, Bhattacharya A, Shapiro MS. A mutually induced conformational fit underlies Ca 2+-directed interactions between calmodulin and the proximal C terminus of KCNQ4 K + channels. J Biol Chem 2019; 294:6094-6112. [PMID: 30808708 PMCID: PMC6463706 DOI: 10.1074/jbc.ra118.006857] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 02/24/2019] [Indexed: 11/06/2022] Open
Abstract
Calmodulin (CaM) conveys intracellular Ca2+ signals to KCNQ (Kv7, "M-type") K+ channels and many other ion channels. Whether this "calmodulation" involves a dramatic structural rearrangement or only slight perturbations of the CaM/KCNQ complex is as yet unclear. A consensus structural model of conformational shifts occurring between low nanomolar and physiologically high intracellular [Ca2+] is still under debate. Here, we used various techniques of biophysical chemical analyses to investigate the interactions between CaM and synthetic peptides corresponding to the A and B domains of the KCNQ4 subtype. We found that in the absence of CaM, the peptides are disordered, whereas Ca2+/CaM imposed helical structure on both KCNQ A and B domains. Isothermal titration calorimetry revealed that Ca2+/CaM has higher affinity for the B domain than for the A domain of KCNQ2-4 and much higher affinity for the B domain when prebound with the A domain. X-ray crystallography confirmed that these discrete peptides spontaneously form a complex with Ca2+/CaM, similar to previous reports of CaM binding KCNQ-AB domains that are linked together. Microscale thermophoresis and heteronuclear single-quantum coherence NMR spectroscopy indicated the C-lobe of Ca2+-free CaM to interact with the KCNQ4 B domain (Kd ∼10-20 μm), with increasing Ca2+ molar ratios shifting the CaM-B domain interactions via only the CaM C-lobe to also include the N-lobe. Our findings suggest that in response to increased Ca2+, CaM undergoes lobe switching that imposes a dramatic mutually induced conformational fit to both the proximal C terminus of KCNQ4 channels and CaM, likely underlying Ca2+-dependent regulation of KCNQ gating.
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Affiliation(s)
- Crystal R Archer
- From the Departments of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas 78229; Departments of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Benjamin T Enslow
- the Long School of Medicine, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Alexander B Taylor
- Departments of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Victor De la Rosa
- From the Departments of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Akash Bhattacharya
- Departments of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, Texas 78229
| | - Mark S Shapiro
- From the Departments of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas 78229.
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35
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Urrutia J, Aguado A, Muguruza-Montero A, Núñez E, Malo C, Casis O, Villarroel A. The Crossroad of Ion Channels and Calmodulin in Disease. Int J Mol Sci 2019; 20:ijms20020400. [PMID: 30669290 PMCID: PMC6359610 DOI: 10.3390/ijms20020400] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/11/2019] [Accepted: 01/16/2019] [Indexed: 01/21/2023] Open
Abstract
Calmodulin (CaM) is the principal Ca2+ sensor in eukaryotic cells, orchestrating the activity of hundreds of proteins. Disease causing mutations at any of the three genes that encode identical CaM proteins lead to major cardiac dysfunction, revealing the importance in the regulation of excitability. In turn, some mutations at the CaM binding site of ion channels cause similar diseases. Here we provide a summary of the two sides of the partnership between CaM and ion channels, describing the diversity of consequences of mutations at the complementary CaM binding domains.
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Affiliation(s)
- Janire Urrutia
- Biofisika Institute (CSIC, UPV/EHU), University of the Basque Country, 48940 Leioa, Spain.
| | - Alejandra Aguado
- Biofisika Institute (CSIC, UPV/EHU), University of the Basque Country, 48940 Leioa, Spain.
| | | | - Eider Núñez
- Biofisika Institute (CSIC, UPV/EHU), University of the Basque Country, 48940 Leioa, Spain.
| | - Covadonga Malo
- Biofisika Institute (CSIC, UPV/EHU), University of the Basque Country, 48940 Leioa, Spain.
| | - Oscar Casis
- Departamento de Fisiología, Facultad de Farmacia, Universidad del País Vasco (UPV/EHU), 01006 Vitoria-Gasteiz, Spain.
| | - Alvaro Villarroel
- Biofisika Institute (CSIC, UPV/EHU), University of the Basque Country, 48940 Leioa, Spain.
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36
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Calmodulin: A Multitasking Protein in Kv7.2 Potassium Channel Functions. Biomolecules 2018; 8:biom8030057. [PMID: 30022004 PMCID: PMC6164012 DOI: 10.3390/biom8030057] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/13/2018] [Accepted: 07/14/2018] [Indexed: 02/06/2023] Open
Abstract
The ubiquitous calcium transducer calmodulin (CaM) plays a pivotal role in many cellular processes, regulating a myriad of structurally different target proteins. Indeed, it is unquestionable that CaM is the most relevant transductor of calcium signals in eukaryotic cells. During the last two decades, different studies have demonstrated that CaM mediates the modulation of several ion channels. Among others, it has been indicated that Kv7.2 channels, one of the members of the voltage gated potassium channel family that plays a critical role in brain excitability, requires CaM binding to regulate the different mechanisms that govern its functions. The purpose of this review is to provide an overview of the most recent advances in structure–function studies on the role of CaM regulation of Kv7.2 and the other members of the Kv7 family.
