1
|
Autism associated mutations in β 2 subunit of voltage-gated calcium channels constitutively activate gene expression. Cell Calcium 2022; 108:102672. [PMID: 36427431 DOI: 10.1016/j.ceca.2022.102672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/23/2022] [Accepted: 11/08/2022] [Indexed: 11/13/2022]
Abstract
Membrane depolarization triggers gene expression through voltage-gated calcium channels (VGCC) in a process called Excitation-transcription (ET) coupling. Mutations in the channel subunits α11.2, or β2d, are associated with neurodevelopmental disorders such as ASD. Here, we found that two mutations S143F and G113S within the rat Cavβ2a corresponding to autistic related mutations Cavβ2dS197F and Cavβ2dG167S in the human Cavβ2d, activate ET-coupling via the RAS/ERK/CREB pathway. Membrane depolarization of HEK293 cells co-expressing α11.2 and α2δ with Cavβ2aS143F or Cavβ2aG113S triggers constitutive transcriptional activation, which is correlated with facilitated channel activity. Similar to the Timothy-associated autistic mutation α11.2G406R, constitutive gene activation is attributed to a hyperpolarizing shift in the activation kinetics of Cav1.2. Pulldown of RasGRF2 and RhoGEF by wt and the Cavβ2a autistic mutants is consistent with Cavβ2/Ras activation in ET coupling and implicates Rho signaling as yet another molecular pathway activated by Cavα11.2/Cavβ2 . Facilitated spontaneous channel activity preceding enhanced gene activation via the Ras/ERK/CREB pathway, appears a general molecular mechanism for Ca2+ channel mediated ASD and other neurodevelopmental disorders.
Collapse
|
2
|
IP3-dependent Ca2+ signals are tightly controlled by Cavβ3, but not by Cavβ1, 2 and 4. Cell Calcium 2022; 104:102573. [DOI: 10.1016/j.ceca.2022.102573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/17/2022] [Accepted: 03/15/2022] [Indexed: 11/18/2022]
|
3
|
Sundararaj S, Ravindran A, Casarotto MG. AHNAK: The quiet giant in calcium homeostasis. Cell Calcium 2021; 96:102403. [PMID: 33813182 DOI: 10.1016/j.ceca.2021.102403] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 03/19/2021] [Accepted: 03/23/2021] [Indexed: 10/21/2022]
Abstract
The phosphoprotein AHNAK is a large, ubiquitously expressed scaffolding protein involved in mediating a host of protein-protein interactions. This enables AHNAK to participate in various multi-protein complexes thereby orchestrating a range of diverse biological processes, including tumour suppression, immune regulation and cell architecture maintenance. A less studied but nonetheless equally important function occurs in calcium homeostasis. It does so by largely interacting with the L-type voltage-gated calcium channel (LVGCC) present in the plasma membrane of excitable cells such as muscles and neurons. Several studies have characterized the underlying basis of AHNAK's functional role in calcium channel modulation, which has led to a greater understanding of this cellular process and its associated pathologies. In this article we review and examine recent advances relating to the physiological aspects of AHNAK in calcium regulation. Specifically, we will provide a broad overview of AHNAK including its structural makeup and its interaction with several isoforms of LVGCC, and how these molecular interactions regulate calcium modulation across various tissues and their implication in muscle and neuronal function.
Collapse
Affiliation(s)
- Srinivasan Sundararaj
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
| | - Agin Ravindran
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - Marco G Casarotto
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia.
| |
Collapse
|
4
|
Autism-associated mutations in the CaVβ2 calcium-channel subunit increase Ba2+-currents and lead to differential modulation by the RGK-protein Gem. Neurobiol Dis 2020; 136:104721. [DOI: 10.1016/j.nbd.2019.104721] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/06/2019] [Accepted: 12/26/2019] [Indexed: 12/26/2022] Open
|
5
|
Kushner J, Ferrer X, Marx SO. Roles and Regulation of Voltage-gated Calcium Channels in Arrhythmias. J Innov Card Rhythm Manag 2019; 10:3874-3880. [PMID: 32494407 PMCID: PMC7252866 DOI: 10.19102/icrm.2019.101006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 03/04/2019] [Indexed: 12/25/2022] Open
Abstract
Calcium flowing through voltage-dependent calcium channels into cardiomyocytes mediates excitation–contraction coupling, controls action-potential duration and automaticity in nodal cells, and regulates gene expression. Proper surface targeting and basal and hormonal regulation of calcium channels are vital for normal cardiac physiology. In this review, we discuss the roles of voltage-gated calcium channels in the heart and the mechanisms by which these channels are regulated by physiological signaling pathways in health and disease.
Collapse
Affiliation(s)
- Jared Kushner
- Division of Cardiology, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Xavier Ferrer
- Division of Cardiology, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Steven O Marx
- Division of Cardiology, Department of Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
| |
Collapse
|
6
|
Postnatal Increases in Axonal Conduction Velocity of an Identified Drosophila Interneuron Require Fast Sodium, L-Type Calcium and Shaker Potassium Channels. eNeuro 2019; 6:ENEURO.0181-19.2019. [PMID: 31253715 PMCID: PMC6709211 DOI: 10.1523/eneuro.0181-19.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/06/2019] [Accepted: 06/12/2019] [Indexed: 11/21/2022] Open
Abstract
During early postnatal life, speed up of signal propagation through many central and peripheral neurons has been associated with an increase in axon diameter or/and myelination. Especially in unmyelinated axons postnatal adjustments of axonal membrane conductances is potentially a third mechanism but solid evidence is lacking. Here, we show that axonal action potential (AP) conduction velocity in the Drosophila giant fiber (GF) interneuron, which is required for fast long-distance signal conduction through the escape circuit, is increased by 80% during the first day of adult life. Genetic manipulations indicate that this postnatal increase in AP conduction velocity in the unmyelinated GF axon is likely owed to adjustments of ion channel expression or properties rather than axon diameter increases. Specifically, targeted RNAi knock-down of either Para fast voltage-gated sodium, Shaker potassium (Kv1 homologue), or surprisingly, L-type like calcium channels counteracts postnatal increases in GF axonal conduction velocity. By contrast, the calcium-dependent potassium channel Slowpoke (BK) is not essential for postnatal speeding, although it also significantly increases conduction velocity. Therefore, we identified multiple ion channels that function to support fast axonal AP conduction velocity, but only a subset of these are regulated during early postnatal life to maximize conduction velocity. Despite its large diameter (∼7 µm) and postnatal regulation of multiple ionic conductances, mature GF axonal conduction velocity is still 20-60 times slower than that of vertebrate Aβ sensory axons and α motoneurons, thus unraveling the limits of long-range information transfer speed through invertebrate circuits.
Collapse
|
7
|
Pang C, Yang H, Hu B, Wang S, Chen M, Cohen DS, Chen HS, Jarrell JT, Carpenter KA, Rosin ER, Huang X. Identification and Analysis of Alzheimer's Candidate Genes by an Amplitude Deviation Algorithm. ACTA ACUST UNITED AC 2019; 9. [PMID: 31080696 PMCID: PMC6505709 DOI: 10.4172/2161-0460.1000460] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Background: Alzheimer’s disease (AD) is the most common form of senile dementia. However, its pathological mechanisms are not fully understood. In order to comprehend AD pathological mechanisms, researchers employed AD-related DNA microarray data and diverse computational algorithms. More efficient computational algorithms are needed to process DNA microarray data for identifying AD-related candidate genes. Methods: In this paper, we propose a specific algorithm that is based on the following observation: When an acrobat walks along a steel-wire, his/her body must have some swing; if the swing can be controlled, then the acrobat can maintain the body balance. Otherwise, the acrobat will fall. Based on this simple idea, we have designed a simple, yet practical, algorithm termed as the Amplitude Deviation Algorithm (ADA). Deviation, overall deviation, deviation amplitude, and 3δ are introduced to characterize ADA. Results: 52 candidate genes for AD have been identified via ADA. The implications for some of the AD candidate genes in AD pathogenesis have been discussed. Conclusions: Through the analysis of these AD candidate genes, we believe that AD pathogenesis may be related to the abnormality of signal transduction (AGTR1 and PTAFR), the decrease in protein transport capacity (COL5A2 (221729_at), COL5A2 (221730_at), COL4A1), the impairment of axon repair (CNR1), and the intracellular calcium dyshomeostasis (CACNB2, CACNA1E). However, their potential implication for AD pathology should be further validated by wet lab experiments as they were only identified by computation using ADA.
Collapse
Affiliation(s)
- Chaoyang Pang
- College of Computer Science, Sichuan Normal University, Chengdu, China
| | - Hualan Yang
- College of Mathematics and Software Science, Sichuan Normal University, Chengdu, China
| | - Benqiong Hu
- College of Management Science, Chengdu University of Technology, Chengdu, China
| | - Shipeng Wang
- College of Mathematics and Software Science, Sichuan Normal University, Chengdu, China
| | - Meixia Chen
- College of Mathematics and Software Science, Sichuan Normal University, Chengdu, China
| | - David S Cohen
- Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Hannah S Chen
- Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Juliet T Jarrell
- Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Kristy A Carpenter
- Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Eric R Rosin
- Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Xudong Huang
- Neurochemistry Laboratory, Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| |
Collapse
|
8
|
Serra SA, Gené GG, Elorza-Vidal X, Fernández-Fernández JM. Cross talk between β subunits, intracellular Ca 2+ signaling, and SNAREs in the modulation of Ca V 2.1 channel steady-state inactivation. Physiol Rep 2019; 6. [PMID: 29380539 PMCID: PMC5789719 DOI: 10.14814/phy2.13557] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 11/23/2017] [Accepted: 12/03/2017] [Indexed: 01/05/2023] Open
Abstract
Modulation of CaV2.1 channel activity plays a key role in interneuronal communication and synaptic plasticity. SNAREs interact with a specific synprint site at the second intracellular loop (LII‐III) of the CaV2.1 pore‐forming α1A subunit to optimize neurotransmitter release from presynaptic terminals by allowing secretory vesicles docking near the Ca2+ entry pathway, and by modulating the voltage dependence of channel steady‐state inactivation. Ca2+ influx through CaV2.1 also promotes channel inactivation. This process seems to involve Ca2+‐calmodulin interaction with two adjacent sites in the α1A carboxyl tail (C‐tail) (the IQ‐like motif and the Calmodulin‐Binding Domain (CBD) site), and contributes to long‐term potentiation and spatial learning and memory. Besides, binding of regulatory β subunits to the α interaction domain (AID) at the first intracellular loop (LI‐II) of α1A determines the degree of channel inactivation by both voltage and Ca2+. Here, we explore the cross talk between β subunits, Ca2+, and syntaxin‐1A‐modulated CaV2.1 inactivation, highlighting the α1A domains involved in such process. β3‐containing CaV2.1 channels show syntaxin‐1A‐modulated but no Ca2+‐dependent steady‐state inactivation. Conversely, β2a‐containing CaV2.1 channels show Ca2+‐dependent but not syntaxin‐1A‐modulated steady‐state inactivation. A LI‐II deletion confers Ca2+‐dependent inactivation and prevents modulation by syntaxin‐1A in β3‐containing CaV2.1 channels. Mutation of the IQ‐like motif, unlike CBD deletion, abolishes Ca2+‐dependent inactivation and confers modulation by syntaxin‐1A in β2a‐containing CaV2.1 channels. Altogether, these results suggest that LI‐II structural modifications determine the regulation of CaV2.1 steady‐state inactivation either by Ca2+ or by SNAREs but not by both.
