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Distinctive malfunctions of calmodulin mutations associated with heart RyR2-mediated arrhythmic disease. Biochim Biophys Acta Gen Subj 2015; 1850:2168-76. [PMID: 26164367 DOI: 10.1016/j.bbagen.2015.07.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 06/22/2015] [Accepted: 07/02/2015] [Indexed: 01/11/2023]
Abstract
Calmodulin (CaM) is a cytoplasmic calcium sensor that interacts with the cardiac ryanodine receptor (RyR2), a large Ca(2+) channel complex that mediates Ca(2+) efflux from the sarcoplasmic reticulum (SR) to activate cardiac muscle contraction. Direct CaM association with RyR2 is an important physiological regulator of cardiac muscle excitation-contraction coupling and defective CaM-RyR2 protein interaction has been reported in cases of heart failure. Recent genetic studies have identified CaM missense mutations in patients with a history of severe cardiac arrhythmogenic disorders that present divergent clinical features, including catecholaminergic polymorphic ventricular tachycardia (CPVT), long QT syndrome (LQTS) and idiopathic ventricular fibrillation (IVF). Herein, we describe how two CPVT- (N54I & N98S) and three LQTS-associated (D96V, D130G & F142L) CaM mutations result in alteration of their biochemical and biophysical properties. Ca(2+)-binding studies indicate that the CPVT-associated CaM mutations, N54I & N98S, exhibit the same or a 3-fold reduced Ca(2+)-binding affinity, respectively, versus wild-type CaM, whereas the LQTS-associated CaM mutants, D96V, D130G & F142L, display more profoundly reduced Ca(2+)-binding affinity. In contrast, all five CaM mutations confer a disparate RyR2 interaction and modulation of [(3)H]ryanodine binding to RyR2, regardless of CPVT or LQTS association. Our findings suggest that the clinical presentation of CPVT or LQTS associated with these five CaM mutations may involve both altered intrinsic Ca(2+)-binding as well as defective interaction with RyR2.
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Potet F, Beckermann TM, Kunic JD, George AL. Intracellular calcium attenuates late current conducted by mutant human cardiac sodium channels. Circ Arrhythm Electrophysiol 2015; 8:933-41. [PMID: 26022185 DOI: 10.1161/circep.115.002760] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 05/07/2015] [Indexed: 12/30/2022]
Abstract
BACKGROUND Mutations of the cardiac voltage-gated sodium channel (SCN5A gene encoding voltage-gated sodium channel [NaV1.5]) cause congenital long-QT syndrome type 3 (LQT3). Most NaV1.5 mutations associated with LQT3 promote a mode of sodium channel gating in which some channels fail to inactivate, contributing to increased late sodium current (INaL), which is directly responsible for delayed repolarization and prolongation of the QT interval. LQT3 patients have highest risk of arrhythmia during sleep or during periods of slow heart rate. During exercise (high heart rate), there is elevated steady-state intracellular free calcium (Ca(2+)) concentration. We hypothesized that higher levels of intracellular Ca(2+) may lower arrhythmia risk in LQT3 subjects through effects on INaL. METHODS AND RESULTS We tested this idea by examining the effects of varying intracellular Ca(2+) concentrations on the level of INaL in cells expressing a typical LQT3 mutation, delKPQ, and another SCN5A mutation, R225P. We found that elevated intracellular Ca(2+) concentration significantly reduced INaL conducted by mutant channels but not wild-type channels. This attenuation of INaL in delKPQ expressing cells by Ca(2+) was not affected by the CaM kinase II inhibitor KN-93 but was partially attenuated by truncating the C-terminus of the channel. CONCLUSIONS We conclude that intracellular Ca(2+) contributes to the regulation of INaL conducted by NaV1.5 mutants and propose that, during excitation-contraction coupling, elevated intracellular Ca(2+) suppresses mutant channel INaL and protects cells from delayed repolarization. These findings offer a plausible explanation for the lower arrhythmia risk in LQT3 subjects during fast heart rates.
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Affiliation(s)
- Franck Potet
- From the Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (F.P., A.L.G.); and Department of Medicine (F.P., J.D.K., A.L.G.) and Department of Pharmacology (T.M.B., A.L.G.), Vanderbilt University, Nashville, TN.
| | - Thomas M Beckermann
- From the Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (F.P., A.L.G.); and Department of Medicine (F.P., J.D.K., A.L.G.) and Department of Pharmacology (T.M.B., A.L.G.), Vanderbilt University, Nashville, TN
| | - Jennifer D Kunic
- From the Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (F.P., A.L.G.); and Department of Medicine (F.P., J.D.K., A.L.G.) and Department of Pharmacology (T.M.B., A.L.G.), Vanderbilt University, Nashville, TN
| | - Alfred L George
- From the Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL (F.P., A.L.G.); and Department of Medicine (F.P., J.D.K., A.L.G.) and Department of Pharmacology (T.M.B., A.L.G.), Vanderbilt University, Nashville, TN
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53
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León Ariza HH, Valenzuela Faccini N, Rojas Ortega AC, Botero Rosas DA. Nav1.5 cardiac sodium channels, regulation and clinical implications. REVISTA DE LA FACULTAD DE MEDICINA 2015. [DOI: 10.15446/revfacmed.v62n4.44015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
<p>Voltage-gated sodium channels constitute a group of membrane<br />proteins widely distributed thought the body. In the heart, there<br />are at least six different isoforms, being the Nav1.5 the most<br />abundant. The channel is composed of an α subunit that is formed<br />by four domains of six segments each, and four much smaller β<br />subunits that provide stability and integrate other channels into<br />the α subunit. The function of the Nav1.5 channel is modulated<br />by intracellular cytoskeleton proteins, extracellular proteins,<br />calcium concentration, free radicals, and medications, among<br />other things. The study of the channel and its alterations has<br />grown thanks to its association with pathogenic conditions such<br />as Long QT syndrome, Brugada syndrome, atrial fibrillation,<br />arrhythmogenic ventricular dysplasia and complications during<br />ischemic processes.</p>
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54
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Fu C, Zhang J, Zheng Y, Xu H, Yu S. Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation. Int J Biol Macromol 2015; 79:235-9. [PMID: 25956027 DOI: 10.1016/j.ijbiomac.2015.04.069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 04/28/2015] [Accepted: 04/29/2015] [Indexed: 12/24/2022]
Abstract
Calcineurin (CN) is a Ca(2+)/calmodulin (CaM) activated serine/threonine phosphatase, and its regulatory region (CNRR) plays a critical role in the coupling of Ca(2+) signals to cellular responses. Ca(2+)/CaM binds to the CNRR, resulting in a conformational change that removes an autoinhibitory domain (CN467-486) from the active site of the phosphatase and activates the enzyme. However, almost the entire regulatory region (CN374-521) is not visible in the electron density maps of reported structures. In this study, we produced separate CN fragments corresponding to the CNRR (CNRR381-521, CN residues 381-521) and determined the binding affinity of CNRR381-521 for Ca(2+)/CaM using isothermal titration calorimetry (ITC). The structural change in CNRR381-521 induced by Ca(2+)/CaM binding was also investigated by Fourier transform infrared spectroscopy (FT-IR). The results indicate that Ca(2+)/CaM binding to CNRR381-521 is an exothermic reaction with a dissociation constant of 2.0×10(-6) M. Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation.
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Affiliation(s)
- Cuiping Fu
- Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Junting Zhang
- Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Ye Zheng
- Shanghai Pinghe Bilingual School, China
| | - Hongbing Xu
- Department of Clinical Pharmacy, Shanghai First People's Hospital, Shanghai Jiaotong University, Shanghai 200080, China.
| | - Shaoning Yu
- Department of Chemistry, Fudan University, Shanghai 200433, China.
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55
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Abstract
Sodium current in the heart flows principally through the pore protein NaV1.5, which is part of a complex of interacting proteins that serve both to target and localize the complex in the membrane, and to modulate function by such post-translational modifications as phosphorylation and nitrosylation. Multiple mutations in seven different NaV1.5 interacting proteins have been associated with dysfunctional sodium current and inherited cardiac diseases, including long QT syndrome, Brugada syndrome, atrial fibrillation, and cardiomyopathy, as well as sudden infant death syndrome (SIDS). Mutations in as yet unidentified interacting proteins may account for cardiac disease for which a genetic basis has not yet been established. Characterizing the mechanisms by which these mutations cause disease may give insight into etiologies and treatments of more common acquired cardiac disease, such as ischemia and heart failure.
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Affiliation(s)
- John W Kyle
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin, Madison, Wisconsin, USA 53792
| | - Jonathan C Makielski
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin, Madison, Wisconsin, USA 53792
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56
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Ben-Johny M, Yue DT. Calmodulin regulation (calmodulation) of voltage-gated calcium channels. ACTA ACUST UNITED AC 2014; 143:679-92. [PMID: 24863929 PMCID: PMC4035741 DOI: 10.1085/jgp.201311153] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Calmodulin regulation (calmodulation) of the family of voltage-gated CaV1-2 channels comprises a prominent prototype for ion channel regulation, remarkable for its powerful Ca(2+) sensing capabilities, deep in elegant mechanistic lessons, and rich in biological and therapeutic implications. This field thereby resides squarely at the epicenter of Ca(2+) signaling biology, ion channel biophysics, and therapeutic advance. This review summarizes the historical development of ideas in this field, the scope and richly patterned organization of Ca(2+) feedback behaviors encompassed by this system, and the long-standing challenges and recent developments in discerning a molecular basis for calmodulation. We conclude by highlighting the considerable synergy between mechanism, biological insight, and promising therapeutics.