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37
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Kim EC, Zhang J, Pang W, Wang S, Lee KY, Cavaretta JP, Walters J, Procko E, Tsai NP, Chung HJ. Reduced axonal surface expression and phosphoinositide sensitivity in K v7 channels disrupts their function to inhibit neuronal excitability in Kcnq2 epileptic encephalopathy. Neurobiol Dis 2018; 118:76-93. [PMID: 30008368 DOI: 10.1016/j.nbd.2018.07.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 06/22/2018] [Accepted: 07/04/2018] [Indexed: 01/08/2023] Open
Abstract
Neuronal Kv7/KCNQ channels are voltage-gated potassium channels composed of Kv7.2/KCNQ2 and Kv7.3/KCNQ3 subunits. Enriched at the axonal membrane, they potently suppress neuronal excitability. De novo and inherited dominant mutations in Kv7.2 cause early onset epileptic encephalopathy characterized by drug resistant seizures and profound psychomotor delay. However, their precise pathogenic mechanisms remain elusive. Here, we investigated selected epileptic encephalopathy causing mutations in calmodulin (CaM)-binding helices A and B of Kv7.2. We discovered that R333W, K526N, and R532W mutations located peripheral to CaM contact sites decreased axonal surface expression of heteromeric channels although only R333W mutation reduced CaM binding to Kv7.2. These mutations also altered gating modulation by phosphatidylinositol 4,5-bisphosphate (PIP2), revealing novel PIP2 binding residues. While these mutations disrupted Kv7 function to suppress excitability, hyperexcitability was observed in neurons expressing Kv7.2-R532W that displayed severe impairment in voltage-dependent activation. The M518 V mutation at the CaM contact site in helix B caused most defects in Kv7 channels by severely reducing their CaM binding, K+ currents, and axonal surface expression. Interestingly, the M518 V mutation induced ubiquitination and accelerated proteasome-dependent degradation of Kv7.2, whereas the presence of Kv7.3 blocked this degradation. Furthermore, expression of Kv7.2-M518V increased neuronal death. Together, our results demonstrate that epileptic encephalopathy mutations in helices A and B of Kv7.2 cause abnormal Kv7 expression and function by disrupting Kv7.2 binding to CaM and/or modulation by PIP2. We propose that such multiple Kv7 channel defects could exert more severe impacts on neuronal excitability and health, and thus serve as pathogenic mechanisms underlying Kcnq2 epileptic encephalopathy.
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Affiliation(s)
- Eung Chang Kim
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Jiaren Zhang
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Weilun Pang
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Shuwei Wang
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Kwan Young Lee
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - John P Cavaretta
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Jennifer Walters
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Erik Procko
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Nien-Pei Tsai
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Hee Jung Chung
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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38
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Chang A, Abderemane-Ali F, Hura GL, Rossen ND, Gate RE, Minor DL. A Calmodulin C-Lobe Ca 2+-Dependent Switch Governs Kv7 Channel Function. Neuron 2018; 97:836-852.e6. [PMID: 29429937 DOI: 10.1016/j.neuron.2018.01.035] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 12/07/2017] [Accepted: 01/12/2018] [Indexed: 12/22/2022]
Abstract
Kv7 (KCNQ) voltage-gated potassium channels control excitability in the brain, heart, and ear. Calmodulin (CaM) is crucial for Kv7 function, but how this calcium sensor affects activity has remained unclear. Here, we present X-ray crystallographic analysis of CaM:Kv7.4 and CaM:Kv7.5 AB domain complexes that reveal an Apo/CaM clamp conformation and calcium binding preferences. These structures, combined with small-angle X-ray scattering, biochemical, and functional studies, establish a regulatory mechanism for Kv7 CaM modulation based on a common architecture in which a CaM C-lobe calcium-dependent switch releases a shared Apo/CaM clamp conformation. This C-lobe switch inhibits voltage-dependent activation of Kv7.4 and Kv7.5 but facilitates Kv7.1, demonstrating that mechanism is shared by Kv7 isoforms despite the different directions of CaM modulation. Our findings provide a unified framework for understanding how CaM controls different Kv7 isoforms and highlight the role of membrane proximal domains for controlling voltage-gated channel function. VIDEO ABSTRACT.
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Affiliation(s)
- Aram Chang
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Fayal Abderemane-Ali
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Greg L Hura
- Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Nathan D Rossen
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Rachel E Gate
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Daniel L Minor
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA; Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Departments of Biochemistry and Biophysics, and Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA; California Institute for Quantitative Biomedical Research, University of California San Francisco, San Francisco, CA 94158, USA; Kavli Institute for Fundamental Neuroscience, University of California San Francisco, San Francisco, CA 94158, USA.
