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Hu XQ, Zhang L. Oxidative Regulation of Vascular Ca v1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders. Antioxidants (Basel) 2022; 11:antiox11122432. [PMID: 36552639 PMCID: PMC9774363 DOI: 10.3390/antiox11122432] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 11/28/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022] Open
Abstract
Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca2+ (Cav1.2) channel in small arteries and arterioles plays an essential role in regulating Ca2+ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Cav1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Cav1.2 and potential roles of ROS-mediated Cav1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.
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Muralidharan P, Cserne Szappanos H, Ingley E, Hool LC. The cardiac L-type calcium channel alpha subunit is a target for direct redox modification during oxidative stress-the role of cysteine residues in the alpha interacting domain. Clin Exp Pharmacol Physiol 2017; 44 Suppl 1:46-54. [PMID: 28306174 DOI: 10.1111/1440-1681.12750] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 02/16/2017] [Accepted: 03/07/2017] [Indexed: 01/21/2023]
Abstract
Cardiovascular disease is the leading cause of death in the Western world. The incidence of cardiovascular disease is predicted to further rise with the increase in obesity and diabetes and with the aging population. Even though the survival rate from ischaemic heart disease has improved over the past 30 years, many patients progress to a chronic pathological condition, known as cardiac hypertrophy that is associated with an increase in morbidity and mortality. Reactive oxygen species (ROS) and calcium play an essential role in mediating cardiac hypertrophy. The L-type calcium channel is the main route for calcium influx into cardiac myocytes. There is now good evidence for a direct role for the L-type calcium channel in the development of cardiac hypertrophy. Cysteines on the channel are targets for redox modification and glutathionylation of the channel can modulate the function of the channel protein leading to the onset of pathology. The cysteine responsible for modification of L-type calcium channel function has now been identified. Detailed understanding of the role of cysteines as possible targets during oxidative stress may assist in designing therapy to prevent the development of hypertrophy and heart failure.
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Affiliation(s)
- Padmapriya Muralidharan
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, WA, Australia
| | - Henrietta Cserne Szappanos
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, WA, Australia
| | - Evan Ingley
- Harry Perkins Institute of Medical Research and Centre for Medical Research, University of Western Australia, Perth, WA, Australia.,School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia
| | - Livia C Hool
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, WA, Australia.,Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
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3
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Chen Y, Barajas-Martinez H, Zhu D, Wang X, Chen C, Zhuang R, Shi J, Wu X, Tao Y, Jin W, Wang X, Hu D. Novel trigenic CACNA1C/DES/MYPN mutations in a family of hypertrophic cardiomyopathy with early repolarization and short QT syndrome. J Transl Med 2017; 15:78. [PMID: 28427417 PMCID: PMC5399316 DOI: 10.1186/s12967-017-1180-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 04/10/2017] [Indexed: 01/12/2023] Open
Abstract
Background Hypertrophic cardiomyopathy (HCM) patients with early repolarization (ER) pattern are at higher risk of ventricular arrhythmia, yet the genetic background of this situation has not been well investigated. Here we report novel trigenic mutations detected in a Chinese family of obstructive HCM with ER and short QT syndrome (SQTS). Methods Proband and family members underwent detailed medical assessments. DNAs were extracted from peripheral blood leukocytes for genetic screening with next generation method. The functional characterization of the mutation was conducted in TSA201 cells with patch-clamp experiment. Results The proband was a 52-year-old male who had a ER pattern ECG in inferioral-lateral leads with atrioventricular block and QTc of 356 ms. He also suffered from severe left ventricular hypertrophy and dysfunction. Targeted sequencing revealed trigenic mutations: c.700G>A/p.E234K in DES, c.2966G>A/p.R989H in MYPN, and c.5918G>C/p.R1973P in CACNA1C. All mutations were also detected in his daughter with ER and mild myocardium hypertrophy. The CACNA1C-R1973P mutation caused significant reduction (68.4%) of ICa compared to CACNA1C-WT (n = 14 and 14, P < 0.05). The computer modeling showed that all 3 mutations were highly disease-causing. The proband received the CRT-D (cardiac resynchronizing therapy) implantation, which lowered the left ventricular outflow tract gradient (LVOTG, 124 mmHg pre vs. 27 mmHg post) and restored the LV function (LVEF 40% pre vs. 63% post). Conclusions The study reveals a novel CACNA1C mutation underlying the unique ER pattern ECGs with SQTS. It also shows the rare trigenic mutations are the pathogenic substrates for the complicated clinical manifestation in HCM patients. Electronic supplementary material The online version of this article (doi:10.1186/s12967-017-1180-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yanhong Chen
- Department of Cardiology, Wuhan Asia Heart Hospital, Wuhan University, Wuhan, 430022, China.,Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | | | - Dongxiao Zhu
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Xihui Wang
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Chonghao Chen
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Ruijuan Zhuang
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Jingjing Shi
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Xueming Wu
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Yijia Tao
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Weidong Jin
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China
| | - Xiaoyan Wang
- Department of Cardiology, Nantong University, 3rd People's Hospital of Wuxi Affiliated To Nantong University, 585 Xingyuan Road, Wuxi, 214043, Jiangsu, China.
| | - Dan Hu
- Department of Cardiology and Cardiovascular Research Institute, Renmin Hospital of Wuhan University, Wuhan, 430060, China. .,Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY, 13501, USA. .,Molecular Genetics Department, SCRO Chair of Stem Cell Center, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY, 13501, USA.
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4
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Viola HM, Hool LC. Role of the cytoskeleton in communication between L-type Ca(2+) channels and mitochondria. Clin Exp Pharmacol Physiol 2015; 40:295-304. [PMID: 23551128 DOI: 10.1111/1440-1681.12072] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 02/25/2013] [Accepted: 02/26/2013] [Indexed: 12/15/2022]
Abstract
The L-type Ca(2+) channel is the main route for Ca(2+) entry into cardiac myocytes, which is essential for the maintenance of cardiac excitation and contraction. Alterations in L-type Ca(2+) channel activity and Ca(2+) homeostasis have been implicated in the development of cardiomyopathies. Cardiac excitation and contraction is fuelled by ATP, synthesized predominantly by the mitochondria via the Ca(2+)-dependent process oxidative phosphorylation. Mitochondrial reactive oxygen species (ROS) are by-products of oxidative phosphorylation and are associated with the development of cardiac pathology. The cytoskeleton plays a role in the communication of signals from the plasma membrane to intracellular organelles. There is good evidence that both L-type Ca(2+) channel activity and mitochondrial function can be modulated by changes in the cytoskeletal network. Activation of the L-type Ca(2+) channel can regulate mitochondrial function through cytoskeletal proteins as a result of transmission of movement from the β(2)-subunit of the channel that occurs during activation and inactivation of the channel. An association between cytoskeletal proteins and the mitochondrial voltage-dependent anion channel (VDAC) may play a role in this response. The L-type Ca(2+) channel is the initiator of contraction in cardiac muscle and the VDAC is responsible for regulating mitochondrial ATP/ADP trafficking. This article presents evidence that a functional coupling between L-type Ca(2+) channels and mitochondria may assist in meeting myocardial energy demand on a beat-to-beat basis.
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Affiliation(s)
- Helena M Viola
- Cardiovascular Electrophysiology Laboratory, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia
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Liao P, Yu D, Hu Z, Liang MC, Wang JJ, Yu CY, Ng G, Yong TF, Soon JL, Chua YL, Soong TW. Alternative splicing generates a novel truncated Cav1.2 channel in neonatal rat heart. J Biol Chem 2015; 290:9262-72. [PMID: 25694430 DOI: 10.1074/jbc.m114.594911] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Indexed: 11/06/2022] Open
Abstract
L-type Cav1.2 Ca(2+) channel undergoes extensive alternative splicing, generating functionally different channels. Alternatively spliced Cav1.2 Ca(2+) channels have been found to be expressed in a tissue-specific manner or under pathological conditions. To provide a more comprehensive understanding of alternative splicing in Cav1.2 channel, we systematically investigated the splicing patterns in the neonatal and adult rat hearts. The neonatal heart expresses a novel 104-bp exon 33L at the IVS3-4 linker that is generated by the use of an alternative acceptor site. Inclusion of exon 33L causes frameshift and C-terminal truncation. Whole-cell electrophysiological recordings of Cav1.233L channels expressed in HEK 293 cells did not detect any current. However, when co-expressed with wild type Cav1.2 channels, Cav1.233L channels reduced the current density and altered the electrophysiological properties of the wild type Cav1.2 channels. Interestingly, the truncated 3.5-domain Cav1.233L channels also yielded a dominant negative effect on Cav1.3 channels, but not on Cav3.2 channels, suggesting that Cavβ subunits is required for Cav1.233L regulation. A biochemical study provided evidence that Cav1.233L channels enhanced protein degradation of wild type channels via the ubiquitin-proteasome system. Although the physiological significance of the Cav1.233L channels in neonatal heart is still unknown, our report demonstrates the ability of this novel truncated channel to modulate the activity of the functional Cav1.2 channels. Moreover, the human Cav1.2 channel also contains exon 33L that is developmentally regulated in heart. Unexpectedly, human exon 33L has a one-nucleotide insertion that allowed in-frame translation of a full Cav1.2 channel. An electrophysiological study showed that human Cav1.233L channel is a functional channel but conducts Ca(2+) ions at a much lower level.
