51
|
Abstract
Voltage-gated calcium (CaV) channels are associated with β and α2δ auxiliary subunits. This review will concentrate on the function of the α2δ protein family, which has four members. The canonical role for α2δ subunits is to convey a variety of properties on the CaV1 and CaV2 channels, increasing the density of these channels in the plasma membrane and also enhancing their function. More recently, a diverse spectrum of non-canonical interactions for α2δ proteins has been proposed, some of which involve competition with calcium channels for α2δ or increase α2δ trafficking and others which mediate roles completely unrelated to their calcium channel function. The novel roles for α2δ proteins which will be discussed here include association with low-density lipoprotein receptor-related protein 1 (LRP1), thrombospondins, α-neurexins, prion proteins, large conductance (big) potassium (BK) channels, and N-methyl-d-aspartate (NMDA) receptors.
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| |
Collapse
|
52
|
Zhou JJ, Li DP, Chen SR, Luo Y, Pan HL. The α2δ-1-NMDA receptor coupling is essential for corticostriatal long-term potentiation and is involved in learning and memory. J Biol Chem 2018; 293:19354-19364. [PMID: 30355732 DOI: 10.1074/jbc.ra118.003977] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 10/18/2018] [Indexed: 11/06/2022] Open
Abstract
The striatum receives extensive cortical input and plays a prominent role in motor learning and habit formation. Glutamate N-methyl-d-aspartate (NMDA) receptor (NMDAR)-mediated long-term potentiation (LTP) is a major synaptic plasticity involved in learning and memory. However, the molecular mechanism underlying NMDAR plasticity in corticostriatal LTP is unclear. Here, we show that theta-burst stimulation (TBS) consistently induced corticostriatal LTP and increased the coincident presynaptic and postsynaptic NMDAR activity of medium spiny neurons. We also found that α2δ-1 (previously known as a subunit of voltage-gated calcium channels; encoded by the Cacna2d1 gene) physically interacted with NMDARs in the striatum of mice and humans, indicating that this cross-talk is conserved across species. Strikingly, inhibiting α2δ-1 trafficking with gabapentin or disrupting the α2δ-1-NMDAR interaction with an α2δ-1 C terminus-interfering peptide abolished TBS-induced LTP. In Cacna2d1-knockout mice, TBS failed to induce corticostriatal LTP and the associated increases in presynaptic and postsynaptic NMDAR activities. Moreover, systemic gabapentin treatment, microinjection of α2δ-1 C terminus-interfering peptide into the dorsomedial striatum, or Cacna2d1 ablation impaired the alternation T-maze task and rotarod performance in mice. Our findings indicate that the interaction between α2δ-1 and NMDARs is of high physiological relevance and that a TBS-induced switch from α2δ-1-free to α2δ-1-bound NMDARs is critically involved in corticostriatal LTP and LTP-associated learning and memory. Gabapentinoids at high doses may adversely affect cognitive function by targeting α2δ-1-NMDAR complexes.
Collapse
Affiliation(s)
- Jing-Jing Zhou
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 and
| | - De-Pei Li
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Shao-Rui Chen
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 and
| | - Yi Luo
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 and.,the Department of Clinical Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuhan, Hubei 430071, China
| | - Hui-Lin Pan
- From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 and
| |
Collapse
|
53
|
An African loss-of-function CACNA1C variant p.T1787M associated with a risk of ventricular fibrillation. Sci Rep 2018; 8:14619. [PMID: 30279520 PMCID: PMC6168548 DOI: 10.1038/s41598-018-32867-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 09/17/2018] [Indexed: 12/13/2022] Open
Abstract
Calcium regulation plays a central role in cardiac function. Several variants in the calcium channel Cav1.2 have been implicated in arrhythmic syndromes. We screened patients with Brugada syndrome, short QT syndrome, early repolarisation syndrome, and idiopathic ventricular fibrillation to determine the frequency and pathogenicity of Cav1.2 variants. Cav1.2 related genes, CACNA1C, CACNB2 and CACNA2D1, were screened in 65 probands. Missense variants were introduced in the Cav1.2 alpha subunit plasmid by mutagenesis to assess their pathogenicity using patch clamp approaches. Six missense variants were identified in CACNA1C in five individuals. Five of them, A1648T, A1689T, G1795R, R1973Q, C1992F, showed no major alterations of the channel function. The sixth C-terminal variant, Cavα1c-T1787M, present mostly in the African population, was identified in two patients with resuscitated cardiac arrest. The first patient originated from Cameroon and the second was an inhabitant of La Reunion Island with idiopathic ventricular fibrillation originating from Purkinje tissues. Patch-clamp analysis revealed that Cavα1c-T1787M reduces the calcium and barium currents by increasing the auto-inhibition mediated by the C-terminal part and increases the voltage-dependent inhibition. We identified a loss-of-function variant, Cavα1c-T1787M, present in 0.8% of the African population, as a new risk factor for ventricular arrhythmia.
Collapse
|
54
|
Ma H, Chen S, Chen H, Zhou J, Li D, Pan H. α2δ-1 couples to NMDA receptors in the hypothalamus to sustain sympathetic vasomotor activity in hypertension. J Physiol 2018; 596:4269-4283. [PMID: 29971791 PMCID: PMC6117594 DOI: 10.1113/jp276394] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 06/29/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS α2δ-1 is upregulated, promoting the interaction with NMDA receptors (NMDARs), in the hypothalamus in a rat model of hypertension. The prevalence of α2δ-1-bound NMDARs at synaptic sites in the hypothalamus is increased in hypertensive animals. α2δ-1 is essential for the increased presynaptic and postsynaptic NMDAR activity of hypothalamic neurons in hypertension. α2δ-1-bound NMDARs in the hypothalamus are critically involved in augmented sympathetic outflow in hypertensive animals. ABSTRACT Increased glutamate NMDA receptor (NMDAR) activity in the paraventricular nucleus (PVN) of the hypothalamus leads to augmented sympathetic outflow in hypertension. However, the molecular mechanisms underlying this effect remain unclear. α2δ-1, previously considered to be a voltage-activated calcium channel subunit, is a newly discovered powerful regulator of NMDARs. In the present study, we determined the role of α2δ-1 in regulating synaptic NMDAR activity of rostral ventrolateral medulla (RVLM)-projecting PVN neurons in spontaneously hypertensive rats (SHRs). We show that the protein levels of α2δ-1 and NMDARs in synaptosomes and the α2δ-1-NMDAR complexes in the hypothalamus were substantially higher in SHRs than in normotensive control rats. The basal amplitude of evoked NMDAR currents and NMDAR-mediated synaptic glutamate release in RVLM-projecting PVN neurons were significantly increased in SHRs. Strikingly, inhibiting α2δ-1 activity with gabapentin or disrupting the α2δ-1-NMDAR association with an α2δ-1 C-terminus peptide completely normalized the amplitude of evoked NMDAR currents and NMDAR-mediated synaptic glutamate release in RVLM-projecting PVN neurons in SHRs. In addition, microinjection of the α2δ-1 C-terminus peptide into the PVN substantially reduced arterial blood pressure and renal sympathetic nerve discharges in SHRs. Our findings indicate that α2δ-1-bound NMDARs in the PVN are required for the potentiated presynaptic and postsynaptic NMDAR activity of PVN presympathetic neurons and for the elevated sympathetic outflow in hypertension. α2δ-1-bound NMDARs may be an opportune target for treating neurogenic hypertension.
Collapse
Affiliation(s)
- Huijie Ma
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative MedicineThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
- Department of PhysiologyHebei Medical UniversityShijiazhuangHebeiChina
| | - Shao‐Rui Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative MedicineThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - Hong Chen
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative MedicineThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - Jing‐Jing Zhou
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative MedicineThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - De‐Pei Li
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative MedicineThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| | - Hui‐Lin Pan
- Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative MedicineThe University of Texas MD Anderson Cancer CenterHoustonTXUSA
| |
Collapse
|
55
|
Ednie AR, Deng W, Yip KP, Bennett ES. Reduced myocyte complex N-glycosylation causes dilated cardiomyopathy. FASEB J 2018; 33:1248-1261. [PMID: 30138037 DOI: 10.1096/fj.201801057r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Protein glycosylation is an essential posttranslational modification that affects a myriad of physiologic processes. Humans with genetic defects in glycosylation, which result in truncated glycans, often present with significant cardiac deficits. Acquired heart diseases and their associated risk factors were also linked to aberrant glycosylation, highlighting its importance in human cardiac disease. In both cases, the link between causation and corollary remains enigmatic. The glycosyltransferase gene, mannosyl (α-1,3-)-glycoprotein β-1,2- N-acetylglucosaminyltransferase (Mgat1), whose product, N-acetylglucosaminyltransferase 1 (GlcNAcT1) is necessary for the formation of hybrid and complex N-glycan structures in the medial Golgi, was shown to be at reduced levels in human end-stage cardiomyopathy, thus making Mgat1 an attractive target for investigating the role of hybrid/complex N-glycosylation in cardiac pathogenesis. Here, we created a cardiomyocyte-specific Mgat1 knockout (KO) mouse to establish a model useful in exploring the relationship between hybrid/complex N-glycosylation and cardiac function and disease. Biochemical and glycomic analyses showed that Mgat1KO cardiomyocytes produce predominately truncated N-glycan structures. All Mgat1KO mice died significantly younger than control mice and demonstrated chamber dilation and systolic dysfunction resembling human dilated cardiomyopathy (DCM). Data also indicate that a cardiomyocyte L-type voltage-gated Ca2+ channel (Cav) subunit (α2δ1) is a GlcNAcT1 target, and Mgat1KO Cav activity is shifted to more-depolarized membrane potentials. Consistently, Mgat1KO cardiomyocyte Ca2+ handling is altered and contraction is dyssynchronous compared with controls. The data demonstrate that reduced hybrid/complex N-glycosylation contributes to aberrant cardiac function at whole-heart and myocyte levels drawing a direct link between altered glycosylation and heart disease. Thus, the Mgat1KO provides a model for investigating the relationship between systemic reductions in glycosylation and cardiac disease, showing that clinically relevant changes in cardiomyocyte hybrid/complex N-glycosylation are sufficient to cause DCM and early death.-Ednie, A. R., Deng, W., Yip, K.-P., Bennett, E. S. Reduced myocyte complex N-glycosylation causes dilated cardiomyopathy.