Collapse
Affiliation(s)
- Selma Angèlica Serra
- Laboratori de Fisiologia Molecular, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain
| | - Gemma G Gené
- Laboratori de Fisiologia Molecular, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain
| | - Xabier Elorza-Vidal
- Laboratori de Fisiologia Molecular, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain
| | - José M Fernández-Fernández
- Laboratori de Fisiologia Molecular, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain
| |
Collapse
|
9
|
Park CG, Suh BC. The HOOK region of β subunits controls gating of voltage-gated Ca 2+ channels by electrostatically interacting with plasma membrane. Channels (Austin) 2017; 11:467-475. [PMID: 28569643 DOI: 10.1080/19336950.2017.1335841] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Recently, we showed that the HOOK region of the β2 subunit electrostatically interacts with the plasma membrane and regulates the current inactivation and phosphatidylinositol 4,5-bisphosphate (PIP2) sensitivity of voltage-gated Ca2+ (CaV) 2.2 channels. Here, we report that voltage-dependent gating and current density of the CaV2.2 channels are also regulated by the HOOK region of the β2 subunit. The HOOK region can be divided into 3 domains: S (polyserine), A (polyacidic), and B (polybasic). We found that the A domain shifted the voltage-dependent inactivation and activation of CaV2.2 channels to more hyperpolarized and depolarized voltages, respectively, whereas the B domain evoked these responses in the opposite directions. In addition, the A domain decreased the current density of the CaV2.2 channels, while the B domain increased it. Together, our data demonstrate that the flexible HOOK region of the β2 subunit plays an important role in determining the overall CaV channel gating properties.
Collapse
Affiliation(s)
- Cheon-Gyu Park
- a Department of Brain and Cognitive Sciences , DGIST , Daegu , South Korea
| | - Byung-Chang Suh
- a Department of Brain and Cognitive Sciences , DGIST , Daegu , South Korea
| |
Collapse
|
10
|
Park CG, Park Y, Suh BC. The HOOK region of voltage-gated Ca2+ channel β subunits senses and transmits PIP2 signals to the gate. J Gen Physiol 2017; 149:261-276. [PMID: 28087621 PMCID: PMC5299622 DOI: 10.1085/jgp.201611677] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 12/12/2016] [Accepted: 12/22/2016] [Indexed: 12/12/2022] Open
Abstract
The β subunit of voltage-gated Ca2+ (CaV) channels plays an important role in regulating gating of the α1 pore-forming subunit and its regulation by phosphatidylinositol 4,5-bisphosphate (PIP2). Subcellular localization of the CaV β subunit is critical for this effect; N-terminal-dependent membrane targeting of the β subunit slows inactivation and decreases PIP2 sensitivity. Here, we provide evidence that the HOOK region of the β subunit plays an important role in the regulation of CaV biophysics. Based on amino acid composition, we broadly divide the HOOK region into three domains: S (polyserine), A (polyacidic), and B (polybasic). We show that a β subunit containing only its A domain in the HOOK region increases inactivation kinetics and channel inhibition by PIP2 depletion, whereas a β subunit with only a B domain decreases these responses. When both the A and B domains are deleted, or when the entire HOOK region is deleted, the responses are elevated. Using a peptide-to-liposome binding assay and confocal microscopy, we find that the B domain of the HOOK region directly interacts with anionic phospholipids via polybasic and two hydrophobic Phe residues. The β2c-short subunit, which lacks an A domain and contains fewer basic amino acids and no Phe residues in the B domain, neither associates with phospholipids nor affects channel gating dynamically. Together, our data suggest that the flexible HOOK region of the β subunit acts as an important regulator of CaV channel gating via dynamic electrostatic and hydrophobic interaction with the plasma membrane.
Collapse
Affiliation(s)
- Cheon-Gyu Park
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea
| | - Yongsoo Park
- Izmir International Biomedicine and Genome Institute (iBG-izmir), Dokuz Eylul University, 35340 Balcova, Izmir, Turkey
| | - Byung-Chang Suh
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea
| |
Collapse
|
11
|
Cox RH, Fromme S. Expression of Calcium Channel Subunit Variants in Small Mesenteric Arteries of WKY and SHR. Am J Hypertens 2015; 28:1229-39. [PMID: 25820242 DOI: 10.1093/ajh/hpv024] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 02/03/2015] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Enhanced function of dihydropyridine-sensitive Ca2+ channels (CaV) in hypertensive arterial myocytes (HAM) is well accepted. Increased protein expression of pore forming α1-subunits contributes to this effect, but cannot explain all of the differences in CaV properties in HAM. We hypothesized that differences in expression of CaV subunits and/or their splice variants also contribute. METHODS RNA, protein, and myocytes were isolated from small mesenteric arteries (SMA) of 20-week-old male WKY and SHR and analyzed by polymerase chain reaction (PCR), sequencing, immunoblotting, and patch clamp methods. RESULTS Cav1.2 α1, β2c, and α2δ1d were the dominant subunits expressed in both WKY and SHR with a smaller amount of β3a. Real-time PCR indicated that the mRNA abundance of β3a and α2δ1 but not total Cav1.2 α1 or β2c were significantly larger in SHR. Analysis of alternative splicing of Cav1.2 α1 showed no differences in abundance of mutually exclusive exons1b, 8, 21 and 32 or alternative exons33 and 45. However, inclusion of exon9* was higher and a 73 nucleotide (nt) deletion in exon15 (exon15Δ73) was lower in SHR. Immunoblot analysis showed higher protein levels of Cav1.2 α1 (1.61±0.05), β3 (1.80±0.32), and α2δ1 (1.80±0.24) but not β2 in SHR. CONCLUSIONS The lower abundance of exon15Δ73 transcripts in SHR results in a larger fraction of total Cav1.2 mRNA coding for full-length CaV protein, and the higher abundance of exon9* transcripts and CaVβ3a protein likely contribute to differences in gating and kinetics of CaV currents in SHR. Functional studies of Ca2+ currents in native SMA myocytes and HEK cells transiently transfected with CaV subunits support these conclusions.
Collapse
Affiliation(s)
- Robert H Cox
- Program in Cardiovascular Disease, Lankenau Institute for Medical Research, Wynnewood, Pennsylvania.
| | - Samantha Fromme
- Program in Cardiovascular Disease, Lankenau Institute for Medical Research, Wynnewood, Pennsylvania
| |
Collapse
|
12
|
Voltage-gated calcium channels: Determinants of channel function and modulation by inorganic cations. Prog Neurobiol 2015; 129:1-36. [PMID: 25817891 DOI: 10.1016/j.pneurobio.2014.12.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 12/15/2014] [Accepted: 12/27/2014] [Indexed: 11/20/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent a key link between electrical signals and non-electrical processes, such as contraction, secretion and transcription. Evolved to achieve high rates of Ca(2+)-selective flux, they possess an elaborate mechanism for selection of Ca(2+) over foreign ions. It has been convincingly linked to competitive binding in the pore, but the fundamental question of how this is reconcilable with high rates of Ca(2+) transfer remains unanswered. By virtue of their similarity to Ca(2+), polyvalent cations can interfere with the function of VGCCs and have proven instrumental in probing the mechanisms underlying selective permeation. Recent emergence of crystallographic data on a set of Ca(2+)-selective model channels provides a structural framework for permeation in VGCCs, and warrants a reconsideration of their diverse modulation by polyvalent cations, which can be roughly separated into three general mechanisms: (I) long-range interactions with charged regions on the surface, affecting the local potential sensed by the channel or influencing voltage-sensor movement by repulsive forces (electrostatic effects), (II) short-range interactions with sites in the ion-conducting pathway, leading to physical obstruction of the channel (pore block), and in some cases (III) short-range interactions with extracellular binding sites, leading to non-electrostatic modifications of channel gating (allosteric effects). These effects, together with the underlying molecular modifications, provide valuable insights into the function of VGCCs, and have important physiological and pathophysiological implications. Allosteric suppression of some of the pore-forming Cavα1-subunits (Cav2.3, Cav3.2) by Zn(2+) and Cu(2+) may play a major role for the regulation of excitability by endogenous transition metal ions. The fact that these ions can often traverse VGCCs can contribute to the detrimental intracellular accumulation of metal ions following excessive release of endogenous Cu(2+) and Zn(2+) or exposure to non-physiological toxic metal ions.
Collapse
|
13
|
Balycheva M, Faggian G, Glukhov AV, Gorelik J. Microdomain-specific localization of functional ion channels in cardiomyocytes: an emerging concept of local regulation and remodelling. Biophys Rev 2015; 7:43-62. [PMID: 28509981 PMCID: PMC5425752 DOI: 10.1007/s12551-014-0159-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/18/2014] [Indexed: 12/26/2022] Open
Abstract
Cardiac excitation involves the generation of action potential by individual cells and the subsequent conduction of the action potential from cell to cell through intercellular gap junctions. Excitation of the cellular membrane results in opening of the voltage-gated L-type calcium ion (Ca2+) channels, thereby allowing a small amount of Ca2+ to enter the cell, which in turn triggers the release of a much greater amount of Ca2+ from the sarcoplasmic reticulum, the intracellular Ca2+ store, and gives rise to the systolic Ca2+ transient and contraction. These processes are highly regulated by the autonomic nervous system, which ensures the acute and reliable contractile function of the heart and the short-term modulation of this function upon changes in heart rate or workload. It has recently become evident that discrete clusters of different ion channels and regulatory receptors are present in the sarcolemma, where they form an interacting network and work together as a part of a macro-molecular signalling complex which in turn allows the specificity, reliability and accuracy of the autonomic modulation of the excitation-contraction processes by a variety of neurohormonal pathways. Disruption in subcellular targeting of ion channels and associated signalling proteins may contribute to the pathophysiology of a variety of cardiac diseases, including heart failure and certain arrhythmias. Recent methodological advances have made it possible to routinely image the topography of live cardiomyocytes, allowing the study of clustering functional ion channels and receptors as well as their coupling within a specific microdomain. In this review we highlight the emerging understanding of the functionality of distinct subcellular microdomains in cardiac myocytes (e.g. T-tubules, lipid rafts/caveolae, costameres and intercalated discs) and their functional role in the accumulation and regulation of different subcellular populations of sodium, Ca2+ and potassium ion channels and their contributions to cellular signalling and cardiac pathology.