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Affiliation(s)
- Manu Ben-Johny
- Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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57
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Gabelli SB, Boto A, HalperinKuhns V, Bianchet MA, Farinelli F, Aripirala S, Yoder J, Jakoncic J, Tomaselli GF, Amzel LM. Regulation of the NaV1.5 cytoplasmic domain by calmodulin. Nat Commun 2014; 5:5126. [PMID: 25370050 PMCID: PMC4223872 DOI: 10.1038/ncomms6126] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 09/02/2014] [Indexed: 12/23/2022] Open
Abstract
Voltage-gated sodium channels (Na(v)) underlie the rapid upstroke of action potentials in excitable tissues. Binding of channel-interactive proteins is essential for controlling fast and long-term inactivation. In the structure of the complex of the carboxy-terminal portion of Na(v)1.5 (CTNa(v)1.5) with calmodulin (CaM)-Mg(2+) reported here, both CaM lobes interact with the CTNa(v)1.5. On the basis of the differences between this structure and that of an inactivated complex, we propose that the structure reported here represents a non-inactivated state of the CTNa(v), that is, the state that is poised for activation. Electrophysiological characterization of mutants further supports the importance of the interactions identified in the structure. Isothermal titration calorimetry experiments show that CaM binds to CTNa(v)1.5 with high affinity. The results of this study provide unique insights into the physiological activation and the pathophysiology of Na(v) channels.
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Affiliation(s)
- Sandra B. Gabelli
- Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross Bldg. 844, Baltimore, MD 21205, USA
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Agedi Boto
- Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA
| | - Victoria HalperinKuhns
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross Bldg. 844, Baltimore, MD 21205, USA
| | - Mario A. Bianchet
- Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, 600 N Wolfe St, Baltimore, MD 21287, USA
| | - Federica Farinelli
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross Bldg. 844, Baltimore, MD 21205, USA
| | - Srinivas Aripirala
- Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA
| | - Jesse Yoder
- Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA
| | - Jean Jakoncic
- Brookhaven National Laboratory, National Synchrotron Light Source, Upton, NY 11973
| | - Gordon F. Tomaselli
- Division of Cardiology, Department of Medicine, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross Bldg. 844, Baltimore, MD 21205, USA
| | - L. Mario Amzel
- Structural Enzymology and Thermodynamics Group. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N Wolfe St, WBSB 608, Baltimore, Maryland 21205, USA
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58
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Horvath B, Bers DM. The late sodium current in heart failure: pathophysiology and clinical relevance. ESC Heart Fail 2014; 1:26-40. [PMID: 28834665 DOI: 10.1002/ehf2.12003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 07/13/2014] [Accepted: 07/14/2014] [Indexed: 12/19/2022] Open
Abstract
Large and growing body of data suggest that an increased late sodium current (INa,late ) can have a significant pathophysiological role in heart failure and other heart diseases. The first goal of this article is to describe how INa,late functions under physiological circumstances. The second goal is to show the wide range of cellular mechanisms that can increase INa,late in cardiac disease, and also to describe how the up-regulated INa,late contributes to the pathophysiology of heart failure. The final section of the article discusses the possible use of INa,late -modifying drugs in heart failure, on the basis of experimental and preclinical data.
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Affiliation(s)
- Balazs Horvath
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
- Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Donald M Bers
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
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59
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Park S, Li C, Haeseleer F, Palczewski K, Ames JB. Structural insights into activation of the retinal L-type Ca²⁺ channel (Cav1.4) by Ca²⁺-binding protein 4 (CaBP4). J Biol Chem 2014; 289:31262-73. [PMID: 25258313 DOI: 10.1074/jbc.m114.604439] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
CaBP4 modulates Ca(2+)-dependent activity of L-type voltage-gated Ca(2+) channels (Cav1.4) in retinal photoreceptor cells. Mg(2+) binds to the first and third EF-hands (EF1 and EF3), and Ca(2+) binds to EF1, EF3, and EF4 of CaBP4. Here we present NMR structures of CaBP4 in both Mg(2+)-bound and Ca(2+)-bound states and model the CaBP4 structural interaction with Cav1.4. CaBP4 contains an unstructured N-terminal region (residues 1-99) and four EF-hands in two separate lobes. The N-lobe consists of EF1 and EF2 in a closed conformation with either Mg(2+) or Ca(2+) bound at EF1. The C-lobe binds Ca(2+) at EF3 and EF4 and exhibits a Ca(2+)-induced closed-to-open transition like that of calmodulin. Exposed residues in Ca(2+)-bound CaBP4 (Phe(137), Glu(168), Leu(207), Phe(214), Met(251), Phe(264), and Leu(268)) make contacts with the IQ motif in Cav1.4, and the Cav1.4 mutant Y1595E strongly impairs binding to CaBP4. We conclude that CaBP4 forms a collapsed structure around the IQ motif in Cav1.4 that we suggest may promote channel activation by disrupting an interaction between IQ and the inhibitor of Ca(2+)-dependent inactivation domain.
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Affiliation(s)
- Saebomi Park
- From the Department of Chemistry, University of California, Davis, California 95616
| | - Congmin Li
- From the Department of Chemistry, University of California, Davis, California 95616
| | - Françoise Haeseleer
- the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, and
| | - Krzysztof Palczewski
- the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965
| | - James B Ames
- From the Department of Chemistry, University of California, Davis, California 95616,
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60
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Structural analyses of Ca²⁺/CaM interaction with NaV channel C-termini reveal mechanisms of calcium-dependent regulation. Nat Commun 2014; 5:4896. [PMID: 25232683 PMCID: PMC4170523 DOI: 10.1038/ncomms5896] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 08/01/2014] [Indexed: 12/15/2022] Open
Abstract
Ca2+ regulates voltage-gated Na+ (NaV) channels and perturbed Ca2+ regulation of NaV function is associated with epilepsy syndromes, autism, and cardiac arrhythmias. Understanding the disease mechanisms, however, has been hindered by a lack of structural information and competing models for how Ca2+ affects NaV channel function. Here, we report the crystal structures of two ternary complexes of a human NaV cytosolic C-terminal domain (CTD), a fibroblast growth factor homologous factor, and Ca2+/calmodulin (Ca2+/CaM). These structures rule out direct binding of Ca2+ to the NaV CTD, and uncover new contacts between CaM and the NaV CTD. Probing these new contacts with biochemical and functional experiments allows us to propose a mechanism by which Ca2+ could regulate NaV channels. Further, our model provides hints towards understanding the molecular basis of the neurologic disorders and cardiac arrhythmias caused by NaV channel mutations.
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61
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Payandeh J, Minor DL. Bacterial voltage-gated sodium channels (BacNa(V)s) from the soil, sea, and salt lakes enlighten molecular mechanisms of electrical signaling and pharmacology in the brain and heart. J Mol Biol 2014; 427:3-30. [PMID: 25158094 DOI: 10.1016/j.jmb.2014.08.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 08/11/2014] [Accepted: 08/18/2014] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels (Na(V)s) provide the initial electrical signal that drives action potential generation in many excitable cells of the brain, heart, and nervous system. For more than 60years, functional studies of Na(V)s have occupied a central place in physiological and biophysical investigation of the molecular basis of excitability. Recently, structural studies of members of a large family of bacterial voltage-gated sodium channels (BacNa(V)s) prevalent in soil, marine, and salt lake environments that bear many of the core features of eukaryotic Na(V)s have reframed ideas for voltage-gated channel function, ion selectivity, and pharmacology. Here, we analyze the recent advances, unanswered questions, and potential of BacNa(V)s as templates for drug development efforts.
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Affiliation(s)
- Jian Payandeh
- Department of Structural Biology, Genentech, Inc., South San Francisco, CA 94080, USA.
| | - Daniel L Minor
- Cardiovascular Research Institute, Departments of Biochemistry and Biophysics and Cellular and Molecular Pharmacology, California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA 93858-2330, USA; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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62
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Functional interaction with filamin A and intracellular Ca2+ enhance the surface membrane expression of a small-conductance Ca2+-activated K+ (SK2) channel. Proc Natl Acad Sci U S A 2014; 111:9989-94. [PMID: 24951510 DOI: 10.1073/pnas.1323541111] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
For an excitable cell to function properly, a precise number of ion channel proteins need to be trafficked to distinct locations on the cell surface membrane, through a network and anchoring activity of cytoskeletal proteins. Not surprisingly, mutations in anchoring proteins have profound effects on membrane excitability. Ca(2+)-activated K(+) channels (KCa2 or SK) have been shown to play critical roles in shaping the cardiac atrial action potential profile. Here, we demonstrate that filamin A, a cytoskeletal protein, augments the trafficking of SK2 channels in cardiac myocytes. The trafficking of SK2 channel is Ca(2+)-dependent. Further, the Ca(2+) dependence relies on another channel-interacting protein, α-actinin2, revealing a tight, yet intriguing, assembly of cytoskeletal proteins that orchestrate membrane expression of SK2 channels in cardiac myocytes. We assert that changes in SK channel trafficking would significantly alter atrial action potential and consequently atrial excitability. Identification of therapeutic targets to manipulate the subcellular localization of SK channels is likely to be clinically efficacious. The findings here may transcend the area of SK2 channel studies and may have implications not only in cardiac myocytes but in other types of excitable cells.