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Tobelaim WS, Dvir M, Lebel G, Cui M, Buki T, Peretz A, Marom M, Haitin Y, Logothetis DE, Hirsch JA, Attali B. Ca 2+-Calmodulin and PIP2 interactions at the proximal C-terminus of Kv7 channels. Channels (Austin) 2017; 11:686-695. [PMID: 28976808 PMCID: PMC5786183 DOI: 10.1080/19336950.2017.1388478] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 09/18/2017] [Accepted: 09/29/2017] [Indexed: 10/18/2022] Open
Abstract
In the heart, co-assembly of Kv7.1 with KCNE1 produces the slow IKS potassium current, which repolarizes the cardiac action potential and mutations in human Kv7.1 and KCNE1 genes cause cardiac arrhythmias. The proximal Kv7.1 C-terminus binds calmodulin (CaM) and phosphatidylinositol-4,5-bisphosphate (PIP2) and recently we revealed the competition of PIP2 with the calcified CaM N-lobe to a previously unidentified site in Kv7.1 helix B, also known to harbor a LQT mutation. Data indicated that PIP2 and Ca2+-CaM perform the same function on IKS channel gating to stabilize the channel open state. Here we show that similar features were observed for Kv7.1 currents expressed alone. We also find that conservation of homologous residues in helix B of other Kv7 subtypes confer similar competition of Ca2+-CaM with PIP2 binding to their proximal C-termini and suggest that PIP2-CaM interactions converge to Kv7 helix B to modulates channel activity in a Kv7 subtype-dependent manner.
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Affiliation(s)
- William S. Tobelaim
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
| | - Meidan Dvir
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
| | - Guy Lebel
- Department of Biochemistry & Molecular Biology, George S. Wise Faculty of Life Sciences, Institute of Structural Biology, Tel Aviv University, Tel Aviv, Israel
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Tal Buki
- Laboratory of Structural Physiology, Department of Physiology & Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Asher Peretz
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
| | - Milit Marom
- Laboratory of Structural Physiology, Department of Physiology & Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yoni Haitin
- Laboratory of Structural Physiology, Department of Physiology & Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | - Joel A. Hirsch
- Department of Biochemistry & Molecular Biology, George S. Wise Faculty of Life Sciences, Institute of Structural Biology, Tel Aviv University, Tel Aviv, Israel
| | - Bernard Attali
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
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Abstract
Retigabine (RTG) is a first-in-class antiepileptic drug that suppresses neuronal excitability through the activation of voltage-gated KCNQ2-5 potassium channels. Retigabine binds to the pore-forming domain, causing a hyperpolarizing shift in the voltage dependence of channel activation. To elucidate how the retigabine binding site is coupled to changes in voltage sensing, we used voltage-clamp fluorometry to track conformational changes of the KCNQ3 voltage-sensing domains (VSDs) in response to voltage, retigabine, and PIP2. Steady-state ionic conductance and voltage sensor fluorescence closely overlap under basal PIP2 conditions. Retigabine stabilizes the conducting conformation of the pore and the activated voltage sensor conformation, leading to dramatic deceleration of current and fluorescence deactivation, but these effects are attenuated upon disruption of channel:PIP2 interactions. These findings reveal an important role for PIP2 in coupling retigabine binding to altered VSD function. We identify a polybasic motif in the proximal C terminus of retigabine-sensitive KCNQ channels that contributes to VSD-pore coupling via PIP2, and thereby influences the unique gating effects of retigabine.
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41
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Alaimo A, Nuñez E, Aivar P, Fernández-Orth J, Gomis-Perez C, Bernardo-Seisdedos G, Malo C, Villarroel A. Calmodulin confers calcium sensitivity to the stability of the distal intracellular assembly domain of Kv7.2 channels. Sci Rep 2017; 7:13425. [PMID: 29044210 PMCID: PMC5647379 DOI: 10.1038/s41598-017-13811-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 09/29/2017] [Indexed: 01/03/2023] Open
Abstract
Tetrameric coiled-coil structures are present in many ion channels, often adjacent to a calmodulin (CaM) binding site, although the relationship between the two is not completely understood. Here we examine the dynamic properties of the ABCD domain located in the intracellular C-terminus of tetrameric, voltage-dependent, potassium selective Kv7.2 channels. This domain encompasses the CaM binding site formed by helices A and B, followed by helix C, which is linked to the helix D coiled-coil. The data reveals that helix D stabilizes CaM binding, promoting trans-binding (CaM embracing neighboring subunits), and they suggest that the ABCD domain can be exchanged between subunits of the tetramer. Exchange is faster when mutations in AB weaken the CaM interaction. The exchange of ABCD domains is slower in the presence of Ca2+, indicating that CaM stabilization of the tetrameric assembly is enhanced when loaded with this cation. Our observations are consistent with a model that involves a dynamic mechanism of helix D assembly, which supports reciprocal allosteric coupling between the A-B module and the coiled-coil formed by the helix D. Thus, formation of the distal helix D tetramer influences CaM binding and CaM-dependent Kv7.2 properties, whereas reciprocally, CaM and Ca2+ influence the dynamic behavior of the helix D coiled-coil.