Collapse
Affiliation(s)
- Marina Balycheva
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK
- Cardiosurgery Department, University of Verona School of Medicine, Verona, Italy
| | - Giuseppe Faggian
- Cardiosurgery Department, University of Verona School of Medicine, Verona, Italy
| | - Alexey V Glukhov
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
| | - Julia Gorelik
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
| |
Collapse
|
14
|
Abstract
The α2δ auxiliary subunits of voltage-gated Ca2+ channels (VGCCs) are important modulators of VGCC function. Gabapentin interacts with α2δ1 and α2δ2 subunits and is reported to reduce Ca2+ channel current amplitude (ICa). This study aimed to determine the effects of gabapentin on VGCCs in retinal ganglion cells (RGCs). Whole cell patch clamp was used to record ICa in isolated RGCs, and calcium imaging was used to measure Ca2+ transients from RGCs in situ. Immunohistochemistry was used to detect the presence of α2δ1-containing VGCCs in isolated RGCs in the absence and presence of gabapentin pretreatment. Acute administration of gabapentin reduced ICa and Ca2+ transients compared to control conditions. In isolated RGCs, pretreatment with gabapentin (4-18 h) reduced ICa, and cell surface α2δ1 staining was reduced compared to nonpretreated cells. Acute administration of gabapentin to isolated RGCs that had been pretreated further reduced ICa. These results show that gabapentin has both short-term and long-term mechanisms to reduce ICa in isolated RGCs. Some Ca2+ channel blockers have been shown to protect RGCs in retinal trauma suggesting that modulation of VGCCs by gabapentin may prevent the deleterious effects of elevated Ca2+ levels in RGCs in trauma and disease.
Collapse
|
15
|
Liu F, Zhou Q, Zhou J, Sun H, Wang Y, Zou X, Feng L, Hou Z, Zhou A, Zhou Y, Li Y. 14-3-3τ promotes surface expression of Cav2.2 (α1B) Ca2+ channels. J Biol Chem 2014; 290:2689-98. [PMID: 25516596 DOI: 10.1074/jbc.m114.567800] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Surface expression of voltage-gated Ca(2+) (Cav) channels is important for their function in calcium homeostasis in the physiology of excitable cells, but whether or not and how the α1 pore-forming subunits of Cav channels are trafficked to plasma membrane in the absence of the known Cav auxiliary subunits, β and α2δ, remains mysterious. Here we showed that 14-3-3 proteins promoted functional surface expression of the Cav2.2 α1B channel in transfected tsA-201 cells in the absence of any known Cav auxiliary subunit. Both the surface to total ratio of the expressed α1B protein and the current density of voltage step-evoked Ba(2+) current were markedly suppressed by the coexpression of a 14-3-3 antagonist construct, pSCM138, but not its inactive control, pSCM174, as determined by immunofluorescence assay and whole cell voltage clamp recording, respectively. By contrast, coexpression with 14-3-3τ significantly enhanced the surface expression and current density of the Cav2.2 α1B channel. Importantly, we found that between the two previously identified 14-3-3 binding regions at the α1B C terminus, only the proximal region (amino acids 1706-1940), closer to the end of the last transmembrane domain, was retained by the endoplasmic reticulum and facilitated by 14-3-3 to traffic to plasma membrane. Additionally, we showed that the 14-3-3/Cav β subunit coregulated the surface expression of Cav2.2 channels in transfected tsA-201 cells and neurons. Altogether, our findings reveal a previously unidentified regulatory function of 14-3-3 proteins in promoting the surface expression of Cav2.2 α1B channels.
Collapse
Affiliation(s)
- Feng Liu
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Qin Zhou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Jie Zhou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Hao Sun
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Yan Wang
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Xiuqun Zou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Lingling Feng
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Zhaoyuan Hou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Aiwu Zhou
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| | - Yi Zhou
- the Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, Florida 32306
| | - Yong Li
- From the Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China and
| |
Collapse
|
16
|
Wang DD, Bansal V, Fisher TE. The Ca2+ channel β2 subunit is selectively targeted to the axon terminals of supraoptic neurons. Channels (Austin) 2014; 8:216-21. [PMID: 24755552 DOI: 10.4161/chan.28863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The assembly of high voltage-activated Ca(2+) channels with different β subunits influences channel properties and possibly subcellular targeting. We studied β subunit expression in the somata and axon terminals of the magnocellular neurosecretory cells, which are located in the supraoptic nucleus (SON) and neurohypophysis, respectively. Antibodies directed against the 4 Ca(V)β subunits (Ca(V)β(1)-Ca(V)β(4)) were used for immunoblots and for immunostaining of slices of these two tissues. We found that all 4 β subunits are expressed in both locations, but that Ca(V)β(2) had the highest relative expression in the neurohypophysis. These data suggest that the Ca(V)β(2) subunit is selectively targeted to axon terminals and may play a role in targeting and/or regulating the properties of Ca(2+) channels.
Collapse
|
17
|
Breitenkamp AFS, Matthes J, Nass RD, Sinzig J, Lehmkuhl G, Nürnberg P, Herzig S. Rare mutations of CACNB2 found in autism spectrum disease-affected families alter calcium channel function. PLoS One 2014; 9:e95579. [PMID: 24752249 PMCID: PMC3994086 DOI: 10.1371/journal.pone.0095579] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 03/27/2014] [Indexed: 01/06/2023] Open
Abstract
Autism Spectrum Disorders (ASD) are complex neurodevelopmental diseases clinically defined by dysfunction of social interaction. Dysregulation of cellular calcium homeostasis might be involved in ASD pathogenesis, and genes coding for the L-type calcium channel subunits CaV1.2 (CACNA1C) and CaVβ2 (CACNB2) were recently identified as risk loci for psychiatric diseases. Here, we present three rare missense mutations of CACNB2 (G167S, S197F, and F240L) found in ASD-affected families, two of them described here for the first time (G167S and F240L). All these mutations affect highly conserved regions while being absent in a sample of ethnically matched controls. We suggest the mutations to be of physiological relevance since they modulate whole-cell Ba2+ currents through calcium channels when expressed in a recombinant system (HEK-293 cells). Two mutations displayed significantly decelerated time-dependent inactivation as well as increased sensitivity of voltage-dependent inactivation. In contrast, the third mutation (F240L) showed significantly accelerated time-dependent inactivation. By altering the kinetic parameters, the mutations are reminiscent of the CACNA1C mutation causing Timothy Syndrome, a Mendelian disease presenting with ASD. In conclusion, the results of our first-time biophysical characterization of these three rare CACNB2 missense mutations identified in ASD patients support the hypothesis that calcium channel dysfunction may contribute to autism.
Collapse
Affiliation(s)
| | - Jan Matthes
- Department of Pharmacology, University of Cologne, Cologne, Germany
| | | | - Judith Sinzig
- Department of Child and Adolescent Psychiatry and Psychotherapy, LVR-Klinik Bonn, Bonn, Germany
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Cologne, Cologne, Germany
| | - Gerd Lehmkuhl
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Cologne, Cologne, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Stefan Herzig
- Department of Pharmacology, University of Cologne, Cologne, Germany
- Center for Molecular Medicine, University of Cologne, Cologne, Germany
- * E-mail:
| |
Collapse
|
18
|
DuPont JJ, Hill MA, Bender SB, Jaisser F, Jaffe IZ. Aldosterone and vascular mineralocorticoid receptors: regulators of ion channels beyond the kidney. Hypertension 2014; 63:632-7. [PMID: 24379184 PMCID: PMC3954941 DOI: 10.1161/hypertensionaha.113.01273] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
19
|
Cardiac functions of voltage-gated Ca(2+) channels: role of the pharmacoresistant type (E-/R-Type) in cardiac modulation and putative implication in sudden unexpected death in epilepsy (SUDEP). Rev Physiol Biochem Pharmacol 2014; 167:115-39. [PMID: 25280639 DOI: 10.1007/112_2014_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Voltage-gated Ca(2+) channels (VGCCs) are ubiquitous in excitable cells. These channels play key roles in many physiological events like cardiac regulation/pacemaker activity due to intracellular Ca(2+) transients. In the myocardium, the Cav1 subfamily (L-type: Cav1.2 and Cav1.3) is the main contributor to excitation-contraction coupling and/or pacemaking, whereas the Cav3 subfamily (T-type: Cav3.1 and Cav3.2) is important in rhythmically firing of the cardiac nodal cells. No established cardiac function has been attributed to the Cav2 family (E-/R-type: Cav2.3) despite accumulating evidence of cardiac dysregulation observed upon deletion of the Cav2.3 gene, the only member of this family so far detected in cardiomyocytes. In this review, we summarize the pathophysiological changes observed after ablation of the E-/R-type VGCC and propose a cardiac mechanism of action for this channel. Also, considering the role played by this channel in epilepsy and its reported sensitivity to antiepileptic drugs, a putative involvement of this channel in the cardiac mechanism of sudden unexpected death in epilepsy is also discussed.