Collapse
Affiliation(s)
- Andrew R Ednie
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA.,College of Science and Mathematics, Wright State University, Dayton, Ohio, USA; and
| | - Wei Deng
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Kay-Pong Yip
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Eric S Bennett
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA.,College of Science and Mathematics, Wright State University, Dayton, Ohio, USA; and
| |
Collapse
|
56
|
Manville RW, Abbott GW. Gabapentin Is a Potent Activator of KCNQ3 and KCNQ5 Potassium Channels. Mol Pharmacol 2018; 94:1155-1163. [PMID: 30021858 DOI: 10.1124/mol.118.112953] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/15/2018] [Indexed: 12/28/2022] Open
Abstract
Synthetic gabapentinoids, exemplified by gapapentin and pregabalin, are in extensive clinical use for indications including epilepsy, neuropathic pain, anxiety, and alcohol withdrawal. Their mechanisms of action are incompletely understood, but are thought to involve inhibition of α2δ subunit-containing voltage-gated calcium channels. Here, we report that gabapentin is a potent activator of the heteromeric KCNQ2/3 voltage-gated potassium channel, the primary molecular correlate of the neuronal M-current, and also homomeric KCNQ3 and KCNQ5 channels. In contrast, the structurally related gabapentinoid, pregabalin, does not activate KCNQ2/3, and at higher concentrations (≥10 µM) is inhibitory. Gabapentin activation of KCNQ2/3 (EC50 = 4.2 nM) or homomeric KCNQ3* (EC50 = 5.3 nM) channels requires KCNQ3-W265, a conserved tryptophan in KCNQ3 transmembrane segment 5. Homomeric KCNQ2 or KCNQ4 channels are insensitive to gabapentin, whereas KCNQ5 is highly sensitive (EC50 = 1.9 nM). Given the potent effects and the known anticonvulsant, antinociceptive, and anxiolytic effects of M-channel activation, our findings suggest the possibility of an unexpected role for M-channel activation in the mechanism of action of gabapentin.
Collapse
Affiliation(s)
- Rían W Manville
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
| |
Collapse
|
57
|
α2δ-1 Is Essential for Sympathetic Output and NMDA Receptor Activity Potentiated by Angiotensin II in the Hypothalamus. J Neurosci 2018; 38:6388-6398. [PMID: 29921713 DOI: 10.1523/jneurosci.0447-18.2018] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 06/12/2018] [Accepted: 06/13/2018] [Indexed: 01/10/2023] Open
Abstract
Both the sympathetic nervous system and the renin-angiotensin system are critically involved in hypertension development. Although angiotensin II (Ang II) stimulates hypothalamic paraventricular nucleus (PVN) neurons to increase sympathetic vasomotor tone, the molecular mechanism mediating this action remains unclear. The glutamate NMDAR in the PVN controls sympathetic outflow in hypertension. In this study, we determined the interaction between α2δ-1 (encoded by Cacna2d1), commonly known as a Ca2+ channel subunit, and NMDARs in the hypothalamus and its role in Ang II-induced synaptic NMDAR activity in PVN presympathetic neurons. Coimmunoprecipitation assays showed that α2δ-1 interacted with the NMDAR in the hypothalamus of male rats and humans (both sexes). Ang II increased the prevalence of synaptic α2δ-1-NMDAR complexes in the hypothalamus. Also, Ang II increased presynaptic and postsynaptic NMDAR activity via AT1 receptors, and such effects were abolished either by treatment with pregabalin, an inhibitory α2δ-1 ligand, or by interrupting the α2δ-1-NMDAR interaction with an α2δ-1 C terminus-interfering peptide. In Cacna2d1 knock-out mice (both sexes), Ang II failed to affect the presynaptic and postsynaptic NMDAR activity of PVN neurons. In addition, the α2δ-1 C terminus-interfering peptide blocked the sympathoexcitatory response to microinjection of Ang II into the PVN. Our findings indicate that Ang II augments sympathetic vasomotor tone and excitatory glutamatergic input to PVN presympathetic neurons by stimulating α2δ-1-bound NMDARs at synapses. This information extends our understanding of the molecular basis for the interaction between the sympathetic nervous and renin-angiotensin systems and suggests new strategies for treating neurogenic hypertension.SIGNIFICANCE STATEMENT Although both the sympathetic nervous system and renin-angiotensin system are closely involved in hypertension development, the molecular mechanisms mediating this involvement remain unclear. We showed that α2δ-1, previously known as a calcium channel subunit, interacts with NMDARs in the hypothalamus of rodents and humans. Angiotensin II (Ang II) increases the synaptic expression level of α2δ-1-NMDAR complexes. Furthermore, inhibiting α2δ-1, interrupting the α2δ-1-NMDAR interaction, or deleting α2δ-1 abolishes the potentiating effects of Ang II on presynaptic and postsynaptic NMDAR activity in the hypothalamus. In addition, the sympathoexcitatory response to Ang II depends on α2δ-1-bound NMDARs. Thus, α2δ-1-NMDAR complexes in the hypothalamus serve as an important molecular substrate for the interaction between the sympathetic nervous system and the renin-angiotensin system. This evidence suggests that α2δ-1 may be a useful target for the treatment neurogenic hypertension.
Collapse
|
58
|
Gong N, Park J, Luo ZD. Injury-induced maladaptation and dysregulation of calcium channel α 2 δ subunit proteins and its contribution to neuropathic pain development. Br J Pharmacol 2018; 175:2231-2243. [PMID: 28646556 PMCID: PMC5980513 DOI: 10.1111/bph.13930] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/05/2017] [Accepted: 06/12/2017] [Indexed: 01/12/2023] Open
Abstract
Voltage-gated calcium channels (VGCCs) play important roles in physiological functions including the modulation of neurotransmitter release, neuronal network activities, intracellular signalling pathways and gene expression. Some pathological conditions, including nerve injuries, can cause the dysregulation of VGCCs and their subunits. This in turn can lead to a functional maladaptation of VGCCs and their subunits, which can contribute to the development of disorders such as pain sensations. This review has summarized recent findings related to maladaptive changes in the dysregulated VGCC α2 δ1 subunit (Cav α2 δ1 ) with a focus on exploring the mechanisms underlying the contribution of Cav α2 δ1 to pain signal transduction. At least under neuropathic pain conditions, the dysregulated Cav α2 δ1 can modulate VGCC functions as well as other plasticity changes. The latter includes abnormal excitatory synaptogenesis resulting from its interactions with injury-induced extracellular matrix glycoprotein molecule thrombospondins, which is independent of the VGCC functions. Blocking Cav α2 δ1 with gabapentinoids can reverse neuropathic pain significantly with relatively mild side effects, but only in a small population of neuropathic pain patients due to reasons yet to be explored. There are emerging data suggesting that early preventive treatment with gabapentinoids can prevent aberrant excitatory synapse formation and the development of chronic pain. If these findings are confirmed clinically, this could be an attractive approach for neuropathic pain management. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
Collapse
Affiliation(s)
- Nian Gong
- Department of Anesthesiology & Perioperative CareSchool of Medicine, University of California IrvineIrvineCAUSA
| | - John Park
- Department of Pharmacology, School of MedicineUniversity of California IrvineIrvineCAUSA
| | - Z David Luo
- Department of Anesthesiology & Perioperative CareSchool of Medicine, University of California IrvineIrvineCAUSA
- Department of Pharmacology, School of MedicineUniversity of California IrvineIrvineCAUSA
| |
Collapse
|
59
|
Regulation of the voltage-gated Ca 2+ channel Ca Vα 2δ-1 subunit expression by the transcription factor Egr-1. Neurosci Lett 2018. [PMID: 29518540 DOI: 10.1016/j.neulet.2018.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is well known that the CaVα2δ auxiliary subunit regulates the density of high voltage-activated Ca2+ channels in the plasma membrane and that alterations in their functional expression might have implications in the pathophysiology of diverse human diseases such as neuropathic pain. However, little is known concerning the transcriptional regulation of this protein. We previously characterized the promoter of CaVα2δ, and here we report its regulation by the transcription factor Egr-1. Using the neuroblastoma N1E-115 cells, we found that Egr-1 interacts specifically with its binding site in the promoter, affecting the transcriptional regulation of CaVα2δ. Overexpression and knockdown analysis of Egr-1 showed significant changes in the transcriptional activity of the CaVα2δ promoter. Egr-1 also regulated the expression of CaVα2δ at the level of protein. Also, functional studies showed that Egr-1 knockdown significantly decreases Ca2+ currents in dorsal root ganglion (DRG) neurons, while overexpression of the transcription factor increased Ca2+ currents in the F11 cell line, a hybrid of DRG and N18TG2 neuroblastoma cells. Studying the effects of Egr-1 on the transcriptional expression of CaVα2δ could help to understand the regulatory mechanisms of this protein in both health and disease.
