1
|
Greene D, Shiferaw Y. Identifying Key Binding Interactions Between the Cardiac L-Type Calcium Channel and Calmodulin Using Molecular Dynamics Simulations. J Phys Chem B 2024; 128:6097-6111. [PMID: 38870543 PMCID: PMC11215769 DOI: 10.1021/acs.jpcb.4c02251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 05/28/2024] [Accepted: 05/30/2024] [Indexed: 06/15/2024]
Abstract
Defects in the binding of the calcium sensing protein calmodulin (CaM) to the L-type calcium channel (CaV1.2) or to the ryanodine receptor type 2 (RyR2) can lead to dangerous cardiac arrhythmias with distinct phenotypes, such as long-QT syndrome (LQTS) and catecholaminergic ventricular tachycardia (CPVT). Certain CaM mutations lead to LQTS while other mutations lead to CPVT, but the mechanisms by which a specific mutation can lead to each disease phenotype are not well-understood. In this study, we use long, 2 μs molecular dynamics simulations and a multitrajectory approach to identify the key binding interactions between the IQ domain of CaV1.2 and CaM. Five key interactions are found between CaV1.2 and CaM in the C-lobe, 1 in the central linker, and 2 in the N-lobe. In addition, while 5 key interactions appear between residues 120-149 in the C-lobe of CaM when it interacts with CaV1.2, only 1 key interaction is found within this region of CaM when it interacts with the RyR2. We show that this difference in the distribution of key interactions correlates with the known distribution of CaM mutations that lead to LQTS or CPVT. This correlation suggests that a disruption of key binding interactions is a plausible mechanism that can lead to these two different disease phenotypes.
Collapse
Affiliation(s)
- D’Artagnan Greene
- Department of Physics and
Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge, California 91330-8268, United States of
America
| | - Yohannes Shiferaw
- Department of Physics and
Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge, California 91330-8268, United States of
America
| |
Collapse
|
2
|
Kang PW, Woodbury L, Angsutararux P, Sambare N, Shi J, Marras M, Abella C, Bedi A, Zinn D, Cui J, Silva JR. Arrhythmia-associated calmodulin variants interact with KCNQ1 to confer aberrant membrane trafficking and function. PNAS NEXUS 2023; 2:pgad335. [PMID: 37965565 PMCID: PMC10642763 DOI: 10.1093/pnasnexus/pgad335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 10/04/2023] [Indexed: 11/16/2023]
Abstract
Missense variants in calmodulin (CaM) predispose patients to arrhythmias associated with high mortality rates ("calmodulinopathy"). As CaM regulates many key cardiac ion channels, an understanding of disease mechanism associated with CaM variant arrhythmias requires elucidating individual CaM variant effects on distinct channels. One key CaM regulatory target is the KCNQ1 (KV7.1) voltage-gated potassium channel that carries the IKs current. Yet, relatively little is known as to how CaM variants interact with KCNQ1 or affect its function. Here, we take a multipronged approach employing a live-cell fluorescence resonance energy transfer binding assay, fluorescence trafficking assay, and functional electrophysiology to characterize >10 arrhythmia-associated CaM variants for effect on KCNQ1 CaM binding, membrane trafficking, and channel function. We identify one variant (G114W) that exhibits severely weakened binding to KCNQ1 but find that most other CaM variants interact with similar binding affinity to KCNQ1 when compared with CaM wild-type over physiological Ca2+ ranges. We further identify several CaM variants that affect KCNQ1 and IKs membrane trafficking and/or baseline current activation kinetics, thereby delineating KCNQ1 dysfunction in calmodulinopathy. Lastly, we identify CaM variants with no effect on KCNQ1 function. This study provides extensive functional data that reveal how CaM variants contribute to creating a proarrhythmic substrate by causing abnormal KCNQ1 membrane trafficking and current conduction. We find that CaM variant regulation of KCNQ1 is not uniform with effects varying from benign to significant loss of function, suggesting how CaM variants predispose patients to arrhythmia via the dysregulation of multiple cardiac ion channels. Classification: Biological, Health, and Medical Sciences, Physiology.
Collapse
Affiliation(s)
- Po wei Kang
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Lucy Woodbury
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Paweorn Angsutararux
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Namit Sambare
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Jingyi Shi
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Martina Marras
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Carlota Abella
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Anish Bedi
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - DeShawn Zinn
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Jianmin Cui
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| | - Jonathan R Silva
- Department of Biomedical Engineering, Washington University in St.Louis, St. Louis, MO 63130, USA
| |
Collapse
|
3
|
Thanassoulas A, Theodoridou M, Barrak L, Riguene E, Alyaarabi T, Elrayess MA, Lai FA, Nomikos M. Arrhythmia-Associated Calmodulin E105A Mutation Alters the Binding Affinity of CaM to a Ryanodine Receptor 2 CaM-Binding Pocket. Int J Mol Sci 2023; 24:15630. [PMID: 37958614 PMCID: PMC10649572 DOI: 10.3390/ijms242115630] [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: 09/23/2023] [Revised: 10/21/2023] [Accepted: 10/24/2023] [Indexed: 11/15/2023] Open
Abstract
Calmodulin (CaM) is a small, multifunctional calcium (Ca2+)-binding sensor that binds and regulates the open probability of cardiac ryanodine receptor 2 (RyR2) at both low and high cytosolic Ca2+ concentrations. Recent isothermal titration calorimetry (ITC) studies of a number of peptides that correspond to different regions of human RyR2 showed that two regions of human RyR2 (3584-3602aa and 4255-4271aa) bind with high affinity to CaM, suggesting that these two regions might contribute to a putative RyR2 intra-subunit CaM-binding pocket. Moreover, a previously characterized de novo long QT syndrome (LQTS)-associated missense CaM mutation (E105A) which was identified in a 6-year-old boy, who experienced an aborted first episode of cardiac arrest revealed that this mutation dysregulates normal cardiac function in zebrafish by a complex mechanism that involves alterations in both CaM-Ca2+ and CaM-RyR2 interactions. Herein, to gain further insight into how the CaM E105A mutation leads to severe cardiac arrhythmia, we generated large quantities of recombinant CaMWT and CaME105A proteins. We then performed ITC experiments to investigate and compare the interactions of CaMWT and CaME105A mutant protein with two synthetic peptides that correspond to the two aforementioned human RyR2 regions, which we have proposed to contribute to the RyR2 CaM-binding pocket. Our data reveal that the E105A mutation has a significant negative effect on the interaction of CaM with both RyR2 regions in the presence and absence of Ca2+, highlighting the potential contribution of these two human RyR2 regions to an RyR2 CaM-binding pocket, which may be essential for physiological CaM/RyR2 association and thus channel regulation.
Collapse
Affiliation(s)
- Angelos Thanassoulas
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
| | - Maria Theodoridou
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar;
| | - Laila Barrak
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
| | - Emna Riguene
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
| | - Tamader Alyaarabi
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
| | - Mohamed A. Elrayess
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar;
| | - F. Anthony Lai
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
| | - Michail Nomikos
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar; (A.T.); (L.B.); (E.R.); (T.A.); (M.A.E.); (F.A.L.)
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Brohus M, Busuioc AO, Wimmer R, Nyegaard M, Overgaard MT. Calmodulin mutations affecting Gly114 impair binding to the Na V1.5 IQ-domain. Front Pharmacol 2023; 14:1210140. [PMID: 37663247 PMCID: PMC10469309 DOI: 10.3389/fphar.2023.1210140] [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: 04/24/2023] [Accepted: 07/25/2023] [Indexed: 09/05/2023] Open
Abstract
Missense variants in CALM genes encoding the Ca2+-binding protein calmodulin (CaM) cause severe cardiac arrhythmias. The disease mechanisms have been attributed to dysregulation of RyR2, for Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) and/or CaV1.2, for Long-QT Syndrome (LQTS). Recently, a novel CALM2 variant, G114R, was identified in a mother and two of her four children, all of whom died suddenly while asleep at a young age. The G114R variant impairs closure of CaV1.2 and RyR2, consistent with a CPVT and/or mild LQTS phenotype. However, the children carrying the CALM2 G114R variant displayed a phenotype commonly observed with variants in NaV1.5, i.e., Brugada Syndrome (BrS) or LQT3, where death while asleep is a common feature. We therefore hypothesized that the G114R variant specifically would interfere with NaV1.5 binding. Here, we demonstrate that CaM binding to the NaV1.5 IQ-domain is severely impaired for two CaM variants G114R and G114W. The impact was most severe at low and intermediate Ca2+ concentrations (up to 4 µM) resulting in more than a 50-fold reduction in NaV1.5 binding affinity, and a smaller 1.5 to 11-fold reduction at high Ca2+ concentrations (25-400 µM). In contrast, the arrhythmogenic CaM-N98S variant only induced a 1.5-fold reduction in NaV1.5 binding and only at 4 µM Ca2+. A non-arrhythmogenic I10T variant in CaM did not impair NaV1.5 IQ binding. These data suggest that the interaction between NaV1.5 and CaM is decreased with certain CaM variants, which may alter the cardiac sodium current, INa. Overall, these results suggest that the phenotypic spectrum of calmodulinopathies may likely expand to include BrS- and/or LQT3-like traits.