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63
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Jones EM, Balakrishnan G, Squier TC, Spiro TG. Distinguishing unfolding and functional conformational transitions of calmodulin using ultraviolet resonance Raman spectroscopy. Protein Sci 2014; 23:1094-101. [PMID: 24895328 DOI: 10.1002/pro.2495] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 05/27/2014] [Accepted: 05/28/2014] [Indexed: 01/09/2023]
Abstract
Calmodulin (CaM) is a ubiquitous moderator protein for calcium signaling in all eukaryotic cells. This small calcium-binding protein exhibits a broad range of structural transitions, including domain opening and folding-unfolding, that allow it to recognize a wide variety of binding partners in vivo. While the static structures of CaM associated with its various binding activities are fairly well-known, it has been challenging to examine the dynamics of transition between these structures in real-time, due to a lack of suitable spectroscopic probes of CaM structure. In this article, we examine the potential of ultraviolet resonance Raman (UVRR) spectroscopy for clarifying the nature of structural transitions in CaM. We find that the UVRR spectral change (with 229 nm excitation) due to thermal unfolding of CaM is qualitatively different from that associated with opening of the C-terminal domain in response to Ca(2+) binding. This spectral difference is entirely due to differences in tertiary contacts at the interdomain tyrosine residue Tyr138, toward which other spectroscopic methods are not sensitive. We conclude that UVRR is ideally suited to identifying the different types of structural transitions in CaM and other proteins with conformation-sensitive tyrosine residues, opening a path to time-resolved studies of CaM dynamics using Raman spectroscopy.
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Affiliation(s)
- Eric M Jones
- Department of Chemistry, University of Washington, Seattle, Washington, 98195-1700
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64
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Mechanism of μ-conotoxin PIIIA binding to the voltage-gated Na+ channel NaV1.4. PLoS One 2014; 9:e93267. [PMID: 24676211 PMCID: PMC3968119 DOI: 10.1371/journal.pone.0093267] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/03/2014] [Indexed: 12/19/2022] Open
Abstract
Several subtypes of voltage-gated Na+ (NaV) channels are important targets for pain management. μ-Conotoxins isolated from venoms of cone snails are potent and specific blockers of different NaV channel isoforms. The inhibitory effect of μ-conotoxins on NaV channels has been examined extensively, but the mechanism of toxin specificity has not been understood in detail. Here the known structure of μ-conotoxin PIIIA and a model of the skeletal muscle channel NaV1.4 are used to elucidate elements that contribute to the structural basis of μ-conotoxin binding and specificity. The model of NaV1.4 is constructed based on the crystal structure of the bacterial NaV channel, NaVAb. Six different binding modes, in which the side chain of each of the basic residues carried by the toxin protrudes into the selectivity filter of NaV1.4, are examined in atomic detail using molecular dynamics simulations with explicit solvent. The dissociation constants (Kd) computed for two selected binding modes in which Lys9 or Arg14 from the toxin protrudes into the filter of the channel are within 2 fold; both values in close proximity to those determined from dose response data for the block of NaV currents. To explore the mechanism of PIIIA specificity, a double mutant of NaV1.4 mimicking NaV channels resistant to μ-conotoxins and tetrodotoxin is constructed and the binding of PIIIA to this mutant channel examined. The double mutation causes the affinity of PIIIA to reduce by two orders of magnitude.
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65
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Zhao Y, Yang H, Meng K, Yu S. Probing the Ca2+/CaM-induced secondary structural and conformational changes in calcineurin. Int J Biol Macromol 2014; 64:453-7. [DOI: 10.1016/j.ijbiomac.2013.12.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 12/24/2013] [Accepted: 12/27/2013] [Indexed: 10/25/2022]
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66
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Alaimo A, Alberdi A, Gomis-Perez C, Fernández-Orth J, Bernardo-Seisdedos G, Malo C, Millet O, Areso P, Villarroel A. Pivoting between calmodulin lobes triggered by calcium in the Kv7.2/calmodulin complex. PLoS One 2014; 9:e86711. [PMID: 24489773 PMCID: PMC3904923 DOI: 10.1371/journal.pone.0086711] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/12/2013] [Indexed: 11/25/2022] Open
Abstract
Kv7.2 (KCNQ2) is the principal molecular component of the slow voltage gated M-channel, which strongly influences neuronal excitability. Calmodulin (CaM) binds to two intracellular C-terminal segments of Kv7.2 channels, helices A and B, and it is required for exit from the endoplasmic reticulum. However, the molecular mechanisms by which CaM controls channel trafficking are currently unknown. Here we used two complementary approaches to explore the molecular events underlying the association between CaM and Kv7.2 and their regulation by Ca2+. First, we performed a fluorometric assay using dansylated calmodulin (D-CaM) to characterize the interaction of its individual lobes to the Kv7.2 CaM binding site (Q2AB). Second, we explored the association of Q2AB with CaM by NMR spectroscopy, using 15N-labeled CaM as a reporter. The combined data highlight the interdependency of the N- and C-lobes of CaM in the interaction with Q2AB, suggesting that when CaM binds Ca2+ the binding interface pivots between the N-lobe whose interactions are dominated by helix B and the C-lobe where the predominant interaction is with helix A. In addition, Ca2+ makes CaM binding to Q2AB more difficult and, reciprocally, the channel weakens the association of CaM with Ca2+.
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Affiliation(s)
- Alessandro Alaimo
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain
| | - Araitz Alberdi
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain
| | | | | | | | - Covadonga Malo
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain
| | - Oscar Millet
- Structural Biology Unit, CICbioGUNE, Bizkaia Technology Park, Derio, Spain
| | - Pilar Areso
- Departamento de Farmacología, UPV/EHU, Universidad del País Vasco, Leioa, Spain
| | - Alvaro Villarroel
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain
- * E-mail:
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67
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Yang Q, Brüschweiler S, Chou JJ. Purification, crystallization and preliminary X-ray diffraction of the N-terminal calmodulin-like domain of the human mitochondrial ATP-Mg/Pi carrier SCaMC1. Acta Crystallogr F Struct Biol Commun 2014; 70:68-71. [PMID: 24419621 PMCID: PMC3943107 DOI: 10.1107/s2053230x1303241x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 11/27/2013] [Indexed: 12/14/2022] Open
Abstract
SCaMC is an ATP-Mg/Pi carrier protein located at the mitochondrial inner membrane. SCaMC has an unusual N-terminal Ca(2+)-binding domain (NTD) in addition to its characteristic six-helix transmembrane bundle. The NTD of human SCaMC1 (residues 1-193) was expressed and purified in order to study its role in Ca(2+)-regulated ATP-Mg/Pi transport mediated by its transmembrane domain. While Ca(2+)-bound NTD could be crystallized, the apo state resisted extensive crystallization trials. Selenomethionine-labeled Ca(2+)-bound NTD crystals, which belonged to space group P6(2)22 with one molecule per asymmetric unit, diffracted X-rays to 2.9 Å resolution.
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Affiliation(s)
- Qin Yang
- Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Sven Brüschweiler
- Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - James J. Chou
- Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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68
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Yang Q, Brüschweiler S, Chou JJ. A self-sequestered calmodulin-like Ca²⁺ sensor of mitochondrial SCaMC carrier and its implication to Ca²⁺-dependent ATP-Mg/P(i) transport. Structure 2013; 22:209-17. [PMID: 24332718 DOI: 10.1016/j.str.2013.10.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 10/11/2013] [Accepted: 10/29/2013] [Indexed: 10/25/2022]
Abstract
The mitochondrial carriers play essential roles in energy metabolism. The short Ca²⁺-binding mitochondrial carrier (SCaMC) transports ATP-Mg in exchange for Pi and is important for activities that depend on adenine nucleotides. SCaMC adopts, in addition to the transmembrane domain (TMD) that transports solutes, an extramembrane N-terminal domain (NTD) that regulates solute transport in a Ca²⁺-dependent manner. Crystal structure of the Ca²⁺-bound NTD reveals a compact architecture in which the functional EF hands are sequestered by an endogenous helical segment. Nuclear magnetic resonance (NMR) relaxation rates indicated that removal of Ca²⁺ from NTD results in a major conformational switch from the rigid and compact Ca²⁺-bound state to the dynamic and loose apo state. Finally, we showed using surface plasmon resonance and NMR titration experiments that free apo NTDs could specifically interact with liposome-incorporated TMD, but that Ca²⁺ binding drastically weakened the interaction. Our results together provide a molecular explanation for Ca²⁺-dependent ATP-Mg flux in mitochondria.