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Affiliation(s)
- Ping Liao
- From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Duke-NUS Graduate Medical School Singapore, Singapore 169857,
| | - Dejie Yu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and
| | - Zhenyu Hu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and
| | - Mui Cheng Liang
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and
| | - Jue Jin Wang
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and
| | - Chye Yun Yu
- From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433
| | - Gandi Ng
- From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433
| | - Tan Fong Yong
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and
| | - Jia Lin Soon
- National Heart Centre Singapore, 5 Hospital Drive, Singapore 169609
| | - Yeow Leng Chua
- National Heart Centre Singapore, 5 Hospital Drive, Singapore 169609
| | - Tuck Wah Soong
- From the National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, and
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Kusch J, Zifarelli G. Patch-clamp fluorometry: electrophysiology meets fluorescence. Biophys J 2014; 106:1250-7. [PMID: 24655500 DOI: 10.1016/j.bpj.2014.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/23/2013] [Accepted: 02/06/2014] [Indexed: 12/26/2022] Open
Abstract
Ion channels and transporters are membrane proteins whose functions are driven by conformational changes. Classical biophysical techniques provide insight into either the structure or the function of these proteins, but a full understanding of their behavior requires a correlation of both these aspects in time. Patch-clamp and voltage-clamp fluorometry combine spectroscopic and electrophysiological techniques to simultaneously detect conformational changes and ionic currents across the membrane. Since its introduction, patch-clamp fluorometry has been responsible for invaluable advances in our knowledge of ion channel biophysics. Over the years, the technique has been applied to many different ion channel families to address several biophysical questions with a variety of spectroscopic approaches and electrophysiological configurations. This review illustrates the strength and the flexibility of patch-clamp fluorometry, demonstrating its potential as a tool for future research.
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Affiliation(s)
- Jana Kusch
- Universitätsklinikum Jena, Institut für Physiologie II, Jena, Germany.
| | - Giovanni Zifarelli
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy.
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Béziau DM, Barc J, O'Hara T, Le Gloan L, Amarouch MY, Solnon A, Pavin D, Lecointe S, Bouillet P, Gourraud JB, Guicheney P, Denjoy I, Redon R, Mabo P, le Marec H, Loussouarn G, Kyndt F, Schott JJ, Probst V, Baró I. Complex Brugada syndrome inheritance in a family harbouring compound SCN5A and CACNA1C mutations. Basic Res Cardiol 2014; 109:446. [PMID: 25341504 DOI: 10.1007/s00395-014-0446-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/19/2014] [Accepted: 10/09/2014] [Indexed: 12/19/2022]
Abstract
Brugada syndrome (BrS) is characterized by ST-segment elevation in the right precordial leads and is associated with increased risk of sudden cardiac death. We have recently reported families with BrS and SCN5A mutations where some affected members do not carry the familial mutation. We evaluated the involvement of additional genetic determinants for BrS in an affected family. We identified three distinct gene variants within a family presenting BrS (5 individuals), cardiac conduction defects (CCD, 3 individuals) and shortened QT interval (4 individuals). The first mutation is nonsense, p.Q1695*, lying within the SCN5A gene, which encodes for NaV1.5, the α-subunit of the cardiac Na(+) channel. The second mutation is missense, p.N300D, and alters the CACNA1C gene, which encodes the α-subunit CaV1.2 of the L-type cardiac Ca(2+) channel. The SCN5A mutation strictly segregates with CCD. Four out of the 5 BrS patients carry the CACNA1C variant, and three of them present shortened QT interval. One of the BrS patients carries none of these mutations but a rare variant located in the ABCC9 gene as well as his asymptomatic mother. Patch-clamp studies identified a loss-of-function of the mutated CaV1.2 channel. Western-blot experiments showed a global expression defect while increased mobility of CaV1.2 channels on cell surface was revealed by FRAP experiments. Finally, computer simulations of the two mutations recapitulated patient phenotypes. We report a rare CACNA1C mutation as causing BrS and/or shortened QT interval in a family also carrying a SCN5A stop mutation, but which does not segregate with BrS. This study underlies the complexity of BrS inheritance and its pre-symptomatic genetic screening interpretation.
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Affiliation(s)
- Delphine M Béziau
- INSERM, UMR 1087, l'institut du thorax, 8 Quai Moncousu, BP 70721, 44007, Nantes cedex 1, France
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Shao D, Zhao M, Xu J, Feng R, Guo F, Hu H, Sun X, Gao Q, He G, Sun W, Wang H, Yu L, Liu S, Zhu Y, Minobe E, Zhu T, Kameyama M, Hao L. The individual N- and C-lobes of calmodulin tether to the Cav1.2 channel and rescue the channel activity from run-down in ventricular myocytes of guinea-pig heart. FEBS Lett 2014; 588:3855-61. [DOI: 10.1016/j.febslet.2014.09.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 08/26/2014] [Accepted: 09/16/2014] [Indexed: 11/28/2022]
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Impaired functional communication between the L-type calcium channel and mitochondria contributes to metabolic inhibition in the mdx heart. Proc Natl Acad Sci U S A 2014; 111:E2905-14. [PMID: 24969422 DOI: 10.1073/pnas.1402544111] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Duchenne muscular dystrophy is a fatal X-linked disease characterized by the absence of dystrophin. Approximately 20% of boys will die of dilated cardiomyopathy that is associated with cytoskeletal protein disarray, contractile dysfunction, and reduced energy production. However, the mechanisms for altered energy metabolism are not yet fully clarified. Calcium influx through the L-type Ca(2+) channel is critical for maintaining cardiac excitation and contraction. The L-type Ca(2+) channel also regulates mitochondrial function and metabolic activity via transmission of movement of the auxiliary beta subunit through intermediate filament proteins. Here, we find that activation of the L-type Ca(2+) channel is unable to induce increases in mitochondrial membrane potential and metabolic activity in intact cardiac myocytes from the murine model of Duchenne muscular dystrophy (mdx) despite robust increases recorded in wt myocytes. Treatment of mdx mice with morpholino oligomers to induce exon skipping of dystrophin exon 23 (that results in functional dystrophin accumulation) or application of a peptide that resulted in block of voltage-dependent anion channel (VDAC) "rescued" mitochondrial membrane potential and metabolic activity in mdx myocytes. The mitochondrial VDAC coimmunoprecipitated with the L-type Ca(2+) channel. We conclude that the absence of dystrophin in the mdx ventricular myocyte leads to impaired functional communication between the L-type Ca(2+) channel and mitochondrial VDAC. This appears to contribute to metabolic inhibition. These findings provide new mechanistic and functional insight into cardiomyopathy associated with Duchenne muscular dystrophy.
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Wolf C, Mohr H, Schneider-Axmann T, Reif A, Wobrock T, Scherk H, Kraft S, Schmitt A, Falkai P, Gruber O. CACNA1C genotype explains interindividual differences in amygdala volume among patients with schizophrenia. Eur Arch Psychiatry Clin Neurosci 2014; 264:93-102. [PMID: 23880959 DOI: 10.1007/s00406-013-0427-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 07/08/2013] [Indexed: 12/13/2022]
Abstract
Affective deficits are one common denominator of schizophrenia (SZ), bipolar disorder (BD) and obsessive compulsive disorder (OCD) with the amygdala indicated as one of the major structures involved in emotion regulation. Previous findings of differences in amygdala volume between healthy controls and patients with SZ, BD or OCD diverge with respect to the affected hemisphere, size and direction of the effect. Variability in the CACNA1C gene has been linked to BD, SZ as well as structural and functional variation in the amygdala in healthy people and patients with BD. We were interested to investigate whether amygdala volumes differ between hemispheres, diagnostic or genotype groups, and whether any interactive effects exist. We combined genotyping of SNP rs1006737 in CACNA1C with structural MRI measurements of relative gray matter (GM) amygdala volume in patients with SZ, BD or OCD as well as healthy controls (N Total = 72). The CACNA1C genotype showed a significant effect on relative GM amygdala volume in patients with SZ. There was a significant left versus right relative GM amygdala volume decrease in patients with SZ or BD. The effects of hemisphere and diagnosis (controls vs. patients with SZ) on relative GM amygdala volume were genotype specific. Our data suggest that the CACNA1C genotype may account for some heterogeneity in the effects of hemisphere and diagnosis on amygdala volume when comparing patients with SZ and controls and point to disturbed Ca(2+)-signaling as a plausible mechanism contributing to the pathology in patients with SZ.