Collapse
Affiliation(s)
- Malene Brohus
- Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Ana-Octavia Busuioc
- Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Reinhard Wimmer
- Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Mette Nyegaard
- Department of Health Science and Technology, Aalborg University, Gistrup, Denmark
| | | |
Collapse
|
6
|
Svensson B, Nitu FR, Rebbeck RT, McGurran LM, Oda T, Thomas DD, Bers DM, Cornea RL. Molecular Mechanism of a FRET Biosensor for the Cardiac Ryanodine Receptor Pathologically Leaky State. Int J Mol Sci 2023; 24:12547. [PMID: 37628726 PMCID: PMC10454150 DOI: 10.3390/ijms241612547] [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: 07/01/2023] [Revised: 07/31/2023] [Accepted: 08/02/2023] [Indexed: 08/27/2023] Open
Abstract
Ca2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide (DPc10) binding promotes leaky RyR2 in cardiomyocytes and reports on that endogenous state. Conversely, calmodulin (CaM) binding inhibits RyR2 leak and low CaM affinity is diagnostic of leaky RyR2. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. We used FRET to clarify the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca2+, DPc10 decreased both FRETmax (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca2+, DPc10 decreased FRETmax without affecting CaM/RyR2 binding affinity. This correlates with the analysis of fluorescence-lifetime-detected FRET, indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca2+ and lengthens D-FKBP/A-CaM distances independent of [Ca2+]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, with this effect being larger in micromolar versus nanomolar Ca2+. Moreover, A-DPc10/RyR2 binding is cooperative in a CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by the analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.
Collapse
Affiliation(s)
- Bengt Svensson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Florentin R. Nitu
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Robyn T. Rebbeck
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Lindsey M. McGurran
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Tetsuro Oda
- Department of Pharmacology, University of California, Davis, CA 95616, USA
| | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis, CA 95616, USA
| | - Razvan L. Cornea
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; (B.S.); (R.T.R.); (L.M.M.)
| |
Collapse
|
7
|
Svensson B, Nitu FR, Rebbeck RT, McGurran LM, Oda T, Thomas DD, Bers DM, Cornea RL. Molecular Mechanism of a FRET Biosensor for the Cardiac Ryanodine Receptor Pathologically Leaky State. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.07.548138. [PMID: 37461514 PMCID: PMC10350043 DOI: 10.1101/2023.07.07.548138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Ca 2+ leak from cardiomyocyte sarcoplasmic reticulum (SR) via hyperactive resting cardiac ryanodine receptor channels (RyR2) is pro-arrhythmic. An exogenous peptide, (DPc10) detects leaky RyR2 in cardiomyocytes. Conversely, calmodulin (CaM) inhibits RyR2 leak. These observations have led to designing a FRET biosensor for drug discovery targeting RyR2. Here we used FRET to understand the molecular mechanism driving the DPc10-CaM interdependence when binding RyR2 in SR vesicles. We used donor-FKBP12.6 (D-FKBP) to resolve RyR2 binding of acceptor-CaM (A-CaM). In low nanomolar Ca 2+ , DPc10 decreased both FRET max (under saturating [A-CaM]) and the CaM/RyR2 binding affinity. In micromolar Ca 2+ , DPc10 decreased FRET max without affecting CaM/RyR2 binding affinity. This correlates with analysis of fluorescence-lifetime-detected FRET indicating that DPc10 lowers occupancy of the RyR2 CaM-binding sites in nanomolar (not micromolar) Ca 2+ and lengthens D-FKBP/A-CaM distances independent of [Ca 2+ ]. To observe DPc10/RyR2 binding, we used acceptor-DPc10 (A-DPc10). CaM weakens A-DPc10/RyR2 binding, this effect being larger in micromolar vs. nanomolar Ca 2+ . Moreover, A-DPc10/RyR2 binding is cooperative in CaM- and FKBP-dependent manner, suggesting that both endogenous modulators promote concerted structural changes between RyR2 protomers for channel regulation. Aided by analysis of cryo-EM structures, these insights inform further development of the DPc10-CaM paradigm for therapeutic discovery targeting RyR2.
Collapse
Affiliation(s)
- Bengt Svensson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Florentin R. Nitu
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Robyn T. Rebbeck
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Lindsey M. McGurran
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Tetsuro Oda
- Department of Pharmacology, University of California, Davis
| | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis
| | - Razvan L. Cornea
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis
| |
Collapse
|
8
|
Marino V, Cortivo GD, Dell'Orco D. Ionic displacement of Ca 2+ by Pb 2+ in calmodulin is affected by arrhythmia-associated mutations. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119490. [PMID: 37201768 DOI: 10.1016/j.bbamcr.2023.119490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 04/14/2023] [Accepted: 05/10/2023] [Indexed: 05/20/2023]
Abstract
Lead is a highly toxic metal that severely perturbs physiological processes even at sub-micromolar levels, often by disrupting the Ca2+ signaling pathways. Recently, Pb2+-associated cardiac toxicity has emerged, with potential involvement of both the ubiquitous Ca2+ sensor protein calmodulin (CaM) and ryanodine receptors. In this work, we explored the hypothesis that Pb2+ contributes to the pathological phenotype of CaM variants associated with congenital arrhythmias. We performed a thorough spectroscopic and computational characterization of CaM conformational switches in the co-presence of Pb2+ and four missense mutations associated with congenital arrhythmias, namely N53I, N97S, E104A and F141L, and analyzed their effects on the recognition of a target peptide of RyR2. When bound to any of the CaM variants, Pb2+ is difficult to displace even under equimolar Ca2+ concentrations, thus locking all CaM variants in a specific conformation, which exhibits characteristics of coiled-coil assemblies. All arrhythmia-associated variants appear to be more susceptible to Pb2+ than WT CaM, as the conformational transition towards the coiled-coil conformation occurs at lower Pb2+, regardless of the presence of Ca2+, with altered cooperativity. The presence of arrhythmia-associated mutations specifically alters the cation coordination of CaM variants, in some cases involving allosteric communication between the EF-hands in the two domains. Finally, while wild type CaM increases the affinity for the RyR2 target in the presence of Pb2+, no specific pattern could be detected for all other variants, ruling out a synergistic effect of Pb2+ and mutations in the recognition process.
Collapse
Affiliation(s)
- Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy
| | - Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, I-37134 Verona, Italy.
| |
Collapse
|
9
|
Life-threatening arrhythmogenic CaM mutations disrupt CaM binding to a distinct RyR2 CaM-binding pocket. Biochim Biophys Acta Gen Subj 2023; 1867:130313. [PMID: 36693454 DOI: 10.1016/j.bbagen.2023.130313] [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: 09/02/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023]
Abstract
Calmodulin (CaM) modulates the activity of several proteins that play a key role in excitation-contraction coupling (ECC). In cardiac muscle, the major binding partner of CaM is the type-2 ryanodine receptor (RyR2) and altered CaM binding contributes to defects in sarcoplasmic reticulum (SR) calcium (Ca2+) release. Many genetic studies have reported a series of CaM missense mutations in patients with a history of severe arrhythmogenic cardiac disorders. In the present study, we generated four missense CaM mutants (CaMN98I, CaMD132E, CaMD134H and CaMQ136P) and we used a CaM-RyR2 co-immunoprecipitation and a [3H]ryanodine binding assay to directly compare the relative RyR2-binding of wild type and mutant CaM proteins and to investigate the functional effects of these CaM mutations on RyR2 activity. Furthermore, isothermal titration calorimetry (ITC) experiments were performed to investigate and compare the interactions of the wild-type and mutant CaM proteins with various synthetic peptides located in the well-established RyR2 CaM-binding region (3584-3602aa), as well as another CaM-binding region (4255-4271aa) of human RyR2. Our data revealed that all four CaM mutants displayed dramatically reduced RyR2 interaction and defective modulation of [3H]ryanodine binding to RyR2, regardless of LQTS or CPVT association. Moreover, our isothermal titration calorimetry ITC data suggest that RyR2 3584-3602aa and 4255-4271aa regions interact with significant affinity with wild-type CaM, in the presence and absence of Ca2+, two regions that might contribute to a putative intra-subunit CaM-binding pocket. In contrast, screening the interaction of the four arrhythmogenic CaM mutants with two synthetic peptides that correspond to these RyR2 regions, revealed disparate binding properties and signifying differential mechanisms that contribute to reduced RyR2 association.