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Affiliation(s)
- Alessandro Alaimo
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Eider Nuñez
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Paloma Aivar
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Juncal Fernández-Orth
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Carolina Gomis-Perez
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Ganeko Bernardo-Seisdedos
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Covadonga Malo
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain
| | - Alvaro Villarroel
- Instituto Biofisika, Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU, Barrio Sarriena s/n, 48940, Leioa, Spain.
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Pedersen PJ, Thomsen KB, Flak JB, Tejada MA, Hauser F, Trachsel D, Buhl R, Kalbfleisch T, DePriest MS, MacLeod JN, Calloe K, Klaerke DA. Molecular cloning and functional expression of the K + channel K V7.1 and the regulatory subunit KCNE1 from equine myocardium. Res Vet Sci 2017; 113:79-86. [PMID: 28917093 DOI: 10.1016/j.rvsc.2017.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 08/05/2017] [Accepted: 09/07/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND The voltage-gated K+-channel KV7.1 and the subunit KCNE1, encoded by the KCNQ1 and KCNE1 genes, respectively, are responsible for termination of the cardiac action potential. In humans, mutations in these genes can predispose patients to arrhythmias and sudden cardiac death (SCD). AIM To characterize equine KV7.1/KCNE1 currents and compare them to human KV7.1/KCNE1 currents to determine whether KV7.1/KCNE1 plays a similar role in equine and human hearts. METHODS mRNA encoding KV7.1 and KCNE1 was isolated from equine hearts, sequenced, and cloned into expression vectors. The channel subunits were heterologously expressed in Xenopus laevis oocytes or CHO-K1 cells and characterized using voltage-clamp techniques. RESULTS Equine KV7.1/KCNE1 expressed in CHO-K1 cells exhibited electrophysiological properties that are overall similar to the human orthologs; however, a slower deactivation was found which could result in more open channels at fast rates. CONCLUSION The results suggest that the equine KV7.1/KCNE1 channel may be important for cardiac repolarization and this could indicate that horses are susceptible to SCD caused by mutations in KCNQ1 and KCNE1.
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Affiliation(s)
- Philip J Pedersen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Kirsten B Thomsen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Jon B Flak
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Maria A Tejada
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Frank Hauser
- Center for Functional and Comparative Insect Genomics, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Dagmar Trachsel
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Theodore Kalbfleisch
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Michael Scott DePriest
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, KY, United States
| | - James N MacLeod
- Maxwell H., Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, United States
| | - Kirstine Calloe
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
| | - Dan A Klaerke
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
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Fischer C, DeFalco TA, Karia P, Snedden WA, Moeder W, Yoshioka K, Dietrich P. Calmodulin as a Ca2+-Sensing Subunit of Arabidopsis Cyclic Nucleotide-Gated Channel Complexes. PLANT & CELL PHYSIOLOGY 2017; 58:1208-1221. [PMID: 28419310 DOI: 10.1093/pcp/pcx052] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 04/06/2017] [Indexed: 05/23/2023]
Abstract
Ca2+ serves as a universal second messenger in eukaryotic signaling pathways, and the spatial and temporal patterns of Ca2+ concentration changes are determined by feedback and feed-forward regulation of the involved transport proteins. Cyclic nucleotide-gated channels (CNGCs) are Ca2+-permeable channels that interact with the ubiquitous Ca2+ sensor calmodulin (CaM). CNGCs interact with CaMs via diverse CaM-binding sites, including an IQ-motif, which has been identified in the C-termini of CNGC20 and CNGC12. Here we present a family-wide analysis of the IQ-motif from all 20 Arabidopsis CNGC isoforms. While most of their IQ-peptides interacted with conserved CaMs in yeast, some were unable to do so, despite high sequence conservation across the family. We showed that the CaM binding ability of the IQ-motif is highly dependent on its proximal and distal vicinity. We determined that two alanine residues positioned N-terminal to the core IQ-sequence play a significant role in CaM binding, and identified a polymorphism at this site that promoted or inhibited CaM binding in yeast. Through detailed biophysical analysis of the CNGC2 IQ-motif, we found that this polymorphism specifically affected the Ca2+-independent interactions with the C-lobe of CaM. This same polymorphism partially suppressed the induction of programmed cell death by CNGC11/12 in planta. Our work expands the model of CNGC regulation, and posits that the C-lobe of apo-CaM is permanently associated with the channel at the N-terminal part of the IQ-domain. This mode allows CaM to function as a Ca2+-sensing regulatory subunit of the channel complex, providing a mechanism by which Ca2+ signals may be fine-tuned.