Collapse
|
60
|
Zhang Q, Chen J, Qin Y, Wang J, Zhou L. Mutations in voltage-gated L-type calcium channel: implications in cardiac arrhythmia. Channels (Austin) 2018; 12:201-218. [PMID: 30027834 PMCID: PMC6104696 DOI: 10.1080/19336950.2018.1499368] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 06/08/2018] [Accepted: 07/05/2018] [Indexed: 02/06/2023] Open
Abstract
The voltage-gated L-type calcium channel (LTCC) is essential for multiple cellular processes. In the heart, calcium influx through LTCC plays an important role in cardiac electrical excitation. Mutations in LTCC genes, including CACNA1C, CACNA1D, CACNB2 and CACNA2D, will induce the dysfunctions of calcium channels, which result in the abnormal excitations of cardiomyocytes, and finally lead to cardiac arrhythmias. Nevertheless, the newly found mutations in LTCC and their functions are continuously being elucidated. This review summarizes recent findings on the mutations of LTCC, which are associated with long QT syndromes, Timothy syndromes, Brugada syndromes, short QT syndromes, and some other cardiac arrhythmias. Indeed, we describe the gain/loss-of-functions of these mutations in LTCC, which can give an explanation for the phenotypes of cardiac arrhythmias. Moreover, we present several challenges in the field at present, and propose some diagnostic or therapeutic approaches to these mutation-associated cardiac diseases in the future.
Collapse
Affiliation(s)
- Qing Zhang
- Department of Cardiology, the Second Affiliated Hospital of Nantong University, Nantong First Hospital, Nantong, Jiangsu, China
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Junjie Chen
- Department of Physiology, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Yao Qin
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| | - Juejin Wang
- Department of Physiology, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Lei Zhou
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China
| |
Collapse
|
61
|
Savalli N, Pantazis A, Sigg D, Weiss JN, Neely A, Olcese R. The α2δ-1 subunit remodels CaV1.2 voltage sensors and allows Ca2+ influx at physiological membrane potentials. J Gen Physiol 2017; 148:147-59. [PMID: 27481713 PMCID: PMC4969795 DOI: 10.1085/jgp.201611586] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/30/2016] [Indexed: 12/30/2022] Open
Abstract
Voltage-sensing domains (VSDs) in voltage-gated calcium channels sense the potential difference across membranes and interact with the pore to open it. Savalli et al. find that the accessory subunit α2δ-1 increases the sensitivity of VSDs I–III and also their efficiency of coupling to the pore. Excitation-evoked calcium influx across cellular membranes is strictly controlled by voltage-gated calcium channels (CaV), which possess four distinct voltage-sensing domains (VSDs) that direct the opening of a central pore. The energetic interactions between the VSDs and the pore are critical for tuning the channel’s voltage dependence. The accessory α2δ-1 subunit is known to facilitate CaV1.2 voltage-dependent activation, but the underlying mechanism is unknown. In this study, using voltage clamp fluorometry, we track the activation of the four individual VSDs in a human L-type CaV1.2 channel consisting of α1C and β3 subunits. We find that, without α2δ-1, the channel complex displays a right-shifted voltage dependence such that currents mainly develop at nonphysiological membrane potentials because of very weak VSD–pore interactions. The presence of α2δ-1 facilitates channel activation by increasing the voltage sensitivity (i.e., the effective charge) of VSDs I–III. Moreover, the α2δ-1 subunit also makes VSDs I–III more efficient at opening the channel by increasing the coupling energy between VSDs II and III and the pore, thus allowing Ca influx within the range of physiological membrane potentials.
Collapse
Affiliation(s)
- Nicoletta Savalli
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Antonios Pantazis
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | | | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Alan Neely
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Riccardo Olcese
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| |
Collapse
|
62
|
Wang T, Jones RT, Whippen JM, Davis GW. α2δ-3 Is Required for Rapid Transsynaptic Homeostatic Signaling. Cell Rep 2017; 16:2875-2888. [PMID: 27626659 DOI: 10.1016/j.celrep.2016.08.030] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 07/12/2016] [Accepted: 08/09/2016] [Indexed: 11/18/2022] Open
Abstract
The homeostatic modulation of neurotransmitter release, termed presynaptic homeostatic potentiation (PHP), is a fundamental type of neuromodulation, conserved from Drosophila to humans, that stabilizes information transfer at synaptic connections throughout the nervous system. Here, we demonstrate that α2δ-3, an auxiliary subunit of the presynaptic calcium channel, is required for PHP. The α2δ gene family has been linked to chronic pain, epilepsy, autism, and the action of two psychiatric drugs: gabapentin and pregabalin. We demonstrate that loss of α2δ-3 blocks both the rapid induction and sustained expression of PHP due to a failure to potentiate presynaptic calcium influx and the RIM-dependent readily releasable vesicle pool. These deficits are independent of α2δ-3-mediated regulation of baseline calcium influx and presynaptic action potential waveform. α2δ proteins reside at the extracellular face of presynaptic release sites throughout the nervous system, a site ideal for mediating rapid, transsynaptic homeostatic signaling in health and disease.
Collapse
Affiliation(s)
- Tingting Wang
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Ryan T Jones
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jenna M Whippen
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Graeme W Davis
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
| |
Collapse
|
63
|
Margas W, Ferron L, Nieto-Rostro M, Schwartz A, Dolphin AC. Effect of knockout of α2δ-1 on action potentials in mouse sensory neurons. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0430. [PMID: 27377724 PMCID: PMC4938030 DOI: 10.1098/rstb.2015.0430] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/11/2016] [Indexed: 12/12/2022] Open
Abstract
Gene deletion of the voltage-gated calcium channel auxiliary subunit α2δ-1 has been shown previously to have a cardiovascular phenotype, and a reduction in mechano- and cold sensitivity, coupled with delayed development of neuropathic allodynia. We have also previously shown that dorsal root ganglion (DRG) neuron calcium channel currents were significantly reduced in α2δ-1 knockout mice. To extend our findings in these sensory neurons, we have examined here the properties of action potentials (APs) in DRG neurons from α2δ-1 knockout mice in comparison to their wild-type (WT) littermates, in order to dissect how the calcium channels that are affected by α2δ-1 knockout are involved in setting the duration of individual APs and their firing frequency. Our main findings are that there is reduced Ca2+ entry on single AP stimulation, particularly in the axon proximal segment, reduced AP duration and reduced firing frequency to a 400 ms stimulation in α2δ-1 knockout neurons, consistent with the expected role of voltage-gated calcium channels in these events. Furthermore, lower intracellular Ca2+ buffering also resulted in reduced AP duration, and a lower frequency of AP firing in WT neurons, mimicking the effect of α2δ-1 knockout. By contrast, we did not obtain any consistent evidence for the involvement of Ca2+-activation of large conductance calcium-activated potassium (BK) and small conductance calcium-activated potassium (SK) channels in these events. In conclusion, the reduced Ca2+ elevation as a result of single AP stimulation is likely to result from the reduced duration of the AP in α2δ-1 knockout sensory neurons. This article is part of the themed issue ‘Evolution brings Ca2+ and ATP together to control life and death’.
Collapse
Affiliation(s)
- Wojciech Margas
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Manuela Nieto-Rostro
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Arnold Schwartz
- College of Medicine, University of Cincinnati, Cincinnati, OH 45267-0557, USA
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| |
Collapse
|
64
|
Flucher BE, Tuluc P. How and why are calcium currents curtailed in the skeletal muscle voltage-gated calcium channels? J Physiol 2017; 595:1451-1463. [PMID: 27896815 PMCID: PMC5330888 DOI: 10.1113/jp273423] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 11/24/2016] [Indexed: 01/09/2023] Open
Abstract
Voltage‐gated calcium channels represent the sole mechanism converting electrical signals of excitable cells into cellular functions such as contraction, secretion and gene regulation. Specific voltage‐sensing domains detect changes in membrane potential and control channel gating. Calcium ions entering through the channel function as second messengers regulating cell functions, with the exception of skeletal muscle, where CaV1.1 essentially does not function as a channel but activates calcium release from intracellular stores. It has long been known that calcium currents are dispensable for skeletal muscle contraction. However, the questions as to how and why the channel function of CaV1.1 is curtailed remained obscure until the recent discovery of a developmental CaV1.1 splice variant with normal channel functions. This discovery provided new means to study the molecular mechanisms regulating the channel gating and led to the understanding that in skeletal muscle, calcium currents need to be restricted to allow proper regulation of fibre type specification and to prevent mitochondrial damage.