Collapse
|
10
|
Kang PW, Woodbury L, Angsutararux P, Sambare N, Shi J, Marras M, Abella C, Bedi A, Zinn D, Cui J, Silva JR. Arrhythmia-associated Calmodulin Variants Interact with KCNQ1 to Confer Aberrant Membrane Trafficking and Function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.28.526031. [PMID: 36747728 PMCID: PMC9900995 DOI: 10.1101/2023.01.28.526031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Rationale Missense variants in calmodulin (CaM) predispose patients to arrhythmias associated with high mortality rates. As CaM regulates several key cardiac ion channels, a mechanistic understanding of CaM variant-associated arrhythmias requires elucidating individual CaM variant effect on distinct channels. One key CaM regulatory target is the KCNQ1 (K V 7.1) voltage-gated potassium channel that underlie the I Ks current. Yet, relatively little is known as to how CaM variants interact with KCNQ1 or affect its function. Objective To observe how arrhythmia-associated CaM variants affect binding to KCNQ1, channel membrane trafficking, and KCNQ1 function. Methods and Results We combine a live-cell FRET binding assay, fluorescence trafficking assay, and functional electrophysiology to characterize >10 arrhythmia-associated CaM variants effect on KCNQ1. We identify one variant (G114W) that exhibits severely weakened binding to KCNQ1 but find that most other CaM variants interact with similar binding affinity to KCNQ1 when compared to CaM wild-type over physiological Ca 2+ ranges. We further identify several CaM variants that affect KCNQ1 and I Ks membrane trafficking and/or baseline current activation kinetics, thereby contextualizing KCNQ1 dysfunction in calmodulinopathy. Lastly, we delineate CaM variants with no effect on KCNQ1 function. Conclusions This study provides comprehensive functional data that reveal how CaM variants contribute to creating a pro-arrhythmic substrate by causing abnormal KCNQ1 membrane trafficking and current conduction. We find that CaM variant regulation of KCNQ1 is not uniform with effects varying from benign to significant loss of function. This study provides a new approach to collecting details of CaM binding that are key for understanding how CaM variants predispose patients to arrhythmia via the dysregulation of multiple cardiac ion channels.
Collapse
|
11
|
Dal Cortivo G, Marino V, Bianconi S, Dell'Orco D. Calmodulin variants associated with congenital arrhythmia impair selectivity for ryanodine receptors. Front Mol Biosci 2023; 9:1100992. [PMID: 36685279 PMCID: PMC9849693 DOI: 10.3389/fmolb.2022.1100992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 12/12/2022] [Indexed: 01/06/2023] Open
Abstract
Among its many molecular targets, the ubiquitous calcium sensor protein calmodulin (CaM) recognizes and regulates the activity of ryanodine receptors type 1 (RyR1) and 2 (RyR2), mainly expressed in skeletal and cardiac muscle, respectively. Such regulation is essential to achieve controlled contraction of muscle cells. To unravel the molecular mechanisms underlying the target recognition process, we conducted a comprehensive biophysical investigation of the interaction between two calmodulin variants associated with congenital arrhythmia, namely N97I and Q135P, and a highly conserved calmodulin-binding region in RyR1 and RyR2. The structural, thermodynamic, and kinetic properties of protein-peptide interactions were assessed together with an in-depth structural and topological investigation based on molecular dynamics simulations. This integrated approach allowed us to identify amino acids that are crucial in mediating allosteric processes, which enable high selectivity in molecular target recognition. Our results suggest that the ability of calmodulin to discriminate between RyR1 an RyR2 targets depends on kinetic discrimination and robust allosteric communication between Ca2+-binding sites (EF1-EF3 and EF3-EF4 pairs), which is perturbed in both N97I and Q135P arrhythmia-associated variants.
Collapse
|
12
|
Keefe JA, Moore OM, Ho KS, Wehrens XHT. Role of Ca 2+ in healthy and pathologic cardiac function: from normal excitation-contraction coupling to mutations that cause inherited arrhythmia. Arch Toxicol 2023; 97:73-92. [PMID: 36214829 PMCID: PMC10122835 DOI: 10.1007/s00204-022-03385-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 09/15/2022] [Indexed: 01/19/2023]
Abstract
Calcium (Ca2+) ions are a key second messenger involved in the rhythmic excitation and contraction of cardiomyocytes throughout the heart. Proper function of Ca2+-handling proteins is required for healthy cardiac function, whereas disruption in any of these can cause cardiac arrhythmias. This comprehensive review provides a broad overview of the roles of Ca2+-handling proteins and their regulators in healthy cardiac function and the mechanisms by which mutations in these proteins contribute to inherited arrhythmias. Major Ca2+ channels and Ca2+-sensitive regulatory proteins involved in cardiac excitation-contraction coupling are discussed, with special emphasis on the function of the RyR2 macromolecular complex. Inherited arrhythmia disorders including catecholaminergic polymorphic ventricular tachycardia, long QT syndrome, Brugada syndrome, short QT syndrome, and arrhythmogenic right-ventricular cardiomyopathy are discussed with particular emphasis on subtypes caused by mutations in Ca2+-handling proteins.
Collapse
Affiliation(s)
- Joshua A Keefe
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA.,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Oliver M Moore
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA.,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Kevin S Ho
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA.,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, One Baylor Plaza, BCM335, Houston, TX, 77030, USA. .,Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Medicine, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA. .,Center for Space Medicine, Baylor College of Medicine, Houston, TX, 77030, USA.
| |
Collapse
|
13
|
Calmodulin variant E140G associated with long QT syndrome impairs CaMKIIδ autophosphorylation and L-type calcium channel inactivation. J Biol Chem 2023; 299:102777. [PMID: 36496072 PMCID: PMC9830374 DOI: 10.1016/j.jbc.2022.102777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 11/29/2022] [Accepted: 12/01/2022] [Indexed: 12/13/2022] Open
Abstract
Long QT syndrome (LQTS) is a human inherited heart condition that can cause life-threatening arrhythmia including sudden cardiac death. Mutations in the ubiquitous Ca2+-sensing protein calmodulin (CaM) are associated with LQTS, but the molecular mechanism by which these mutations lead to irregular heartbeats is not fully understood. Here, we use a multidisciplinary approach including protein biophysics, structural biology, confocal imaging, and patch-clamp electrophysiology to determine the effect of the disease-associated CaM mutation E140G on CaM structure and function. We present novel data showing that mutant-regulated CaMKIIδ kinase activity is impaired with a significant reduction in enzyme autophosphorylation rate. We report the first high-resolution crystal structure of a LQTS-associated CaM variant in complex with the CaMKIIδ peptide, which shows significant structural differences, compared to the WT complex. Furthermore, we demonstrate that the E140G mutation significantly disrupted Cav1.2 Ca2+/CaM-dependent inactivation, while cardiac ryanodine receptor (RyR2) activity remained unaffected. In addition, we show that the LQTS-associated mutation alters CaM's Ca2+-binding characteristics, secondary structure content, and interaction with key partners involved in excitation-contraction coupling (CaMKIIδ, Cav1.2, RyR2). In conclusion, LQTS-associated CaM mutation E140G severely impacts the structure-function relationship of CaM and its regulation of CaMKIIδ and Cav1.2. This provides a crucial insight into the molecular factors contributing to CaM-mediated arrhythmias with a central role for CaMKIIδ.
Collapse
|
14
|
McCoy MD, Ullah A, Lederer WJ, Jafri MS. Understanding Calmodulin Variants Affecting Calcium-Dependent Inactivation of L-Type Calcium Channels through Whole-Cell Simulation of the Cardiac Ventricular Myocyte. Biomolecules 2022; 13:72. [PMID: 36671457 PMCID: PMC9855640 DOI: 10.3390/biom13010072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/21/2022] [Accepted: 12/23/2022] [Indexed: 12/31/2022] Open
Abstract
Mutations in the calcium-sensing protein calmodulin (CaM) have been linked to two cardiac arrhythmia diseases, Long QT Syndrome 14 (LQT14) and Catecholaminergic Polymorphic Ventricular Tachycardia Type 4 (CPVT4), with varying degrees of severity. Functional characterization of the CaM mutants most strongly associated with LQT14 show a clear disruption of the calcium-dependent inactivation (CDI) of the L-Type calcium channel (LCC). CPVT4 mutants on the other hand are associated with changes in their affinity to the ryanodine receptor. In clinical studies, some variants have been associated with both CPVT4 and LQT15. This study uses simulations in a model for excitation-contraction coupling in the rat ventricular myocytes to understand how LQT14 variant might give the functional phenotype similar to CPVT4. Changing the CaM-dependent transition rate by a factor of 0.75 corresponding to the D96V variant and by a factor of 0.90 corresponding to the F142L or N98S variants, in a physiologically based stochastic model of the LCC prolonger, the action potential duration changed by a small amount in a cardiac myocyte but did not disrupt CICR at 1, 2, and 4 Hz. Under beta-adrenergic simulation abnormal excitation-contraction coupling was observed above 2 Hz pacing for the mutant CaM. The same conditions applied under beta-adrenergic stimulation led to the rapid onset of arrhythmia in the mutant CaM simulations. Simulations with the LQT14 mutations under the conditions of rapid pacing with beta-adrenergic stimulation drives the cardiac myocyte toward an arrhythmic state known as Ca2+ overload. These simulations provide a mechanistic link to a disease state for LQT14-associated mutations in CaM to yield a CPVT4 phenotype. The results show that small changes to the CaM-regulated inactivation of LCC promote arrhythmia and underscore the significance of CDI in proper heart function.