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Affiliation(s)
- Cornelia Fischer
- Molecular Plant Physiology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
| | - Thomas A DeFalco
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada, M5S 3B2
| | - Purva Karia
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada, M5S 3B2
| | - Wayne A Snedden
- Department of Biology, Biosciences Complex, Queen's University, Kingston, ON, Canada, K7L 3N6
| | - Wolfgang Moeder
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada, M5S 3B2
| | - Keiko Yoshioka
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada, M5S 3B2
- Center for the Analysis of Genome Evolution and Function (CAGEF), University of Toronto, Toronto, ON, Canada, M5S 3B2
| | - Petra Dietrich
- Molecular Plant Physiology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, D-91058 Erlangen, Germany
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Hovey L, Fowler CA, Mahling R, Lin Z, Miller MS, Marx DC, Yoder JB, Kim EH, Tefft KM, Waite BC, Feldkamp MD, Yu L, Shea MA. Calcium triggers reversal of calmodulin on nested anti-parallel sites in the IQ motif of the neuronal voltage-dependent sodium channel Na V1.2. Biophys Chem 2017; 224:1-19. [PMID: 28343066 PMCID: PMC5503752 DOI: 10.1016/j.bpc.2017.02.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 02/23/2017] [Accepted: 02/23/2017] [Indexed: 01/26/2023]
Abstract
Several members of the voltage-gated sodium channel family are regulated by calmodulin (CaM) and ionic calcium. The neuronal voltage-gated sodium channel NaV1.2 contains binding sites for both apo (calcium-depleted) and calcium-saturated CaM. We have determined equilibrium dissociation constants for rat NaV1.2 IQ motif [IQRAYRRYLLK] binding to apo CaM (~3nM) and (Ca2+)4-CaM (~85nM), showing that apo CaM binding is favored by 30-fold. For both apo and (Ca2+)4-CaM, NMR demonstrated that NaV1.2 IQ motif peptide (NaV1.2IQp) exclusively made contacts with C-domain residues of CaM (CaMC). To understand how calcium triggers conformational change at the CaM-IQ interface, we determined a solution structure (2M5E.pdb) of (Ca2+)2-CaMC bound to NaV1.2IQp. The polarity of (Ca2+)2-CaMC relative to the IQ motif was opposite to that seen in apo CaMC-Nav1.2IQp (2KXW), revealing that CaMC recognizes nested, anti-parallel sites in Nav1.2IQp. Reversal of CaM may require transient release from the IQ motif during calcium binding, and facilitate a re-orientation of CaMN allowing interactions with non-IQ NaV1.2 residues or auxiliary regulatory proteins interacting in the vicinity of the IQ motif.
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Affiliation(s)
- Liam Hovey
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - C Andrew Fowler
- NMR Facility, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 52242-1109 Iowa City, United States
| | - Ryan Mahling
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Zesen Lin
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Mark Stephen Miller
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Dagan C Marx
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Jesse B Yoder
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Elaine H Kim
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Kristin M Tefft
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Brett C Waite
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Michael D Feldkamp
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States
| | - Liping Yu
- NMR Facility, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 52242-1109 Iowa City, United States
| | - Madeline A Shea
- Department of Biochemistry, University of Iowa, 52242-1109 Iowa City, United States.
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Competition of calcified calmodulin N lobe and PIP2 to an LQT mutation site in Kv7.1 channel. Proc Natl Acad Sci U S A 2017; 114:E869-E878. [PMID: 28096388 DOI: 10.1073/pnas.1612622114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Voltage-gated potassium 7.1 (Kv7.1) channel and KCNE1 protein coassembly forms the slow potassium current IKS that repolarizes the cardiac action potential. The physiological importance of the IKS channel is underscored by the existence of mutations in human Kv7.1 and KCNE1 genes, which cause cardiac arrhythmias, such as the long-QT syndrome (LQT) and atrial fibrillation. The proximal Kv7.1 C terminus (CT) binds calmodulin (CaM) and phosphatidylinositol-4,5-bisphosphate (PIP2), but the role of CaM in channel function is still unclear, and its possible interaction with PIP2 is unknown. Our recent crystallographic study showed that CaM embraces helices A and B with the apo C lobe and calcified N lobe, respectively. Here, we reveal the competition of PIP2 and the calcified CaM N lobe to a previously unidentified site in Kv7.1 helix B, also known to harbor an LQT mutation. Protein pulldown, molecular docking, molecular dynamics simulations, and patch-clamp recordings indicate that residues K526 and K527 in Kv7.1 helix B form a critical site where CaM competes with PIP2 to stabilize the channel open state. Data indicate that both PIP2 and Ca2+-CaM perform the same function on IKS channel gating by producing a left shift in the voltage dependence of activation. The LQT mutant K526E revealed a severely impaired channel function with a right shift in the voltage dependence of activation, a reduced current density, and insensitivity to gating modulation by Ca2+-CaM. The results suggest that, after receptor-mediated PIP2 depletion and increased cytosolic Ca2+, calcified CaM N lobe interacts with helix B in place of PIP2 to limit excessive IKS current inhibition.