![]()
Collapse
Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Austria
| | - Petronel Tuluc
- Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Austria
| |
Collapse
|
65
|
The Ca 2+ influx through the mammalian skeletal muscle dihydropyridine receptor is irrelevant for muscle performance. Nat Commun 2017; 8:475. [PMID: 28883413 PMCID: PMC5589907 DOI: 10.1038/s41467-017-00629-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 07/14/2017] [Indexed: 01/01/2023] Open
Abstract
Skeletal muscle excitation-contraction (EC) coupling is initiated by sarcolemmal depolarization, which is translated into a conformational change of the dihydropyridine receptor (DHPR), which in turn activates sarcoplasmic reticulum (SR) Ca2+ release to trigger muscle contraction. During EC coupling, the mammalian DHPR embraces functional duality, as voltage sensor and L-type Ca2+ channel. Although its unique role as voltage sensor for conformational EC coupling is firmly established, the conventional function as Ca2+ channel is still enigmatic. Here we show that Ca2+ influx via DHPR is not necessary for muscle performance by generating a knock-in mouse where DHPR-mediated Ca2+ influx is eliminated. Homozygous knock-in mice display SR Ca2+ release, locomotor activity, motor coordination, muscle strength and susceptibility to fatigue comparable to wild-type controls, without any compensatory regulation of multiple key proteins of the EC coupling machinery and Ca2+ homeostasis. These findings support the hypothesis that the DHPR-mediated Ca2+ influx in mammalian skeletal muscle is an evolutionary remnant.In mammalian skeletal muscle, the DHPR functions as a voltage sensor to trigger muscle contraction and as a Ca2+ channel. Here the authors show that mice where Ca2+ influx through the DHPR is eliminated display no difference in skeletal muscle function, suggesting that the Ca2+ influx through this channel is vestigial.
Collapse
|
66
|
Lau LA, Noubary F, Wang D, Dulla CG. α2δ-1 Signaling Drives Cell Death, Synaptogenesis, Circuit Reorganization, and Gabapentin-Mediated Neuroprotection in a Model of Insult-Induced Cortical Malformation. eNeuro 2017; 4:ENEURO.0316-17.2017. [PMID: 29109971 PMCID: PMC5672548 DOI: 10.1523/eneuro.0316-17.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 10/10/2017] [Accepted: 10/13/2017] [Indexed: 01/08/2023] Open
Abstract
Developmental cortical malformations (DCMs) result from pre- and perinatal insults, as well as genetic mutations. Hypoxia, viral infection, and traumatic injury are the most common environmental causes of DCMs, and are associated with the subsyndromes focal polymicrogyria and focal cortical dysplasia (FCD) Type IIId, both of which have a high incidence of epilepsy. Understanding the molecular signals that lead to the formation of a hyperexcitable network in DCMs is critical to devising novel treatment strategies. In a previous study using the freeze-lesion (FL) murine model of DCM, we found that levels of thrombospondin (TSP) and the calcium channel auxiliary subunit α2δ-1 were elevated. TSP binds to α2δ-1 to drive the formation of excitatory synapses during development, suggesting that overactivation of this pathway may lead to exuberant excitatory synaptogenesis and network hyperexcitability seen in DCMs. In that study, antagonizing TSP/α2δ-1 signaling using the drug gabapentin (GBP) reduced many FL-induced pathologies. Here, we used mice with a genetic deletion of α2δ-1 to determine how α2δ-1 contributes to cell death, elevated excitatory synapse number, and in vitro network function after FL and to examine the molecular specificity of GBP's effects. We identified a critical role for α2δ-1 in FL-induced pathologies and in mediating the neuroprotective effects of GBP. Interestingly, genetic deletion of α2δ-1 did not eliminate GBP's effects on synaptogenesis, suggesting that GBP can have α2δ-1-independent effects. Taken together these studies suggests that inhibiting α2δ-1 signaling may have therapeutic promise to reduce cell death and network reorganization associated with insult-induced DCMs.
Collapse
Affiliation(s)
- Lauren A. Lau
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
- Neuroscience Program, Tufts Sackler School of Biomedical Sciences, Boston, MA 02111
| | - Farzad Noubary
- The Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Boston, MA 02111
- Tufts Clinical and Translational Science Institute, Tufts University, Boston, MA 02111
| | - Dongqing Wang
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Chris G. Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111
| |
Collapse
|
67
|
Bourdin B, Briot J, Tétreault MP, Sauvé R, Parent L. Negatively charged residues in the first extracellular loop of the L-type Ca V1.2 channel anchor the interaction with the Ca Vα2δ1 auxiliary subunit. J Biol Chem 2017; 292:17236-17249. [PMID: 28864774 PMCID: PMC5655503 DOI: 10.1074/jbc.m117.806893] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/18/2017] [Indexed: 12/20/2022] Open
Abstract
Voltage-gated L-type CaV1.2 channels in cardiomyocytes exist as heteromeric complexes. Co-expression of CaVα2δ1 with CaVβ/CaVα1 proteins reconstitutes the functional properties of native L-type currents, but the interacting domains at the CaV1.2/CaVα2δ1 interface are unknown. Here, a homology-based model of CaV1.2 identified protein interfaces between the extracellular domain of CaVα2δ1 and the extracellular loops of the CaVα1 protein in repeats I (IS1S2 and IS5S6), II (IIS5S6), and III (IIIS5S6). Insertion of a 9-residue hemagglutinin epitope in IS1S2, but not in IS5S6 or in IIS5S6, prevented the co-immunoprecipitation of CaV1.2 with CaVα2δ1. IS1S2 contains a cluster of three conserved negatively charged residues Glu-179, Asp-180, and Asp-181 that could contribute to non-bonded interactions with CaVα2δ1. Substitutions of CaV1.2 Asp-181 impaired the co-immunoprecipitation of CaVβ/CaV1.2 with CaVα2δ1 and the CaVα2δ1-dependent shift in voltage-dependent activation gating. In contrast, single substitutions in CaV1.2 in neighboring positions in the same loop (179, 180, and 182–184) did not significantly alter the functional up-regulation of CaV1.2 whole-cell currents. However, a negatively charged residue at position 180 was necessary to convey the CaVα2δ1-mediated shift in the activation gating. We also found a more modest contribution from the positively charged Arg-1119 in the extracellular pore region in repeat III of CaV1.2. We conclude that CaV1.2 Asp-181 anchors the physical interaction that facilitates the CaVα2δ1-mediated functional modulation of CaV1.2 currents. By stabilizing the first extracellular loop of CaV1.2, CaVα2δ1 may up-regulate currents by promoting conformations of the voltage sensor that are associated with the channel's open state.
Collapse
Affiliation(s)
- Benoîte Bourdin
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Julie Briot
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada.,From the Département de Pharmacologie et Physiologie, Faculté de Médecine, and
| | - Marie-Philippe Tétreault
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Rémy Sauvé
- From the Département de Pharmacologie et Physiologie, Faculté de Médecine, and
| | - Lucie Parent
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada .,From the Département de Pharmacologie et Physiologie, Faculté de Médecine, and
| |
Collapse
|
68
|
Landmann J, Richter F, Oros-Peusquens AM, Shah NJ, Classen J, Neely GG, Richter A, Penninger JM, Bechmann I. Neuroanatomy of pain-deficiency and cross-modal activation in calcium channel subunit (CACN) α2δ3 knockout mice. Brain Struct Funct 2017; 223:111-130. [PMID: 28733833 DOI: 10.1007/s00429-017-1473-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 07/05/2017] [Indexed: 11/29/2022]
Abstract
The phenotype of calcium channel subunit (CACN) α2δ3 knockout (KO) mice includes sensory cross-activation and deficient pain perception. Sensory cross-activation defines the activation of a sensory cortical region by input from another modality due to reorganization in the brain such as after sensory loss. To obtain mechanistic insight into both phenomena, we employed a comprehensive battery of neuroanatomical techniques. While CACNα2δ3 was ubiquitously expressed in wild-type mice, it was absent in α2δ3 KO animals. Immunostaining of α1A, α1B, and α1E revealed upregulation of N-type and R-type, but not P/Q-type Cav2 channels in cortical neurons of CACNα2δ3 KO mice. Compared to wild-type mice, axonal processes in somatosensory cortex were enhanced, and dendritic processes reduced, in CACNα2δ3 KO mice. Immunohistochemical and MRI analyses, investigating morphology, thalamocortical and intra-/intercortical trajectories, revealed a disparity between projection and commissural fibers with reduction of the number of spatial specificity of thalamocortical projections. L1cam staining revealed wide-ranging projections of thalamocortical fibers reaching both somatosensory/motor and visual cortical areas. Activation (c-fos+) of excitatory and inhibitory neurons suggested that deficient pain perception in α2δ3 KO mice is unlikely to result from cortical disinhibition. Collectively, our data demonstrate that knock out of CACN α2δ3 results in some structural abnormalities whose functional implications converge to dedifferentiation of sensory activation.