Collapse
Affiliation(s)
- Matthew D. McCoy
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA
- Innovation Center for Biomedical Informatics, Department of Oncology, Georgetown University Medical Center, Georgetown University, Washington, DC 20057, USA
| | - Aman Ullah
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA
| | - W. Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 20201, USA
| | - M. Saleet Jafri
- School of Systems Biology, George Mason University, Fairfax, VA 22030, USA
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 20201, USA
| |
Collapse
|
15
|
Dal Cortivo G, Barracchia CG, Marino V, D'Onofrio M, Dell'Orco D. Alterations in calmodulin-cardiac ryanodine receptor molecular recognition in congenital arrhythmias. Cell Mol Life Sci 2022; 79:127. [PMID: 35133504 PMCID: PMC8825638 DOI: 10.1007/s00018-022-04165-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 12/27/2021] [Accepted: 01/23/2022] [Indexed: 12/03/2022]
Abstract
Calmodulin (CaM), a ubiquitous and highly conserved Ca2+-sensor protein involved in the regulation of over 300 molecular targets, has been recently associated with severe forms of lethal arrhythmia. Here, we investigated how arrhythmia-associated mutations in CaM localized at the C-terminal lobe alter the molecular recognition with Ryanodine receptor 2 (RyR2), specifically expressed in cardiomyocytes. We performed an extensive structural, thermodynamic, and kinetic characterization of the variants D95V/H in the EF3 Ca2+-binding motif and of the D129V and D131H/E variants in the EF4 motif, and probed their interaction with RyR2. Our results show that the specific structural changes observed for individual CaM variants do not extend to the complex with the RyR2 target. Indeed, some common alterations emerge at the protein–protein interaction level, suggesting the existence of general features shared by the arrhythmia-associated variants. All mutants showed a faster rate of dissociation from the target peptide than wild-type CaM. Integration of spectroscopic data with exhaustive molecular dynamics simulations suggests that, in the presence of Ca2+, functional recognition involves allosteric interactions initiated by the N-terminal lobe of CaM, which shows a lower affinity for Ca2+ compared to the C-terminal lobe in the isolated protein.
Collapse
Affiliation(s)
- Giuditta Dal Cortivo
- Department of Neurosciences Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada le Grazie 8, 37134, Verona, Italy
| | | | - Valerio Marino
- Department of Neurosciences Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada le Grazie 8, 37134, Verona, Italy
| | - Mariapina D'Onofrio
- Department of Biotechnology, University of Verona, Strada le Grazie 15, 37134, Verona, Italy.
| | - Daniele Dell'Orco
- Department of Neurosciences Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada le Grazie 8, 37134, Verona, Italy.
| |
Collapse
|
16
|
Prakash O, Held M, McCormick LF, Gupta N, Lian LY, Antonyuk S, Haynes LP, Thomas NL, Helassa N. CPVT-associated calmodulin variants N53I and A102V dysregulate Ca2+ signalling via different mechanisms. J Cell Sci 2022; 135:274029. [PMID: 34888671 PMCID: PMC8917356 DOI: 10.1242/jcs.258796] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 11/29/2021] [Indexed: 12/26/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited condition that can cause fatal cardiac arrhythmia. Human mutations in the Ca2+ sensor calmodulin (CaM) have been associated with CPVT susceptibility, suggesting that CaM dysfunction is a key driver of the disease. However, the detailed molecular mechanism remains unclear. Focusing on the interaction with the cardiac ryanodine receptor (RyR2), we determined the effect of CPVT-associated variants N53I and A102V on the structural characteristics of CaM and on Ca2+ fluxes in live cells. We provide novel data showing that interaction of both Ca2+/CaM-N53I and Ca2+/CaM-A102V with the RyR2 binding domain is decreased. Ca2+/CaM-RyR23583-3603 high-resolution crystal structures highlight subtle conformational changes for the N53I variant, with A102V being similar to wild type (WT). We show that co-expression of CaM-N53I or CaM-A102V with RyR2 in HEK293 cells significantly increased the duration of Ca2+ events; CaM-A102V exhibited a lower frequency of Ca2+ oscillations. In addition, we show that CaMKIIδ (also known as CAMK2D) phosphorylation activity is increased for A102V, compared to CaM-WT. This paper provides novel insight into the molecular mechanisms of CPVT-associated CaM variants and will facilitate the development of strategies for future therapies.
Collapse
Affiliation(s)
- Ohm Prakash
- Liverpool Centre for Cardiovascular Science, Department of Cardiovascular Science and Metabolic Medicine, Institute of Life Course and Medical Sciences, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 3BX, UK
| | - Marie Held
- Liverpool Centre for Cardiovascular Science, Department of Cardiovascular Science and Metabolic Medicine, Institute of Life Course and Medical Sciences, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 3BX, UK
| | - Liam F. McCormick
- Liverpool Centre for Cardiovascular Science, Department of Cardiovascular Science and Metabolic Medicine, Institute of Life Course and Medical Sciences, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 3BX, UK
| | - Nitika Gupta
- Department of Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 3BX, UK
| | - Lu-Yun Lian
- Nuclear Magnetic Resonance Centre for Structural Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZB, UK
| | - Svetlana Antonyuk
- Molecular Biophysics Group, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZB, UK
| | - Lee P. Haynes
- Department of Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 3BX, UK
| | - N. Lowri Thomas
- School of Pharmacy & Pharmaceutical Sciences, Cardiff University, Cardiff, Redwood Building, CF10 3NB, UK
| | - Nordine Helassa
- Liverpool Centre for Cardiovascular Science, Department of Cardiovascular Science and Metabolic Medicine, Institute of Life Course and Medical Sciences, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 3BX, UK,Author for correspondence ()
| |
Collapse
|
17
|
Mahling R, Hovey L, Isbell HM, Marx DC, Miller MS, Kilpatrick AM, Weaver LD, Yoder JB, Kim EH, Andresen CNJ, Li S, Shea MA. Na V1.2 EFL domain allosterically enhances Ca 2+ binding to sites I and II of WT and pathogenic calmodulin mutants bound to the channel CTD. Structure 2021; 29:1339-1356.e7. [PMID: 33770503 PMCID: PMC8458505 DOI: 10.1016/j.str.2021.03.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 12/23/2020] [Accepted: 03/03/2021] [Indexed: 11/23/2022]
Abstract
Neuronal voltage-gated sodium channel NaV1.2 C-terminal domain (CTD) binds calmodulin (CaM) constitutively at its IQ motif. A solution structure (6BUT) and other NMR evidence showed that the CaM N domain (CaMN) is structurally independent of the C-domain (CaMC) whether CaM is bound to the NaV1.2IQp (1,901-1,927) or NaV1.2CTD (1,777-1,937) with or without calcium. However, in the CaM + NaV1.2CTD complex, the Ca2+ affinity of CaMN was more favorable than in free CaM, while Ca2+ affinity for CaMC was weaker than in the CaM + NaV1.2IQp complex. The CTD EF-like (EFL) domain allosterically widened the energetic gap between CaM domains. Cardiomyopathy-associated CaM mutants (N53I(N54I), D95V(D96V), A102V(A103V), E104A(E105A), D129G(D130G), and F141L(F142L)) all bound the NaV1.2 IQ motif favorably under resting (apo) conditions and bound calcium normally at CaMN sites. However, only N53I and A102V bound calcium at CaMC sites at [Ca2+] < 100 μM. Thus, they are expected to respond like wild-type CaM to Ca2+ spikes in excitable cells.
Collapse
Affiliation(s)
- Ryan Mahling
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Liam Hovey
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Holly M Isbell
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Dagan C Marx
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Mark S Miller
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Adina M Kilpatrick
- Department of Physics and Astronomy, Drake University, Des Moines, IA 50311-4516, USA
| | - Lisa D Weaver
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Jesse B Yoder
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Elaine H Kim
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Corinne N J Andresen
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Shuxiang Li
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Madeline A Shea
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, USA.
| |
Collapse
|
18
|
Woll KA, Van Petegem F. Calcium Release Channels: Structure and Function of IP3 Receptors and Ryanodine Receptors. Physiol Rev 2021; 102:209-268. [PMID: 34280054 DOI: 10.1152/physrev.00033.2020] [Citation(s) in RCA: 87] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ca2+-release channels are giant membrane proteins that control the release of Ca2+ from the endoplasmic and sarcoplasmic reticulum. The two members, ryanodine receptors (RyRs) and inositol-1,4,5-trisphosphate Receptors (IP3Rs), are evolutionarily related and are both activated by cytosolic Ca2+. They share a common architecture, but RyRs have evolved additional modules in the cytosolic region. Their massive size allows for the regulation by tens of proteins and small molecules, which can affect the opening and closing of the channels. In addition to Ca2+, other major triggers include IP3 for the IP3Rs, and depolarization of the plasma membrane for a particular RyR subtype. Their size has made them popular targets for study via electron microscopic methods, with current structures culminating near 3Å. The available structures have provided many new mechanistic insights int the binding of auxiliary proteins and small molecules, how these can regulate channel opening, and the mechanisms of disease-associated mutations. They also help scrutinize previously proposed binding sites, as some of these are now incompatible with the structures. Many questions remain around the structural effects of post-translational modifications, additional binding partners, and the higher-order complexes these channels can make in situ. This review summarizes our current knowledge about the structures of Ca2+-release channels and how this informs on their function.