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Affiliation(s)
- Qin Yang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Sven Brüschweiler
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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69
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Bazzazi H, Ben Johny M, Adams PJ, Soong TW, Yue DT. Continuously tunable Ca(2+) regulation of RNA-edited CaV1.3 channels. Cell Rep 2013; 5:367-77. [PMID: 24120865 DOI: 10.1016/j.celrep.2013.09.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 08/02/2013] [Accepted: 09/05/2013] [Indexed: 11/18/2022] Open
Abstract
CaV1.3 ion channels are dominant Ca(2+) portals into pacemaking neurons, residing at the epicenter of brain rhythmicity and neurodegeneration. Negative Ca(2+) feedback regulation of CaV1.3 channels (CDI) is therefore critical for Ca(2+) homeostasis. Intriguingly, nearly half the CaV1.3 transcripts in the brain are RNA edited to reduce CDI and influence oscillatory activity. It is then mechanistically remarkable that this editing occurs precisely within an IQ domain, whose interaction with Ca(2+)-bound calmodulin (Ca(2+)/CaM) is believed to induce CDI. Here, we sought the mechanism underlying the altered CDI of edited channels. Unexpectedly, editing failed to attenuate Ca(2+)/CaM binding. Instead, editing weakened the prebinding of Ca(2+)-free CaM (apoCaM) to channels, which proves essential for CDI. Thus, editing might render CDI continuously tunable by fluctuations in ambient CaM, a prominent effect we substantiate in substantia nigral neurons. This adjustability of Ca(2+) regulation by CaM now looms as a key element of CNS Ca(2+) homeostasis.
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Affiliation(s)
- Hojjat Bazzazi
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, USA
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70
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Herbst S, Maucher D, Schneider M, Ihling CH, Jahn O, Sinz A. Munc13-like skMLCK variants cannot mimic the unique calmodulin binding mode of Munc13 as evidenced by chemical cross-linking and mass spectrometry. PLoS One 2013; 8:e75119. [PMID: 24130683 PMCID: PMC3794949 DOI: 10.1371/journal.pone.0075119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 08/08/2013] [Indexed: 11/18/2022] Open
Abstract
Among the neuronal binding partners of calmodulin (CaM) are Munc13 proteins as essential presynaptic regulators that play a key role in synaptic vesicle priming and are crucial for presynaptic short-term plasticity. Recent NMR structural investigations of a CaM/Munc13-1 peptide complex have revealed an extended structure, which contrasts the compact structures of most classical CaM/target complexes. This unusual binding mode is thought to be related to the presence of an additional hydrophobic anchor residue at position 26 of the CaM binding motif of Munc13-1, resulting in a novel 1-5-8-26 motif. Here, we addressed the question whether the 1-5-8-26 CaM binding motif is a Munc13-related feature or whether it can be induced in other CaM targets by altering the motif's core residues. For this purpose, we chose skeletal muscle myosin light chain kinase (skMLCK) with a classical 1-5-8-14 CaM binding motif and constructed three skMLCK peptide variants mimicking Munc13-1, in which the hydrophobic anchor amino acid at position 14 was moved to position 26. Chemical cross-linking between CaM and skMLCK peptide variants combined with high-resolution mass spectrometry yielded insights into the peptides' binding modes. This structural comparison together with complementary binding data from surface plasmon resonance experiments revealed that skMLCK variants with an artificial 1-5-8-26 motif cannot mimic CaM binding of Munc13-1. Apparently, additional features apart from the spacing of the hydrophobic anchor residues are required to define the functional 1-5-8-26 motif of Munc13-1. We conclude that Munc13 proteins display a unique CaM binding behavior to fulfill their role as efficient presynaptic calcium sensors over broad range of Ca(2+) concentrations.
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Affiliation(s)
- Sabine Herbst
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Daniel Maucher
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Marian Schneider
- Research Group Artificial Binding Proteins, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Christian H. Ihling
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Olaf Jahn
- Proteomics Group, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
| | - Andrea Sinz
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
- * E-mail:
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71
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Chichili VPR, Xiao Y, Seetharaman J, Cummins TR, Sivaraman J. Structural basis for the modulation of the neuronal voltage-gated sodium channel NaV1.6 by calmodulin. Sci Rep 2013; 3:2435. [PMID: 23942337 PMCID: PMC3743062 DOI: 10.1038/srep02435] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 07/29/2013] [Indexed: 01/07/2023] Open
Abstract
The neuronal-voltage gated sodium channel (VGSC), Na(V)1.6, plays an important role in propagating action potentials along myelinated axons. Calmodulin (CaM) is known to modulate the inactivation kinetics of Na(V)1.6 by interacting with its IQ motif. Here we report the crystal structure of apo-CaM:Na(V)1.6IQ motif, along with functional studies. The IQ motif of Na(V)1.6 adopts an α-helical conformation in its interaction with the C-lobe of CaM. CaM uses different residues to interact with Na(V)1.6IQ motif depending on the presence or absence of Ca²⁺. Three residues from Na(V)1.6, Arg1902, Tyr1904 and Arg1905 were identified as the key common interacting residues in both the presence and absence of Ca²⁺. Substitution of Arg1902 and Tyr1904 with alanine showed a reduced rate of Na(V)1.6 inactivation in electrophysiological experiments in vivo. Compared with other CaM:Na(V) complexes, our results reveal a different mode of interaction for CaM:Na(V)1.6 and provides structural insight into the isoform-specific modulation of VGSCs.
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Affiliation(s)
| | - Yucheng Xiao
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - J. Seetharaman
- X4 Beamline, Brookhaven National Laboratory, Upton, New York, USA
| | - Theodore R. Cummins
- Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - J. Sivaraman
- Department of Biological Sciences, National University of Singapore, Singapore, 117543,
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Adsit GS, Vaidyanathan R, Galler CM, Kyle JW, Makielski JC. Channelopathies from mutations in the cardiac sodium channel protein complex. J Mol Cell Cardiol 2013; 61:34-43. [PMID: 23557754 PMCID: PMC3720718 DOI: 10.1016/j.yjmcc.2013.03.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Revised: 03/15/2013] [Accepted: 03/21/2013] [Indexed: 12/19/2022]
Abstract
The cardiac sodium current underlies excitability in heart, and inherited abnormalities of the proteins regulating and conducting this current cause inherited arrhythmia syndromes. This review focuses on inherited mutations in non-pore forming proteins of sodium channel complexes that cause cardiac arrhythmia, and the deduced mechanisms by which they affect function and dysfunction of the cardiac sodium current. Defining the structure and function of these complexes and how they are regulated will contribute to understanding the possible roles for this complex in normal and abnormal physiology and homeostasis. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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Affiliation(s)
- Graham S. Adsit
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin, Madison, Wisconsin, USA 53792
| | - Ravi Vaidyanathan
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin, Madison, Wisconsin, USA 53792
| | - Carla M. Galler
- School of Business and Applied Arts, Division of Visual Communication, Madison College, Madison, WI, USA 53704
| | - John W. Kyle
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin, Madison, Wisconsin, USA 53792
| | - Jonathan C. Makielski
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin, Madison, Wisconsin, USA 53792
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73
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Van Petegem F, Lobo PA, Ahern CA. Seeing the forest through the trees: towards a unified view on physiological calcium regulation of voltage-gated sodium channels. Biophys J 2013; 103:2243-51. [PMID: 23283222 DOI: 10.1016/j.bpj.2012.10.020] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 09/26/2012] [Accepted: 10/18/2012] [Indexed: 12/23/2022] Open
Abstract
Voltage-gated sodium channels (Na(V)s) underlie the upstroke of the action potential in the excitable tissues of nerve and muscle. After opening, Na(V)s rapidly undergo inactivation, a crucial process through which sodium conductance is negatively regulated. Disruption of inactivation by inherited mutations is an established cause of lethal cardiac arrhythmia, epilepsy, or painful syndromes. Intracellular calcium ions (Ca(2+)) modulate sodium channel inactivation, and multiple players have been suggested in this process, including the cytoplasmic Na(V) C-terminal region including two EF-hands and an IQ motif, the Na(V) domain III-IV linker, and calmodulin. Calmodulin can bind to the IQ domain in both Ca(2+)-bound and Ca(2+)-free conditions, but only to the DIII-IV linker in a Ca(2+)-loaded state. The mechanism of Ca(2+) regulation, and its composite effect(s) on channel gating, has been shrouded in much controversy owing to numerous apparent experimental inconsistencies. Herein, we attempt to summarize these disparate data and propose a novel, to our knowledge, physiological mechanism whereby calcium ions promote sodium current facilitation due to Ca(2+) memory at high-action-potential frequencies where Ca(2+) levels may accumulate. The available data suggest that this phenomenon may be disrupted in diseases where cytoplasmic calcium ion levels are chronically high and where targeted phosphorylation may decouple the Ca(2+) regulatory machinery. Many Na(V) disease mutations associated with electrical dysfunction are located in the Ca(2+)-sensing machinery and misregulation of Ca(2+)-dependent channel modulation is likely to contribute to disease phenotypes.
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Affiliation(s)
- Filip Van Petegem
- The Department of Biochemistry and Molecular Biology, Vancouver, British Columbia, Canada.