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Affiliation(s)
- Claudia Wolf
- Department of Psychiatry and Psychotherapy, Center for Translational Research in Systems Neuroscience and Psychiatry, Georg-August-University Göttingen, Von-Siebold-Str. 5, 37075, Göttingen, Germany,
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How does calcium regulate mitochondrial energetics in the heart? - new insights. Heart Lung Circ 2014; 23:602-9. [PMID: 24657282 DOI: 10.1016/j.hlc.2014.02.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 02/17/2014] [Indexed: 02/07/2023]
Abstract
Maintenance of cellular calcium homeostasis is critical to regulating mitochondrial ATP production and cardiac contraction. The ion channel known as the L-type calcium channel is the main route for calcium entry into cardiac myocytes. The channel associates with cytoskeletal proteins that assist with the communication of signals from the plasma membrane to intracellular organelles, including mitochondria. This article explores the roles of calcium and the cytoskeleton in regulation of mitochondrial function in response to alterations in L-type calcium channel activity. Direct activation of the L-type calcium channel results in an increase in intracellular calcium and increased mitochondrial calcium uptake. As a result, mitochondrial NADH production, oxygen consumption and reactive oxygen species production increase. In addition the L-type calcium channel is able to regulate mitochondrial membrane potential via cytoskeletal proteins when conformational changes in the channel occur during activation and inactivation. Since the L-type calcium channel is the initiator of contraction, a functional coupling between the channel and mitochondria via the cytoskeleton may represent a synchronised process by which mitochondrial function is regulated in addition to calcium influx to meet myocardial energy demand on a beat to beat basis.
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Simms BA, Souza IA, Zamponi GW. A novel calmodulin site in the Cav1.2 N-terminus regulates calcium-dependent inactivation. Pflugers Arch 2013; 466:1793-803. [DOI: 10.1007/s00424-013-1423-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 12/05/2013] [Accepted: 12/06/2013] [Indexed: 01/04/2023]
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Venom peptides as a rich source of cav2.2 channel blockers. Toxins (Basel) 2013; 5:286-314. [PMID: 23381143 PMCID: PMC3640536 DOI: 10.3390/toxins5020286] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 01/07/2013] [Accepted: 01/25/2013] [Indexed: 11/24/2022] Open
Abstract
Cav2.2 is a calcium channel subtype localized at nerve terminals, including nociceptive fibers, where it initiates neurotransmitter release. Cav2.2 is an important contributor to synaptic transmission in ascending pain pathways, and is up-regulated in the spinal cord in chronic pain states along with the auxiliary α2δ1 subunit. It is therefore not surprising that toxins that inhibit Cav2.2 are analgesic. Venomous animals, such as cone snails, spiders, snakes, assassin bugs, centipedes and scorpions are rich sources of remarkably potent and selective Cav2.2 inhibitors. However, side effects in humans currently limit their clinical use. Here we review Cav2.2 inhibitors from venoms and their potential as drug leads.
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Cav1.2, cell proliferation, and new target in atherosclerosis. ISRN BIOCHEMISTRY 2013; 2013:463527. [PMID: 25937960 PMCID: PMC4392978 DOI: 10.1155/2013/463527] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 03/20/2013] [Indexed: 11/18/2022]
Abstract
Cav1.2 calcium channels are the principal proteins involved in electrical, mechanical, and/or signaling functions of the cell. Cav1.2 couples membrane depolarization to the transient increase in intracellular Ca2+ concentration that is a trigger for muscle contraction and CREB-dependent transcriptional activation. The CACNA1C gene coding for the Cav1.2 pore-forming α1C subunit is subject to extensive alternative splicing. This review is the first attempt to follow the association between cell proliferation, Cav1.2 expression and splice variation, and atherosclerosis. Based on insights into the association between the atherosclerosis-induced molecular remodeling of Cav1.2, proliferation of vascular smooth muscle cells, and CREB-dependent transcriptional signaling, this review will give a perspective outlook for the use of the CACNA1C exon skipping as a new potential gene therapy approach to atherosclerosis.
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Soldatov NM. Molecular Determinants of Cav1.2 Calcium Channel Inactivation. ISRN MOLECULAR BIOLOGY 2012; 2012:691341. [PMID: 27335667 PMCID: PMC4890872 DOI: 10.5402/2012/691341] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 09/13/2012] [Indexed: 12/13/2022]
Abstract
Voltage-gated L-type Cav1.2 calcium channels couple membrane depolarization to transient increase in cytoplasmic free Ca2+ concentration that initiates a number of essential cellular functions including cardiac and vascular muscle contraction, gene expression, neuronal plasticity, and exocytosis. Inactivation or spontaneous termination of the calcium current through Cav1.2 is a critical step in regulation of these processes. The pathophysiological significance of this process is manifested in hypertension, heart failure, arrhythmia, and a number of other diseases where acceleration of the calcium current decay should present a benefit function. The central issue of this paper is the inactivation of the Cav1.2 calcium channel mediated by multiple determinants.
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Buraei Z, Yang J. Structure and function of the β subunit of voltage-gated Ca²⁺ channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1530-40. [PMID: 22981275 DOI: 10.1016/j.bbamem.2012.08.028] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 08/22/2012] [Accepted: 08/25/2012] [Indexed: 12/31/2022]
Abstract
The voltage-gated Ca²⁺ channel β subunit (Ca(v)β) is a cytosolic auxiliary subunit that plays an essential role in regulating the surface expression and gating properties of high-voltage activated (HVA) Ca²⁺ channels. It is also crucial for the modulation of HVA Ca²⁺ channels by G proteins, kinases, Ras-related RGK GTPases, and other proteins. There are indications that Ca(v)β may carry out Ca²⁺ channel-independent functions. Ca(v)β knockouts are either non-viable or result in a severe pathophysiology, and mutations in Ca(v)β have been implicated in disease. In this article, we review the structure and various biological functions of Ca(v)β, as well as recent advances. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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Kobrinsky E, Lee JH, Soldatov NM. Selective fluorophore-assisted light inactivation of voltage-gated calcium channels. Channels (Austin) 2012; 6:154-6. [PMID: 22909954 PMCID: PMC3431587 DOI: 10.4161/chan.20867] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Fluorophore-assisted light inactivation (FALI) is an investigative tool to inactivate fluorescently labeled proteins by a mechanism of in situ photodestruction. We found that Ca(v)1.2 (L-type) and Ca(v)3.1 (T-type) calcium channels, labeled by genetic fusion with GFP derivatives, show differential sensitivity to FALI. Specifically, FALI silences Ca(v)1.2 calcium channels containing EYFP-labeled α(1C)subunits but does not affect the EYFP-α(1G) Ca(v)3.1 calcium channels or Ca(v)1.2 channels containing EYFP-labeled β subunits. Our findings limit the applicability of acceptor photobleaching for the measurements of FRET but open an opportunity to combine the fluorescent imaging of the live cell expressing labeled calcium channels with selective functional inactivation of their specific subsets.
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Affiliation(s)
- Evgeny Kobrinsky
- National Institute on Aging; National Institutes of Health; Baltimore, MD USA
| | - Jung-Ha Lee
- Department of Life Science; Sogang University; Seoul, South Korea
| | - Nikolai M. Soldatov
- National Institute on Aging; National Institutes of Health; Baltimore, MD USA
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Simms BA, Zamponi GW. The Brugada syndrome mutation A39V does not affect surface expression of neuronal rat Cav1.2 channels. Mol Brain 2012; 5:9. [PMID: 22385640 PMCID: PMC3307476 DOI: 10.1186/1756-6606-5-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 03/02/2012] [Indexed: 11/19/2022] Open
Abstract
Background A loss of function of the L-type calcium channel, Cav1.2, results in a cardiac specific disease known as Brugada syndrome. Although many Brugada syndrome channelopathies reduce channel function, one point mutation in the N-terminus of Cav1.2 (A39V) has been shown to elicit disease a phenotype because of a loss of surface trafficking of the channel. This lack of cell membrane expression could not be rescued by the trafficking chaperone Cavβ. Findings We report that despite the striking loss of trafficking described previously in the cardiac Cav1.2 channel, the A39V mutation while in the background of the brain isoform traffics and functions normally. We detected no differences in biophysical properties between wild type Cav1.2 and A39V-Cav1.2 in the presence of either a cardiac (Cavβ2b), or a neuronal beta subunit (Cavβ1b). In addition, the A39V-Cav1.2 mutant showed a normal Cavβ2b mediated increase in surface expression in tsA-201 cells. Conclusions The Brugada syndrome mutation A39V when introduced into rat brain Cav1.2 does not trigger the loss-of-trafficking phenotype seen in a previous study on the human heart isoform of the channel.
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Affiliation(s)
- Brett A Simms
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
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Simms BA, Zamponi GW. Trafficking and stability of voltage-gated calcium channels. Cell Mol Life Sci 2012; 69:843-56. [PMID: 21964928 PMCID: PMC11115007 DOI: 10.1007/s00018-011-0843-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 02/07/2023]
Abstract
Voltage-gated calcium channels are important mediators of calcium influx into electrically excitable cells. The amount of calcium entering through this family of channel proteins is not only determined by the functional properties of channels embedded in the plasma membrane but also by the numbers of channels that are expressed at the cell surface. The trafficking of channels is controlled by numerous processes, including co-assembly with ancillary calcium channel subunits, ubiquitin ligases, and interactions with other membrane proteins such as G protein coupled receptors. Here we provide an overview about the current state of knowledge of calcium channel trafficking to the cell membrane, and of the mechanisms regulating the stability and internalization of this important ion channel family.
