1
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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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2
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Hendricks EL, Smith IR, Prates B, Barmaleki F, Liebl FLW. The CD63 homologs, Tsp42Ee and Tsp42Eg, restrict endocytosis and promote neurotransmission through differential regulation of synaptic vesicle pools. Front Cell Neurosci 2022; 16:957232. [PMID: 36072568 PMCID: PMC9441712 DOI: 10.3389/fncel.2022.957232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 08/04/2022] [Indexed: 11/30/2022] Open
Abstract
The Tetraspanin (Tsp), CD63, is a transmembrane component of late endosomes and facilitates vesicular trafficking through endosomal pathways. Despite being widely expressed in the human brain and localized to late endosomes, CD63's role in regulating endo- and exocytic cycling at the synapse has not been investigated. Synaptic vesicle pools are highly dynamic and disruptions in the mobilization and replenishment of these vesicle pools have adverse neuronal effects. We find that the CD63 homologs, Tsp42Ee and Tsp42Eg, are expressed at the Drosophila neuromuscular junction to regulate synaptic vesicle pools through both shared and unique mechanisms. Tsp42Ee and Tsp42Eg negatively regulate endocytosis and positively regulate neurotransmitter release. Both tsp mutants show impaired locomotion, reduced miniature endplate junctional current frequencies, and increased endocytosis. Expression of human CD63 in Drosophila neurons leads to impaired endocytosis suggesting the role of Tsps in endocytosis is conserved. We further show that Tsps influence the synaptic cytoskeleton and membrane composition by regulating Futsch loop formation and synaptic levels of SCAR and PI(4,5)P2. Finally, Tsp42Ee and Tsp42Eg influence the synaptic localization of several vesicle-associated proteins including Synapsin, Synaptotagmin, and Cysteine String Protein. Together, our results present a novel function for Tsps in the regulation of vesicle pools and provide insight into the molecular mechanisms of Tsp-related synaptic dysfunction.
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Affiliation(s)
| | | | | | | | - Faith L. W. Liebl
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL, United States
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3
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Dwivedi D, Bhalla US. Physiology and Therapeutic Potential of SK, H, and M Medium AfterHyperPolarization Ion Channels. Front Mol Neurosci 2021; 14:658435. [PMID: 34149352 PMCID: PMC8209339 DOI: 10.3389/fnmol.2021.658435] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/13/2021] [Indexed: 12/19/2022] Open
Abstract
SK, HCN, and M channels are medium afterhyperpolarization (mAHP)-mediating ion channels. The three channels co-express in various brain regions, and their collective action strongly influences cellular excitability. However, significant diversity exists in the expression of channel isoforms in distinct brain regions and various subcellular compartments, which contributes to an equally diverse set of specific neuronal functions. The current review emphasizes the collective behavior of the three classes of mAHP channels and discusses how these channels function together although they play specialized roles. We discuss the biophysical properties of these channels, signaling pathways that influence the activity of the three mAHP channels, various chemical modulators that alter channel activity and their therapeutic potential in treating various neurological anomalies. Additionally, we discuss the role of mAHP channels in the pathophysiology of various neurological diseases and how their modulation can alleviate some of the symptoms.
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Affiliation(s)
- Deepanjali Dwivedi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India.,Department of Neurobiology, Harvard Medical School, Boston, MA, United States.,Stanley Center at the Broad, Cambridge, MA, United States
| | - Upinder S Bhalla
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India
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4
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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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5
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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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6
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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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7
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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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8
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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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9
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Surur AS, Beirow K, Bock C, Schulig L, Kindermann MK, Bodtke A, Siegmund W, Bednarski PJ, Link A. Flupirtine Analogues: Explorative Synthesis and Influence of Chemical Structure on K V7.2/K V7.3 Channel Opening Activity. ChemistryOpen 2019; 8:41-44. [PMID: 30652063 PMCID: PMC6331712 DOI: 10.1002/open.201800244] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 11/26/2018] [Indexed: 12/19/2022] Open
Abstract
Neuronal voltage‐gated potassium channels KV7.2/KV7.3 are sensitive to small‐molecule drugs such as flupirtine, even though physiological response occurs in the absence of ligands. Clinically, prolonged use of flupirtine as a pain medication is associated with rare cases of drug‐induced liver injury. Thus, safety concerns prevent a broader use of this non‐opioid and non‐steroidal analgesic in therapeutic areas with unmet medical needs such as hyperactive bladder or neonatal seizures. With the goal of studying influences of chemical structure on activity and toxicity of flupirtine, we explored modifications of the benzylamino bridge and the substitution pattern in both rings of flupirtine. Among twelve derivatives, four novel thioether derivatives showed the desired activity in cellular assays and may serve as leads for safer KV channel openers.
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Affiliation(s)
- Abdrrahman S Surur
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Kristin Beirow
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Christian Bock
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Lukas Schulig
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Markus K Kindermann
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Anja Bodtke
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | | | - Patrick J Bednarski
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
| | - Andreas Link
- Institute of Pharmacy University of Greifswald Friedrich-Ludwig-Jahn-Str. 17 17489 Greifswald Germany
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10
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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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11
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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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12
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Ambrosino P, Freri E, Castellotti B, Soldovieri MV, Mosca I, Manocchio L, Gellera C, Canafoglia L, Franceschetti S, Salis B, Iraci N, Miceli F, Ragona F, Granata T, DiFrancesco JC, Taglialatela M. Kv7.3 Compound Heterozygous Variants in Early Onset Encephalopathy Reveal Additive Contribution of C-Terminal Residues to PIP2-Dependent K+ Channel Gating. Mol Neurobiol 2018; 55:7009-7024. [DOI: 10.1007/s12035-018-0883-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 01/08/2018] [Indexed: 11/28/2022]
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13
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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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