Collapse
|
20
|
Joseph BK, Thakali KM, Moore CL, Rhee SW. Ion channel remodeling in vascular smooth muscle during hypertension: Implications for novel therapeutic approaches. Pharmacol Res 2013; 70:126-38. [PMID: 23376354 PMCID: PMC3607210 DOI: 10.1016/j.phrs.2013.01.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 01/10/2013] [Accepted: 01/17/2013] [Indexed: 02/07/2023]
Abstract
Ion channels are multimeric, transmembrane proteins that selectively mediate ion flux across the plasma membrane in a variety of cells including vascular smooth muscle cells (VSMCs). The dynamic interplay of Ca(2+) and K(+) channels on the plasma membrane of VSMCs plays a pivotal role in modulating the vascular tone of small arteries and arterioles. The abnormally-elevated arterial tone observed in hypertension thus points to an aberrant expression and function of Ca(2+) and K(+) channels in the VSMCs. In this short review, we focus on the three well-studied ion channels in VSMCs, namely the L-type Ca(2+) (CaV1.2) channels, the voltage-gated K(+) (KV) channels, and the large-conductance Ca(2+)-activated K(+) (BK) channels. First, we provide a brief overview on the physiological role of vascular CaV1.2, KV and BK channels in regulating arterial tone. Second, we discuss the current understanding of the expression changes and regulation of CaV1.2, KV and BK channels in the vasculature during hypertension. Third, based on available proof-of-concept studies, we describe the potential therapeutic approaches targeting these vascular ion channels in order to restore blood pressure to normotensive levels.
Collapse
Affiliation(s)
- Biny K Joseph
- Venenum Biodesign, 8 Black Forest Road, Hamilton, NJ 08691, USA
| | | | | | | |
Collapse
|
21
|
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.
Collapse
|
22
|
Rosa AO, Yamaguchi N, Morad M. Mechanical regulation of native and the recombinant calcium channel. Cell Calcium 2013; 53:264-74. [PMID: 23357406 DOI: 10.1016/j.ceca.2012.12.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 12/25/2012] [Indexed: 11/30/2022]
Abstract
L-type calcium channels are modulated by a host of mechanisms that include voltage, calcium ions (Ca(2+) dependent inactivation and facilitation), cytosolic proteins (CAM, CAMKII, PKA, PKC, etc.), and oxygen radicals. Here we describe yet another Ca(2+) channel regulatory mechanism that is induced by pressure-flow (PF) forces of ∼25dyn/cm(2) producing 35-60% inhibition of channel current. Only brief periods (300ms) of such PF pulses were required to suppress reversibly the current. Recombinant Ca(2+) channels (α1c77/β2a/α2δ and α1c77/β1/α2δ), expressed in HEK293 cells, were similarly suppressed by PF pulses. To examine whether Ca(2+) released by PF pulses triggered from different sub-cellular compartments (SR, ER, mitochondria) underlies the inhibitory effect of PF on the channel current, pharmacological agents and ionic substitutions were employed to probe this possibility. No significant difference in effectiveness of PF pulses to suppress ICa or IBa (used to inhibit CICR) was found between control cells and those exposed to U73122 and 2-APB (PLC and IP3R pathway modulators), thapsigargin and BAPTA (SERCA2a modulator), dinitrophenol, FCCP and Ru360 (mitochondrial inhibitors), l-NAME (NOS inhibitor signaling), cAMP and Pertussis toxin (Gi protein modulator). We concluded that the rapid and reversible modulation of the Ca(2+) channel by PF pulses is independent of intracellular release of Ca(2+) and Ca(2+) dependent inactivation of the channel and may represent direct mechanical regulatory effect on the channel protein in addition to previously reported Ca(2+)-release or entry dependent mechanism.
Collapse
Affiliation(s)
- Angelo O Rosa
- Cardiac Signaling Center, University of South Carolina, Charleston, SC 29425, USA
| | | | | |
Collapse
|
23
|
Nasca C, Orlando R, Marchiafava M, Boldrini P, Battaglia G, Scaccianoce S, Matrisciano F, Pittaluga A, Nicoletti F. Exposure to predator odor and resulting anxiety enhances the expression of the α2 δ subunit of voltage-sensitive calcium channels in the amygdala. J Neurochem 2013; 125:649-56. [PMID: 22849384 DOI: 10.1111/j.1471-4159.2012.07895.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/11/2012] [Accepted: 07/12/2012] [Indexed: 11/28/2022]
Abstract
The α2 δ subunit of voltage-sensitive calcium channels (VSCCs) is the molecular target of pregabalin and gabapentin, two drugs marked for the treatment of focal epilepsy, neuropathic pain, and anxiety disorders. Expression of the α2 δ subunit is up-regulated in the dorsal horns of the spinal cord in models of neuropathic pain, suggesting that plastic changes in the α2 δ subunit are associated with pathological states. Here, we examined the expression of the α2 δ-1 subunit in the amygdala, hippocampus, and frontal cortex in the trimethyltiazoline (TMT) mouse model of innate anxiety. TMT is a volatile molecule present in the feces of the rodent predator, red fox. Mice that show a high defensive behavior during TMT exposure developed anxiety-like behavior in the following 72 h, as shown by the light-dark test. Anxiety was associated with an increased expression of the α2 δ-1 subunit of VSCCs in the amygdaloid complex at all times following TMT exposure (4, 24, and 72 h). No changes in the α2 δ-1 protein levels were seen in the hippocampus and frontal cortex of mice exposed to TMT. Pregabalin (30 mg/kg, i.p.) reduced anxiety-like behavior in TMT-exposed mice, but not in control mice. These data offer the first demonstration that the α2 δ-1 subunit of VSCCs undergoes plastic changes in a model of innate anxiety, and supports the use of pregabalin as a disease-dependent drug in the treatment of anxiety disorders.
Collapse
Affiliation(s)
- Carla Nasca
- Department of Physiology and Pharmacology, University Sapienza, Roma, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
24
|
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.
Collapse
Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | | |
Collapse
|
25
|
CaV2.1 voltage activated calcium channels and synaptic transmission in familial hemiplegic migraine pathogenesis. ACTA ACUST UNITED AC 2011; 106:12-22. [PMID: 22074995 DOI: 10.1016/j.jphysparis.2011.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 10/12/2011] [Accepted: 10/17/2011] [Indexed: 12/28/2022]
Abstract
Studies on the genetic forms of epilepsy, chronic pain, and migraine caused by mutations in ion channels have given crucial insights into the molecular mechanisms, pathogenesis, and therapeutic approaches to complex neurological disorders. In this review we focus on the role of mutated CaV2.1 (i.e., P/Q-type) voltage-activated Ca2+ channels, and on the ultimate consequences that mutations causing familial hemiplegic migraine type-1 (FHM1) have in neurotransmitter release. Transgenic mice harboring the human pathogenic FHM1 mutation R192Q or S218L (KI) have been used as models to study neurotransmission at several central and peripheral synapses. FHM1 KI mice are a powerful tool to explore presynaptic regulation associated with expression of CaV2.1 channels. Mutated CaV2.1 channels activate at more hyperpolarizing potentials and lead to a gain-of-function in synaptic transmission. This gain-of-function might underlie alterations in the excitatory/ inhibitory balance of synaptic transmission, favoring a persistent state of hyperexcitability in cortical neurons that would increase the susceptibility for cortical spreading depression (CSD), a mechanism believed to initiate the attacks of migraine with aura.
Collapse
|
26
|
Pankonien I, Alvarez JL, Doller A, Köhncke C, Rotte D, Regitz-Zagrosek V, Morano I, Haase H. Ahnak1 is a tuneable modulator of cardiac Ca(v)1.2 calcium channel activity. J Muscle Res Cell Motil 2011; 32:281-90. [PMID: 22038483 DOI: 10.1007/s10974-011-9269-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 10/13/2011] [Indexed: 11/29/2022]
Abstract
Ahnak1 has been implicated in the beta-adrenergic regulation of the cardiac L-type Ca(2+) channel current (I (CaL)) by its binding to the regulatory Cavβ(2) subunit. In this study, we addressed the question whether ahnak1/Cavβ(2) interactions are essential or redundant for beta-adrenergic stimulation of I (CaL). Three naturally occurring ahnak1 variants (V5075 M, G5242R, and T5796 M) identified by genetic screening of cardiomyopathy patients did essentially not influence the in vitro Cavβ(2) interaction as assessed by recombinant proteins. But, we observed a robust increase in Cavβ(2) binding by mutating Ala at position 4984 to Pro which creates a PxxP consensus motif in the ahnak1 protein fragment. Surface plasmon resonance measurements revealed that this mutation introduced an additional Cavβ(2) binding site. The functionality of A4984P was supported by the specific action of the Pro-containing ahnak1-derived peptide (P4984) in beta-adrenergic regulation of I (CaL). Patch clamp recordings on cardiomyocytes showed that intracellular perfusion of P4984 markedly reduced I (CaL) response to the beta-adrenergic agonist, isoprenaline, while the Ala-containing counterpart failed to affect I (CaL). Interestingly, I (CaL) of ahnak1-deficient cardiomyocytes was not affected by peptide application. Moreover, I (CaL) of ahnak1-deficient cardiomyocytes showed intact beta-adrenergic responsiveness. Similarly isolated ahnak1-deficient mouse hearts responded normally to adrenergic challenge. Our results indicate that ahnak1 is not essential for beta-adrenergic up-regulation of I (CaL) and cardiac contractility in mice. But, tuning ahnak1/Cavβ(2) interaction provides a tool for modulating the beta-adrenergic response of I (CaL).
Collapse
Affiliation(s)
- Ines Pankonien
- Max Delbrück Center for Molecular Medicine, Robert-Rössle-Str.10, 13125, Berlin, Germany
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Madhvani RV, Xie Y, Pantazis A, Garfinkel A, Qu Z, Weiss JN, Olcese R. Shaping a new Ca²⁺ conductance to suppress early afterdepolarizations in cardiac myocytes. J Physiol 2011; 589:6081-92. [PMID: 22025660 DOI: 10.1113/jphysiol.2011.219600] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Sudden cardiac death (SCD) due to ventricular fibrillation (VF) is a major world-wide health problem. A common trigger of VF involves abnormal repolarization of the cardiac action potential causing early afterdepolarizations (EADs). Here we used a hybrid biological-computational approach to investigate the dependence of EADs on the biophysical properties of the L-type Ca(2+) current (I(Ca,L)) and to explore how modifications of these properties could be designed to suppress EADs. EADs were induced in isolated rabbit ventricular myocytes by exposure to 600 μmol l(-1) H(2)O(2) (oxidative stress) or lowering the external [K(+)] from 5.4 to 2.0-2.7 mmol l(-1) (hypokalaemia). The role of I(Ca,L) in EAD formation was directly assessed using the dynamic clamp technique: the paced myocyte's V(m) was input to a myocyte model with tunable biophysical parameters, which computed a virtual I(Ca,L), which was injected into the myocyte in real time. This virtual current replaced the endogenous I(Ca,L), which was suppressed with nifedipine. Injecting a current with the biophysical properties of the native I(Ca,L) restored EAD occurrence in myocytes challenged by H(2)O(2) or hypokalaemia. A mere 5 mV depolarizing shift in the voltage dependence of activation or a hyperpolarizing shift in the steady-state inactivation curve completely abolished EADs in myocytes while maintaining a normal Ca(i) transient. We propose that modifying the biophysical properties of I(Ca,L) has potential as a powerful therapeutic strategy for suppressing EADs and EAD-mediated arrhythmias.