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74
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Sorensen AB, Søndergaard MT, Overgaard MT. Calmodulin in a Heartbeat. FEBS J 2013; 280:5511-32. [DOI: 10.1111/febs.12337] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 04/28/2013] [Accepted: 05/07/2013] [Indexed: 01/16/2023]
Affiliation(s)
- Anders B. Sorensen
- Department of Biotechnology, Chemistry and Environmental Engineering; Aalborg University; Denmark
| | - Mads T. Søndergaard
- Department of Biotechnology, Chemistry and Environmental Engineering; Aalborg University; Denmark
| | - Michael T. Overgaard
- Department of Biotechnology, Chemistry and Environmental Engineering; Aalborg University; Denmark
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75
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Herren AW, Bers DM, Grandi E. Post-translational modifications of the cardiac Na channel: contribution of CaMKII-dependent phosphorylation to acquired arrhythmias. Am J Physiol Heart Circ Physiol 2013; 305:H431-45. [PMID: 23771687 DOI: 10.1152/ajpheart.00306.2013] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The voltage-gated Na channel isoform 1.5 (NaV1.5) is the pore forming α-subunit of the voltage-gated cardiac Na channel, which is responsible for the initiation and propagation of cardiac action potentials. Mutations in the SCN5A gene encoding NaV1.5 have been linked to changes in the Na current leading to a variety of arrhythmogenic phenotypes, and alterations in the NaV1.5 expression level, Na current density, and/or gating have been observed in acquired cardiac disorders, including heart failure. The precise mechanisms underlying these abnormalities have not been fully elucidated. However, several recent studies have made it clear that NaV1.5 forms a macromolecular complex with a number of proteins that modulate its expression levels, localization, and gating and is the target of extensive post-translational modifications, which may also influence all these properties. We review here the molecular aspects of cardiac Na channel regulation and their functional consequences. In particular, we focus on the molecular and functional aspects of Na channel phosphorylation by the Ca/calmodulin-dependent protein kinase II, which is hyperactive in heart failure and has been causally linked to cardiac arrhythmia. Understanding the mechanisms of altered NaV1.5 expression and function is crucial for gaining insight into arrhythmogenesis and developing novel therapeutic strategies.
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Affiliation(s)
- Anthony W Herren
- Department of Pharmacology, University of California Davis, Davis, California
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76
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Zhou Y, Xue S, Yang JJ. Calciomics: integrative studies of Ca2+-binding proteins and their interactomes in biological systems. Metallomics 2013; 5:29-42. [PMID: 23235533 DOI: 10.1039/c2mt20009k] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Calcium ion (Ca(2+)), the fifth most common chemical element in the earth's crust, represents the most abundant mineral in the human body. By binding to a myriad of proteins distributed in different cellular organelles, Ca(2+) impacts nearly every aspect of cellular life. In prokaryotes, Ca(2+) plays an important role in bacterial movement, chemotaxis, survival reactions and sporulation. In eukaryotes, Ca(2+) has been chosen through evolution to function as a universal and versatile intracellular signal. Viruses, as obligate intracellular parasites, also develop smart strategies to manipulate the host Ca(2+) signaling machinery to benefit their own life cycles. This review focuses on recent advances in applying both bioinformatic and experimental approaches to predict and validate Ca(2+)-binding proteins and their interactomes in biological systems on a genome-wide scale (termed "calciomics"). Calmodulin is used as an example of Ca(2+)-binding protein (CaBP) to demonstrate the role of CaBPs on the regulation of biological functions. This review is anticipated to rekindle interest in investigating Ca(2+)-binding proteins and Ca(2+)-modulated functions at the systems level in the post-genomic era.
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Affiliation(s)
- Yubin Zhou
- Center for Translational Cancer Research, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, TX 77030, USA
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77
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Tidow H, Nissen P. Structural diversity of calmodulin binding to its target sites. FEBS J 2013; 280:5551-65. [PMID: 23601118 DOI: 10.1111/febs.12296] [Citation(s) in RCA: 203] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/11/2013] [Accepted: 04/16/2013] [Indexed: 11/28/2022]
Abstract
Calmodulin (CaM) is a ubiquitous, highly conserved, eukaryotic protein that binds to and regulates a number of diverse target proteins involved in different functions such as metabolism, muscle contraction, apoptosis, memory, inflammation and the immune response. In this minireview, we analyze the large number of CaM-complex structures deposited in the Protein Data Bank (i.e. crystal and nuclear magnetic resonance structures) to gain insight into the structural diversity of CaM-binding sites and mechanisms, such as those for CaM-activated protein kinases and phosphatases, voltage-gated Ca(2+)-channels and the plasma membrane Ca(2+)-ATPase.
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Affiliation(s)
- Henning Tidow
- Centre for Membrane Pumps in Cells and Disease - PUMPkin, Aarhus University, Denmark; Department of Molecular Biology and Genetics, Aarhus University, Denmark
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78
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Kovalevskaya NV, van de Waterbeemd M, Bokhovchuk FM, Bate N, Bindels RJM, Hoenderop JGJ, Vuister GW. Structural analysis of calmodulin binding to ion channels demonstrates the role of its plasticity in regulation. Pflugers Arch 2013; 465:1507-19. [PMID: 23609407 DOI: 10.1007/s00424-013-1278-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 03/18/2013] [Accepted: 04/02/2013] [Indexed: 12/17/2022]
Abstract
The Ca²⁺-binding protein calmodulin (CaM) is a well-known regulator of ion-channel activity. Consequently, the Protein Data Bank contains many structures of CaM in complex with different fragments of ion channels that together display a variety of binding modes. In addition to the canonical interaction, in which CaM engages its target with both its domains, many of the ion-channel-CaM complexes demonstrate alternative non-canonical binding modes that depend on the target and experimental conditions. Based on these findings, several mechanisms of ion-channel regulation by CaM have been proposed, all exploiting its plasticity and flexibility in interacting with its targets. In this review, we focus on complexes of CaM with either the voltage-gated calcium channels; the voltage-gated sodium channels or the small conductance calcium-activated potassium channels, for which both structural and functional data are available. For each channel, the functional relevance of these structural data and possible mechanism of calcium-dependent (in)activation and/or facilitation are discussed in detail.
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Affiliation(s)
- Nadezda V Kovalevskaya
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Geert Grooteplein Zuid 26-28, Nijmegen, 6525, GA, The Netherlands
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79
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Kuttner YY, Nagar T, Engel S. Surface dynamics in allosteric regulation of protein-protein interactions: modulation of calmodulin functions by Ca2+. PLoS Comput Biol 2013; 9:e1003028. [PMID: 23592972 PMCID: PMC3617199 DOI: 10.1371/journal.pcbi.1003028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Accepted: 02/25/2013] [Indexed: 11/19/2022] Open
Abstract
Knowledge of the structural basis of protein-protein interactions (PPI) is of fundamental importance for understanding the organization and functioning of biological networks and advancing the design of therapeutics which target PPI. Allosteric modulators play an important role in regulating such interactions by binding at site(s) orthogonal to the complex interface and altering the protein's propensity for complex formation. In this work, we apply an approach recently developed by us for analyzing protein surfaces based on steered molecular dynamics simulation (SMD) to the study of the dynamic properties of functionally distinct conformations of a model protein, calmodulin (CaM), whose ability to interact with target proteins is regulated by the presence of the allosteric modulator Ca(2+). Calmodulin is a regulatory protein that acts as an intracellular Ca(2+) sensor to control a wide variety of cellular processes. We demonstrate that SMD analysis is capable of pinpointing CaM surfaces implicated in the recognition of both the allosteric modulator Ca(2+) and target proteins. Our analysis of changes in the dynamic properties of the CaM backbone elicited by Ca(2+) binding yielded new insights into the molecular mechanism of allosteric regulation of CaM-target interactions.
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Affiliation(s)
- Yosef Y. Kuttner
- Bioinformatics Core Facility, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Tal Nagar
- Bioinformatics Core Facility, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Stanislav Engel
- Department of Clinical Biochemistry and Pharmacology, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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80
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Ben Johny M, Yang PS, Bazzazi H, Yue DT. Dynamic switching of calmodulin interactions underlies Ca2+ regulation of CaV1.3 channels. Nat Commun 2013; 4:1717. [PMID: 23591884 PMCID: PMC3856249 DOI: 10.1038/ncomms2727] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 03/08/2013] [Indexed: 11/30/2022] Open
Abstract
Calmodulin regulation of CaV channels is a prominent Ca(2+) feedback mechanism orchestrating vital adjustments of Ca(2+) entry. The long-held structural correlation of this regulation has been Ca(2+)-bound calmodulin, complexed alone with an IQ domain on the channel carboxy terminus. Here, however, systematic alanine mutagenesis of the entire carboxyl tail of an L-type CaV1.3 channel casts doubt on this paradigm. To identify the actual molecular states underlying channel regulation, we develop a structure-function approach relating the strength of regulation to the affinity of underlying calmodulin/channel interactions, by a Langmuir relation (individually transformed Langmuir analysis). Accordingly, we uncover frank exchange of Ca(2+)-calmodulin to interfaces beyond the IQ domain, initiating substantial rearrangements of the calmodulin/channel complex. The N-lobe of Ca(2+)-calmodulin binds an N-terminal spatial Ca(2+) transforming element module on the channel amino terminus, whereas the C-lobe binds an EF-hand region upstream of the IQ domain. This system of structural plasticity furnishes a next-generation blueprint for CaV channel modulation.