Collapse
Affiliation(s)
- Kellie A Woll
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
19
|
Yu Q, Anderson DE, Kaur R, Fisher AJ, Ames JB. The Crystal Structure of Calmodulin Bound to the Cardiac Ryanodine Receptor (RyR2) at Residues Phe4246-Val4271 Reveals a Fifth Calcium Binding Site. Biochemistry 2021; 60:1088-1096. [PMID: 33754699 PMCID: PMC8211408 DOI: 10.1021/acs.biochem.1c00152] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Calmodulin (CaM) regulates the activity of a Ca2+ channel known as the cardiac ryanodine receptor (RyR2), which facilitates the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling in cardiomyocytes. Mutations that disrupt this CaM-dependent channel inactivation result in cardiac arrhythmias. RyR2 contains three different CaM binding sites: CaMBD1 (residues 1940-1965), CaMBD2 (residues 3580-3611), and CaMBD3 (residues 4246-4275). Here, we report a crystal structure of Ca2+-bound CaM bound to RyR2 CaMBD3. The structure reveals Ca2+ bound to the four EF-hands of CaM as well as a fifth Ca2+ bound to CaM in the interdomain linker region involving Asp81 and Glu85. The CaM mutant E85A abolishes the binding of the fifth Ca2+ and weakens the binding of CaMBD3 to Ca2+-bound CaM. Thus, the binding of the fifth Ca2+ is important for stabilizing the complex in solution and is not a crystalline artifact. The CaMBD3 peptide in the complex adopts an α-helix (between Phe4246 and Val4271) that interacts with both lobes of CaM. Hydrophobic residues in the CaMBD3 helix (Leu4255 and Leu4259) form intermolecular contacts with the CaM N-lobe, and the CaMBD3 mutations (L4255A and L4259A) each weaken the binding of CaM to RyR2. Aromatic residues on the opposite side of the CaMBD3 helix (Phe4246 and Tyr4250) interact with the CaM C-lobe, but the mutants (F4246A and Y4250A) have no detectable effect on CaM binding in solution. We suggest that the binding of CaM to CaMBD3 and the binding of a fifth Ca2+ to CaM may contribute to the regulation of RyR2 channel function.
Collapse
Affiliation(s)
- Qinhong Yu
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - David E Anderson
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Ramanjeet Kaur
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Andrew J Fisher
- Department of Chemistry, University of California, Davis, California 95616, United States
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616, United States
| | - James B Ames
- Department of Chemistry, University of California, Davis, California 95616, United States
| |
Collapse
|
20
|
Dashwood A, Cheesman E, Beard N, Haqqani H, Wong YW, Molenaar P. Understanding How Phosphorylation and Redox Modifications Regulate Cardiac Ryanodine Receptor Type 2 Activity to Produce an Arrhythmogenic Phenotype in Advanced Heart Failure. ACS Pharmacol Transl Sci 2020; 3:563-582. [PMID: 32832863 DOI: 10.1021/acsptsci.0c00003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Indexed: 12/17/2022]
Abstract
Heart failure (HF) is a global pandemic with significant mortality and morbidity. Despite current medications, 50% of individuals die within 5 years of diagnosis. Of these deaths, 30-50% will be a result of sudden cardiac death from ventricular arrhythmias. This review discusses two stress-induced mechanisms, phosphorylation from chronic β-adrenoceptor (β-AR) stimulation and thiol modifications from oxidative stress, and how they modulate the cardiac ryanodine receptor type 2 (RyR2) and foster an arrhythmogenic phenotype. Calcium (Ca2+) is the ubiquitous secondary messenger of excitation-contraction coupling and provides a common pathway for contractile dysfunction and arrhythmia genesis. In a healthy heart, Ca2+ is released from the sarcoplasmic reticulum (SR) by RyR2. The open probability of RyR2 is under the dynamic influence of co-proteins, ions, and kinases that are in strict balance to ensure normal physiological functioning. In HF, chronic β-AR activity and production of reactive oxygen species and reactive nitrogen species provide two stress-induced mechanisms uncoupling RyR2 control, resulting in pathological diastolic SR Ca2+ leak. This increased cytosolic [Ca2+] promotes Ca2+ extrusion via the local Na+/Ca2+ exchanger, resulting in net sarcolemmal depolarization, delayed after depolarization and ventricular arrhythmia. Experimental models researching oxidative stress and phosphorylation have aimed to identify how post-translational modifications to the RyR2 macromolecular complex, and the associated Na+/Ca2+ cycling proteins, result in pathological Ca2+ handling and diastolic leak. However, the causative molecular changes remain controversial and undefined. Through understanding the molecular mechanisms that produce an arrhythmic phenotype, novel therapeutic targets to treat HF and prevent its malignant course can be identified.
Collapse
Affiliation(s)
- Alexander Dashwood
- Heart Lung Institute, The Prince Charles Hospital, Chermside, Brisbane, Queensland 4032, Australia.,Cardio-Vascular Molecular & Therapeutics Translational Research Group, Northside Clinical School of Medicine, Faculty of Medicine, University of Queensland, Brisbane, Queensland 4032, Australia.,Griffith University, Southport, Queensland 4215, Australia
| | - Elizabeth Cheesman
- Cardio-Vascular Molecular & Therapeutics Translational Research Group, Northside Clinical School of Medicine, Faculty of Medicine, University of Queensland, Brisbane, Queensland 4032, Australia
| | - Nicole Beard
- Queensland University of Technology (QUT), School of Biomedical Sciences, Institute of Health and Biomedical Innovation, 60 Musk Avenue, Kelvin Grove, Queensland 4059, Australia.,Faculty of Science and Technology, University of Canberra, Bruce, Australian Capital Territory 2617, Australia
| | - Haris Haqqani
- Heart Lung Institute, The Prince Charles Hospital, Chermside, Brisbane, Queensland 4032, Australia.,Cardio-Vascular Molecular & Therapeutics Translational Research Group, Northside Clinical School of Medicine, Faculty of Medicine, University of Queensland, Brisbane, Queensland 4032, Australia
| | - Yee Weng Wong
- Heart Lung Institute, The Prince Charles Hospital, Chermside, Brisbane, Queensland 4032, Australia.,Cardio-Vascular Molecular & Therapeutics Translational Research Group, Northside Clinical School of Medicine, Faculty of Medicine, University of Queensland, Brisbane, Queensland 4032, Australia
| | - Peter Molenaar
- Cardio-Vascular Molecular & Therapeutics Translational Research Group, Northside Clinical School of Medicine, Faculty of Medicine, University of Queensland, Brisbane, Queensland 4032, Australia.,Queensland University of Technology (QUT), School of Biomedical Sciences, Institute of Health and Biomedical Innovation, 60 Musk Avenue, Kelvin Grove, Queensland 4059, Australia
| |
Collapse
|
21
|
Holt C, Hamborg L, Lau K, Brohus M, Sørensen AB, Larsen KT, Sommer C, Van Petegem F, Overgaard MT, Wimmer R. The arrhythmogenic N53I variant subtly changes the structure and dynamics in the calmodulin N-terminal domain, altering its interaction with the cardiac ryanodine receptor. J Biol Chem 2020; 295:7620-7634. [PMID: 32317284 DOI: 10.1074/jbc.ra120.013430] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/18/2020] [Indexed: 12/11/2022] Open
Abstract
Mutations in the genes encoding the highly conserved Ca2+-sensing protein calmodulin (CaM) cause severe cardiac arrhythmias, including catecholaminergic polymorphic ventricular tachycardia or long QT syndrome and sudden cardiac death. Most of the identified arrhythmogenic mutations reside in the C-terminal domain of CaM and mostly affect Ca2+-coordinating residues. One exception is the catecholaminergic polymorphic ventricular tachycardia-causing N53I substitution, which resides in the N-terminal domain (N-domain). It does not affect Ca2+ coordination and has only a minor impact on binding affinity toward Ca2+ and on other biophysical properties. Nevertheless, the N53I substitution dramatically affects CaM's ability to reduce the open probability of the cardiac ryanodine receptor (RyR2) while having no effect on the regulation of the plasmalemmal voltage-gated Ca2+ channel, Cav1.2. To gain more insight into the molecular disease mechanism of this mutant, we used NMR to investigate the structures and dynamics of both apo- and Ca2+-bound CaM-N53I in solution. We also solved the crystal structures of WT and N53I CaM in complex with the primary calmodulin-binding domain (CaMBD2) from RyR2 at 1.84-2.13 Å resolutions. We found that all structures of the arrhythmogenic CaM-N53I variant are highly similar to those of WT CaM. However, we noted that the N53I substitution exposes an additional hydrophobic surface and that the intramolecular dynamics of the protein are significantly altered such that they destabilize the CaM N-domain. We conclude that the N53I-induced changes alter the interaction of the CaM N-domain with RyR2 and thereby likely cause the arrhythmogenic phenotype of this mutation.