Collapse
Affiliation(s)
- Julia Landmann
- Institute of Anatomy, University of Leipzig, Oststrasse 25, 04317, Leipzig, Germany.
| | - Franziska Richter
- Department of Veterinary Medicine, Institute of Pharmacology, Pharmacy and Toxicology, University of Leipzig, An den Tierkliniken 15, 04103, Leipzig, Germany
| | - Ana-Maria Oros-Peusquens
- Institute of Neuroscience and Medicine (INM-4), Research Centre Jülich, Forschungszentrum Jülich, 52425, Jülich, Germany
| | - N Jon Shah
- Institute of Neuroscience and Medicine (INM-4), Research Centre Jülich, Forschungszentrum Jülich, 52425, Jülich, Germany.,Department of Neurology, Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany
| | - Joseph Classen
- Department of Neurology, University of Leipzig, Liebigstrasse 20, 04103, Leipzig, Germany
| | - G Gregory Neely
- Dr. John and Anne Chong Lab for Functional Genomics, Charles Perkins Centre and School of Life & Environmental Sciences, The University of Sydney, 2006, Camperdown, NSW, Australia
| | - Angelika Richter
- Department of Veterinary Medicine, Institute of Pharmacology, Pharmacy and Toxicology, University of Leipzig, An den Tierkliniken 15, 04103, Leipzig, Germany
| | - Josef M Penninger
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr-Gasse 3, 1030, Vienna, Austria
| | - Ingo Bechmann
- Institute of Anatomy, University of Leipzig, Oststrasse 25, 04317, Leipzig, Germany
| |
Collapse
|
69
|
α2δ2 Controls the Function and Trans-Synaptic Coupling of Cav1.3 Channels in Mouse Inner Hair Cells and Is Essential for Normal Hearing. J Neurosci 2017; 36:11024-11036. [PMID: 27798183 DOI: 10.1523/jneurosci.3468-14.2016] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 09/03/2016] [Indexed: 11/21/2022] Open
Abstract
The auxiliary subunit α2δ2 modulates the abundance and function of voltage-gated calcium channels. Here we show that α2δ2 mRNA is expressed in neonatal and mature hair cells. A functional α2δ2-null mouse, the ducky mouse (du), showed elevated auditory brainstem response click and frequency-dependent hearing thresholds. Otoacoustic emissions were not impaired pointing to normal outer hair cell function. Peak Ca2+ and Ba2+ currents of mature du/du inner hair cells (IHCs) were reduced by 30-40%, respectively, and gating properties, such as the voltage of half-maximum activation and voltage sensitivity, were altered, indicating that Cav1.3 channels normally coassemble with α2δ2 at IHC presynapses. The reduction of depolarization-evoked exocytosis in du/du IHCs reflected their reduced Ca2+ currents. Ca2+- and voltage-dependent K+ (BK) currents and the expression of the pore-forming BKα protein were normal. Cav1.3 and Cavβ2 protein expression was unchanged in du/du IHCs, forming clusters at presynaptic ribbons. However, the close apposition of presynaptic Cav1.3 clusters with postsynaptic glutamate receptor GluA4 and PSD-95 clusters was significantly impaired in du/du mice. This implies that, in addition to controlling the expression and gating properties of Cav1.3 channels, the largely extracellularly localized α2δ2 subunit moreover plays a so far unknown role in mediating trans-synaptic alignment of presynaptic Ca2+ channels and postsynaptic AMPA receptors. SIGNIFICANCE STATEMENT Inner hair cells possess calcium channels that are essential for transmitting sound information into synaptic transmitter release. Voltage-gated calcium channels can coassemble with auxiliary subunit α2δ isoforms 1-4. We found that hair cells of the mouse express the auxiliary subunit α2δ2, which is needed for normal hearing thresholds. Using a mouse model with a mutant, nonfunctional α2δ2 protein, we showed that the α2δ2 protein is necessary for normal calcium currents and exocytosis in inner hair cells. Unexpectedly, the α2δ2 protein is moreover required for the optimal spatial alignment of presynaptic calcium channels and postsynaptic glutamate receptor proteins across the synaptic cleft. This suggests that α2δ2 plays a novel role in organizing the synapse.
Collapse
|
70
|
Segura E, Bourdin B, Tétreault MP, Briot J, Allen BG, Mayer G, Parent L. Proteolytic cleavage of the hydrophobic domain in the Ca Vα2δ1 subunit improves assembly and activity of cardiac Ca V1.2 channels. J Biol Chem 2017; 292:11109-11124. [PMID: 28495885 DOI: 10.1074/jbc.m117.784355] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 04/24/2017] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated L-type CaV1.2 channels in cardiomyocytes exist as heteromeric complexes with the pore-forming CaVα1, CaVβ, and CaVα2δ1 subunits. The full complement of subunits is required to reconstitute the native-like properties of L-type Ca2+ currents, but the molecular determinants responsible for the formation of the heteromeric complex are still being studied. Enzymatic treatment with phosphatidylinositol-specific phospholipase C, a phospholipase C specific for the cleavage of glycosylphosphatidylinositol (GPI)-anchored proteins, disrupted plasma membrane localization of the cardiac CaVα2δ1 prompting us to investigate deletions of its hydrophobic transmembrane domain. Patch-clamp experiments indicated that the C-terminally cleaved CaVα2δ1 proteins up-regulate CaV1.2 channels. In contrast, deleting the residues before the single hydrophobic segment (CaVα2δ1 Δ1059-1063) impaired current up-regulation. CaVα2δ1 mutants G1060I and G1061I nearly eliminated the cell-surface fluorescence of CaVα2δ1, indicated by two-color flow cytometry assays and confocal imaging, and prevented CaVα2δ1-mediated increase in peak current density and modulation of the voltage-dependent gating of CaV1.2. These impacts were specific to substitutions with isoleucine residues because functional modulation was partially preserved in CaVα2δ1 G1060A and G1061A proteins. Moreover, C-terminal fragments exhibited significantly altered mobility in denatured immunoblots of CaVα2δ1 G1060I and CaVα2δ1 G1061I, suggesting that these mutant proteins were impaired in proteolytic processing. Finally, CaVα2δ1 Δ1059-1063, but not CaVα2δ1 G1060A, failed to co-immunoprecipitate with CaV1.2. Altogether, our data support a model in which small neutral hydrophobic residues facilitate the post-translational cleavage of the CaVα2δ1 subunit at the predicted membrane interface and further suggest that preventing GPI anchoring of CaVα2δ1 averts its cell-surface expression, its interaction with CaVα1, and modulation of CaV1.2 currents.
Collapse
Affiliation(s)
- Emilie Segura
- From the Départements de Pharmacologie et Physiologie and.,the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Benoîte Bourdin
- the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Marie-Philippe Tétreault
- the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Julie Briot
- From the Départements de Pharmacologie et Physiologie and.,the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Bruce G Allen
- the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada.,Médecine, Faculté de Médecine
| | - Gaétan Mayer
- the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada.,the Faculté de Pharmacie, and
| | - Lucie Parent
- From the Départements de Pharmacologie et Physiologie and .,the Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| |
Collapse
|
71
|
Mastrolia V, Flucher SM, Obermair GJ, Drach M, Hofer H, Renström E, Schwartz A, Striessnig J, Flucher BE, Tuluc P. Loss of α 2δ-1 Calcium Channel Subunit Function Increases the Susceptibility for Diabetes. Diabetes 2017; 66:897-907. [PMID: 28115397 PMCID: PMC7360433 DOI: 10.2337/db16-0336] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 01/18/2017] [Indexed: 11/13/2022]
Abstract
Reduced pancreatic β-cell function or mass is the critical problem in developing diabetes. Insulin release from β-cells depends on Ca2+ influx through high voltage-gated Ca2+ channels (HVCCs). Ca2+ influx also regulates insulin synthesis and insulin granule priming and contributes to β-cell electrical activity. The HVCCs are multisubunit protein complexes composed of a pore-forming α1 and auxiliary β and α2δ subunits. α2δ is a key regulator of membrane incorporation and function of HVCCs. Here we show that genetic deletion of α2δ-1, the dominant α2δ subunit in pancreatic islets, results in glucose intolerance and diabetes without affecting insulin sensitivity. Lack of the α2δ-1 subunit reduces the Ca2+ currents through all HVCC isoforms expressed in β-cells equally in male and female mice. The reduced Ca2+ influx alters the kinetics and amplitude of the global Ca2+ response to glucose in pancreatic islets and significantly reduces insulin release in both sexes. The progression of diabetes in males is aggravated by a selective loss of β-cell mass, while a stronger basal insulin release alleviates the diabetes symptoms in most α2δ-1-/- female mice. Together, these findings demonstrate that the loss of the Ca2+ channel α2δ-1 subunit function increases the susceptibility for developing diabetes in a sex-dependent manner.