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46
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Peycheva V, Ivanova N, Kamenarova K, Tsekova I, Aleksandrova I, Bozhinova V, Bozhidarova M, Litvinenko I, Hristova D, Mitev V, Kaneva R, Jordanova A. Impact of KCNQ2 mutations in Bulgarian patients with electroclinical syndromes with onset in the first year of life. BIOTECHNOL BIOTEC EQ 2017. [DOI: 10.1080/13102818.2016.1259017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- Valentina Peycheva
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
| | - Neviana Ivanova
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
| | - Kunka Kamenarova
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
| | - Irina Tsekova
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
| | - Iliyana Aleksandrova
- Department of Neurology, Clinic of Child Neurology, University Hospital of Neurology and Psychiatry “St' Naum”, Medical University of Sofia, Sofia, Bulgaria
| | - Veneta Bozhinova
- Department of Neurology, Clinic of Child Neurology, University Hospital of Neurology and Psychiatry “St' Naum”, Medical University of Sofia, Sofia, Bulgaria
| | - Maria Bozhidarova
- Department of Pediatric Neurology, University Pediatrics Hospital, Medical University of Sofia, Sofia, Bulgaria
| | - Ivan Litvinenko
- Department of Pediatric Neurology, University Pediatrics Hospital, Medical University of Sofia, Sofia, Bulgaria
| | - Dimitrina Hristova
- Children Neurology Unit, Pediatrics Clinic, Tokuda Hospital, Sofia, Bulgaria
| | - Vanyo Mitev
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
| | - Radka Kaneva
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
| | - Albena Jordanova
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University of Sofia, Sofia, Bulgaria
- VIB Department of Molecular Genetics, Molecular Neurogenomics Group, University of Antwerp, Antwerp, Belgium
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47
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Abstract
KCNQ2/3 (Kv7.2/7.3) channels and voltage-gated sodium channels (VGSCs) are enriched in the axon initial segment (AIS) where they bind to ankyrin-G and coregulate membrane potential in central nervous system neurons. The molecular mechanisms supporting coordinated regulation of KCNQ and VGSCs and the cellular mechanisms governing KCNQ trafficking to the AIS are incompletely understood. Here, we show that fibroblast growth factor 14 (FGF14), previously described as a VGSC regulator, also affects KCNQ function and localization. FGF14 knockdown leads to a reduction of KCNQ2 in the AIS and a reduction in whole-cell KCNQ currents. FGF14 positively regulates KCNQ2/3 channels in a simplified expression system. FGF14 interacts with KCNQ2 at a site distinct from the FGF14-VGSC interaction surface, thus enabling the bridging of NaV1.6 and KCNQ2. These data implicate FGF14 as an organizer of channel localization in the AIS and provide insight into the coordination of KCNQ and VGSC conductances in the regulation of membrane potential.
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48
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Salzer I, Erdem FA, Chen WQ, Heo S, Koenig X, Schicker KW, Kubista H, Lubec G, Boehm S, Yang JW. Phosphorylation regulates the sensitivity of voltage-gated Kv7.2 channels towards phosphatidylinositol-4,5-bisphosphate. J Physiol 2016; 595:759-776. [PMID: 27621207 PMCID: PMC5215842 DOI: 10.1113/jp273274] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 08/30/2016] [Indexed: 12/22/2022] Open
Abstract
Key points Phosphatidylinositol‐4,5‐bisphosphate (PIP2) is a key regulator of many membrane proteins, including voltage‐gated Kv7.2 channels. In this study, we identified the residues in five phosphorylation sites and their corresponding protein kinases, the former being clustered within one of four putative PIP2‐binding domains in Kv7.2. Dephosphorylation of these residues reduced the sensitivity of Kv7.2 channels towards PIP2. Dephosphorylation of Kv7.2 affected channel inhibition via M1 muscarinic receptors, but not via bradykinin receptors. Our data indicated that phosphorylation of the Kv7.2 channel was necessary to maintain its low affinity for PIP2, thereby ensuring the tight regulation of the channel via G protein‐coupled receptors.