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Affiliation(s)
- Brett A. Simms
- Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1 Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1 Canada
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Domes K, Ding J, Lemke T, Blaich A, Wegener JW, Brandmayr J, Moosmang S, Hofmann F. Truncation of murine CaV1.2 at Asp-1904 results in heart failure after birth. J Biol Chem 2011; 286:33863-71. [PMID: 21832054 DOI: 10.1074/jbc.m111.252312] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The carboxyl-terminal intracellular tail of the L-type Ca(2+) channel CaV1.2 modulates various aspects of channel activity.For example, deletion of the carboxyl-terminal sequence at Ser-1905 increased CaV1.2 currents in an expression model. To verify this finding in an animal model, we inserted three stop codons at the corresponding Asp-1904 in the murine CaV1.2 gene. Mice homozygous for the Stop mutation (Stop/Stop mice)were born at a Mendelian ratio but died after birth. Stop/Stop hearts showed reduced beating frequencies and contractions.Surprisingly, Stop/Stop cardiomyocytes displayed reduced IBa and a minor expression of the CaV1.2Stop protein. In contrast,expression of the CaV1.2Stop protein was normal in pooled smooth muscle samples from Stop/Stop embryos. As the CaV1.2 channel exists in a cardiac and smooth muscle splice variant, HK1 and LK1, respectively, we analyzed the consequences of the deletion of the carboxyl terminus in the respective splice variant using the rabbit CaV1.2 clone expressed in HEK293 cells.HEK293 cells transfected with the HK1Stop channel showed a reduced IBa and CaV1.2 expression. Treatment with proteasome inhibitors increased the expression of HK1Stop protein and IBa in HEK293 cells and in Stop/Stop cardiomyocytes indicating that truncation of CaV1.2 containing the cardiac exon 1a amino terminus results in proteasomal degradation of the translated protein. In contrast, HEK293 cells transfected with the LK1Stop channel had normal IBa and CaV1.2 expression. These findings indicate that absence of the carboxyl-terminal tail differentially determines the fate of the cardiac and smooth muscle splice variant of the CaV1.2 channel in the mouse.
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Affiliation(s)
- Katrin Domes
- From the Forschergruppe 923, Institut für Pharmakologie und Toxikologie, Technische Universität München, Biedersteiner Strasse 29, 80802 München, Germany
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Napolitano C, Antzelevitch C. Phenotypical manifestations of mutations in the genes encoding subunits of the cardiac voltage-dependent L-type calcium channel. Circ Res 2011; 108:607-18. [PMID: 21372292 DOI: 10.1161/circresaha.110.224279] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The L-type cardiac calcium channel (LTCC) plays a prominent role in the electric and mechanical function of the heart. Mutations in the LTCC have been associated with a number of inherited cardiac arrhythmia syndromes, including Timothy, Brugada, and early repolarization syndromes. Elucidation of the genetic defects associated with these syndromes has led to a better understanding of molecular and cellular mechanisms and the development of novel therapeutic approaches to dealing with the arrhythmic manifestations. This review provides an overview of the molecular structure and function of the LTCC, the genetic defects in these channels known to contribute to inherited disorders, and the underlying molecular and cellular mechanisms contributing to the development of life-threatening arrhythmias.
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Affiliation(s)
- Carlo Napolitano
- Executive Director and Director of Research, Gordon K. Moe Scholar, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501, USA.
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22
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Oz S, Tsemakhovich V, Christel CJ, Lee A, Dascal N. CaBP1 regulates voltage-dependent inactivation and activation of Ca(V)1.2 (L-type) calcium channels. J Biol Chem 2011; 286:13945-53. [PMID: 21383011 DOI: 10.1074/jbc.m110.198424] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
CaBP1 is a Ca(2+)-binding protein that regulates the gating of voltage-gated (Ca(V)) Ca(2+) channels. In the Ca(V)1.2 channel α(1)-subunit (α(1C)), CaBP1 interacts with cytosolic N- and C-terminal domains and blunts Ca(2+)-dependent inactivation. To clarify the role of the α(1C) N-terminal domain in CaBP1 regulation, we compared the effects of CaBP1 on two alternatively spliced variants of α(1C) containing a long or short N-terminal domain. In both isoforms, CaBP1 inhibited Ca(2+)-dependent inactivation but also caused a depolarizing shift in voltage-dependent activation and enhanced voltage-dependent inactivation (VDI). In binding assays, CaBP1 interacted with the distal third of the N-terminal domain in a Ca(2+)-independent manner. This segment is distinct from the previously identified calmodulin-binding site in the N terminus. However, deletion of a segment in the proximal N-terminal domain of both α(1C) isoforms, which spared the CaBP1-binding site, inhibited the effect of CaBP1 on VDI. This result suggests a modular organization of the α(1C) N-terminal domain, with separate determinants for CaBP1 binding and transduction of the effect on VDI. Our findings expand the diversity and mechanisms of Ca(V) channel regulation by CaBP1 and define a novel modulatory function for the initial segment of the N terminus of α(1C).
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Affiliation(s)
- Shimrit Oz
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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23
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Satin J, Schroder EA, Crump SM. L-type calcium channel auto-regulation of transcription. Cell Calcium 2011; 49:306-13. [PMID: 21295347 DOI: 10.1016/j.ceca.2011.01.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/06/2011] [Accepted: 01/07/2011] [Indexed: 01/24/2023]
Abstract
L-type calcium channels (LTCC) impact the function of nearly all excitable cells. The classical LTCC function is to mediate trans-sarcolemmal Ca(2+) flux. This review focuses on the contribution of a mobile segment of the LTCC that regulates ion channel function, and also serves as a regulator of transcription in the nucleus. Specifically we highlight recent work demonstrating an auto-feedback regulatory pathway whereby the LTCC transcription factor regulates the LTCC. Also discussed is acute and long-term regulation of function by the LTCC-transcription regulator.
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Affiliation(s)
- Jonathan Satin
- Department of Physiology, MS-508, University of Kentucky College of Medicine, 800 Rose Street, Lexington, KY 40536-0298, USA.
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24
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Abstract
Calcium regulates a wide spectrum of physiological processes such as heartbeat, muscle contraction, neuronal communication, hormone release, cell division, and gene transcription. Major entryways for Ca(2+) in excitable cells are high-voltage activated (HVA) Ca(2+) channels. These are plasma membrane proteins composed of several subunits, including α(1), α(2)δ, β, and γ. Although the principal α(1) subunit (Ca(v)α(1)) contains the channel pore, gating machinery and most drug binding sites, the cytosolic auxiliary β subunit (Ca(v)β) plays an essential role in regulating the surface expression and gating properties of HVA Ca(2+) channels. Ca(v)β is also crucial for the modulation of HVA Ca(2+) channels by G proteins, kinases, and the Ras-related RGK GTPases. New proteins have emerged in recent years that modulate HVA Ca(2+) channels by binding to Ca(v)β. There are also indications that Ca(v)β may carry out Ca(2+) channel-independent functions, including directly regulating gene transcription. All four subtypes of Ca(v)β, encoded by different genes, have a modular organization, consisting of three variable regions, a conserved guanylate kinase (GK) domain, and a conserved Src-homology 3 (SH3) domain, placing them into the membrane-associated guanylate kinase (MAGUK) protein family. Crystal structures of Ca(v)βs reveal how they interact with Ca(v)α(1), open new research avenues, and prompt new inquiries. In this article, we review the structure and various biological functions of Ca(v)β, with both a historical perspective as well as an emphasis on recent advances.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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25
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Mutations in the cardiac L-type calcium channel associated with inherited J-wave syndromes and sudden cardiac death. Heart Rhythm 2010; 7:1872-82. [PMID: 20817017 DOI: 10.1016/j.hrthm.2010.08.026] [Citation(s) in RCA: 296] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 08/30/2010] [Indexed: 12/15/2022]
Abstract
BACKGROUND L-type calcium channel (LTCC) mutations have been associated with Brugada syndrome (BrS), short QT (SQT) syndrome, and Timothy syndrome (LQT8). Little is known about the extent to which LTCC mutations contribute to the J-wave syndromes associated with sudden cardiac death. OBJECTIVE The purpose of this study was to identify mutations in the α1, β2, and α2δ subunits of LTCC (Ca(v)1.2) among 205 probands diagnosed with BrS, idiopathic ventricular fibrillation (IVF), and early repolarization syndrome (ERS). CACNA1C, CACNB2b, and CACNA2D1 genes of 162 probands with BrS and BrS+SQT, 19 with IVF, and 24 with ERS were screened by direct sequencing. METHODS/RESULTS Overall, 23 distinct mutations were identified. A total of 12.3%, 5.2%, and 16% of BrS/BrS+SQT, IVF, and ERS probands displayed mutations in α1, β2, and α2δ subunits of LTCC, respectively. When rare polymorphisms were included, the yield increased to 17.9%, 21%, and 29.1% for BrS/BrS+SQT, IVF, and ERS probands, respectively. Functional expression of two CACNA1C mutations associated with BrS and BrS+SQT led to loss of function in calcium channel current. BrS probands displaying a normal QTc had additional variations known to prolong the QT interval. CONCLUSION The study results indicate that mutations in the LTCCs are detected in a high percentage of probands with J-wave syndromes associated with inherited cardiac arrhythmias, suggesting that genetic screening of Ca(v) genes may be a valuable diagnostic tool in identifying individuals at risk. These results are the first to identify CACNA2D1 as a novel BrS susceptibility gene and CACNA1C, CACNB2, and CACNA2D1 as possible novel ERS susceptibility genes.