Collapse
Affiliation(s)
- Vincenzo Mastrolia
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
| | - Sylvia M Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Mathias Drach
- Department of General Pathology, Medical University Innsbruck, Innsbruck, Austria
| | - Helene Hofer
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Erik Renström
- Department of Clinical Sciences Malmö, Lund University, Lund, Sweden
| | - Arnold Schwartz
- College of Medicine, University of Cincinnati, Cincinnati, OH
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
- Department of Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria
| |
Collapse
|
72
|
LRP1 influences trafficking of N-type calcium channels via interaction with the auxiliary α 2δ-1 subunit. Sci Rep 2017; 7:43802. [PMID: 28256585 PMCID: PMC5335561 DOI: 10.1038/srep43802] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 01/30/2017] [Indexed: 01/18/2023] Open
Abstract
Voltage-gated Ca2+ (CaV) channels consist of a pore-forming α1 subunit, which determines the main functional and pharmacological attributes of the channel. The CaV1 and CaV2 channels are associated with auxiliary β- and α2δ-subunits. The molecular mechanisms involved in α2δ subunit trafficking, and the effect of α2δ subunits on trafficking calcium channel complexes remain poorly understood. Here we show that α2δ-1 is a ligand for the Low Density Lipoprotein (LDL) Receptor-related Protein-1 (LRP1), a multifunctional receptor which mediates trafficking of cargoes. This interaction with LRP1 is direct, and is modulated by the LRP chaperone, Receptor-Associated Protein (RAP). LRP1 regulates α2δ binding to gabapentin, and influences calcium channel trafficking and function. Whereas LRP1 alone reduces α2δ-1 trafficking to the cell-surface, the LRP1/RAP combination enhances mature glycosylation, proteolytic processing and cell-surface expression of α2δ-1, and also increase plasma-membrane expression and function of CaV2.2 when co-expressed with α2δ-1. Furthermore RAP alone produced a small increase in cell-surface expression of CaV2.2, α2δ-1 and the associated calcium currents. It is likely to be interacting with an endogenous member of the LDL receptor family to have these effects. Our findings now provide a key insight and new tools to investigate the trafficking of calcium channel α2δ subunits.
Collapse
|
73
|
Briot J, Tétreault MP, Bourdin B, Parent L. Inherited Ventricular Arrhythmias: The Role of the Multi-Subunit Structure of the L-Type Calcium Channel Complex. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 966:55-64. [PMID: 28315127 DOI: 10.1007/5584_2016_186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The normal heartbeat is conditioned by transient increases in the intracellular free Ca2+ concentration. Ca2+ influx in cardiomyocytes is regulated by the activity of the heteromeric L-type voltage-activated CaV1.2 channel. A complex network of interactions between the different proteins forming the ion channel supports the kinetics and the activation gating of the Ca2+ influx. Alterations in the biophysical and biochemical properties or in the biogenesis in any of these proteins can lead to serious disturbances in the cardiac rhythm. The multi-subunit nature of the channel complex is better comprehended by examining the high-resolution three-dimensional structure of the closely related CaV1.1 channel. The architectural map identifies precise interaction loci between the different subunits and paves the way for elucidating the mechanistic basis for the regulation of Ca2+ balance in cardiac myocytes under physiological and pathological conditions.
Collapse
Affiliation(s)
- Julie Briot
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Institut Cardiologie de Montréal, Université de Montréal, 5000 Bélanger, Montréal, QC, H1T 1C8, Canada
| | - Marie-Philippe Tétreault
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Institut Cardiologie de Montréal, Université de Montréal, 5000 Bélanger, Montréal, QC, H1T 1C8, Canada
| | - Benoîte Bourdin
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Institut Cardiologie de Montréal, Université de Montréal, 5000 Bélanger, Montréal, QC, H1T 1C8, Canada
| | - Lucie Parent
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Institut Cardiologie de Montréal, Université de Montréal, 5000 Bélanger, Montréal, QC, H1T 1C8, Canada.
| |
Collapse
|
74
|
Bodi I, Nakayama H, Schwartz A. Tetrodotoxin-sensitive Ca2+ Currents, but No T-type Currents in Normal, Hypertrophied, and Failing Mouse Cardiomyocytes. J Cardiovasc Pharmacol 2016; 68:452-464. [PMID: 27617699 PMCID: PMC5145783 DOI: 10.1097/fjc.0000000000000432] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To obtain functional evidence that ICa,T is involved in the pathogenesis of cardiac hypertrophy and heart failure. We unexpectedly identified ICa(TTX) rather than ICa,T, therefore, we adjusted our aim to encompass these findings. METHODS AND RESULTS We investigated (1) Cav3.1 (α1G) transgenic (Tg) mice compared with nontransgenic (tTA-Ntg); (2) Cav3.1-deficient mice (Cav3.1) compared with wild type (Wt) after chemically and surgically induced cardiac remodeling; and (3) spontaneous hypertensive rats and thoracic aortic constriction (TAC) rats. Whole-cell patch-clamp technique was used to measure ICa in ventricular myocytes. Cav3.1-Tg expressed ICa,T (-18.35 ± 1.02 pA/pF at -40 mV) without signs of compromised cardiac function. While we failed to detect ICa,T after hypertrophic stimuli, instead we demonstrated that both Wt and Cav3.1 mouse exhibit ICa(TTX). Using TAC rats, only 2 of 24 VMs showed ICa,T under our experimental conditions. Without TTX, ICa(TTX) occurred in VMs from Wt, spontaneous hypertensive rats, and TAC rats also. CONCLUSIONS These findings demonstrate for the first time that mouse VMs express ICa(TTX). We suggest that future studies should take into consideration the measuring conditions when interpreting ICa,T reappearance in ventricular myocytes in response to hypertrophic stress. Contamination with ICa(TTX) could possibly confuse the relevance of the data.
Collapse
Affiliation(s)
- Ilona Bodi
- Department of Pediatrics, Division of Molecular Cardiovascular Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Hiroyuki Nakayama
- Department of Pediatrics, Division of Molecular Cardiovascular Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | | |
Collapse
|
75
|
McKinnon D, Rosati B. Transmural gradients in ion channel and auxiliary subunit expression. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 122:165-186. [PMID: 27702655 DOI: 10.1016/j.pbiomolbio.2016.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 09/30/2016] [Indexed: 12/11/2022]
Abstract
Evolution has acted to shape the action potential in different regions of the heart in order to produce a maximally stable and efficient pump. This has been achieved by creating regional differences in ion channel expression levels within the heart as well as differences between equivalent cardiac tissues in different species. These region- and species-dependent differences in channel expression are established by regulatory evolution, evolution of the regulatory mechanisms that control channel expression levels. Ion channel auxiliary subunits are obvious targets for regulatory evolution, in order to change channel expression levels and/or modify channel function. This review focuses on the transmural gradients of ion channel expression in the heart and the role that regulation of auxiliary subunit expression plays in generating and shaping these gradients.
Collapse
Affiliation(s)
- David McKinnon
- Department of Veterans Affairs Medical Center, Northport, NY, USA; Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA; Department of Neurobiology and Behavior, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Barbara Rosati
- Department of Veterans Affairs Medical Center, Northport, NY, USA; Institute of Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA; Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, 11794, USA.
| |
Collapse
|
76
|
Goto T, Oh SB, Takeda M, Shinoda M, Sato T, Gunjikake KK, Iwata K. Recent advances in basic research on the trigeminal ganglion. J Physiol Sci 2016; 66:381-6. [PMID: 27023716 PMCID: PMC10717556 DOI: 10.1007/s12576-016-0448-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 03/16/2016] [Indexed: 10/22/2022]
Abstract
Peripheral tissue inflammation can alter the properties of somatic sensory pathways, causing behavioral hypersensitivity and resulting in increased responses to pain caused by noxious stimulation (hyperalgesia) and normally innocuous stimulation (allodynia). These hypersensitivities for nociception are caused by changes in the excitability of trigeminal ganglion (TG) neurons. These changes alter sensory information processing in the neurons in the medullary trigeminal nucleus of caudalis. Increasing information is becoming available regarding trigeminal neuron-neuron/neuron-satellite glial cells (SGCs) communication. The activation of intraganglionic communication plays an important role in the creation and maintenance of trigeminal pathological pain. Therefore, in this review, we focus on the recent findings for sensory functions and pharmacological modulation of TG neurons and SGCs under normal and pathological conditions, and we discuss potential therapeutic targets in glia-neuronal interactions for the prevention of trigeminal neuropathic and inflammatory pain.
Collapse
Affiliation(s)
- Tetsuya Goto
- Department of Oral Anatomy and Cell Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, 890-6544, Japan.
| | - Seog Bae Oh
- Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, South Korea
| | - Mamoru Takeda
- Department of Food and Life Sciences, School of Life and Environmental Sciences, Azabu University, Sagamihara, Japan
| | - Masamichi Shinoda
- Department of Physiology, School of Dentistry, Nihon University, Tokyo, Japan
| | - Tadasu Sato
- Division of Oral and Craniofacial Anatomy, Graduate School of Dentistry, Tohoku University, Sendai, Japan
| | - Kaori K Gunjikake
- Department of Orthodontics, School of Dentistry, Kyushu Dental University, Kitakyushu, Japan
| | - Koichi Iwata
- Department of Physiology, School of Dentistry, Nihon University, Tokyo, Japan
| |
Collapse
|
77
|
Dolphin AC. Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology. J Physiol 2016; 594:5369-90. [PMID: 27273705 PMCID: PMC5043047 DOI: 10.1113/jp272262] [Citation(s) in RCA: 208] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/09/2016] [Indexed: 12/22/2022] Open
Abstract
Voltage‐gated calcium channels are essential players in many physiological processes in excitable cells. There are three main subdivisions of calcium channel, defined by the pore‐forming α1 subunit, the CaV1, CaV2 and CaV3 channels. For all the subtypes of voltage‐gated calcium channel, their gating properties are key for the precise control of neurotransmitter release, muscle contraction and cell excitability, among many other processes. For the CaV1 and CaV2 channels, their ability to reach their required destinations in the cell membrane, their activation and the fine tuning of their biophysical properties are all dramatically influenced by the auxiliary subunits that associate with them. Furthermore, there are many diseases, both genetic and acquired, involving voltage‐gated calcium channels. This review will provide a general introduction and then concentrate particularly on the role of auxiliary α2δ subunits in both physiological and pathological processes involving calcium channels, and as a therapeutic target.