Collapse
Affiliation(s)
- Roshni V Madhvani
- Division of Molecular Medicine, Department of Anesthesiology, David Geffen School of Medicine at University of California, Los Angeles, CA 90095-7115, USA
| | | | | | | | | | | | | |
Collapse
|
28
|
Hill-Eubanks DC, Werner ME, Heppner TJ, Nelson MT. Calcium signaling in smooth muscle. Cold Spring Harb Perspect Biol 2011; 3:a004549. [PMID: 21709182 DOI: 10.1101/cshperspect.a004549] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Changes in intracellular Ca(2+) are central to the function of smooth muscle, which lines the walls of all hollow organs. These changes take a variety of forms, from sustained, cell-wide increases to temporally varying, localized changes. The nature of the Ca(2+) signal is a reflection of the source of Ca(2+) (extracellular or intracellular) and the molecular entity responsible for generating it. Depending on the specific channel involved and the detection technology employed, extracellular Ca(2+) entry may be detected optically as graded elevations in intracellular Ca(2+), junctional Ca(2+) transients, Ca(2+) flashes, or Ca(2+) sparklets, whereas release of Ca(2+) from intracellular stores may manifest as Ca(2+) sparks, Ca(2+) puffs, or Ca(2+) waves. These diverse Ca(2+) signals collectively regulate a variety of functions. Some functions, such as contractility, are unique to smooth muscle; others are common to other excitable cells (e.g., modulation of membrane potential) and nonexcitable cells (e.g., regulation of gene expression).
Collapse
Affiliation(s)
- David C Hill-Eubanks
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405, USA
| | | | | | | |
Collapse
|
29
|
Ball SL, McEnery MW, Yunker AMR, Shin HS, Gregg RG. Distribution of voltage gated calcium channel β subunits in the mouse retina. Brain Res 2011; 1412:1-8. [PMID: 21831364 DOI: 10.1016/j.brainres.2011.07.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 07/14/2011] [Accepted: 07/14/2011] [Indexed: 01/03/2023]
Abstract
Voltage gated calcium channels (VGCCs) are essential to neuronal excitation and signal transduction. They are multimeric in structure and comprised of an alpha subunit that functions as a calcium pore and two additional subunits: an alpha2delta subunit and a cytoplasmic beta subunit. To better understand the role of VGCCs in the retina we used immunohistochemical methods to determine the distribution of VGCC β subunits in normal and mutant mice. To verify the specificity of each antibody and to examine the potential for subunit redistribution when beta subunit expression is perturbed, we used 4 mutant mouse lines that each lack a specific β subunit isoform (β(1)-β(4)). We found the β(1) subunit distributed on cell bodies in the inner nuclear layer (INL) and on processes within both the inner and outer limiting membrane; the β(2) subunit localized to the outer plexiform layer (OPL) and inner plexiform layer (IPL); the β(3) subunit was localized to three narrow and distinct bands within the IPL; the β(4) subunit was localized to three diffuse bands within the IPL. Loss of one β subunit affected labeling intensity but not general distribution patterns of other β subunits. It is likely that VGCCs critical for retinal signal transmission are comprised of the β(2) subunit in the OPL and any of the 4 β subunits in the IPL. Our results suggest that within the OPL the α(1F) subunit pairs predominantly with the β(2) subunit while within the IPL it may pair with either any β subunit.
Collapse
Affiliation(s)
- Sherry L Ball
- Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
| | | | | | | | | |
Collapse
|
30
|
Wall-Lacelle S, Hossain MI, Sauvé R, Blunck R, Parent L. Double mutant cycle analysis identified a critical leucine residue in the IIS4S5 linker for the activation of the Ca(V)2.3 calcium channel. J Biol Chem 2011; 286:27197-205. [PMID: 21652722 DOI: 10.1074/jbc.m111.237412] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mutations in distal S6 were shown to significantly alter the stability of the open state of Ca(V)2.3 (Raybaud, A., Baspinar, E. E., Dionne, F., Dodier, Y., Sauvé, R., and Parent, L. (2007) J. Biol. Chem. 282, 27944-27952). By analogy with K(V) channels, we tested the hypothesis that channel activation involves electromechanical coupling between S6 and the S4S5 linker in Ca(V)2.3. Among the 11 positions tested in the S4S5 linker of domain II, mutations of the leucine residue at position 596 were found to destabilize significantly the closed state with a -50 mV shift in the activation potential and a -20 mV shift in its charge-voltage relationship as compared with Ca(V)2.3 wt. A double mutant cycle analysis was performed by introducing pairs of glycine residues between S4S5 and S6 of Domain II. Strong coupling energies (ΔΔG(interact) > 2 kcal mol(-1)) were measured for the activation gating of 12 of 39 pairs of mutants. Leu-596 (IIS4S5) was strongly coupled with distal residues in IIS6 from Leu-699 to Asp-704. In particular, the double mutant L596G/I701G showed strong cooperativity with a ΔΔG(interact) ≈6 kcal mol(-1) suggesting that both positions contribute to the activation gating of the channel. Altogether, our results highlight the role of a leucine residue in S4S5 and provide the first series of evidence that the IIS4S5 and IIS6 regions are energetically coupled during the activation of a voltage-gated Ca(V) channel.
Collapse
Affiliation(s)
- Sébastien Wall-Lacelle
- Department of Physiologie, Membrane Protein Research Group, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | | | | | | | | |
Collapse
|
31
|
Altier C, Garcia-Caballero A, Simms B, You H, Chen L, Walcher J, Tedford HW, Hermosilla T, Zamponi GW. The Cavβ subunit prevents RFP2-mediated ubiquitination and proteasomal degradation of L-type channels. Nat Neurosci 2010; 14:173-80. [PMID: 21186355 DOI: 10.1038/nn.2712] [Citation(s) in RCA: 196] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 11/12/2010] [Indexed: 01/19/2023]
Abstract
It is well established that the auxiliary Cavβ subunit regulates calcium channel density in the plasma membrane, but the cellular mechanism by which this occurs has remained unclear. We found that the Cavβ subunit increased membrane expression of Cav1.2 channels by preventing the entry of the channels into the endoplasmic reticulum-associated protein degradation (ERAD) complex. Without Cavβ, Cav1.2 channels underwent robust ubiquitination by the RFP2 ubiquitin ligase and interacted with the ERAD complex proteins derlin-1 and p97, culminating in targeting of the channels to the proteasome for degradation. On treatment with the proteasomal inhibitor MG132, Cavβ-free channels were rescued from degradation and trafficked to the plasma membrane. The coexpression of Cavβ interfered with ubiquitination and targeting of the channel to the ERAD complex, thereby facilitating export from the endoplasmic reticulum and promoting expression on the cell surface. Thus, Cavββ regulates the ubiquitination and stability of the calcium channel complex.
Collapse
Affiliation(s)
- Christophe Altier
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Dilger EK, Shin HS, Guido W. Requirements for synaptically evoked plateau potentials in relay cells of the dorsal lateral geniculate nucleus of the mouse. J Physiol 2010; 589:919-37. [PMID: 21173075 DOI: 10.1113/jphysiol.2010.202499] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In developing cells of the mouse dorsal lateral geniculate nucleus (dLGN), synaptic responses evoked by optic tract (OT) stimulation give rise to long-lasting, high-amplitude depolarizations known as plateau potentials. These events are mediated by L-type Ca2+ channels and occur during early postnatal life, a time when retinogeniculate connections are remodelling. To better understand the relationship between L-type activity and dLGN development we used an in vitro thalamic slice preparation which preserves the retinal connections and intrinsic circuitry in dLGN and examined how synaptic responses evoked by OT stimulation lead to the activation of plateau potentials. By varying the strength and temporal frequency of OT stimulation we identified at least three factors that contribute to the developmental regulation of plateau activity: the degree of retinal convergence, the temporal pattern of retinal stimulation and the emergence of feed-forward inhibition. Before natural eye opening (postnatal day 14), the excitatory synaptic responses of relay cells receiving multiple retinal inputs summated in both the spatial and temporal domains to produce depolarizations sufficient to activate L-type activity. After eye opening, when inhibitory responses are fully developed, plateau activity was rarely evoked even with high temporal rates of OT stimulation. When the bulk of this inhibition was blocked by bath application of bicuculline, the incidence of plateau activity increased significantly. We also made use of a transgenic mouse that lacks the β3 subunit of the L-type Ca2+ channel. These mutants have far fewer membrane-bound Ca2+ channels and attenuated L-type activity. In β3 nulls, L-type plateau activity was rarely observed even at young ages when plateau activity prevails. Thus, in addition to the changing patterns of synaptic connectivity and retinal activity, the expression of L-type Ca2+ channels is a requisite component in the manifestation of plateau activity.
Collapse
Affiliation(s)
- Emily K Dilger
- Department of Anatomy and Neurobiology, Virginia Commonwealth University Medical Centre, Sanger Hall, 1101 E. Marshall St, Richmond, VA 23298, USA
| | | | | |
Collapse
|
33
|
Transcriptome profile reveals AMPA receptor dysfunction in the hippocampus of the Rsk2-knockout mice, an animal model of Coffin–Lowry syndrome. Hum Genet 2010; 129:255-69. [DOI: 10.1007/s00439-010-0918-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/05/2010] [Indexed: 10/18/2022]
|
34
|
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.