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Teng J, Iida K, Ito M, Izumi-Nakaseko H, Kojima I, Adachi-Akahane S, Iida H. Role of glycine residues highly conserved in the S2-S3 linkers of domains I and II of voltage-gated calcium channel alpha(1) subunits. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:966-74. [PMID: 20067760 DOI: 10.1016/j.bbamem.2010.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Revised: 12/19/2009] [Accepted: 01/04/2010] [Indexed: 11/24/2022]
Abstract
The pore-forming component of voltage-gated calcium channels, alpha(1) subunit, contains four structurally conserved domains (I-IV), each of which contains six transmembrane segments (S1-S6). We have shown previously that a Gly residue in the S2-S3 linker of domain III is completely conserved from yeasts to humans and important for channel activity. The Gly residues in the S2-S3 linkers of domains I and II, which correspond positionally to the Gly in the S2-S3 linker of domain III, are also highly conserved. Here, we investigated the role of the Gly residues in the S2-S3 linkers of domains I and II of Ca(v)1.2. Each of the Gly residues was replaced with Glu or Gln to produce mutant Ca(v)1.2s; G182E, G182Q, G579E, G579Q, and the resulting mutants were transfected into BHK6 cells. Whole-cell patch-clamp recordings showed that current-voltage relationships of the four mutants were the same as those of wild-type Ca(v)1.2. However, G182E and G182Q showed significantly smaller current densities because of mislocalization of the mutant proteins, suggesting that Gly(182) in domain I is involved in the membrane trafficking or surface expression of alpha(1) subunit. On the other hand, G579E showed a slower voltage-dependent current inactivation (VDI) compared to Ca(v)1.2, although G579Q showed a normal VDI, implying that Gly(579) in domain II is involved in the regulation of VDI and that the incorporation of a negative charge alters the VDI kinetics. Our findings indicate that the two conserved Gly residues are important for alpha(1) subunit to become functional.
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Affiliation(s)
- Jinfeng Teng
- Department of Biology, Tokyo Gakugei University, 4-1-1 Nukui kita-machi, Koganei-shi, Tokyo 184-8501, Japan
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Cell Cycle-Dependent Localization of Voltage-Dependent Calcium Channels and the Mitotic Apparatus in a Neuroendocrine Cell Line(AtT-20). Int J Cell Biol 2010; 2009:487959. [PMID: 20130814 PMCID: PMC2814229 DOI: 10.1155/2009/487959] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 07/13/2009] [Accepted: 10/10/2009] [Indexed: 12/15/2022] Open
Abstract
Changes in intracellular calcium are necessary for the successful progression of mitosis in many cells. Both elevation and reduction in intracellular calcium can disrupt mitosis by mechanisms that remain ill defined. In this study we explore the role of transmembrane voltage-gated calcium channels (CaV channels) as regulators of mitosis in the mouse corticotroph cell line (AtT-20). We report that the nifedipine-sensitive isoform CaV1.2 is localized to the "poleward side" of kinetechores during metaphase and at the midbody during cytokinesis. A second nifedipine-sensitive isoform, CaV1.3, is present at the mid-spindle zone in telophase, but is also seen at the midbody. Nifedipine reduces the rate of cell proliferation, and, utilizing time-lapse microscopy, we show that this is due to a block at the prometaphase stage of the cell cycle. Using Fluo-4 we detect calcium fluxes at sites corresponding to the mid-spindle zone and the midbody region. Another calcium dye, Fura PE3/AM, causes an inhibition of mitosis prior to anaphase that we attribute to a chelation of intracellular calcium. Our results demonstrate a novel, isoform-specific localization of CaV1 channels during cell division and suggest a possible role for these channels in the calcium-dependent events underlying mitotic progression in pituitary corticotrophs.
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Abstract
1. Calcium is necessary for myocardial function, including contraction and maintenance of cardiac output. Calcium is also necessary for myocardial energetics and production of ATP by mitochondria, but the mechanisms for calcium regulation by mitochondria are still not fully resolved. 2. The cytoskeleton plays an important role in maintaining a cell's integrity. It is now recognized that cytoskeletal proteins can also assist in the transmission of signals from the plasma membrane to intracellular organelles. Cytoskeletal proteins can regulate the function of the L-type Ca(2+) channel and alter intracellular calcium homeostasis. 3. Recent evidence suggests that calcium influx through the L-type Ca(2+) channel is sufficient to alter a number of mitochondrial functional parameters, including superoxide production, NADH production and metabolic activity, assessed as the formation of formazan from tetrazolium salt. This occurs in a calcium-dependent manner. 4. Activation of the L-type Ca(2+) channel also alters mitochondrial membrane potential in a calcium-independent manner and this is assisted by movement of the auxiliary beta(2)-subunit through F-actin filaments. 5. Because the L-type Ca(2+) channel is the initiator of contraction, a functional coupling between the channels and mitochondria may assist in meeting myocardial energy demand on a beat-to-beat basis.
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Affiliation(s)
- Helena M Viola
- Cardiovascular Electrophysiology Laboratory, School of Biomedical Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, Australia
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Benitah JP, Alvarez JL, Gómez AM. L-type Ca(2+) current in ventricular cardiomyocytes. J Mol Cell Cardiol 2009; 48:26-36. [PMID: 19660468 DOI: 10.1016/j.yjmcc.2009.07.026] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 07/09/2009] [Accepted: 07/27/2009] [Indexed: 12/24/2022]
Abstract
L-type Ca(2+) channels are mediators of Ca(2+) influx and the regulatory events accompanying it and are pivotal in the function and dysfunction of ventricular cardiac myocytes. L-type Ca(2+) channels are located in sarcolemma, including the T-tubules facing the sarcoplasmic reticulum junction, and are activated by membrane depolarization, but intracellular Ca(2+)-dependent inactivation limits Ca(2+) influx during action potential. I(CaL) is important in heart function because it triggers excitation-contraction coupling, modulates action potential shape and is involved in cardiac arrhythmia. L-type Ca(2+) channels are multi-subunit complexes that interact with several molecules involved in their regulations, notably by beta-adrenergic signaling. The present review highlights some of the recent findings on L-type Ca(2+) channel function, regulation, and alteration in acquired pathologies such as cardiac hypertrophy, heart failure and diabetic cardiomyopathy, as well as in inherited arrhythmic cardiac diseases such as Timothy and Brugada syndromes.
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Kobrinsky E, Abrahimi P, Duong SQ, Thomas S, Harry JB, Patel C, Lao QZ, Soldatov NM. Effect of Ca(v)beta subunits on structural organization of Ca(v)1.2 calcium channels. PLoS One 2009; 4:e5587. [PMID: 19492014 PMCID: PMC2688388 DOI: 10.1371/journal.pone.0005587] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Accepted: 04/18/2009] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Voltage-gated Ca(v)1.2 calcium channels play a crucial role in Ca(2+) signaling. The pore-forming alpha(1C) subunit is regulated by accessory Ca(v)beta subunits, cytoplasmic proteins of various size encoded by four different genes (Ca(v)beta(1)-beta(4)) and expressed in a tissue-specific manner. METHODS AND RESULTS Here we investigated the effect of three major Ca(v)beta types, beta(1b), beta(2d) and beta(3), on the structure of Ca(v)1.2 in the plasma membrane of live cells. Total internal reflection fluorescence microscopy showed that the tendency of Ca(v)1.2 to form clusters depends on the type of the Ca(v)beta subunit present. The highest density of Ca(v)1.2 clusters in the plasma membrane and the smallest cluster size were observed with neuronal/cardiac beta(1b) present. Ca(v)1.2 channels containing beta(3), the predominant Ca(v)beta subunit of vascular smooth muscle cells, were organized in a significantly smaller number of larger clusters. The inter- and intramolecular distances between alpha(1C) and Ca(v)beta in the plasma membrane of live cells were measured by three-color FRET microscopy. The results confirm that the proximity of Ca(v)1.2 channels in the plasma membrane depends on the Ca(v)beta type. The presence of different Ca(v)beta subunits does not result in significant differences in the intramolecular distance between the termini of alpha(1C), but significantly affects the distance between the termini of neighbor alpha(1C) subunits, which varies from 67 A with beta(1b) to 79 A with beta(3). CONCLUSIONS Thus, our results show that the structural organization of Ca(v)1.2 channels in the plasma membrane depends on the type of Ca(v)beta subunits present.
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Affiliation(s)
- Evgeny Kobrinsky
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Parwiz Abrahimi
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Son Q. Duong
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Sam Thomas
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Jo Beth Harry
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Chirag Patel
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Qi Zong Lao
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Nikolai M. Soldatov
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
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Findeisen F, Minor DL. Disruption of the IS6-AID linker affects voltage-gated calcium channel inactivation and facilitation. ACTA ACUST UNITED AC 2009; 133:327-43. [PMID: 19237593 PMCID: PMC2654080 DOI: 10.1085/jgp.200810143] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Two processes dominate voltage-gated calcium channel (CaV) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The CaVβ/CaVα1-I-II loop and Ca2+/calmodulin (CaM)/CaVα1–C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6–α-interaction domain (AID) linker provides a rigid connection between the pore and CaVβ/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate CaV1.2 (L-type) and CaV2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt CaVβ/I-II association sharply decelerate CDI and reduce a second Ca2+/CaM/CaVα1–C-terminal–mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, CaVβ and the IS6-AID linker, are essential for calcium-dependent modulation, and that both CaVβ-dependent and CaM-dependent components couple to the pore by a common mechanism requiring CaVβ and an intact IS6-AID linker.