![]()
Collapse
Affiliation(s)
- Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| |
Collapse
|
78
|
Kobrinsky E, Soldatov NM. Electrophysiological evidences of interaction between calcium channels and PA of anthrax. Channels (Austin) 2016; 10:253-5. [PMID: 27045324 DOI: 10.1080/19336950.2016.1172886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Affiliation(s)
- Evgeny Kobrinsky
- a National Institute on Aging, National Institutes of Health , Baltimore , MD, USA
| | - Nikolai M Soldatov
- a National Institute on Aging, National Institutes of Health , Baltimore , MD, USA
| |
Collapse
|
79
|
Patel R, Dickenson AH. Mechanisms of the gabapentinoids and α 2 δ-1 calcium channel subunit in neuropathic pain. Pharmacol Res Perspect 2016; 4:e00205. [PMID: 27069626 PMCID: PMC4804325 DOI: 10.1002/prp2.205] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 11/17/2015] [Accepted: 11/19/2015] [Indexed: 12/18/2022] Open
Abstract
The gabapentinoid drugs gabapentin and pregabalin are key front‐line therapies for various neuropathies of peripheral and central origin. Originally designed as analogs of GABA, the gabapentinoids bind to the α2δ‐1 and α2δ‐2 auxiliary subunits of calcium channels, though only the former has been implicated in the development of neuropathy in animal models. Transgenic approaches also identify α2δ‐1 as key in mediating the analgesic effects of gabapentinoids, however the precise molecular mechanisms remain unclear. Here we review the current understanding of the pathophysiological role of the α2δ‐1 subunit, the mechanisms of analgesic action of gabapentinoid drugs and implications for efficacy in the clinic. Despite widespread use, the number needed to treat for gabapentin and pregabalin averages from 3 to 8 across neuropathies. The failure to treat large numbers of patients adequately necessitates a novel approach to treatment selection. Stratifying patients by sensory profiles may imply common underlying mechanisms, and a greater understanding of these mechanisms could lead to more direct targeting of gabapentinoids.
Collapse
Affiliation(s)
- Ryan Patel
- Department of Neuroscience, Physiology and Pharmacology University College London Gower Street London WC1E 6BT UK
| | - Anthony H Dickenson
- Department of Neuroscience, Physiology and Pharmacology University College London Gower Street London WC1E 6BT UK
| |
Collapse
|
80
|
Tétreault MP, Bourdin B, Briot J, Segura E, Lesage S, Fiset C, Parent L. Identification of Glycosylation Sites Essential for Surface Expression of the CaVα2δ1 Subunit and Modulation of the Cardiac CaV1.2 Channel Activity. J Biol Chem 2016; 291:4826-43. [PMID: 26742847 DOI: 10.1074/jbc.m115.692178] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Indexed: 12/15/2022] Open
Abstract
Alteration in the L-type current density is one aspect of the electrical remodeling observed in patients suffering from cardiac arrhythmias. Changes in channel function could result from variations in the protein biogenesis, stability, post-translational modification, and/or trafficking in any of the regulatory subunits forming cardiac L-type Ca(2+) channel complexes. CaVα2δ1 is potentially the most heavily N-glycosylated subunit in the cardiac L-type CaV1.2 channel complex. Here, we show that enzymatic removal of N-glycans produced a 50-kDa shift in the mobility of cardiac and recombinant CaVα2δ1 proteins. This change was also observed upon simultaneous mutation of the 16 Asn sites. Nonetheless, the mutation of only 6/16 sites was sufficient to significantly 1) reduce the steady-state cell surface fluorescence of CaVα2δ1 as characterized by two-color flow cytometry assays and confocal imaging; 2) decrease protein stability estimated from cycloheximide chase assays; and 3) prevent the CaVα2δ1-mediated increase in the peak current density and voltage-dependent gating of CaV1.2. Reversing the N348Q and N812Q mutations in the non-operational sextuplet Asn mutant protein partially restored CaVα2δ1 function. Single mutation N663Q and double mutations N348Q/N468Q, N348Q/N812Q, and N468Q/N812Q decreased protein stability/synthesis and nearly abolished steady-state cell surface density of CaVα2δ1 as well as the CaVα2δ1-induced up-regulation of L-type currents. These results demonstrate that Asn-663 and to a lesser extent Asn-348, Asn-468, and Asn-812 contribute to protein stability/synthesis of CaVα2δ1, and furthermore that N-glycosylation of CaVα2δ1 is essential to produce functional L-type Ca(2+) channels.
Collapse
Affiliation(s)
| | - Benoîte Bourdin
- From the Départment de Physiologie Moléculaire et Intégrative, Faculté de Médecine, and
| | - Julie Briot
- From the Départment de Physiologie Moléculaire et Intégrative, Faculté de Médecine, and
| | - Emilie Segura
- From the Départment de Physiologie Moléculaire et Intégrative, Faculté de Médecine, and
| | - Sylvie Lesage
- Départment de Microbiologie, Infectiologie, and Immunologie, Faculté de Médecine, Centre de Recherche de l'Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Céline Fiset
- Faculté de Pharmacie, Institut de Cardiologie de Montréal and
| | - Lucie Parent
- From the Départment de Physiologie Moléculaire et Intégrative, Faculté de Médecine, and
| |
Collapse
|
81
|
Cardiac voltage-gated calcium channel macromolecular complexes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:1806-12. [PMID: 26707467 DOI: 10.1016/j.bbamcr.2015.12.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 12/14/2015] [Accepted: 12/16/2015] [Indexed: 11/21/2022]
Abstract
Over the past 20 years, a new field of research, called channelopathies, investigating diseases caused by ion channel dysfunction has emerged. Cardiac ion channels play an essential role in the generation of the cardiac action potential. Investigators have largely determined the physiological roles of different cardiac ion channels, but little is known about the molecular determinants of their regulation. The voltage-gated calcium channel Ca(v)1.2 shapes the plateau phase of the cardiac action potential and allows the influx of calcium leading to cardiomyocyte contraction. Studies suggest that the regulation of Ca(v)1.2 channels is not uniform in working cardiomyocytes. The notion of micro-domains containing Ca(v)1.2 channels and different calcium channel interacting proteins, called macro-molecular complex, has been proposed to explain these observations. The objective of this review is to summarize the currently known information on the Ca(v)1.2 macromolecular complexes in the cardiac cell and discuss their implication in cardiac function and disorder. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.
Collapse
|
82
|
Zamponi GW, Striessnig J, Koschak A, Dolphin AC. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential. Pharmacol Rev 2015; 67:821-70. [PMID: 26362469 PMCID: PMC4630564 DOI: 10.1124/pr.114.009654] [Citation(s) in RCA: 704] [Impact Index Per Article: 78.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and anxiety. Use-dependent N-type calcium channel blockers are likely to be of therapeutic use in chronic pain conditions. Thus, more selective calcium channel blockers hold promise for therapeutic intervention.
Collapse
Affiliation(s)
- Gerald W Zamponi
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Joerg Striessnig
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Alexandra Koschak
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| | - Annette C Dolphin
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada (G.W.Z.); Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria (J.S., A.K.); and Department of Neuroscience, Physiology, and Pharmacology, Division of Biosciences, University College London, London, United Kingdom (A.C.D.)
| |
Collapse
|
83
|
Heyes S, Pratt WS, Rees E, Dahimene S, Ferron L, Owen MJ, Dolphin AC. Genetic disruption of voltage-gated calcium channels in psychiatric and neurological disorders. Prog Neurobiol 2015; 134:36-54. [PMID: 26386135 PMCID: PMC4658333 DOI: 10.1016/j.pneurobio.2015.09.002] [Citation(s) in RCA: 164] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/08/2015] [Accepted: 09/08/2015] [Indexed: 12/15/2022]
Abstract
Voltage-gated calcium channel classification—genes and proteins. Genetic analysis of neuropsychiatric syndromes. Calcium channel genes identified from GWA studies of psychiatric disorders. Rare mutations in calcium channel genes in psychiatric disorders. Pathophysiological sequelae of CACNA1C mutations and polymorphisms. Monogenic disorders resulting from harmful mutations in other voltage-gated calcium channel genes. Changes in calcium channel gene expression in disease. Involvement of voltage-gated calcium channels in early brain development.