Collapse
Affiliation(s)
- Christian Holt
- Aalborg University, Department of Chemistry and Bioscience, 9220 Aalborg, Denmark
| | - Louise Hamborg
- Aalborg University, Department of Chemistry and Bioscience, 9220 Aalborg, Denmark
| | - Kelvin Lau
- University of British Columbia, Department of Biochemistry and Molecular Biology, V6T 1Z3 Vancouver, British Columbia, Canada
| | - Malene Brohus
- Aalborg University, Department of Chemistry and Bioscience, 9220 Aalborg, Denmark
| | | | | | - Cordula Sommer
- Aalborg University, Department of Chemistry and Bioscience, 9220 Aalborg, Denmark
| | - Filip Van Petegem
- University of British Columbia, Department of Biochemistry and Molecular Biology, V6T 1Z3 Vancouver, British Columbia, Canada
| | | | - Reinhard Wimmer
- Aalborg University, Department of Chemistry and Bioscience, 9220 Aalborg, Denmark
| |
Collapse
|
22
|
Dürvanger Z, Harmat V. Structural Diversity in Calmodulin - Peptide Interactions. Curr Protein Pept Sci 2020; 20:1102-1111. [PMID: 31553290 DOI: 10.2174/1389203720666190925101937] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 03/13/2019] [Accepted: 04/12/2019] [Indexed: 01/17/2023]
Abstract
Calmodulin (CaM) is a highly conserved eukaryotic Ca2+ sensor protein that is able to bind a large variety of target sequences without a defined consensus sequence. The recognition of this diverse target set allows CaM to take part in the regulation of several vital cell functions. To fully understand the structural basis of the regulation functions of CaM, the investigation of complexes of CaM and its targets is essential. In this minireview we give an outline of the different types of CaM - peptide complexes with 3D structure determined, also providing an overview of recently determined structures. We discuss factors defining the orientations of peptides within the complexes, as well as roles of anchoring residues. The emphasis is on complexes where multiple binding modes were found.
Collapse
Affiliation(s)
- Zsolt Dürvanger
- Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
| | - Veronika Harmat
- Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary.,MTA-ELTE Protein Modelling Research Group, Budapest, Hungary
| |
Collapse
|
23
|
Kistamás K, Veress R, Horváth B, Bányász T, Nánási PP, Eisner DA. Calcium Handling Defects and Cardiac Arrhythmia Syndromes. Front Pharmacol 2020; 11:72. [PMID: 32161540 PMCID: PMC7052815 DOI: 10.3389/fphar.2020.00072] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 01/24/2020] [Indexed: 12/13/2022] Open
Abstract
Calcium ions (Ca2+) play a major role in the cardiac excitation-contraction coupling. Intracellular Ca2+ concentration increases during systole and falls in diastole thereby determining cardiac contraction and relaxation. Normal cardiac function also requires perfect organization of the ion currents at the cellular level to drive action potentials and to maintain action potential propagation and electrical homogeneity at the tissue level. Any imbalance in Ca2+ homeostasis of a cardiac myocyte can lead to electrical disturbances. This review aims to discuss cardiac physiology and pathophysiology from the elementary membrane processes that can cause the electrical instability of the ventricular myocytes through intracellular Ca2+ handling maladies to inherited and acquired arrhythmias. Finally, the paper will discuss the current therapeutic approaches targeting cardiac arrhythmias.
Collapse
Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, Manchester, United Kingdom
| | - Roland Veress
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - David A Eisner
- Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, Manchester, United Kingdom
| |
Collapse
|
24
|
Calmodulin Mutations Associated with Heart Arrhythmia: A Status Report. Int J Mol Sci 2020; 21:ijms21041418. [PMID: 32093079 PMCID: PMC7073091 DOI: 10.3390/ijms21041418] [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: 02/03/2020] [Revised: 02/11/2020] [Accepted: 02/12/2020] [Indexed: 02/06/2023] Open
Abstract
Calmodulin (CaM) is a ubiquitous intracellular Ca2+ sensing protein that modifies gating of numerous ion channels. CaM has an extraordinarily high level of evolutionary conservation, which led to the fundamental assumption that mutation would be lethal. However, in 2012, complete exome sequencing of infants suffering from recurrent cardiac arrest revealed de novo mutations in the three human CALM genes. The correlation between mutations and pathophysiology suggests defects in CaM-dependent ion channel functions. Here, we review the current state of the field for all reported CaM mutations associated with cardiac arrhythmias, including knowledge of their biochemical and structural characteristics, and progress towards understanding how these mutations affect cardiac ion channel function.
Collapse
|
25
|
Federico M, Valverde CA, Mattiazzi A, Palomeque J. Unbalance Between Sarcoplasmic Reticulum Ca 2 + Uptake and Release: A First Step Toward Ca 2 + Triggered Arrhythmias and Cardiac Damage. Front Physiol 2020; 10:1630. [PMID: 32038301 PMCID: PMC6989610 DOI: 10.3389/fphys.2019.01630] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 12/24/2019] [Indexed: 12/19/2022] Open
Abstract
The present review focusses on the regulation and interplay of cardiac SR Ca2+ handling proteins involved in SR Ca2+ uptake and release, i.e., SERCa2/PLN and RyR2. Both RyR2 and SERCA2a/PLN are highly regulated by post-translational modifications and/or different partners' proteins. These control mechanisms guarantee a precise equilibrium between SR Ca2+ reuptake and release. The review then discusses how disruption of this balance alters SR Ca2+ handling and may constitute a first step toward cardiac damage and malignant arrhythmias. In the last part of the review, this concept is exemplified in different cardiac diseases, like prediabetic and diabetic cardiomyopathy, digitalis intoxication and ischemia-reperfusion injury.
Collapse
Affiliation(s)
- Marilén Federico
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", CCT-La Plata/CONICET, Facultad de Cs. Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", CCT-La Plata/CONICET, Facultad de Cs. Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", CCT-La Plata/CONICET, Facultad de Cs. Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", CCT-La Plata/CONICET, Facultad de Cs. Médicas, Universidad Nacional de La Plata, La Plata, Argentina.,Centro de Altos Estudios en Ciencias Humanas y de la Salud, Universidad Abierta Interamericana, Buenos Aires, Argentina
| |
Collapse
|
26
|
Søndergaard MT, Liu Y, Guo W, Wei J, Wang R, Brohus M, Overgaard MT, Chen SRW. Role of cardiac ryanodine receptor calmodulin-binding domains in mediating the action of arrhythmogenic calmodulin N-domain mutation N54I. FEBS J 2019; 287:2256-2280. [PMID: 31763755 DOI: 10.1111/febs.15147] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 09/12/2019] [Accepted: 11/19/2019] [Indexed: 11/27/2022]
Abstract
The Ca2+ -sensing protein calmodulin (CaM) inhibits cardiac ryanodine receptor (RyR2)-mediated Ca2+ release. CaM mutations associated with arrhythmias and sudden cardiac death have been shown to diminish CaM-dependent inhibition of RyR2, but the underlying mechanisms are not well understood. Nearly all arrhythmogenic CaM mutations identified are located in the C-domain of CaM and exert marked effects on Ca2+ binding to CaM and on the CaM C-domain interaction with the CaM-binding domain 2 (CaMBD2) in RyR2. Interestingly, the arrhythmogenic N-domain mutation CaM-N54I has little or no effect on Ca2+ binding to CaM or the CaM C-domain-RyR2 CaMBD2 interaction, unlike all CaM C-domain mutations. This suggests that CaM-N54I may diminish CaM-dependent RyR2 inhibition by affecting CaM N-domain interactions with RyR2 CaMBDs other than CaMBD2. To explore this possibility, we assessed the effects of deleting each of the four known CaMBDs in RyR2 (CaMBD1a, -1b, -2, or -3) on the CaM-dependent inhibition of RyR2-mediated Ca2+ release in HEK293 cells. We found that removing CaMBD1a, CaMBD1b, or CaMBD3 did not alter the effects of CaM-N54I or CaM-WT on RyR2 inhibition. On the other hand, deleting RyR2-CaMBD2 abolished the effects of both CaM-N54I and CaM-WT. Our results support that CaM-N54I causes aberrant RyR2 regulation via an uncharacterized CaMBD or less likely CaMBD2, and that RyR2 CaMBD2 is required for the actions of both N- and C-domain CaM mutations. Moreover, our results show that CaMBD1a is central to RyR2 regulation, but CaMBD1a, CaMBD1b, and CaMBD3 are not required for CaM-dependent inhibition of RyR2 in HEK293 cells.