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Affiliation(s)
- Felix Findeisen
- Cardiovascular Research Institute, Department of Biochemistry and Biophysics, California Institute for Quantitative Biosciences, University of California, San Francisco, CA 94158, USA
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Catalucci D, Zhang DH, DeSantiago J, Aimond F, Barbara G, Chemin J, Bonci D, Picht E, Rusconi F, Dalton ND, Peterson KL, Richard S, Bers DM, Brown JH, Condorelli G. Akt regulates L-type Ca2+ channel activity by modulating Cavalpha1 protein stability. ACTA ACUST UNITED AC 2009; 184:923-33. [PMID: 19307602 PMCID: PMC2699149 DOI: 10.1083/jcb.200805063] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The insulin IGF-1–PI3K–Akt signaling pathway has been suggested to
improve cardiac inotropism and increase Ca2+ handling through
the effects of the protein kinase Akt. However, the underlying molecular
mechanisms remain largely unknown. In this study, we provide evidence for an
unanticipated regulatory function of Akt controlling L-type Ca2+
channel (LTCC) protein density. The pore-forming channel subunit
Cavα1 contains highly conserved PEST sequences (signals for
rapid protein degradation), and in-frame deletion of these PEST sequences
results in increased Cavα1 protein levels. Our findings show
that Akt-dependent phosphorylation of Cavβ2, the LTCC chaperone
for Cavα1, antagonizes Cavα1 protein
degradation by preventing Cavα1 PEST sequence recognition,
leading to increased LTCC density and the consequent modulation of
Ca2+ channel function. This novel mechanism by which Akt
modulates LTCC stability could profoundly influence cardiac myocyte
Ca2+ entry, Ca2+ handling, and
contractility.
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Affiliation(s)
- Daniele Catalucci
- Division of Cardiology, Department of Medicine, University of California-San Diego, La Jolla, CA 92093, USA.
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Viola HM, Arthur PG, Hool LC. Evidence for regulation of mitochondrial function by the L-type Ca2+ channel in ventricular myocytes. J Mol Cell Cardiol 2009; 46:1016-26. [PMID: 19166857 DOI: 10.1016/j.yjmcc.2008.12.015] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 12/12/2008] [Accepted: 12/16/2008] [Indexed: 10/21/2022]
Abstract
The L-type Ca(2+) channel is responsible for initiating contraction in the heart. Mitochondria are responsible for meeting the cellular energy demands and calcium is required for the activity of metabolic intermediates. We examined whether activation of the L-type Ca(2+) channel alone is sufficient to alter mitochondrial function. The channel was activated directly with the dihydropyridine agonist BayK(-) or voltage-clamp of the plasma membrane and indirectly by depolarization of the membrane with high KCl. Activation of the channel increased superoxide production (assessed as changes in dihydroethidium fluorescence), NADH production and metabolic activity (assessed as formation of formazan from tetrazolium) in a calcium-dependent manner. Activation of the channel also increased mitochondrial membrane potential assessed as changes in JC-1 fluorescence. The response was reversible upon inactivation of the channel during voltage-clamp of the plasma membrane and did not appear to require calcium. We examined whether the response may be mediated through movement of cytoskeletal proteins. Depolymerization of actin or exposing cells to a peptide directed against the alpha-interacting domain of the alpha(1C)-subunit of the channel (thereby preventing movement of the beta-subunit) attenuated the increase in mitochondrial membrane potential. We conclude that activation of the L-type Ca(2+) channel can regulate mitochondrial function and the response appears to be modulated by movement through the cytoskeleton.
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Affiliation(s)
- Helena M Viola
- School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, Australia
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Hool LC. The L-type Ca(2+) channel as a potential mediator of pathology during alterations in cellular redox state. Heart Lung Circ 2008; 18:3-10. [PMID: 19119068 DOI: 10.1016/j.hlc.2008.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The L-type Ca(2+) channel is the main route for calcium influx into cardiac myocytes and an important determinant of calcium homeostasis. There is now considerable evidence that the function of the L-type Ca(2+) channel is influenced by the cell's redox state. Reactive oxygen species such as hydrogen peroxide and superoxide can regulate biological function by directly altering the thiol redox state of proteins. Under conditions where cellular redox state varies, L-type Ca(2+) channel function and diastolic calcium levels can be significantly altered. This article will present the evidence for alterations in L-type Ca(2+) channel function by reactive oxygen species and the potential role for the channel in development of acute electrophysiological instability or chronic pathological remodelling under conditions of persistent oxidative stress.
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Affiliation(s)
- Livia C Hool
- School of Biomedical, Biomolecular and Chemical Sciences and The Western Australian Institute for Medical Research, The University of Western Australia, Crawley, Western Australia, Australia.
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35
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Lao QZ, Kobrinsky E, Harry JB, Ravindran A, Soldatov NM. New Determinant for the CaVbeta2 subunit modulation of the CaV1.2 calcium channel. J Biol Chem 2008; 283:15577-88. [PMID: 18411278 PMCID: PMC2414265 DOI: 10.1074/jbc.m802035200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Indexed: 11/06/2022] Open
Abstract
Ca(v)beta subunits support voltage gating of Ca(v)1.2 calcium channels and play important role in excitation-contraction coupling. The common central membrane-associated guanylate kinase (MAGUK) region of Ca(v)beta binds to the alpha-interaction domain (AID) and the IQ motif of the pore-forming alpha(1C) subunit, but these two interactions do not explain why the cardiac Ca(v)beta(2) subunit splice variants differentially modulate inactivation of Ca(2+) currents (I(Ca)). Previously we described beta(2Deltag), a functionally active splice variant of human Ca(v)beta(2) lacking MAGUK. By deletion analysis of beta(2Deltag), we have now identified a 41-amino acid C-terminal essential determinant (beta(2)CED) that stimulates I(Ca) in the absence of Ca(v)beta subunits and conveys a +20-mV shift in the peak of the I(Ca)-voltage relationship. The beta(2)CED is targeted by alpha(1C) to the plasma membrane, forms a complex with alpha(1C) but does not bind to AID. Electrophysiology and binding studies point to the calmodulin-interacting LA/IQ region in the alpha(1C) subunit C terminus as a functionally relevant beta(2)CED binding site. The beta(2)CED interacts with LA/IQ in a Ca(2+)- and calmodulin-independent manner and need LA, but not IQ, to activate the channel. Deletion/mutation analyses indicated that each of the three Ca(v)beta(2)/alpha(1C) interactions is sufficient to support I(Ca). However, beta(2)CED does not support Ca(2+)-dependent inactivation, suggesting that interactions of MAGUK with AID and IQ are crucial for Ca(2+)-induced inactivation. The beta(2)CED is conserved only in Ca(v)beta(2) subunits. Thus, beta(2)CED constitutes a previously unknown integrative part of the multifactorial mechanism of Ca(v)beta(2)-subunit differential modulation of the Ca(v)1.2 calcium channel that in beta(2Deltag) occurs without MAGUK.
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Calmodulin-dependent gating of Ca(v)1.2 calcium channels in the absence of Ca(v)beta subunits. Proc Natl Acad Sci U S A 2008; 105:8154-9. [PMID: 18535142 DOI: 10.1073/pnas.0711624105] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It is generally accepted that to generate calcium currents in response to depolarization, Ca(v)1.2 calcium channels require association of the pore-forming alpha(1C) subunit with accessory Ca(v)beta and alpha(2)delta subunits. A single calmodulin (CaM) molecule is tethered to the C-terminal alpha(1C)-LA/IQ region and mediates Ca2+-dependent inactivation of the channel. Ca(v)beta subunits are stably associated with the alpha(1C)-interaction domain site of the cytoplasmic linker between internal repeats I and II and also interact dynamically, in a Ca2+-dependent manner, with the alpha(1C)-IQ region. Here, we describe a surprising discovery that coexpression of exogenous CaM (CaM(ex)) with alpha(1C)/alpha(2)delta in COS1 cells in the absence of Ca(v)beta subunits stimulates the plasma membrane targeting of alpha(1C), facilitates calcium channel gating, and supports Ca2+-dependent inactivation. Neither real-time PCR with primers complementary to monkey Ca(v)beta subunits nor coimmunoprecipitation analysis with exogenous alpha(1C) revealed an induction of endogenous Ca(v)beta subunits that could be linked to the effect of CaM(ex). Coexpression of a calcium-insensitive CaM mutant CaM(1234) also facilitated gating of Ca(v)beta-free Ca(v)1.2 channels but did not support Ca2+-dependent inactivation. Our results show there is a functional matchup between CaM(ex) and Ca(v)beta subunits that, in the absence of Ca(v)beta, renders Ca2+ channel gating facilitated by CaM molecules other than the one tethered to LA/IQ to support Ca2+-dependent inactivation. Thus, coexpression of CaM(ex) creates conditions when the channel gating, voltage- and Ca2+-dependent inactivation, and plasma-membrane targeting occur in the absence of Ca(v)beta. We suggest that CaM(ex) affects specific Ca(v)beta-free conformations of the channel that are not available to endogenous CaM.