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Affiliation(s)
- Manu Ben Johny
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, voice: (410) 955-0078, fax: (410) 614-8269,
| | - Philemon S. Yang
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, voice: (410) 955-0078, fax: (410) 614-8269,
| | - Hojjat Bazzazi
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, voice: (410) 955-0078, fax: (410) 614-8269,
| | - David T. Yue
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, voice: (410) 955-0078, fax: (410) 614-8269,
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81
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Damo SM, Feldkamp MD, Chagot B, Chazin WJ. NMR studies of the interaction of calmodulin with IQ motif peptides. Methods Mol Biol 2013; 963:173-86. [PMID: 23296611 DOI: 10.1007/978-1-62703-230-8_11] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Calmodulin (CaM) is a ubiquitous EF-hand calcium sensor protein that transduces calcium signals in a wide range of signaling pathways. Structural analysis of complexes with peptides has provided valuable insights into the remarkable variety in the way in which CaM interacts with and activates its targets. Among these various targets, CaM has been shown to be an essential component of a calcium-sensing regulatory apparatus for a number of voltage-gated ion channels. NMR spectroscopy has proven to be a powerful tool for the structural characterization of CaM-peptide complexes, in particular for the study of IQ motifs, which bind CaM at the basal level of calcium in cells and thereby serve to localize CaM to its sites of action. We describe here methods for the robust expression and purification of CaM isotopically enriched for NMR analysis, as well as for the complex of CaM with a peptide derived from the IQ motif sequence of the human cardiac sodium channel Na(V)1.5. We also describe methods for NMR analysis of titrations of CaM with IQ motif peptides to determine the stoichiometry of the complex and to identify the residues at the binding interface.
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Affiliation(s)
- Steven M Damo
- Department of Biochemistry, Vanderbilt University, Nashville, TN, USA
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82
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Xu Q, Chang A, Tolia A, Minor DL. Structure of a Ca(2+)/CaM:Kv7.4 (KCNQ4) B-helix complex provides insight into M current modulation. J Mol Biol 2012. [PMID: 23178170 DOI: 10.1016/j.jmb.2012.11.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Calmodulin (CaM) is an important regulator of Kv7.x (KCNQx) voltage-gated potassium channels. Channels from this family produce neuronal M currents and cardiac and auditory I(KS) currents and harbor mutations that cause arrhythmias, epilepsy, and deafness. Despite extensive functional characterization, biochemical and structural details of the interaction between CaM and the channel have remained elusive. Here, we show that both apo-CaM and Ca(2+)/CaM bind to the C-terminal tail of the neuronal channel Kv7.4 (KCNQ4), which is involved in both hearing and mechanosensation. Interactions between apo-CaM and the Kv7.4 tail involve two C-terminal tail segments, known as the A and B segments, whereas the interaction between Ca(2+)/CaM and the Kv7.4 C-terminal tail requires only the B segment. Biochemical studies show that the calcium dependence of the CaM:B segment interaction is conserved in all Kv7 subtypes. X-ray crystallographic determination of the structure of the Ca(2+)/CaM:Kv7.4 B segment complex shows that Ca(2+)/CaM wraps around the Kv7.4 B segment, which forms an α-helix, in an antiparallel orientation that embodies a variation of the classic 1-14 Ca(2+)/CaM interaction motif. Taken together with the context of prior studies, our data suggest a model for modulation of neuronal Kv7 channels involving a calcium-dependent conformational switch from an apo-CaM form that bridges the A and B segments to a Ca(2+)/CaM form bound to the B-helix. The structure presented here also provides a context for a number of disease-causing mutations and for further dissection of the mechanisms by which CaM controls Kv7 function.
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Affiliation(s)
- Qiang Xu
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158-2156, USA
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83
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Weininger U, Liu Z, McIntyre DD, Vogel HJ, Akke M. Specific 12CβD(2)12CγD(2)S13CεHD(2) isotopomer labeling of methionine to characterize protein dynamics by 1H and 13C NMR relaxation dispersion. J Am Chem Soc 2012; 134:18562-5. [PMID: 23106551 PMCID: PMC3497853 DOI: 10.1021/ja309294u] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
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Protein dynamics on the micro- to millisecond time scale
is increasingly
found to be critical for biological function, as demonstrated by numerous
NMR relaxation dispersion studies. Methyl groups are excellent probes
of protein interactions and dynamics because of their favorable NMR
relaxation properties, which lead to sharp signals in the 1H and 13C NMR spectra. Out of the six different methyl-bearing
amino acid residue types in proteins, methionine plays a special role
because of its extensive side-chain flexibility and the high polarizability
of the sulfur atom. Methionine is over-represented in many protein–protein
recognition sites, making the methyl group of this residue type an
important probe of the relationships among dynamics, interactions,
and biological function. Here we present a straightforward method
to label methionine residues with specific 13CHD2 methyl isotopomers against a deuterated background. The resulting
protein samples yield NMR spectra with improved sensitivity due to
the essentially 100% population of the desired 13CHD2 methyl isotopomer, which is ideal for 1H and 13C spin relaxation experiments to investigate protein dynamics
in general and conformational exchange in particular. We demonstrate
the approach by measuring 1H and 13C CPMG relaxation
dispersion for the nine methionines in calcium-free calmodulin (apo-CaM).
The results show that the C-terminal domain, but not the N-terminal
domain, of apo-CaM undergoes fast exchange between the ground state
and a high-energy state. Since target proteins are known to bind specifically
to the C-terminal domain of apo-CaM, we speculate that the high-energy
state might be involved in target binding through conformational selection.
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Affiliation(s)
- Ulrich Weininger
- Department of Biophysical Chemistry, Center for Molecular Protein Science, Lund University, Sweden
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84
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Liu Y, Zheng X, Mueller GA, Sobhany M, DeRose EF, Zhang Y, London RE, Birnbaumer L. Crystal structure of calmodulin binding domain of orai1 in complex with Ca2+ calmodulin displays a unique binding mode. J Biol Chem 2012; 287:43030-41. [PMID: 23109337 DOI: 10.1074/jbc.m112.380964] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Orai1 is a plasma membrane protein that in its tetrameric form is responsible for calcium influx from the extracellular environment into the cytosol in response to interaction with the Ca(2+)-depletion sensor STIM1. This is followed by a fast Ca(2+)·calmodulin (CaM)-dependent inhibition, resulting from CaM binding to an Orai1 region called the calmodulin binding domain (CMBD). The interaction between Orai1 and CaM at the atomic level remains unknown. Here, we report the crystal structure of a CaM·Orai1-CMBD complex showing one CMBD bound to the C-terminal lobe of CaM, differing from other CaM-target protein complexes, in which both N- and C-terminal lobes of CaM (CaM-N and CaM-C) are involved in target binding. Orai1-CMBD binds CaM-C mainly through hydrophobic interactions, primarily involving residue Trp(76) of Orai1-CMBD, which interacts with the hydrophobic pocket of CaM-C. However, NMR data, isothermal titration calorimetry data, and pulldown assays indicated that CaM-N and CaM-C both can bind Orai1-CMBD, with CaM-N having ∼4 times weaker affinity than CaM-C. Pulldown assays of a Orai1-CMBD(W76E) mutant, gel filtration chromatography data, and NOE signals indicated that CaM-N and CaM-C can each bind one Orai1-CMBD. Thus our studies support an unusual, extended 1:2 binding mode of CaM to Orai1-CMBDs, and quantify the affinity of Orai1 for CaM. We propose a two-step mechanism for CaM-dependent Orai1 inactivation initiated by binding of the C-lobe of CaM to the CMBD of one Orai1 followed by the binding of the N-lobe of CaM to the CMBD of a neighboring Orai1.
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Affiliation(s)
- Yanshun Liu
- Laboratory of Neurobiology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
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85
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Zhang M, Abrams C, Wang L, Gizzi A, He L, Lin R, Chen Y, Loll PJ, Pascal JM, Zhang JF. Structural basis for calmodulin as a dynamic calcium sensor. Structure 2012; 20:911-23. [PMID: 22579256 DOI: 10.1016/j.str.2012.03.019] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 02/20/2012] [Accepted: 03/08/2012] [Indexed: 12/14/2022]
Abstract
Calmodulin is a prototypical and versatile Ca(2+) sensor with EF hands as its high-affinity Ca(2+) binding domains. Calmodulin is present in all eukaryotic cells, mediating Ca(2+)-dependent signaling. Upon binding Ca(2+), calmodulin changes its conformation to form complexes with a diverse array of target proteins. Despite a wealth of knowledge on calmodulin, little is known on how target proteins regulate calmodulin's ability to bind Ca(2+). Here, we take advantage of two splice variants of SK2 channels, which are activated by Ca(2+)-bound calmodulin but show different sensitivity to Ca(2+) for their activation. Protein crystal structures and other experiments show that, depending on which SK2 splice variant it binds to, calmodulin adopts drastically different conformations with different affinities for Ca(2+) at its C-lobe. Such target protein-induced conformational changes make calmodulin a dynamic Ca(2+) sensor capable of responding to different Ca(2+) concentrations in cellular Ca(2+) signaling.