Collapse
Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | | |
Collapse
|
35
|
Xu KY, Zhu W, Xiao RP. Serine496 of β2 subunit of L-type Ca2+ channel participates in molecular crosstalk between activation of (Na++K+)-ATPase and the channel. Biochem Biophys Res Commun 2010; 402:319-23. [PMID: 20937253 DOI: 10.1016/j.bbrc.2010.10.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 11/29/2022]
Abstract
Activation of (Na++K+)-ATPase (NKA) regulates cardiac L-type Ca2+ channel (LTCC) function through molecular crosstalk. The mechanism underlying NKA-LTCC crosstalk remains poorly understood. We have previously shown that activation of NKA leads to phosphorylation of LTCC α1 Ser1928. Here we investigated whether LTCC β2 subunit is modulated by NKA activation and found that LTCC β2 Ser496 is phosphorylated in response to activation of NKA. Src inhibitor PP1 and Erk1/2 inhibitor PD98059 abolish LTCC β2 Ser496 phosphorylation, suggesting that NKA-mediated β2 Ser496 phosphorylation is dependent of Src/Erk1/2 signaling pathway. Protein kinase G (PKG) inhibitor KT5823 failed to inhibit the phosphorylation of β2 Ser496, indicating that the NKA-LTCC crosstalk is independent of PKG activity. The results of nifedipine sensitive 45Ca influx experiments suggest that phosphorylation of β2 Ser496 may play a key down-regulation role in attenuating the accelerated activity of α1 subunit of the channel. Ouabain does not cause a phosphorylation on β2 Ser496, indicating a fundamental difference between activation and inhibition of NKA-mediated biological processes. This study provides the first evidence to demonstrate that LTCC β2 subunit is coupled with the movement of signals in the mechanism of activation of NKA-mediated crosstalk with LTCC.
Collapse
Affiliation(s)
- Kai Y Xu
- Department of Surgery, Division of Cardiac Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | | | | |
Collapse
|
36
|
ORTIZ-MIRANDA SONIAI, DAYANITHI GOVINDAN, VELÁZQUEZ-MARRERO CRISTINA, CUSTER EDWARDE, TREISTMAN STEVENN, LEMOS JOSÉR. Differential modulation of N-type calcium channels by micro-opioid receptors in oxytocinergic versus vasopressinergic neurohypophysial terminals. J Cell Physiol 2010; 225:276-88. [PMID: 20509142 PMCID: PMC4060829 DOI: 10.1002/jcp.22263] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Opioids modulate the electrical activity of magnocellular neurons (MCN) and inhibit neuropeptide release at their terminals in the neurohypophysis. We have previously shown that micro-opioid receptor (MOR) activation induces a stronger inhibition of oxytocin (OT) than vasopressin (AVP) release from isolated MCN terminals. This higher sensitivity of OT release is due, at least in part, to the selective targeting of R-type calcium channels. We now describe the underlying basis for AVP's weaker inhibition by MOR activation and provide a more complete explanation of the complicated effects on neuropeptide release. We found that N-type calcium channels in AVP terminals are differentially modulated by MOR; enhanced at lower concentrations but increasingly inhibited at higher concentrations of agonists. On the other hand, N-type calcium channels in OT terminals were always inhibited. The response pattern in co-labeled terminals was analogous to that observed in AVP-containing terminals. Changes in intracellular calcium concentration and neuropeptide release corroborated these results as they showed a similar pattern of enhancement and inhibition in AVP terminals contrasting with solely inhibitory responses in OT terminals to MOR agonists. We established that fast translocation of Ca(2+) channels to the plasma membrane was not mediating current increments and thus, changes in channel kinetic properties are most likely involved. Finally, we reveal a distinct Ca-channel beta-subunit expression between each type of nerve endings that could explain some of the differences in responses to MOR activation. These results help advance our understanding of the complex modulatory mechanisms utilized by MORs in regulating presynaptic neuropeptide release.
Collapse
Affiliation(s)
- SONIA I. ORTIZ-MIRANDA
- Department of Physiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts
| | | | - CRISTINA VELÁZQUEZ-MARRERO
- Department of Physiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts
| | - EDWARD E. CUSTER
- Department of Physiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts
| | - STEVEN N. TREISTMAN
- Brudnick Neuropsychiatric Institute, University of Massachusetts Medical School, Worcester, Massachusetts
| | - JOSÉ R. LEMOS
- Department of Physiology & Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts
| |
Collapse
|
37
|
Bourdin B, Marger F, Wall-Lacelle S, Schneider T, Klein H, Sauvé R, Parent L. Molecular determinants of the CaVbeta-induced plasma membrane targeting of the CaV1.2 channel. J Biol Chem 2010; 285:22853-63. [PMID: 20478999 DOI: 10.1074/jbc.m110.111062] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ca(V)beta subunits modulate cell surface expression and voltage-dependent gating of high voltage-activated (HVA) Ca(V)1 and Ca(V)2 alpha1 subunits. High affinity Ca(V)beta binding onto the so-called alpha interaction domain of the I-II linker of the Ca(V)alpha1 subunit is required for Ca(V)beta modulation of HVA channel gating. It has been suggested, however, that Ca(V)beta-mediated plasma membrane targeting could be uncoupled from Ca(V)beta-mediated modulation of channel gating. In addition to Ca(V)beta, Ca(V)alpha2delta and calmodulin have been proposed to play important roles in HVA channel targeting. Indeed we show that co-expression of Ca(V)alpha2delta caused a 5-fold stimulation of the whole cell currents measured with Ca(V)1.2 and Ca(V)beta3. To gauge the synergetic role of auxiliary subunits in the steady-state plasma membrane expression of Ca(V)1.2, extracellularly tagged Ca(V)1.2 proteins were quantified using fluorescence-activated cell sorting analysis. Co-expression of Ca(V)1.2 with either Ca(V)alpha2delta, calmodulin wild type, or apocalmodulin (alone or in combination) failed to promote the detection of fluorescently labeled Ca(V)1.2 subunits. In contrast, co-expression with Ca(V)beta3 stimulated plasma membrane expression of Ca(V)1.2 by a 10-fold factor. Mutations within the alpha interaction domain of Ca(V)1.2 or within the nucleotide kinase domain of Ca(V)beta3 disrupted the Ca(V)beta3-induced plasma membrane targeting of Ca(V)1.2. Altogether, these data support a model where high affinity binding of Ca(V)beta to the I-II linker of Ca(V)alpha1 largely accounts for Ca(V)beta-induced plasma membrane targeting of Ca(V)1.2.
Collapse
Affiliation(s)
- Benoîte Bourdin
- Institute of Neurophysiology and Center for Molecular Medicine, Cologne University, D-50931 Cologne, Germany
| | | | | | | | | | | | | |
Collapse
|
38
|
Roberts-Crowley ML, Rittenhouse AR. Arachidonic acid inhibition of L-type calcium (CaV1.3b) channels varies with accessory CaVbeta subunits. ACTA ACUST UNITED AC 2010; 133:387-403. [PMID: 19332620 PMCID: PMC2699108 DOI: 10.1085/jgp.200810047] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Arachidonic acid (AA) inhibits the activity of several different voltage-gated Ca2+ channels by an unknown mechanism at an unknown site. The Ca2+ channel pore-forming subunit (CaVα1) is a candidate for the site of AA inhibition because T-type Ca2+ channels, which do not require accessory subunits for expression, are inhibited by AA. Here, we report the unanticipated role of accessory CaVβ subunits on the inhibition of CaV1.3b L-type (L-) current by AA. Whole cell Ba2+ currents were measured from recombinant channels expressed in human embryonic kidney 293 cells at a test potential of −10 mV from a holding potential of −90 mV. A one-minute exposure to 10 µM AA inhibited currents with β1b, β3, or β4 58, 51, or 44%, respectively, but with β2a only 31%. At a more depolarized holding potential of −60 mV, currents were inhibited to a lesser degree. These data are best explained by a simple model where AA stabilizes CaV1.3b in a deep closed-channel conformation, resulting in current inhibition. Consistent with this hypothesis, inhibition by AA occurred in the absence of test pulses, indicating that channels do not need to open to become inhibited. AA had no effect on the voltage dependence of holding potential–dependent inactivation or on recovery from inactivation regardless of CaVβ subunit. Unexpectedly, kinetic analysis revealed evidence for two populations of L-channels that exhibit willing and reluctant gating previously described for CaV2 channels. AA preferentially inhibited reluctant gating channels, revealing the accelerated kinetics of willing channels. Additionally, we discovered that the palmitoyl groups of β2a interfere with inhibition by AA. Our novel findings that the CaVβ subunit alters kinetic changes and magnitude of inhibition by AA suggest that CaVβ expression may regulate how AA modulates Ca2+-dependent processes that rely on L-channels, such as gene expression, enzyme activation, secretion, and membrane excitability.
Collapse
Affiliation(s)
- Mandy L Roberts-Crowley
- Department of Physiology and Program in Neuroscience, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | |
Collapse
|
39
|
Wang G, Zhu X, Xie W, Han P, Li K, Sun Z, Wang Y, Chen C, Song R, Cao C, Zhang J, Wu C, Liu J, Cheng H. Rad As a Novel Regulator of Excitation–Contraction Coupling and β-Adrenergic Signaling in Heart. Circ Res 2010; 106:317-27. [DOI: 10.1161/circresaha.109.208272] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Rationale
:
Rad (Ras associated with diabetes) GTPase, a monomeric small G protein, binds to Ca
v
β subunit of the L-type Ca
2+
channel (LCC) and thereby regulates LCC trafficking and activity. Emerging evidence suggests that Rad is an important player in cardiac arrhythmogenesis and hypertrophic remodeling. However, whether and how Rad involves in the regulation of excitation–contraction (EC) coupling is unknown.
Objective
:
This study aimed to investigate possible role of Rad in cardiac EC coupling and β-adrenergic receptor (βAR) inotropic mechanism.
Methods and Results
:
Adenoviral overexpression of Rad by 3-fold in rat cardiomyocytes suppressed LCC current (
I
Ca
), [Ca
2+
]
i
transients, and contractility by 60%, 42%, and 38%, respectively, whereas the “gain” function of EC coupling was significantly increased, due perhaps to reduced “redundancy” of LCC in triggering sarcoplasmic reticulum release. Conversely, ≈70% Rad knockdown by RNA interference increased
I
Ca
(50%), [Ca
2+
]
i
transients (52%) and contractility (58%) without altering EC coupling efficiency; and the dominant negative mutant RadS105N exerted a similar effect on
I
Ca
. Rad upregulation caused depolarizing shift of LCC activation and hastened time-dependent LCC inactivation; Rad downregulation, however, failed to alter these attributes. The Na
+
/Ca
2+
exchange activity, sarcoplasmic reticulum Ca
2+
content, properties of Ca
2+
sparks and propensity for Ca
2+
waves all remained unperturbed regardless of Rad manipulation. Rad overexpression, but not knockdown, negated βAR effects on
I
Ca
and Ca
2+
transients.