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37
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Morad M, Soldatov N. Calcium channel inactivation: possible role in signal transduction and Ca2+ signaling. Cell Calcium 2008; 38:223-31. [PMID: 16098584 DOI: 10.1016/j.ceca.2005.06.027] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 10/25/2022]
Abstract
Voltage gated Ca2+ channels are major routes for the entry of intracellular Ca2+ coupled to membrane depolarization that appear to vary greatly with respect to their voltage dependence and kinetics. Such variability maybe in part related to the attached signaling properties of the channel, in addition to the transport of calcium. In the present review we consider the possible role of calcium-dependent inactivation of Cav1.2 in Ca2+ signal transduction and signaling of calcium release from the cardiac sarcoplasmic reticulum. We explore the specific roles of Ca2+-sensing calmodulin-binding domains of the C-terminal tail (LA and K) of the channel in mediating Ca2+-induced Ca2+ release and signal transduction. Our experiments point to an intriguing possibility that the C-terminal tail of Cav1.2 may translocate the Ca2+ signal as a part of inactivation mechanism and the corresponding voltage-gated rearrangement of the C-terminus. We show how a dynamic and transient regulation, in a Ca2+-dependent manner, defines molecular events including Ca2+ release and signaling of cAMP-responsive element-binding protein (CREB)-dependent transcription. We propose that such Ca2+-dependent C-tail translocation that also initiates the channel inactivation, may have evolved specifically for the Cav1.2 channel.
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Affiliation(s)
- Martin Morad
- Department of Pharmacology, Georgetown University Medical Center, 3900 Reservoir Road NW, Washington, DC 20057, USA.
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38
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Cheng X, Liu J, Asuncion-Chin M, Blaskova E, Bannister JP, Dopico AM, Jaggar JH. A novel Ca(V)1.2 N terminus expressed in smooth muscle cells of resistance size arteries modifies channel regulation by auxiliary subunits. J Biol Chem 2007; 282:29211-21. [PMID: 17699517 PMCID: PMC2276565 DOI: 10.1074/jbc.m610623200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-dependent L-type Ca(2+) (Ca(V)1.2) channels are the principal Ca(2+) entry pathway in arterial myocytes. Ca(V)1.2 channels regulate multiple vascular functions and are implicated in the pathogenesis of human disease, including hypertension. However, the molecular identity of Ca(V)1.2 channels expressed in myocytes of myogenic arteries that regulate vascular pressure and blood flow is unknown. Here, we cloned Ca(V)1.2 subunits from resistance size cerebral arteries and demonstrate that myocytes contain a novel, cysteine rich N terminus that is derived from exon 1 (termed "exon 1c"), which is located within CACNA1C, the Ca(V)1.2 gene. Quantitative PCR revealed that exon 1c was predominant in arterial myocytes, but rare in cardiac myocytes, where exon 1a prevailed. When co-expressed with alpha(2)delta subunits, Ca(V)1.2 channels containing the novel exon 1c-derived N terminus exhibited: 1) smaller whole cell current density, 2) more negative voltages of half activation (V(1/2,act)) and half-inactivation (V(1/2,inact)), and 3) reduced plasma membrane insertion, when compared with channels containing exon 1b. beta(1b) and beta(2a) subunits caused negative shifts in the V(1/2,act) and V(1/2,inact) of exon 1b-containing Ca(V)1.2alpha(1)/alpha(2)delta currents that were larger than those in exon 1c-containing Ca(V)1.2alpha(1)/alpha(2)delta currents. In contrast, beta(3) similarly shifted V(1/2,act) and V(1/2,inact) of currents generated by exon 1b- and exon 1c-containing channels. beta subunits isoform-dependent differences in current inactivation rates were also detected between N-terminal variants. Data indicate that through novel alternative splicing at exon 1, the Ca(V)1.2 N terminus modifies regulation by auxiliary subunits. The novel exon 1c should generate distinct voltage-dependent Ca(2+) entry in arterial myocytes, resulting in tissue-specific Ca(2+) signaling.
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Affiliation(s)
- Xiaoyang Cheng
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Jianxi Liu
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Maria Asuncion-Chin
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Eva Blaskova
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - John P. Bannister
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Alejandro M. Dopico
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Jonathan H. Jaggar
- Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
- To whom correspondence should be addressed: Dept. of Physiology, University of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163. Tel.: 901-448-1208; Fax: 901-448-7126; E-mail:
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Sonkusare S, Fraer M, Marsh JD, Rusch NJ. Disrupting calcium channel expression to lower blood pressure: new targeting of a well-known channel. Mol Interv 2007; 6:304-10. [PMID: 17200457 PMCID: PMC4917382 DOI: 10.1124/mi.6.6.3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Swapnil Sonkusare
- Department of Pharmacology & Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA.
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40
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Calin-Jageman I, Yu K, Hall RA, Mei L, Lee A. Erbin enhances voltage-dependent facilitation of Ca(v)1.3 Ca2+ channels through relief of an autoinhibitory domain in the Ca(v)1.3 alpha1 subunit. J Neurosci 2007; 27:1374-85. [PMID: 17287512 PMCID: PMC6673595 DOI: 10.1523/jneurosci.5191-06.2007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 12/27/2006] [Accepted: 12/29/2006] [Indexed: 11/21/2022] Open
Abstract
Ca(v)1.3 (L-type) voltage-gated Ca2+ channels have emerged as key players controlling Ca2+ signals at excitatory synapses. Compared with the more widely expressed Ca(v)1.2 L-type channel, relatively little is known about the mechanisms that regulate Ca(v)1.3 channels. Here, we describe a new role for the PSD-95 (postsynaptic density-95)/Discs large/ZO-1 (zona occludens-1) (PDZ) domain-containing protein, erbin, in directly potentiating Ca(v)1.3. Erbin specifically forms a complex with Ca(v)1.3, but not Ca(v)1.2, in transfected cells. The significance of erbin/Ca(v)1.3 interactions is supported by colocalization in somatodendritic domains of cortical neurons in culture and coimmunoprecipitation from rat brain lysates. In electrophysiological recordings, erbin augments facilitation of Ca(v)1.3 currents by a conditioning prepulse, a process known as voltage-dependent facilitation (VDF). This effect requires a direct interaction of the erbin PDZ domain with a PDZ recognition site in the C-terminal domain (CT) of the long variant of the Ca(v)1.3 alpha1 subunit (alpha1 1.3). Compared with Ca(v)1.3, the Ca(v)1.3b splice variant, which lacks a large fraction of the alpha1 1.3 CT, shows robust VDF that is not further affected by erbin. When coexpressed as an independent entity with Ca(v)1.3b or Ca(v)1.3 plus erbin, the alpha1 1.3 CT strongly suppresses VDF, signifying an autoinhibitory function of this part of the channel. These modulatory effects of erbin, but not alpha1 1.3 CT, depend on the identity of the auxiliary Ca2+ channel beta subunit. Our findings reveal a novel mechanism by which PDZ interactions and alternative splicing of alpha1 1.3 may influence activity-dependent regulation of Ca(v)1.3 channels at the synapse.
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Affiliation(s)
- Irina Calin-Jageman
- Department of Pharmacology and
- Center for Neurodegenerative Disease, Emory University, Atlanta, Georgia 30322, and
| | - Kuai Yu
- Department of Pharmacology and
- Center for Neurodegenerative Disease, Emory University, Atlanta, Georgia 30322, and
| | | | - Lin Mei
- Program of Developmental Neurobiology, Institute of Molecular Medicine and Genetics and Department of Neurology, Medical College of Georgia, Augusta, Georgia 30912
| | - Amy Lee
- Department of Pharmacology and
- Center for Neurodegenerative Disease, Emory University, Atlanta, Georgia 30322, and
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41
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Antzelevitch C, Pollevick GD, Cordeiro JM, Casis O, Sanguinetti MC, Aizawa Y, Guerchicoff A, Pfeiffer R, Oliva A, Wollnik B, Gelber P, Bonaros EP, Burashnikov E, Wu Y, Sargent JD, Schickel S, Oberheiden R, Bhatia A, Hsu LF, Haïssaguerre M, Schimpf R, Borggrefe M, Wolpert C. Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death. Circulation 2007; 115:442-9. [PMID: 17224476 PMCID: PMC1952683 DOI: 10.1161/circulationaha.106.668392] [Citation(s) in RCA: 743] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Cardiac ion channelopathies are responsible for an ever-increasing number and diversity of familial cardiac arrhythmia syndromes. We describe a new clinical entity that consists of an ST-segment elevation in the right precordial ECG leads, a shorter-than-normal QT interval, and a history of sudden cardiac death. METHODS AND RESULTS Eighty-two consecutive probands with Brugada syndrome were screened for ion channel gene mutations with direct sequencing. Site-directed mutagenesis was performed, and CHO-K1 cells were cotransfected with cDNAs encoding wild-type or mutant CACNB2b (Ca(v beta2b)), CACNA2D1 (Ca(v alpha2delta1)), and CACNA1C tagged with enhanced yellow fluorescent protein (Ca(v)1.2). Whole-cell patch-clamp studies were performed after 48 to 72 hours. Three probands displaying ST-segment elevation and corrected QT intervals < or = 360 ms had mutations in genes encoding the cardiac L-type calcium channel. Corrected QT ranged from 330 to 370 ms among probands and clinically affected family members. Rate adaptation of QT interval was reduced. Quinidine normalized the QT interval and prevented stimulation-induced ventricular tachycardia. Genetic and heterologous expression studies revealed loss-of-function missense mutations in CACNA1C (A39V and G490R) and CACNB2 (S481L) encoding the alpha1- and beta2b-subunits of the L-type calcium channel. Confocal microscopy revealed a defect in trafficking of A39V Ca(v)1.2 channels but normal trafficking of channels containing G490R Ca(v)1.2 or S481L Ca(v beta2b)-subunits. CONCLUSIONS This is the first report of loss-of-function mutations in genes encoding the cardiac L-type calcium channel to be associated with a familial sudden cardiac death syndrome in which a Brugada syndrome phenotype is combined with shorter-than-normal QT intervals.