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Affiliation(s)
- Miao Zhang
- Department of Molecular Physiology and Biophysics, Jefferson Medical College, Philadelphia, PA 19107, USA
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86
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Irene D, Huang JW, Chung TY, Li FY, Tzen JTC, Lin TH, Chyan CL. Binding orientation and specificity of calmodulin to rat olfactory cyclic nucleotide-gated ion channel. J Biomol Struct Dyn 2012; 31:414-25. [PMID: 22877078 DOI: 10.1080/07391102.2012.703069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Calmodulin (CaM), the primary intracellular Ca(2+) receptor, regulates a large number of key enzymes and controls a wide spectrum of important biological responses. Recognition between CaM and its target sequence in rat olfactory cyclic nucleotide-gated ion channel (OLFp) was investigated by circular dichroism (CD), fluorescence, and NMR spectroscopy. Fluorescence data showed the OLFp tightly bound to CaM with a dissociation constant of 12 nM in a 1:1 stoichiometry. Far-UV CD data showed that approximately 60% of OLFp residues formed α-helical structures when associated with CaM. NMR data showed that most of the (15)N-(1)H HSQC cross-peaks of the (15)N-labeled CaM not only shifted but also split into two sets of peaks upon association with the OLFp. Our data indicated that the two distinct CaM/OLFp complexes existed simultaneously with stable structures that were not interexchangeable within the NMR time scale. In light of the palindromic sequence of OLFp (FQRIVRLVGVIRDW) for CaM targeting, we proposed that the helical OLFp with C2 symmetry may bind to CaM in two orientations. This hypothesis is supported by the observation that only one set of (15)N-(1)H HSQC cross-peaks of the (15)N-labeled CaM was detected upon association with OLFp-M13 chimeric peptide (OLFMp), a mutated OLFp lacking the palindromic feature. The binding specificity of OLFMp to CaM was restored when the palindromic feature was destroyed. Binding modes of CaM/OLFp and CaM/OLFMp simulated by molecular docking were in accord with their distinct patterns observed in HSQC spectra. Our studies suggest that the palindromic residues in OLFp are crucial for the orientation-specific recognition by CaM.
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Affiliation(s)
- Deli Irene
- Department of Chemistry, National Dong Hwa University, Hualien 974, Taiwan, ROC
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87
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Wang C, Chung BC, Yan H, Lee SY, Pitt GS. Crystal structure of the ternary complex of a NaV C-terminal domain, a fibroblast growth factor homologous factor, and calmodulin. Structure 2012; 20:1167-76. [PMID: 22705208 PMCID: PMC3610540 DOI: 10.1016/j.str.2012.05.001] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 05/03/2012] [Accepted: 05/04/2012] [Indexed: 01/07/2023]
Abstract
Voltage-gated Na⁺ (Na(V)) channels initiate neuronal action potentials. Na(V) channels are composed of a transmembrane domain responsible for voltage-dependent Na⁺ conduction and a cytosolic C-terminal domain (CTD) that regulates channel function through interactions with many auxiliary proteins, including fibroblast growth factor homologous factors (FHFs) and calmodulin (CaM). Most ion channel structural studies have focused on mechanisms of permeation and voltage-dependent gating but less is known about how intracellular domains modulate channel function. Here we report the crystal structure of the ternary complex of a human Na(V) CTD, an FHF, and Ca²⁺-free CaM at 2.2 Å. Combined with functional experiments based on structural insights, we present a platform for understanding the roles of these auxiliary proteins in Na(V) channel regulation and the molecular basis of mutations that lead to neuronal and cardiac diseases. Furthermore, we identify a critical interaction that contributes to the specificity of individual Na(V) CTD isoforms for distinctive FHFs.
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Affiliation(s)
- Chaojian Wang
- Division of Cardiology, Department of Medicine, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA,Ion Channel Research Unit, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA
| | - Ben C. Chung
- Department of Biochemistry, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA,Ion Channel Research Unit, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA
| | - Haidun Yan
- Division of Cardiology, Department of Medicine, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA,Ion Channel Research Unit, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA,Ion Channel Research Unit, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA
| | - Geoffrey S. Pitt
- Division of Cardiology, Department of Medicine, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA,Ion Channel Research Unit, Duke University Medical Center, 2 Genome Ct, Durham, North Carolina, 27710, USA
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88
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Glaaser IW, Osteen JD, Puckerin A, Sampson KJ, Jin X, Kass RS. Perturbation of sodium channel structure by an inherited Long QT Syndrome mutation. Nat Commun 2012; 3:706. [PMID: 22426227 PMCID: PMC3518026 DOI: 10.1038/ncomms1717] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 01/31/2012] [Indexed: 12/22/2022] Open
Abstract
The cardiac voltage-gated sodium channel (NaV1.5) underlies impulse conduction in the heart and its depolarization-induced inactivation is essential in control of the duration of the QT interval of the electrocardiogram (ECG). Perturbation of Nav1.5 inactivation by drugs or inherited mutation can underlie and trigger cardiac arrhythmias. The carboxy terminus plays an important role in channel inactivation, but complete structural information on its predicted structural domain is unknown. Here we measure interactions between the functionally critical distal C-T alpha helix (H6) and the proximal structured EF hand motif using transition metal ion FRET. We measure distances at three loci along H6 relative to an intrinsic tryptophan, demonstrating the proximal-distal interaction in a contiguous carboxy terminus polypeptide. Using these data together with the existing NaV1.5 carboxy terminus NMR structure, we construct a model of the predicted structured region of the carboxy terminus. An arrhythmia associated H6 mutant which impairs inactivation decreases FRET, indicating destabilization of the distal-proximal intramolecular interaction. These data provide a structural correlate to the pathological phenotype of the mutant channel.
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Affiliation(s)
- Ian W Glaaser
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, Columbia University Medical Center, 630 W 168th Street, New York, NY 10032, USA
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89
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Abstract
Voltage-gated sodium channels underlie the rapid regenerative upstroke of action potentials and are modulated by cytoplasmic calcium ions through a poorly understood mechanism. We describe the 1.35 Å crystal structure of Ca(2+)-bound calmodulin (Ca(2+)/CaM) in complex with the inactivation gate (DIII-IV linker) of the cardiac sodium channel (Na(V)1.5). The complex harbors the positions of five disease mutations involved with long Q-T type 3 and Brugada syndromes. In conjunction with isothermal titration calorimetry, we identify unique inactivation-gate mutations that enhance or diminish Ca(2+)/CaM binding, which, in turn, sensitize or abolish Ca(2+) regulation of full-length channels in electrophysiological experiments. Additional biochemical experiments support a model whereby a single Ca(2+)/CaM bridges the C-terminal IQ motif to the DIII-IV linker via individual N and C lobes, respectively. The data suggest that Ca(2+)/CaM destabilizes binding of the inactivation gate to its receptor, thus biasing inactivation toward more depolarized potentials.
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90
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Black DJ, Persechini A. In calmodulin-IQ domain complexes, the Ca(2+)-free and Ca(2+)-bound forms of the calmodulin C-lobe direct the N-lobe to different binding sites. Biochemistry 2011; 50:10061-8. [PMID: 21999573 DOI: 10.1021/bi201300v] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have investigated the roles played by the calmodulin (CaM) N- and C-lobes in establishing the conformations of CaM-IQ domain complexes in different Ca(2+)-free and Ca(2+)-bound states. Our results indicate a dominant role for the C-lobe in these complexes. When the C-lobe is Ca(2+)-free, it directs the N-lobe to a binding site within the IQ domain consensus sequence. It appears that the N-lobe must be Ca(2+)-free to interact productively with this site. When the C-lobe is Ca(2+)-bound, it directs the N-lobe to a site upstream of the consensus sequence, and it appears that the N-lobe must be Ca(2+)-bound to interact productively with this site. A model for switching in CaM-IQ domain complexes is presented in which the N-lobe adopts bound and extended positions that depend on the status of the Ca(2+)-binding sites in each CaM lobe and the compositions of the two N-lobe binding sites. Ca(2+)-dependent changes in the conformation of the bound C-lobe that appear to be responsible for directed N-lobe binding are also identified. Changes in the equilibria between extended and bound N-lobe positions may control bridging interactions in which the extended N-lobe is bound to another CaM-binding domain. Ca(2+)-dependent control of bridging interactions with CaM has been implicated in the regulation of ion channel and unconventional myosin activities.
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Affiliation(s)
- D J Black
- Division of Molecular Biology and Biochemistry, University of Missouri, Kansas City, Missouri 64110-2499, USA
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91
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Dempsey BR, Shaw GS. Identification of calcium-independent and calcium-enhanced binding between S100B and the dopamine D2 receptor. Biochemistry 2011; 50:9056-65. [PMID: 21932834 PMCID: PMC3196243 DOI: 10.1021/bi201054x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
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S100B is a dimeric EF-hand protein that undergoes a calcium-induced
conformational change and exposes a hydrophobic protein-binding surface.
Recently S100B was identified as a binding partner of the dopamine
D2 receptor in a bacterial two-hybrid screen involving the third intracellular
loop (IC3). The low in vivo calcium concentration
in bacteria (100–300 nM) suggests this interaction may occur
in the absence of calcium. In this work the calcium-sensitive ability
for S100B to recruit the IC3 of the dopamine D2 receptor was examined,
and regions in both proteins required for complex formation were identified.