Conclusion
:
These results establish Rad as a novel endogenous regulator of cardiac EC coupling and βAR signaling and support a parsimonious model in which Rad buffers Ca
v
β to modulate LCC activity, EC coupling, and βAR responsiveness.
Collapse
Affiliation(s)
- Gang Wang
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Xiaojun Zhu
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Wenjun Xie
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Peidong Han
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Kaitao Li
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Zhongcui Sun
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Yanru Wang
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Chunlei Chen
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Ruisheng Song
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Chunmei Cao
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Jifeng Zhang
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Caihong Wu
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Jie Liu
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| | - Heping Cheng
- From the Institute of Molecular Medicine (G.W., X.Z., W.X., P.H., K.L., Z.S., Y.W., C. Chen, R.S., C. Cao, C.W., J.L., H.C.) and State Key Laboratory of Biomembrane and Membrane Biotechnology (G.W., C.W.) of College of Life Science, Peking University, Beijing, China; Cardiovascular Center (J.Z.), University of Michigan, Ann Arbor, Mich; and Department of Pathophysiology (J.L.), Medical School of Shenzhen University, China
| |
Collapse
|
40
|
Heneghan JF, Mitra-Ganguli T, Stanish LF, Liu L, Zhao R, Rittenhouse AR. The Ca2+ channel beta subunit determines whether stimulation of Gq-coupled receptors enhances or inhibits N current. ACTA ACUST UNITED AC 2010; 134:369-84. [PMID: 19858357 PMCID: PMC2768801 DOI: 10.1085/jgp.200910203] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In superior cervical ganglion (SCG) neurons, stimulation of M1 receptors (M1Rs) produces a distinct pattern of modulation of N-type calcium (N-) channel activity, enhancing currents elicited with negative test potentials and inhibiting currents elicited with positive test potentials. Exogenously applied arachidonic acid (AA) reproduces this profile of modulation, suggesting AA functions as a downstream messenger of M1Rs. In addition, techniques that diminish AA's concentration during M1R stimulation minimize N-current modulation. However, other studies suggest depletion of phosphatidylinositol-4,5-bisphosphate during M1R stimulation suffices to elicit modulation. In this study, we used an expression system to examine the physiological mechanisms regulating modulation. We found the β subunit (CaVβ) acts as a molecular switch regulating whether modulation results in enhancement or inhibition. In human embryonic kidney 293 cells, stimulation of M1Rs or neurokinin-1 receptors (NK-1Rs) inhibited activity of N channels formed by CaV2.2 and coexpressed with CaVβ1b, CaVβ3, or CaVβ4 but enhanced activity of N channels containing CaVβ2a. Exogenously applied AA produced the same pattern of modulation. Coexpression of CaVβ2a, CaVβ3, and CaVβ4 recapitulated the modulatory response previously seen in SCG neurons, implying heterogeneous association of CaVβ with CaV2.2. Further experiments with mutated, chimeric CaVβ subunits and free palmitic acid revealed that palmitoylation of CaVβ2a is essential for loss of inhibition. The data presented here fit a model in which CaVβ2a blocks inhibition, thus unmasking enhancement. Our discovery that the presence or absence of palmitoylated CaVβ2a toggles M1R- or NK-1R–mediated modulation of N current between enhancement and inhibition identifies a novel role for palmitoylation. Moreover, these findings predict that at synapses, modulation of N-channel activity by M1Rs or NK-1Rs will fluctuate between enhancement and inhibition based on the presence of palmitoylated CaVβ2a.
Collapse
Affiliation(s)
- John F Heneghan
- Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | | | | | | | | | | |
Collapse
|
41
|
A mutation in the first intracellular loop of CACNA1A prevents P/Q channel modulation by SNARE proteins and lowers exocytosis. Proc Natl Acad Sci U S A 2010; 107:1672-7. [PMID: 20080591 DOI: 10.1073/pnas.0908359107] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Familial hemiplegic migraine (FHM)-causing mutations in the gene encoding the P/Q Ca(2+) channel alpha(1A) subunit (CACNA1A) locate to the pore and voltage sensor regions and normally involve gain-of-channel function. We now report on a mutation identified in the first intracellular loop of CACNA1A (alpha(1A(A454T))) that does not cause FHM but is associated with the absence of sensorimotor symptoms in a migraine with aura pedigree. Alpha(1A(A454T)) channels showed weakened regulation of voltage-dependent steady-state inactivation by Ca(V)beta subunits. More interestingly, A454T mutation suppressed P/Q channel modulation by syntaxin 1A or SNAP-25 and decreased exocytosis. Our findings reveal the importance of I-II loop structural integrity in the functional interaction between P/Q channel and proteins of the vesicle-docking/fusion machinery, and that genetic variation in CACNA1A may be not only a cause but also a modifier of migraine phenotype.
Collapse
|
42
|
Zhang Y, Yamada Y, Fan M, Bangaru SD, Lin B, Yang J. The beta subunit of voltage-gated Ca2+ channels interacts with and regulates the activity of a novel isoform of Pax6. J Biol Chem 2009; 285:2527-36. [PMID: 19917615 DOI: 10.1074/jbc.m109.022236] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Ca(2+) channel beta subunits (Ca(v)betas) are essential for regulating the surface expression and gating of high voltage-activated Ca(2+) channels through their interaction with Ca(2+) channel alpha(1) subunits. In efforts to uncover new interacting partners and new functions for Ca(v)beta, we identified a new splicing isoform of Pax6, a transcription factor crucial for the development of the eye, nose, brain, and pancreas. Pax6 contains two DNA binding domains (paired domain and homeodomain), a glycine-rich linker connecting these two domains and a C-terminal proline-, serine-, and threonine-rich transactivation domain. The protein sequence and function of Pax6 are highly conserved from invertebrate to human. The newly isolated isoform, named Pax6(S), retains the paired domain, linker, and homeodomain of Pax6, but its C terminus is composed of a truncated classic proline, serine, and threonine domain and a unique S tail. Pax6(S) shows a similar level of transcriptional activity in vitro as does Pax6, but only in primates is the protein sequence highly conserved. Its spatial-temporal expression profiles are also different from those of Pax6. These divergences suggest a noncanonical role of Pax6(S) during development. The interaction between Pax6(S) and Ca(v)beta is mainly endowed by the S tail. Co-expression of Pax6(S) with a Ca(2+) channel complex containing the beta(3) subunit in Xenopus oocytes does not affect channel properties. Conversely, however, beta(3) is able to suppress the transcriptional activity of Pax6(S). Furthermore, in the presence of Pax6(S), beta(3) is translocated from the cytoplasm to the nucleus. These results suggest that full-length Ca(v)beta may act directly as a transcription regulator independent of its role in regulating Ca(2+) channel activity.
Collapse
Affiliation(s)
- Yun Zhang
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | | | | | | | | | | |
Collapse
|
43
|
Abiria SA, Colbran RJ. CaMKII associates with CaV1.2 L-type calcium channels via selected beta subunits to enhance regulatory phosphorylation. J Neurochem 2009; 112:150-61. [PMID: 19840220 DOI: 10.1111/j.1471-4159.2009.06436.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Calcium/calmodulin-dependent kinase II (CaMKII) facilitates L-type calcium channel (LTCC) activity physiologically, but may exacerbate LTCC-dependent pathophysiology. We previously showed that CaMKII forms stable complexes with voltage-gated calcium channel (VGCC) beta(1b) or beta(2a) subunits, but not with the beta(3) or beta(4) subunits (Grueter et al. 2008). CaMKII-dependent facilitation of Ca(V)1.2 LTCCs requires Thr498 phosphorylation in the beta(2a) subunit (Grueter et al. 2006), but the relationship of this modulation to CaMKII interactions with LTCC subunits is unknown. Here we show that CaMKII co-immunoprecipitates with forebrain LTCCs that contain Ca(V)1.2alpha(1) and beta(1) or beta(2) subunits, but is not detected in LTCC complexes containing beta(4) subunits. CaMKIIalpha can be specifically tethered to the I/II linker of Ca(V)1.2 alpha(1) subunits in vitro by the beta(1b) or beta(2a) subunits. Efficient targeting of CaMKIIalpha to the full-length Ca(V)1.2alpha(1) subunit in transfected HEK293 cells requires CaMKII binding to the beta(2a) subunit. Moreover, disruption of CaMKII binding substantially reduced phosphorylation of beta(2a) at Thr498 within the LTCC complex, without altering overall phosphorylation of Ca(V)1.2alpha(1) and beta subunits. These findings demonstrate a biochemical mechanism underlying LTCC facilitation by CaMKII.
Collapse
Affiliation(s)
- Sunday A Abiria
- Brain Institute, Vanderbilt University, Nashville, Tennessee, USA
| | | |
Collapse
|
44
|
van Gemert NG, Carvalho DMM, Karst H, van der Laan S, Zhang M, Meijer OC, Hell JW, Joëls M. Dissociation between rat hippocampal CA1 and dentate gyrus cells in their response to corticosterone: effects on calcium channel protein and current. Endocrinology 2009; 150:4615-24. [PMID: 19589863 PMCID: PMC2754681 DOI: 10.1210/en.2009-0525] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Stress and corticosterone affect, via glucocorticoid receptors, cellular physiology in the rodent brain. A well-documented example concerns corticosteroid effects on high-voltage activated (L type) calcium currents in the hippocampal CA1 area. We tested whether corticosterone also affects calcium currents in another hippocampal area that highly expresses glucocorticoid receptors, i.e. the dentate gyrus (DG). Remarkably, corticosterone (100 nm, given for 20 min, 1-4.5 hr before recording) did not change high-voltage activated calcium currents in the DG, whereas currents in the CA1 area of the same rats were increased. Follow-up studies revealed that no apparent dissociation between the two areas was observed with respect to transcriptional regulation of calcium channel subunits; thus, in both areas corticosterone increased mRNA levels of the calcium channel-beta4 but not the (alpha) Ca(v)1.2 subunit. At the protein level, however, beta4 and Ca(v)1.2 levels were significantly up-regulated by corticosterone in the CA1 but not the DG area. These data suggest that stress-induced elevations in the level of corticosterone result in a regionally differentiated physiological response that is not simply determined by the glucocorticoid receptor distribution and that the observed regional differentiation may be caused by a gene involved in the translational machinery or in mechanisms regulating mRNA or protein stability.