Collapse
Affiliation(s)
- Mads T Søndergaard
- Department of Chemistry and Bioscience, Aalborg University, Denmark.,Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
| | - Yingjie Liu
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
| | - Wenting Guo
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
| | - Jinhong Wei
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
| | - Ruiwu Wang
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
| | - Malene Brohus
- Department of Chemistry and Bioscience, Aalborg University, Denmark
| | | | - S R Wayne Chen
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, AB, Canada
| |
Collapse
|
27
|
Søndergaard MT, Liu Y, Brohus M, Guo W, Nani A, Carvajal C, Fill M, Overgaard MT, Chen SRW. Diminished inhibition and facilitated activation of RyR2-mediated Ca 2+ release is a common defect of arrhythmogenic calmodulin mutations. FEBS J 2019; 286:4554-4578. [PMID: 31230402 DOI: 10.1111/febs.14969] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 04/23/2019] [Accepted: 06/20/2019] [Indexed: 02/06/2023]
Abstract
A number of calmodulin (CaM) mutations cause severe cardiac arrhythmias, but their arrhythmogenic mechanisms are unclear. While some of the arrhythmogenic CaM mutations have been shown to impair CaM-dependent inhibition of intracellular Ca2+ release through the ryanodine receptor type 2 (RyR2), the impact of a majority of these mutations on RyR2 function is unknown. Here, we investigated the effect of 14 arrhythmogenic CaM mutations on the CaM-dependent RyR2 inhibition. We found that all the arrhythmogenic CaM mutations tested diminished CaM-dependent inhibition of RyR2-mediated Ca2+ release and increased store-overload induced Ca2+ release (SOICR) in HEK293 cells. Moreover, all the arrhythmogenic CaM mutations tested either failed to inhibit or even promoted RyR2-mediated Ca2+ release in permeabilized HEK293 cells with elevated cytosolic Ca2+ , which was markedly different from the inhibitory action of CaM wild-type. The CaM mutations also altered the Ca2+ -dependency of CaM binding to the RyR2 CaM-binding domain. These results demonstrate that diminished inhibition, and even facilitated activation, of RyR2-mediated Ca2+ release is a common defect of arrhythmogenic CaM mutations.
Collapse
Affiliation(s)
- Mads T Søndergaard
- Department of Chemistry and Bioscience, Aalborg University, Denmark.,Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada
| | - Yingjie Liu
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada
| | - Malene Brohus
- Department of Chemistry and Bioscience, Aalborg University, Denmark
| | - Wenting Guo
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada
| | - Alma Nani
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, USA
| | - Catherine Carvajal
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, USA
| | - Michael Fill
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, USA
| | | | - S R Wayne Chen
- Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, Department of Biochemistry and Molecular Biology, University of Calgary, Alberta, Canada.,Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, USA
| |
Collapse
|
28
|
Gomez-Hurtado N, Blackwell DJ, Knollmann BC. Modelling human calmodulinopathies with induced pluripotent stem cells: progress and challenges. Cardiovasc Res 2019; 113:437-439. [PMID: 28384370 DOI: 10.1093/cvr/cvx041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
|
29
|
Da'as SI, Thanassoulas A, Calver BL, Beck K, Salem R, Saleh A, Kontogianni I, Al-Maraghi A, Nasrallah GK, Safieh-Garabedian B, Toft E, Nounesis G, Lai FA, Nomikos M. Arrhythmogenic calmodulin E105A mutation alters cardiac RyR2 regulation leading to cardiac dysfunction in zebrafish. Ann N Y Acad Sci 2019; 1448:19-29. [PMID: 30937913 DOI: 10.1111/nyas.14033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 01/28/2019] [Accepted: 01/29/2019] [Indexed: 01/03/2023]
Abstract
Calmodulin (CaM) is a universal calcium (Ca2+ )-binding messenger that regulates many vital cellular events. In cardiac muscle, CaM associates with ryanodine receptor 2 (RyR2) and regulates excitation-contraction coupling. Mutations in human genes CALM1, CALM2, and CALM3 have been associated with life-threatening heart disorders, such as long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia. A novel de novo LQTS-associated missense CaM mutation (E105A) was recently identified in a 6-year-old boy, who experienced an aborted first episode of cardiac arrest. Herein, we report the first molecular characterization of the CaM E105A mutation. Expression of the CaM E105A mutant in zebrafish embryos resulted in cardiac arrhythmia and increased heart rate, suggestive of ventricular tachycardia. In vitro biophysical and biochemical analysis revealed that E105A confers a deleterious effect on protein stability and a reduced Ca2+ -binding affinity due to loss of cooperativity. Finally, the CaM E105A mutation resulted in reduced CaM-RyR2 interaction and defective modulation of ryanodine binding. Our findings suggest that the CaM E105A mutation dysregulates normal cardiac function by a complex mechanism involving alterations in both CaM-Ca2+ and CaM-RyR2 interactions.
Collapse
Affiliation(s)
- Sahar I Da'as
- Translational Medicine, Sidra Medicine, Doha, Qatar.,College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
| | | | - Brian L Calver
- College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
| | - Konrad Beck
- College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK
| | - Rola Salem
- College of Medicine, Member of QU Health, Qatar University, Doha, Qatar
| | - Alaaeldin Saleh
- College of Medicine, Member of QU Health, Qatar University, Doha, Qatar
| | - Iris Kontogianni
- National Center for Scientific Research "Demokritos,", Aghia Paraskevi, Greece
| | - Ali Al-Maraghi
- College of Medicine, Member of QU Health, Qatar University, Doha, Qatar
| | - Gheyath K Nasrallah
- Biomedical Research Center, Qatar University, Doha, Qatar.,Department of Biomedical Sciences, College of Health Science, Qatar University, Doha, Qatar
| | | | - Egon Toft
- College of Medicine, Member of QU Health, Qatar University, Doha, Qatar
| | - George Nounesis
- National Center for Scientific Research "Demokritos,", Aghia Paraskevi, Greece
| | - F Anthony Lai
- College of Biomedical and Life Sciences, Cardiff University, Cardiff, UK.,College of Medicine, Member of QU Health, Qatar University, Doha, Qatar.,Biomedical Research Center, Qatar University, Doha, Qatar
| | - Michail Nomikos
- College of Medicine, Member of QU Health, Qatar University, Doha, Qatar
| |
Collapse
|
30
|
Ca 2+-dependent calmodulin binding to cardiac ryanodine receptor (RyR2) calmodulin-binding domains. Biochem J 2019; 476:193-209. [PMID: 30530841 PMCID: PMC6340113 DOI: 10.1042/bcj20180545] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 12/05/2018] [Accepted: 12/10/2018] [Indexed: 12/17/2022]
Abstract
The Ca2+ sensor calmodulin (CaM) regulates cardiac ryanodine receptor (RyR2)-mediated Ca2+ release from the sarcoplasmic reticulum. CaM inhibits RyR2 in a Ca2+-dependent manner and aberrant CaM-dependent inhibition results in life-threatening cardiac arrhythmias. However, the molecular details of the CaM–RyR2 interaction remain unclear. Four CaM-binding domains (CaMBD1a, -1b, -2, and -3) in RyR2 have been proposed. Here, we investigated the Ca2+-dependent interactions between CaM and these CaMBDs by monitoring changes in the fluorescence anisotropy of carboxytetramethylrhodamine (TAMRA)-labeled CaMBD peptides during titration with CaM at a wide range of Ca2+ concentrations. We showed that CaM bound to all four CaMBDs with affinities that increased with Ca2+ concentration. CaM bound to CaMBD2 and -3 with high affinities across all Ca2+ concentrations tested, but bound to CaMBD1a and -1b only at Ca2+ concentrations above 0.2 µM. Binding experiments using individual CaM domains revealed that the CaM C-domain preferentially bound to CaMBD2, and the N-domain to CaMBD3. Moreover, the Ca2+ affinity of the CaM C-domain in complex with CaMBD2 or -3 was so high that these complexes are essentially Ca2+ saturated under resting Ca2+ conditions. Conversely, the N-domain senses Ca2+ exactly in the transition from resting to activating Ca2+ when complexed to either CaMBD2 or -3. Altogether, our results support a binding model where the CaM C-domain is anchored to RyR2 CaMBD2 and saturated with Ca2+ during Ca2+ oscillations, while the CaM N-domain functions as a dynamic Ca2+ sensor that can bridge noncontiguous regions of RyR2 or clamp down onto CaMBD2.
Collapse
|
31
|
Pancaroglu R, Van Petegem F. Calcium Channelopathies: Structural Insights into Disorders of the Muscle Excitation–Contraction Complex. Annu Rev Genet 2018; 52:373-396. [DOI: 10.1146/annurev-genet-120417-031311] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ion channels are membrane proteins responsible for the passage of ions down their electrochemical gradients and across biological membranes. In this, they generate and shape action potentials and provide secondary messengers for various signaling pathways. They are often part of larger complexes containing auxiliary subunits and regulatory proteins. Channelopathies arise from mutations in the genes encoding ion channels or their associated proteins. Recent advances in cryo-electron microscopy have resulted in an explosion of ion channel structures in multiple states, generating a wealth of new information on channelopathies. Disease-associated mutations fall into different categories, interfering with ion permeation, protein folding, voltage sensing, ligand and protein binding, and allosteric modulation of channel gating. Prime examples of these are Ca2+-selective channels expressed in myocytes, for which multiple structures in distinct conformational states have recently been uncovered. We discuss the latest insights into these calcium channelopathies from a structural viewpoint.