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Kobrinsky E, Stevens L, Kazmi Y, Wray D, Soldatov NM. Molecular rearrangements of the Kv2.1 potassium channel termini associated with voltage gating. J Biol Chem 2006; 281:19233-40. [PMID: 16690619 DOI: 10.1074/jbc.m601231200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The voltage-gated Kv2.1 channel is composed of four identical subunits folded around the central pore and does not inactivate appreciably during short depolarizing pulses. To study voltage-induced relative molecular rearrangements of the channel, Kv2.1 subunits were genetically fused with enhanced cyan fluorescent protein and/or enhanced yellow fluorescent protein, expressed in COS1 cells, and investigated using fluorescence resonance energy transfer (FRET) microscopy combined with patch clamp. Fusion of fluorophores to either or both termini of the Kv2.1 monomer did not significantly affect the gating properties of the channel. FRET between the N- and C-terminal tags fused to the same or different Kv2.1 monomers decreased upon activation of the channel by depolarization from -80 to +60 mV, suggesting voltage-gated relative rearrangement between the termini. Because FRET between the Kv2.1 N- or C-terminal tags and the membrane-trapped EYFP(N)-PH pleckstrin homology domains did not change on depolarization, voltage-gated relative movements between the Kv2.1 termini occurred in a plane parallel to the plasma membrane, within a distance of 1-10 nm. FRET between the N-terminal tags did not change upon depolarization, indicating that the N termini do not rearrange relative to each other, but they could either move cooperatively with the Kv2.1 tetramer or not move at all. No FRET was detected between the C-terminal tags. Assuming their randomized orientation in the symmetrically arranged Kv2.1 subunits, C termini may move outwards in order to produce relative rearrangements between N and C termini upon depolarization.
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Affiliation(s)
- Evgeny Kobrinsky
- NIA, National Institutes of Health, Baltimore, Maryland 21224, USA
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43
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Bodi I, Mikala G, Koch SE, Akhter SA, Schwartz A. The L-type calcium channel in the heart: the beat goes on. J Clin Invest 2006; 115:3306-17. [PMID: 16322774 PMCID: PMC1297268 DOI: 10.1172/jci27167] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sydney Ringer would be overwhelmed today by the implications of his simple experiment performed over 120 years ago showing that the heart would not beat in the absence of Ca2+. Fascination with the role of Ca2+ has proliferated into all aspects of our understanding of normal cardiac function and the progression of heart disease, including induction of cardiac hypertrophy, heart failure, and sudden death. This review examines the role of Ca2+ and the L-type voltage-dependent Ca2+ channels in cardiac disease.
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Affiliation(s)
- Ilona Bodi
- Institute of Molecular Pharmacology and Biophysics, University of Cincinnati College of Medicine, Ohio 45267, USA
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44
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Sonkusare S, Palade PT, Marsh JD, Telemaque S, Pesic A, Rusch NJ. Vascular calcium channels and high blood pressure: pathophysiology and therapeutic implications. Vascul Pharmacol 2006; 44:131-42. [PMID: 16427812 PMCID: PMC4917380 DOI: 10.1016/j.vph.2005.10.005] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Accepted: 10/05/2005] [Indexed: 10/25/2022]
Abstract
Long-lasting Ca(2+) (Ca(L)) channels of the Ca(v)1.2 gene family are heteromultimeric structures that are minimally composed of a pore-forming alpha(1C) subunit and regulatory beta and alpha(2)delta subunits in vascular smooth muscle cells. The Ca(L) channels are the primary pathways for voltage-gated Ca(2+) influx that trigger excitation-contraction coupling in small resistance vessels. Notably, vascular smooth muscle cells of hypertensive rats show an increased expression of Ca(L) channel alpha(1C) subunits, which is associated with elevated Ca(2+) influx and the development of abnormal arterial tone. Indeed, blood pressure per se appears to promote Ca(L) channel expression in small arteries, and even short-term rises in pressure may alter channel expression. Membrane depolarization has been shown to be one stimulus associated with elevated blood pressure that promotes Ca(L) channel expression at the plasma membrane. Future studies to define the molecular processes that regulate Ca(L) channel expression in vascular smooth muscle cells will provide a rational basis for designing antihypertensive therapies to normalize Ca(L) channel expression and the development of anomalous vascular tone in hypertensive pathologies.
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Affiliation(s)
- Swapnil Sonkusare
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, #611 Little Rock, AR 72205-7199, United States
| | - Philip T. Palade
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, #611 Little Rock, AR 72205-7199, United States
| | - James D. Marsh
- Department of Internal Medicine, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205-7199, United States
| | - Sabine Telemaque
- Department of Internal Medicine, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR 72205-7199, United States
| | - Aleksandra Pesic
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, #611 Little Rock, AR 72205-7199, United States
| | - Nancy J. Rusch
- Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, #611 Little Rock, AR 72205-7199, United States
- Corresponding author. Tel.: +1 501 686 8038; fax: +1 501 686 5521. (N.J. Rusch)
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45
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Fallon JL, Halling DB, Hamilton SL, Quiocho FA. Structure of Calmodulin Bound to the Hydrophobic IQ Domain of the Cardiac Cav1.2 Calcium Channel. Structure 2005; 13:1881-6. [PMID: 16338416 DOI: 10.1016/j.str.2005.09.021] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2005] [Revised: 09/29/2005] [Accepted: 09/30/2005] [Indexed: 11/29/2022]
Abstract
Ca2+-dependent inactivation (CDI) and facilitation (CDF) of the Ca(v)1.2 Ca2+ channel require calmodulin binding to a putative IQ motif in the carboxy-terminal tail of the pore-forming subunit. We present the 1.45 A crystal structure of Ca2+-calmodulin bound to a 21 residue peptide corresponding to the IQ domain of Ca(v)1.2. This structure shows that parallel binding of calmodulin to the IQ domain is governed by hydrophobic interactions. Mutations of residues I1672 and Q1673 in the peptide to alanines, which abolish CDI but not CDF in the channel, do not greatly alter the structure. Both lobes of Ca2+-saturated CaM bind to the IQ peptide but isoleucine 1672, thought to form an intramolecular interaction that drives CDI, is buried. These findings suggest that this structure could represent the conformation that calmodulin assumes in CDF.
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Affiliation(s)
- Jennifer L Fallon
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Zhou H, Yu K, McCoy KL, Lee A. Molecular Mechanism for Divergent Regulation of Cav1.2 Ca2+ Channels by Calmodulin and Ca2+-binding Protein-1. J Biol Chem 2005; 280:29612-9. [PMID: 15980432 DOI: 10.1074/jbc.m504167200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+)-binding protein-1 (CaBP1) and calmodulin (CaM) are highly related Ca(2+)-binding proteins that directly interact with, and yet differentially regulate, voltage-gated Ca(2+) channels. Whereas CaM enhances inactivation of Ca(2+) currents through Ca(v)1.2 (L-type) Ca(2+) channels, CaBP1 completely prevents this process. How CaBP1 and CaM mediate such opposing effects on Ca(v)1.2 inactivation is unknown. Here, we identified molecular determinants in the alpha(1)-subunit of Ca(v)1.2 (alpha(1)1.2) that distinguish the effects of CaBP1 and CaM on inactivation. Although both proteins bind to a well characterized IQ-domain in the cytoplasmic C-terminal domain of alpha(1)1.2, mutations of the IQ-domain that significantly weakened CaM and CaBP1 binding abolished the functional effects of CaM, but not CaBP1. Pulldown binding assays revealed Ca(2+)-independent binding of CaBP1 to the N-terminal domain (NT) of alpha(1)1.2, which was in contrast to Ca(2+)-dependent binding of CaM to this region. Deletion of the NT abolished the effects of CaBP1 in prolonging Ca(v)1.2 Ca(2+) currents, but spared Ca(2+)-dependent inactivation due to CaM. We conclude that the NT and IQ-domains of alpha(1)1.2 mediate functionally distinct interactions with CaBP1 and CaM that promote conformational alterations that either stabilize or inhibit inactivation of Ca(v)1.2.
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Affiliation(s)
- Hong Zhou
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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