Peptide array experiments identified the C-terminal 58 residues of
the IC3 (IC3-C58) as the major interacting site for S100B. These experiments
along with pull-down assays showed the IC3 interacts with S100B in
the absence and presence of calcium. 1H–15N HSQC experiments were used to identify residues, primarily in helices
III and IV, utilized in the IC3-C58 interaction. NMR titration data
indicated that although an interaction between apo-S100B and IC3-C58
occurs without calcium, the binding was enhanced more than 100-fold
upon calcium binding. Further, it was established that shorter regions
within IC3-C58 comprising its N- and C-terminal halves had diminished
binding to Ca2+-S100B and did not display any observable
affinity in the absence of calcium. This indicates that residue or
structural components within both regions are required for optimal
interaction with Ca2+-S100B. This work represents the first
example of an S100B target that interacts with both the apo- and calcium-saturated
forms of S100B.
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Affiliation(s)
- Brian R Dempsey
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada N6A 5C1
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92
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Rook MB, Evers MM, Vos MA, Bierhuizen MFA. Biology of cardiac sodium channel Nav1.5 expression. Cardiovasc Res 2011; 93:12-23. [PMID: 21937582 DOI: 10.1093/cvr/cvr252] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Na(v)1.5, the pore forming α-subunit of the voltage-dependent cardiac Na(+) channel, is an integral membrane protein involved in the initiation and conduction of action potentials. Mutations in the gene-encoding Na(v)1.5, SCN5A, have been associated with a variety of arrhythmic disorders, including long QT, Brugada, and sick sinus syndromes as well as progressive cardiac conduction defect and atrial standstill. Moreover, alterations in the Na(v)1.5 expression level and/or sodium current density have been frequently noticed in acquired cardiac disorders, such as heart failure. The molecular mechanisms underlying these alterations are poorly understood, but are considered essential for conception of arrhythmogenesis and the development of therapeutic strategies for prevention or treatment of arrhythmias. The unravelling of such mechanisms requires critical molecular insight into the biology of Na(v)1.5 expression and function. Therefore, the aim of this review is to provide an up-to-date account of molecular determinants of normal Na(v)1.5 expression and function. The parts of the Na(v)1.5 life cycle that are discussed include (i) regulatory aspects of the SCN5A gene and transcript structure, (ii) the nature, molecular determinants, and functional consequences of Na(v)1.5 post-translational modifications, and (iii) the role of Na(v)1.5 interacting proteins in cellular trafficking. The reviewed studies have provided valuable information on how the Na(v)1.5 expression level, localization, and biophysical properties are regulated, but also revealed that our understanding of the underlying mechanisms is still limited.
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Affiliation(s)
- Martin B Rook
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, The Netherlands
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93
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Evans TIA, Hell JW, Shea MA. Thermodynamic linkage between calmodulin domains binding calcium and contiguous sites in the C-terminal tail of Ca(V)1.2. Biophys Chem 2011; 159:172-87. [PMID: 21757287 DOI: 10.1016/j.bpc.2011.06.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 06/15/2011] [Accepted: 06/15/2011] [Indexed: 11/30/2022]
Abstract
Calmodulin (CaM) binding to the intracellular C-terminal tail (CTT) of the cardiac L-type Ca(2+) channel (Ca(V)1.2) regulates Ca(2+) entry by recognizing sites that contribute to negative feedback mechanisms for channel closing. CaM associates with Ca(V)1.2 under low resting [Ca(2+)], but is poised to change conformation and position when intracellular [Ca(2+)] rises. CaM binding Ca(2+), and the domains of CaM binding the CTT are linked thermodynamic functions. To better understand regulation, we determined the energetics of CaM domains binding to peptides representing pre-IQ sites A(1588), and C(1614) and the IQ motif studied as overlapping peptides IQ(1644) and IQ'(1650) as well as their effect on calcium binding. (Ca(2+))(4)-CaM bound to all four peptides very favorably (K(d)≤2 nM). Linkage analysis showed that IQ(1644-1670) bound with a K(d)~1 pM. In the pre-IQ region, (Ca(2+))(2)-N-domain bound preferentially to A(1588), while (Ca(2+))(2)-C-domain preferred C(1614). When bound to C(1614), calcium binding in the N-domain affected the tertiary conformation of the C-domain. Based on the thermodynamics, we propose a structural mechanism for calcium-dependent conformational change in which the linker between CTT sites A and C buckles to form an A-C hairpin that is bridged by calcium-saturated CaM.
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Affiliation(s)
- T Idil Apak Evans
- Department of Biochemistry, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, United States.
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94
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Feldkamp MD, Yu L, Shea MA. Structural and energetic determinants of apo calmodulin binding to the IQ motif of the Na(V)1.2 voltage-dependent sodium channel. Structure 2011; 19:733-47. [PMID: 21439835 PMCID: PMC3094505 DOI: 10.1016/j.str.2011.02.009] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2010] [Revised: 02/03/2011] [Accepted: 02/06/2011] [Indexed: 11/29/2022]
Abstract
The neuronal voltage-dependent sodium channel (Na(v)1.2), essential for generation and propagation of action potentials, is regulated by calmodulin (CaM) binding to the IQ motif in its α subunit. A peptide (Na(v)1.2(IQp), KRKQEEVSAIVIQRAYRRYLLKQKVKK) representing the IQ motif had higher affinity for apo CaM than (Ca(2+))(4)-CaM. Association was mediated solely by the C-domain of CaM. A solution structure (2KXW.pdb) of apo (13)C,(15)N-CaM C-domain bound to Na(v)1.2(IQp) was determined with NMR. The region of Na(v)1.2(IQp) bound to CaM was helical; R1902, an Na(v)1.2 residue implicated in familial autism, did not contact CaM. The apo C-domain of CaM in this complex shares features of the same domain bound to myosin V IQ motifs (2IX7) and bound to an SK channel peptide (1G4Y) that does not contain an IQ motif. Thermodynamic and structural studies of CaM-Na(v)1.2(IQp) interactions show that apo and (Ca(2+))(4)-CaM adopt distinct conformations that both permit tight association with Na(v)1.2(IQp) during gating.
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Affiliation(s)
- Michael D. Feldkamp
- Department of Biochemistry Roy J. and Lucille A. Carver College of Medicine University of Iowa Iowa City, Iowa 52242-1109, USA
| | - Liping Yu
- Department of Biochemistry Roy J. and Lucille A. Carver College of Medicine University of Iowa Iowa City, Iowa 52242-1109, USA
- NMR Facility Roy J. and Lucille A. Carver College of Medicine University of Iowa Iowa City, Iowa 52242-1109, USA
| | - Madeline A. Shea
- Department of Biochemistry Roy J. and Lucille A. Carver College of Medicine University of Iowa Iowa City, Iowa 52242-1109, USA
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Mori MX, Imai Y, Itsuki K, Inoue R. Quantitative measurement of Ca(2+)-dependent calmodulin-target binding by Fura-2 and CFP and YFP FRET imaging in living cells. Biochemistry 2011; 50:4685-96. [PMID: 21517110 DOI: 10.1021/bi200287x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calcium dynamics and its linked molecular interactions cause a variety of biological responses; thus, exploiting techniques for detecting both concurrently is essential. Here we describe a method for measuring the cytosolic Ca(2+) concentration ([Ca(2+)](i)) and protein-protein interactions within the same cell, using Fura-2 and superenhanced cyan and yellow fluorescence protein (seCFP and seYFP, respectively) FRET imaging techniques. Concentration-independent corrections for bleed-through of Fura-2 into FRET cubes across different time points and [Ca(2+)](i) values allowed for an effective separation of Fura-2 cross-talk signals and seCFP and seYFP cross-talk signals, permitting calculation of [Ca(2+)](i) and FRET with high fidelity. This correction approach was particularly effective at lower [Ca(2+)](i) levels, eliminating bleed-through signals that resulted in an artificial enhancement of FRET. By adopting this correction approach combined with stepwise [Ca(2+)](i) increases produced in living cells, we successfully elucidated steady-state relationships between [Ca(2+)](i) and FRET derived from the interaction of seCFP-tagged calmodulin (CaM) and the seYFP-fused CaM binding domain of myosin light chain kinase. The [Ca(2+)](i) versus FRET relationship for voltage-gated sodium, calcium, and TRPC6 channel CaM binding domains (IQ domain or CBD) revealed distinct sensitivities for [Ca(2+)](i). Moreover, the CaM binding strength at basal or subbasal [Ca(2+)](i) levels provided evidence of CaM tethering or apoCaM binding in living cells. Of the ion channel studies, apoCaM binding was weakest for the TRPC6 channel, suggesting that more global Ca(2+) and CaM changes rather than the local CaM-channel interface domain may be involved in Ca(2+)CaM-mediated regulation of this channel. This simultaneous Fura-2 and CFP- and YFP-based FRET imaging system will thus serve as a simple but powerful means of quantitatively elucidating cellular events associated with Ca(2+)-dependent functions.
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Affiliation(s)
- Masayuki X Mori
- Department of Physiology, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Fukuoka, Japan.
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