Collapse
Affiliation(s)
- Raika Pancaroglu
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| |
Collapse
|
32
|
Jensen HH, Brohus M, Nyegaard M, Overgaard MT. Human Calmodulin Mutations. Front Mol Neurosci 2018; 11:396. [PMID: 30483049 PMCID: PMC6243062 DOI: 10.3389/fnmol.2018.00396] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 10/11/2018] [Indexed: 01/18/2023] Open
Abstract
Fluxes of calcium (Ca2+) across cell membranes enable fast cellular responses. Calmodulin (CaM) senses local changes in Ca2+ concentration and relays the information to numerous interaction partners. The critical role of accurate Ca2+ signaling on cellular function is underscored by the fact that there are three independent CaM genes (CALM1-3) in the human genome. All three genes are functional and encode the exact same CaM protein. Moreover, CaM has a completely conserved amino acid sequence across all vertebrates. Given this degree of conservation, it was long thought that mutations in CaM were incompatible with life. It was therefore a big surprise when the first CaM mutations in humans were identified six years ago. Today, more than a dozen human CaM missense mutations have been described, all found in patients with severe cardiac arrhythmias. Biochemical studies have demonstrated differential effects on Ca2+ binding affinities for these CaM variants. Moreover, CaM regulation of central cardiac ion channels is impaired, including the voltage-gated Ca2+ channel, CaV1.2, and the sarcoplasmic reticulum Ca2+ release channel, ryanodine receptor isoform 2, RyR2. Currently, no non-cardiac phenotypes have been described for CaM variant carriers. However, sequencing of large human cohorts reveals a cumulative frequency of additional rare CaM mutations that raise the possibility of CaM variants not exclusively causing severe cardiac arrhythmias. Here, we provide an overview of the identified CaM variants and their known consequences for target regulation and cardiac disease phenotype. We discuss experimental data, patient genotypes and phenotypes as well as which questions remain open to understand this complexity.
Collapse
Affiliation(s)
- Helene H Jensen
- Section for Biotechnology, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Malene Brohus
- Section for Biotechnology, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Mette Nyegaard
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Michael T Overgaard
- Section for Biotechnology, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| |
Collapse
|
33
|
Arrhythmia mutations in calmodulin cause conformational changes that affect interactions with the cardiac voltage-gated calcium channel. Proc Natl Acad Sci U S A 2018; 115:E10556-E10565. [PMID: 30348784 DOI: 10.1073/pnas.1808733115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Calmodulin (CaM) represents one of the most conserved proteins among eukaryotes and is known to bind and modulate more than a 100 targets. Recently, several disease-associated mutations have been identified in the CALM genes that are causative of severe cardiac arrhythmia syndromes. Although several mutations have been shown to affect the function of various cardiac ion channels, direct structural insights into any CaM disease mutation have been lacking. Here we report a crystallographic and NMR investigation of several disease mutant CaMs, linked to long-QT syndrome, in complex with the IQ domain of the cardiac voltage-gated calcium channel (CaV1.2). Surprisingly, two mutants (D95V, N97I) cause a major distortion of the C-terminal lobe, resulting in a pathological conformation not reported before. These structural changes result in altered interactions with the CaV1.2 IQ domain. Another mutation (N97S) reduces the affinity for Ca2+ by introducing strain in EF hand 3. A fourth mutant (F141L) shows structural changes in the Ca2+-free state that increase the affinity for the IQ domain. These results thus show that different mechanisms underlie the ability of CaM disease mutations to affect Ca2+-dependent inactivation of the voltage-gated calcium channel.
Collapse
|
34
|
Meissner G. The structural basis of ryanodine receptor ion channel function. J Gen Physiol 2017; 149:1065-1089. [PMID: 29122978 PMCID: PMC5715910 DOI: 10.1085/jgp.201711878] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/12/2017] [Indexed: 01/25/2023] Open
Abstract
Large-conductance Ca2+ release channels known as ryanodine receptors (RyRs) mediate the release of Ca2+ from an intracellular membrane compartment, the endo/sarcoplasmic reticulum. There are three mammalian RyR isoforms: RyR1 is present in skeletal muscle; RyR2 is in heart muscle; and RyR3 is expressed at low levels in many tissues including brain, smooth muscle, and slow-twitch skeletal muscle. RyRs form large protein complexes comprising four 560-kD RyR subunits, four ∼12-kD FK506-binding proteins, and various accessory proteins including calmodulin, protein kinases, and protein phosphatases. RyRs share ∼70% sequence identity, with the greatest sequence similarity in the C-terminal region that forms the transmembrane, ion-conducting domain comprising ∼500 amino acids. The remaining ∼4,500 amino acids form the large regulatory cytoplasmic "foot" structure. Experimental evidence for Ca2+, ATP, phosphorylation, and redox-sensitive sites in the cytoplasmic structure have been described. Exogenous effectors include the two Ca2+ releasing agents caffeine and ryanodine. Recent work describing the near atomic structures of mammalian skeletal and cardiac muscle RyRs provides a structural basis for the regulation of the RyRs by their multiple effectors.
Collapse
Affiliation(s)
- Gerhard Meissner
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC
| |
Collapse
|
35
|
Abstract
There has been a significant progress in our understanding of the molecular mechanisms by which calcium (Ca2+) ions mediate various types of cardiac arrhythmias. A growing list of inherited gene defects can cause potentially lethal cardiac arrhythmia syndromes, including catecholaminergic polymorphic ventricular tachycardia, congenital long QT syndrome, and hypertrophic cardiomyopathy. In addition, acquired deficits of multiple Ca2+-handling proteins can contribute to the pathogenesis of arrhythmias in patients with various types of heart disease. In this review article, we will first review the key role of Ca2+ in normal cardiac function-in particular, excitation-contraction coupling and normal electric rhythms. The functional involvement of Ca2+ in distinct arrhythmia mechanisms will be discussed, followed by various inherited arrhythmia syndromes caused by mutations in Ca2+-handling proteins. Finally, we will discuss how changes in the expression of regulation of Ca2+ channels and transporters can cause acquired arrhythmias, and how these mechanisms might be targeted for therapeutic purposes.
Collapse
Affiliation(s)
- Andrew P Landstrom
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.)
| | - Dobromir Dobrev
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.)
| | - Xander H T Wehrens
- From the Section of Cardiology, Department of Pediatrics (A.P.L.), Cardiovascular Research Institute (A.P.L., X.H.T.W.), and Departments of Molecular Physiology and Biophysics, Medicine (Cardiology), Center for Space Medicine (X.H.T.W.), Baylor College of Medicine, Houston, TX; and Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Essen, Germany (D.D.).
| |
Collapse
|
36
|
Xu L, Gomez AC, Pasek DA, Meissner G, Yamaguchi N. Two EF-hand motifs in ryanodine receptor calcium release channels contribute to isoform-specific regulation by calmodulin. Cell Calcium 2017; 66:62-70. [PMID: 28807150 DOI: 10.1016/j.ceca.2017.05.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 05/08/2017] [Accepted: 05/24/2017] [Indexed: 01/03/2023]
Abstract
The mammalian ryanodine receptor Ca2+ release channel (RyR) has a single conserved high affinity calmodulin (CaM) binding domain. However, the skeletal muscle RyR1 is activated and cardiac muscle RyR2 is inhibited by CaM at submicromolar Ca2+. This suggests isoform-specific domains are involved in RyR regulation by CaM. To gain insight into the differential regulation of cardiac and skeletal muscle RyRs by CaM, RyR1/RyR2 chimeras and mutants were expressed in HEK293 cells, and their single channel activities were measured using a lipid bilayer method. All RyR1/RyR2 chimeras and mutants were inhibited by CaM at 2μM Ca2+, consistent with CaM inhibition of RyR1 and RyR2 at micromolar Ca2+ concentrations. An RyR1/RyR2 chimera with RyR1 N-terminal amino acid residues (aa) 1-3725 and RyR2 C-terminal aa 3692-4968 were inhibited by CaM at <1μM Ca2+ similar to RyR2. In contrast, RyR1/RyR2 chimera with RyR1 aa 1-4301 and RyR2 4254-4968 was activated at <1μM Ca2+ similar to RyR1. Replacement of RyR1 aa 3726-4298 with corresponding residues from RyR2 conferred CaM inhibition at <1μM Ca2+, which suggests RyR1 aa 3726-4298 are required for activation by CaM. Characterization of additional RyR1/RyR2 chimeras and mutants in two predicted Ca2+ binding motifs in RyR1 aa 4081-4092 (EF1) and aa 4116-4127 (EF2) suggests that both EF-hand motifs and additional sequences in the large N-terminal regions are required for isoform-specific RyR1 and RyR2 regulation by CaM at submicromolar Ca2+ concentrations.
Collapse
Affiliation(s)
- Le Xu
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, United States
| | - Angela C Gomez
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, United States; Cardiac Signaling Center, University of South Carolina, Medical University of South Carolina and Clemson University, Charleston, SC 29425, United States
| | - Daniel A Pasek
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, United States
| | - Gerhard Meissner
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599-7260, United States
| | - Naohiro Yamaguchi
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, United States; Cardiac Signaling Center, University of South Carolina, Medical University of South Carolina and Clemson University, Charleston, SC 29425, United States.
| |
Collapse
|