Abstract The function of numerous ion channels is tightly controlled by G protein‐coupled receptors (GPCRs). The underlying signalling mechanisms may involve phosphorylation of channel proteins and participation of phosphatidylinositol‐4,5‐bisphosphate (PIP2). Although the roles of both mechanisms have been investigated extensively, thus far only little has been reported on their interaction in channel modulation. GPCRs govern Kv7 channels, the latter playing a major role in the regulation of neuronal excitability by determining the levels of PIP2 and through phosphorylation. Using liquid chromatography‐coupled mass spectrometry for Kv7.2 immunoprecipitates of rat brain membranes and transfected cells, we mapped a cluster of five phosphorylation sites in one of the PIP2‐binding domains. To evaluate the effect of phosphorylation on PIP2‐mediated Kv7.2 channel regulation, a quintuple alanine mutant of these serines (S427/S436/S438/S446/S455; A5 mutant) was generated to mimic the dephosphorylated state. Currents passing through these mutated channels were less sensitive towards PIP2 depletion via the voltage‐sensitive phosphatase Dr‐VSP than were wild‐type channels. In vitro phosphorylation assays with the purified C‐terminus of Kv7.2 revealed that CDK5, p38 MAPK, CaMKIIα and PKA were able to phosphorylate the five serines. Inhibition of these protein kinases reduced the sensitivity of wild‐type but not mutant Kv7.2 channels towards PIP2 depletion via Dr‐VSP. In superior cervical ganglion neurons, the protein kinase inhibitors attenuated Kv7 current regulation via M1 receptors, but left unaltered the control by B2 receptors. Our results revealed that the phosphorylation status of serines located within a putative PIP2‐binding domain determined the phospholipid sensitivity of Kv7.2 channels and supported GPCR‐mediated channel regulation. Phosphatidylinositol‐4,5‐bisphosphate (PIP2) is a key regulator of many membrane proteins, including voltage‐gated Kv7.2 channels. In this study, we identified the residues in five phosphorylation sites and their corresponding protein kinases, the former being clustered within one of four putative PIP2‐binding domains in Kv7.2. Dephosphorylation of these residues reduced the sensitivity of Kv7.2 channels towards PIP2. Dephosphorylation of Kv7.2 affected channel inhibition via M1 muscarinic receptors, but not via bradykinin receptors. Our data indicated that phosphorylation of the Kv7.2 channel was necessary to maintain its low affinity for PIP2, thereby ensuring the tight regulation of the channel via G protein‐coupled receptors.
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Affiliation(s)
- Isabella Salzer
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Fatma Asli Erdem
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Wei-Qiang Chen
- Department of Pediatrics, Medical University of Vienna, 1090, Vienna, Austria
| | - Seok Heo
- Department of Pediatrics, Medical University of Vienna, 1090, Vienna, Austria
| | - Xaver Koenig
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Klaus W Schicker
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Helmut Kubista
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Gert Lubec
- Department of Pharmaceutical Chemistry, University of Vienna, 1090, Vienna, Austria
| | - Stefan Boehm
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
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Strulovich R, Tobelaim WS, Attali B, Hirsch JA. Structural Insights into the M-Channel Proximal C-Terminus/Calmodulin Complex. Biochemistry 2016; 55:5353-65. [PMID: 27564677 DOI: 10.1021/acs.biochem.6b00477] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The Kv7 (KCNQ) channel family, comprising voltage-gated potassium channels, plays major roles in fine-tuning cellular excitability by reducing firing frequency and controlling repolarization. Kv7 channels have a unique intracellular C-terminal (CT) domain bound constitutively by calmodulin (CaM). This domain plays key functions in channel tetramerization, trafficking, and gating. CaM binds to the proximal CT, comprising helices A and B. Kv7.2 and Kv7.3 are expressed in neural tissues. Together, they form the heterotetrameric M channel. We characterized Kv7.2, Kv7.3, and chimeric Kv7.3 helix A-Kv7.2 helix B (Q3A-Q2B) proximal CT/CaM complexes by solution methods at various Ca(2+)concentrations and determined them all to have a 1:1 stoichiometry. We then determined the crystal structure of the Q3A-Q2B/CaM complex at high Ca(2+) concentration to 2.0 Å resolution. CaM hugs the antiparallel coiled coil of helices A and B, braced together by an additional helix. The structure displays a hybrid apo-Ca(2+) CaM conformation even though four Ca(2+) ions are bound. Our results pinpoint unique interactions enabling the possible intersubunit pairing of Kv7.3 helix A and Kv7.2 helix B while underlining the potential importance of Kv7.3 helix A's role in stabilizing channel oligomerization. Also, the structure can be used to rationalize various channelopathic mutants. Functional testing of the chimeric channel found it to have a voltage-dependence similar to the M channel, thereby demonstrating helix A's importance in imparting gating properties.