Collapse
Affiliation(s)
- Neeltje G van Gemert
- Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM Amsterdam, The Netherlands
| | | | | | | | | | | | | | | |
Collapse
|
45
|
Taylor JR, Zheng Z, Wang ZM, Payne AM, Messi ML, Delbono O. Increased CaVbeta1A expression with aging contributes to skeletal muscle weakness. Aging Cell 2009; 8:584-94. [PMID: 19663902 DOI: 10.1111/j.1474-9726.2009.00507.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Ca2+ release from the sarcoplasmic reticulum (SR) into the cytosol is a crucial part of excitation-contraction (E-C) coupling. Excitation-contraction uncoupling, a deficit in Ca2+ release from the SR, is thought to be responsible for at least some of the loss in specific force observed in aging skeletal muscle. Excitation-contraction uncoupling may be caused by alterations in expression of the voltage-dependent calcium channel alpha1s (CaV1.1) and beta1a (CaVbeta1a) subunits, both of which are necessary for E-C coupling to occur. While previous studies have found CaV1.1 expression declines in old rodents, CaVbeta1a expression has not been previously examined in aging models. Western blot analysis shows a substantial increase of CaVbeta1a expression over the full lifespan of Friend Virus B (FVB) mice. To examine the specific effects of CaVbeta1a overexpression, a CaVbeta1a-YFP plasmid was electroporated in vivo into young animals. The resulting increase in expression of CaVbeta1a corresponded to decline of CaV1.1 over the same time period. YFP fluorescence, used as a measure of CaVbeta1a-YFP expression in individual fibers, also showed an inverse relationship with charge movement, measured using the whole-cell patch-clamp technique. Specific force was significantly reduced in young CaVbeta1a-YFP electroporated muscle fibers compared with sham-electroporated, age-matched controls. siRNA interference of CaVbeta1a in young muscles reduced charge movement, while charge movement in old was restored to young control levels. These studies imply CaVbeta1a serves as both a positive and negative regulator CaV1.1 expression, and that endogenous overexpression of CaVbeta1a during old age may play a role in the loss of specific force.
Collapse
Affiliation(s)
- Jackson R Taylor
- Department of Internal Medicine-Gerontology, Wake Forest University School of Medicine, 1 Medical Center Boulvard, Winston Salem, NC 27157, USA
| | | | | | | | | | | |
Collapse
|
46
|
Zhou W, Horstick EJ, Hirata H, Kuwada JY. Identification and expression of voltage-gated calcium channel β subunits in Zebrafish. Dev Dyn 2008; 237:3842-52. [DOI: 10.1002/dvdy.21776] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
47
|
Schredelseker J, Dayal A, Schwerte T, Franzini-Armstrong C, Grabner M. Proper restoration of excitation-contraction coupling in the dihydropyridine receptor beta1-null zebrafish relaxed is an exclusive function of the beta1a subunit. J Biol Chem 2008; 284:1242-51. [PMID: 19008220 DOI: 10.1074/jbc.m807767200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The paralyzed zebrafish strain relaxed carries a null mutation for the skeletal muscle dihydropyridine receptor (DHPR) beta(1a) subunit. Lack of beta(1a) results in (i) reduced membrane expression of the pore forming DHPR alpha(1S) subunit, (ii) elimination of alpha(1S) charge movement, and (iii) impediment of arrangement of the DHPRs in groups of four (tetrads) opposing the ryanodine receptor (RyR1), a structural prerequisite for skeletal muscle-type excitation-contraction (EC) coupling. In this study we used relaxed larvae and isolated myotubes as expression systems to discriminate specific functions of beta(1a) from rather general functions of beta isoforms. Zebrafish and mammalian beta(1a) subunits quantitatively restored alpha(1S) triad targeting and charge movement as well as intracellular Ca(2+) release, allowed arrangement of DHPRs in tetrads, and most strikingly recovered a fully motile phenotype in relaxed larvae. Interestingly, the cardiac/neuronal beta(2a) as the phylogenetically closest, and the ancestral housefly beta(M) as the most distant isoform to beta(1a) also completely recovered alpha(1S) triad expression and charge movement. However, both revealed drastically impaired intracellular Ca(2+) transients and very limited tetrad formation compared with beta(1a). Consequently, larval motility was either only partially restored (beta(2a)-injected larvae) or not restored at all (beta(M)). Thus, our results indicate that triad expression and facilitation of 1,4-dihydropyridine receptor (DHPR) charge movement are common features of all tested beta subunits, whereas the efficient arrangement of DHPRs in tetrads and thus intact DHPR-RyR1 coupling is only promoted by the beta(1a) isoform. Consequently, we postulate a model that presents beta(1a) as an allosteric modifier of alpha(1S) conformation enabling skeletal muscle-type EC coupling.
Collapse
Affiliation(s)
- Johann Schredelseker
- Department of Medical Genetics, Clinical and Molecular Pharmacology, Division of Biochemical Pharmacology, Innsbruck Medical University, A-6020 Innsbruck, Austria
| | | | | | | | | |
Collapse
|
48
|
Orientation of the calcium channel beta relative to the alpha(1)2.2 subunit is critical for its regulation of channel activity. PLoS One 2008; 3:e3560. [PMID: 18958281 PMCID: PMC2570331 DOI: 10.1371/journal.pone.0003560] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Accepted: 10/09/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The Ca(v)beta subunits of high voltage-activated Ca(2+) channels control the trafficking and biophysical properties of the alpha(1) subunit. The Ca(v)beta-alpha(1) interaction site has been mapped by crystallographic studies. Nevertheless, how this interaction leads to channel regulation has not been determined. One hypothesis is that betas regulate channel gating by modulating movements of IS6. A key requirement for this direct-coupling model is that the linker connecting IS6 to the alpha-interaction domain (AID) be a rigid structure. METHODOLOGY/PRINCIPAL FINDINGS The present study tests this hypothesis by altering the flexibility and orientation of this region in alpha(1)2.2, then testing for Ca(v)beta regulation using whole cell patch clamp electrophysiology. Flexibility was induced by replacement of the middle six amino acids of the IS6-AID linker with glycine (PG6). This mutation abolished beta2a and beta3 subunits ability to shift the voltage dependence of activation and inactivation, and the ability of beta2a to produce non-inactivating currents. Orientation of Ca(v)beta with respect to alpha(1)2.2 was altered by deletion of 1, 2, or 3 amino acids from the IS6-AID linker (Bdel1, Bdel2, Bdel3, respectively). Again, the ability of Ca(v)beta subunits to regulate these biophysical properties were totally abolished in the Bdel1 and Bdel3 mutants. Functional regulation by Ca(v)beta subunits was rescued in the Bdel2 mutant, indicating that this part of the linker forms beta-sheet. The orientation of beta with respect to alpha was confirmed by the bimolecular fluorescence complementation assay. CONCLUSIONS/SIGNIFICANCE These results show that the orientation of the Ca(v)beta subunit relative to the alpha(1)2.2 subunit is critical, and suggests additional points of contact between these subunits are required for Ca(v)beta to regulate channel activity.
Collapse
|
49
|
Hirenallur-S DK, Haworth ST, Leming JT, Chang J, Hernandez G, Gordon JB, Rusch NJ. Upregulation of vascular calcium channels in neonatal piglets with hypoxia-induced pulmonary hypertension. Am J Physiol Lung Cell Mol Physiol 2008; 295:L915-24. [PMID: 18776054 DOI: 10.1152/ajplung.90286.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inhibition of voltage-gated, L-type Ca(2+) (Ca(L)) channels by clinical calcium channel blockers provides symptomatic improvement to some pediatric patients with pulmonary arterial hypertension (PAH). The present study investigated whether abnormalities of vascular Ca(L) channels contribute to the pathogenesis of neonatal PAH using a newborn piglet model of hypoxia-induced PAH. Neonatal piglets exposed to chronic hypoxia (CH) developed PAH by 21 days, which was evident as a 2.1-fold increase in pulmonary vascular resistance in vivo compared with piglets raised in normoxia (N). Transpulmonary pressures (DeltaPtp) in the corresponding isolated perfused lungs were 20.5 +/- 2.1 mmHg (CH) and 11.6 +/- 0.8 mmHg (N). Nifedipine reduced the elevated DeltaPtp in isolated lungs of CH piglets by 6.4 +/- 1.3 mmHg but only reduced DeltaPtp in lungs of N piglets by 1.9 +/- 0.2 mmHg. Small pulmonary arteries from CH piglets also demonstrated accentuated Ca(2+)-dependent contraction, and Ca(2+) channel current was 3.94-fold higher in the resident vascular muscle cells. Finally, although the level of mRNA encoding the pore-forming alpha(1C)-subunit of the Ca(L) channel was similar between small pulmonary arteries from N and CH piglets, a profound and persistent upregulation of the vascular alpha(1C) protein was detected by 10 days in CH piglets at a time when pulmonary vascular resistance was only mildly elevated. Thus chronic hypoxia in the neonate is associated with the anomalous upregulation of Ca(L) channels in small pulmonary arteries in vivo and the resulting abnormal Ca(2+)-dependent resistance may contribute to the pathogenesis of PAH.
Collapse
Affiliation(s)
- Dinesh K Hirenallur-S
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, 4301 West Markham St., Little Rock, AR 72205, USA
| | | | | | | | | | | | | |
Collapse
|
50
|
Urbano FJ, Pagani MR, Uchitel OD. Calcium channels, neuromuscular synaptic transmission and neurological diseases. J Neuroimmunol 2008; 201-202:136-44. [PMID: 18678414 DOI: 10.1016/j.jneuroim.2008.06.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 06/16/2008] [Accepted: 06/17/2008] [Indexed: 01/20/2023]
Abstract
Voltage-dependent calcium channels are essential in neuronal signaling and synaptic transmission, and their functional alterations underlie numerous human disorders whether monogenic (e.g., ataxia, migraine, etc.) or autoimmune. We review recent work on Ca(V)2.1 or P/Q channelopathies, mostly using neuromuscular junction preparations, and focus specially on the functional hierarchy among the calcium channels recruited to mediate neurotransmitter release when Ca(V)2.1 channels are mutated or depleted. In either case, synaptic transmission is greatly compromised; evidently, none of the reported functional replacements with other calcium channels compensates fully.
Collapse
Affiliation(s)
- Francisco J Urbano
- Laboratorio de Fisiología y Biología Molecular, Instituto de Fisiología y Biología Molecular y Neurociencias, Universidad de Buenos Aires-CONICET, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, C1428-Buenos Aires, Argentina
| | | | | |
Collapse
|