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Affiliation(s)
- Roi Strulovich
- Department of Biochemistry and Molecular Biology, Institute of Structural Biology, George S. Wise Faculty of Life Sciences, ‡Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and §Sagol School of Neuroscience, Tel Aviv University , Ramat Aviv 69978, Israel
| | - William Sam Tobelaim
- Department of Biochemistry and Molecular Biology, Institute of Structural Biology, George S. Wise Faculty of Life Sciences, ‡Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and §Sagol School of Neuroscience, Tel Aviv University , Ramat Aviv 69978, Israel
| | - Bernard Attali
- Department of Biochemistry and Molecular Biology, Institute of Structural Biology, George S. Wise Faculty of Life Sciences, ‡Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and §Sagol School of Neuroscience, Tel Aviv University , Ramat Aviv 69978, Israel
| | - Joel A Hirsch
- Department of Biochemistry and Molecular Biology, Institute of Structural Biology, George S. Wise Faculty of Life Sciences, ‡Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and §Sagol School of Neuroscience, Tel Aviv University , Ramat Aviv 69978, Israel
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50
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Sogo T, Morikawa K, Kurata Y, Li P, Ichinose T, Yuasa S, Nozaki D, Miake J, Ninomiya H, Shimizu W, Fukuda K, Yamamoto K, Shirayoshi Y, Hisatome I. Electrophysiological properties of iPS cell-derived cardiomyocytes from a patient with long QT syndrome type 1 harboring the novel mutation M437V of KCNQ1. Regen Ther 2016; 4:9-17. [PMID: 31245483 PMCID: PMC6581809 DOI: 10.1016/j.reth.2015.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/17/2015] [Accepted: 12/24/2015] [Indexed: 02/03/2023] Open
Abstract
Introduction Long QT syndrome type 1 (LQT1) is caused by mutations in KCNQ1 coding slowly-activating delayed-rectifier K+ channels. We identified the novel missense mutation M437V of KCNQ1 in a LQT1 patient. Here, we employed iPS cell (iPSC)-derived cardiomyocytes to investigate electrophysiological properties of the mutant channel and LQT1 cardiomyocytes. Methods To generate iPSCs from the patient and a healthy subject, peripheral blood T cells were reprogrammed by Sendai virus vector encoding human OCT3/4, SOX2, KLF4, and c-MYC. Cardiomyocytes were prepared from iPSCs and human embryonic stem cells using a cytokine-based two-step differentiation method and were subjected to patch clamp experiments. Results LQT1 iPSC-derived cardiomyocytes exhibited prolongation of action potential duration (APD), which was due to a reduction of the KCNQ1-mediated current IKs; Na+, Ca2+ and other K+ channel currents were comparable. When expressed in HEK293 and COS7 cells, the mutant KCNQ1 was normally expressed in the plasma membrane but generated smaller currents than the wild type. Isoproterenol significantly prolonged APDs of LQT1 cardiomyocytes, while shortening those of healthy ones. A mathematical model for IKs-reduced human ventricular myocytes reproduced APD prolongation and generation of early afterdepolarizations (EADs) under β-adrenergic stimulation. Conclusions QT prolongation of the LQT1 patient with the mutation M437V of KCNQ1 was caused by IKs reduction, which may render the patient vulnerable to generation of EADs and arrhythmias. M437V mutation of KCNQ1 reduces channel conductance without trafficking defect. Reduced IKs of the mutant channel accounts for the prolongation of APD and QTc. Lack of medical history in this case is due to relatively small reduction in IKs. The patient is more vulnerable to generation of EAD and TdP than healthy subjects.
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Key Words
- AP(D), action potential (duration)
- C-terminus mutation
- EAD, early afterdepolarization
- EB, embryoid body
- ESC, embryonic stem cell
- Early afterdepolarization
- HP, holding potential
- ICaL, L-type Ca2+ channel current
- IK1, inward-rectifier K+ channel current
- IKr, rapidly-activating delayed-rectifier K+ channel current
- IKs, slowly-activating delayed-rectifier K+ channel current
- INa, sodium channel current
- KCNQ1
- LQT1
- LQTS, long QT syndrome
- TdP, Torsade de points
- iPS cell
- iPSC, induced pluripotent stem cell
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Affiliation(s)
- Tatsufumi Sogo
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan
| | - Kumi Morikawa
- Center for Promoting Next-Generation Highly Advanced Medicine, Tottori University Hospital, 36-1 Nishi-cho, Yonago 683-8504, Japan
| | - Yasutaka Kurata
- Department of Physiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada-machi, Ishikawa 920-0293, Japan
| | - Peili Li
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan
| | - Takafumi Ichinose
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan
| | - Shinsuke Yuasa
- Department of Cardiology, Keio University School of Medicine, 35 Shinano-machi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Daizou Nozaki
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan
| | - Junichiro Miake
- Division of Cardiovascular Medicine, Endocrinology and Metabolism, Department of Molecular Medicine and Therapeutics, Tottori University Faculty of Medicine, 86-1 Nishi-cho, Yonago 683-8504, Japan
| | - Haruaki Ninomiya
- Department of Biological Regulation, School of Health Science, Tottori University Faculty of Medicine, 36-1 Nishi-cho, Yonago 683-8503, Japan
| | - Wataru Shimizu
- Department of Cardiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, 35 Shinano-machi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Kazuhiro Yamamoto
- Division of Cardiovascular Medicine, Endocrinology and Metabolism, Department of Molecular Medicine and Therapeutics, Tottori University Faculty of Medicine, 86-1 Nishi-cho, Yonago 683-8504, Japan
| | - Yasuaki Shirayoshi
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan
| | - Ichiro Hisatome
- Division of Regenerative Medicine and Therapeutics, Department of Genetic Medicine and Regenerative Therapeutics, Tottori University Graduate School of Medical Science, 86 Nishi-cho, Yonago 683-8503, Japan.,Center for Promoting Next-Generation Highly Advanced Medicine, Tottori University Hospital, 36-1 Nishi-cho, Yonago 683-8504, Japan
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