This review summarises genetic studies in which calcium channel genes have been connected to the spectrum of neuropsychiatric syndromes, from bipolar disorder and schizophrenia to autism spectrum disorders and intellectual impairment. Among many other genes, striking numbers of the calcium channel gene superfamily have been implicated in the aetiology of these diseases by various DNA analysis techniques. We will discuss how these relate to the known monogenic disorders associated with point mutations in calcium channels. We will then examine the functional evidence for a causative link between these mutations or single nucleotide polymorphisms and the disease processes. A major challenge for the future will be to translate the expanding psychiatric genetic findings into altered physiological function, involvement in the wider pathology of the diseases, and what potential that provides for personalised and stratified treatment options for patients.
Collapse
Affiliation(s)
- Samuel Heyes
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Elliott Rees
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Michael J Owen
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
| |
Collapse
|
84
|
Abriel H, Rougier JS, Jalife J. Ion channel macromolecular complexes in cardiomyocytes: roles in sudden cardiac death. Circ Res 2015; 116:1971-88. [PMID: 26044251 DOI: 10.1161/circresaha.116.305017] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The movement of ions across specific channels embedded on the membrane of individual cardiomyocytes is crucial for the generation and propagation of the cardiac electric impulse. Emerging evidence over the past 20 years strongly suggests that the normal electric function of the heart is the result of dynamic interactions of membrane ion channels working in an orchestrated fashion as part of complex molecular networks. Such networks work together with exquisite temporal precision to generate each action potential and contraction. Macromolecular complexes play crucial roles in transcription, translation, oligomerization, trafficking, membrane retention, glycosylation, post-translational modification, turnover, function, and degradation of all cardiac ion channels known to date. In addition, the accurate timing of each cardiac beat and contraction demands, a comparable precision on the assembly and organizations of sodium, calcium, and potassium channel complexes within specific subcellular microdomains, where physical proximity allows for prompt and efficient interaction. This review article, part of the Compendium on Sudden Cardiac Death, discusses the major issues related to the role of ion channel macromolecular assemblies in normal cardiac electric function and the mechanisms of arrhythmias leading to sudden cardiac death. It provides an idea of how these issues are being addressed in the laboratory and in the clinic, which important questions remain unanswered, and what future research will be needed to improve knowledge and advance therapy.
Collapse
Affiliation(s)
- Hugues Abriel
- From the Department of Clinical Research, University of Bern, Bern, Switzerland (H.A., J.-S.R.); Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor (J.J.); and Area of Myocardial Pathophysiology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain (J.J.)
| | - Jean-Sébastien Rougier
- From the Department of Clinical Research, University of Bern, Bern, Switzerland (H.A., J.-S.R.); Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor (J.J.); and Area of Myocardial Pathophysiology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain (J.J.)
| | - José Jalife
- From the Department of Clinical Research, University of Bern, Bern, Switzerland (H.A., J.-S.R.); Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor (J.J.); and Area of Myocardial Pathophysiology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain (J.J.).
| |
Collapse
|
85
|
Campiglio M, Flucher BE. The role of auxiliary subunits for the functional diversity of voltage-gated calcium channels. J Cell Physiol 2015; 230:2019-31. [PMID: 25820299 PMCID: PMC4672716 DOI: 10.1002/jcp.24998] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 11/18/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent the sole mechanism to convert membrane depolarization into cellular functions like secretion, contraction, or gene regulation. VGCCs consist of a pore-forming α1 subunit and several auxiliary channel subunits. These subunits come in multiple isoforms and splice-variants giving rise to a stunning molecular diversity of possible subunit combinations. It is generally believed that specific auxiliary subunits differentially regulate the channels and thereby contribute to the great functional diversity of VGCCs. If auxiliary subunits can associate and dissociate from pre-existing channel complexes, this would allow dynamic regulation of channel properties. However, most auxiliary subunits modulate current properties very similarly, and proof that any cellular calcium channel function is indeed modulated by the physiological exchange of auxiliary subunits is still lacking. In this review we summarize available information supporting a differential modulation of calcium channel functions by exchange of auxiliary subunits, as well as experimental evidence in support of alternative functions of the auxiliary subunits. At the heart of the discussion is the concept that, in their native environment, VGCCs function in the context of macromolecular signaling complexes and that the auxiliary subunits help to orchestrate the diverse protein–protein interactions found in these calcium channel signalosomes. Thus, in addition to a putative differential modulation of current properties, differential subcellular targeting properties and differential protein–protein interactions of the auxiliary subunits may explain the need for their vast molecular diversity. J. Cell. Physiol. 999: 00–00, 2015. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc. J. Cell. Physiol. 230: 2019–2031, 2015. © 2015 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Marta Campiglio
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| |
Collapse
|
86
|
Pérez de Sevilla Müller L, Sargoy A, Fernández-Sánchez L, Rodriguez A, Liu J, Cuenca N, Brecha N. Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina. J Comp Neurol 2015; 523:1443-60. [PMID: 25631988 DOI: 10.1002/cne.23751] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 01/21/2015] [Accepted: 01/24/2015] [Indexed: 12/11/2022]
Abstract
High-voltage-activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes, including the influx of extracellular Ca(2+), neurotransmitter release, gene transcription, and synaptic plasticity. These channels consist of a primary α(1) pore-forming subunit, which is associated with an extracellular α(2)δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α(2)δ(3) subunit in the mouse and rat retina is unknown. In this study using RT-PCR, a single band at ∼ 305 bp corresponding to the predicted size of the α(2)δ(3) subunit fragment was found in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123-kDa band. Immunohistochemistry with an affinity-purified antibody to the α(2)δ(3) subunit revealed immunoreactive cell bodies in the ganglion cell layer and inner nuclear layer and immunoreactive processes in the inner plexiform layer and the outer plexiform layer. α(2)δ(3) immunoreactivity was localized to multiple cell types, including ganglion, amacrine, and bipolar cells and photoreceptors, but not horizontal cells. The expression of the α(2)δ(3) calcium channel subunit to multiple cell types suggests that this subunit participates widely in Ca-channel-mediated signaling in the retina.
Collapse
Affiliation(s)
- Luis Pérez de Sevilla Müller
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095
| | - Allison Sargoy
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095.,Department of Medicine, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095.,Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095
| | | | - Allen Rodriguez
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095
| | - Janelle Liu
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095
| | - Nicolás Cuenca
- Physiology, Genetics and Microbiology, University of Alicante, 03690, Alicante, Spain
| | - Nicholas Brecha
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095.,Department of Medicine, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095.,Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095.,CURE-Digestive Diseases Research Center, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California, 90095.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, California, 90073
| |
Collapse
|
87
|
Bourdin B, Shakeri B, Tétreault MP, Sauvé R, Lesage S, Parent L. Functional characterization of CaVα2δ mutations associated with sudden cardiac death. J Biol Chem 2014; 290:2854-69. [PMID: 25527503 DOI: 10.1074/jbc.m114.597930] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
L-type Ca(2+) channels play a critical role in cardiac rhythmicity. These ion channels are oligomeric complexes formed by the pore-forming CaVα1 with the auxiliary CaVβ and CaVα2δ subunits. CaVα2δ increases the peak current density and improves the voltage-dependent activation gating of CaV1.2 channels without increasing the surface expression of the CaVα1 subunit. The functional impact of genetic variants of CACNA2D1 (the gene encoding for CaVα2δ), associated with shorter repolarization QT intervals (the time interval between the Q and the T waves on the cardiac electrocardiogram), was investigated after recombinant expression of the full complement of L-type CaV1.2 subunits in human embryonic kidney 293 cells. By performing side-by-side high resolution flow cytometry assays and whole-cell patch clamp recordings, we revealed that the surface density of the CaVα2δ wild-type protein correlates with the peak current density. Furthermore, the cell surface density of CaVα2δ mutants S755T, Q917H, and S956T was not significantly different from the cell surface density of the CaVα2δ wild-type protein expressed under the same conditions. In contrast, the cell surface expression of CaVα2δ D550Y, CaVα2δ S709N, and the double mutant D550Y/Q917H was reduced, respectively, by ≈30-33% for the single mutants and by 60% for the latter. The cell surface density of D550Y/Q917H was more significantly impaired than protein stability, suggesting that surface trafficking of CaVα2δ was disrupted by the double mutation. Co-expression with D550Y/Q917H significantly decreased CaV1.2 currents as compared with results obtained with CaVα2δ wild type. It is concluded that D550Y/Q917H reduced inward Ca(2+) currents through a defect in the cell surface trafficking of CaVα2δ. Altogether, our results provide novel insight in the molecular mechanism underlying the modulation of CaV1.2 currents by CaVα2δ.
Collapse
Affiliation(s)
- Benoîte Bourdin
- From the Département de Physiologie, Montreal Heart Institute Research Centre, and
| | - Behzad Shakeri
- From the Département de Physiologie, Montreal Heart Institute Research Centre, and
| | | | - Rémy Sauvé
- From the Département de Physiologie, Montreal Heart Institute Research Centre, and
| | - Sylvie Lesage
- Département de Microbiologie, Infectiologie et Immunologie, Centre de Recherche de l'Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Lucie Parent
- From the Département de Physiologie, Montreal Heart Institute Research Centre, and
| |
Collapse
|
88
|
Geisler S, Schöpf CL, Obermair GJ. Emerging evidence for specific neuronal functions of auxiliary calcium channel α₂δ subunits. Gen Physiol Biophys 2014; 34:105-118. [PMID: 25504062 DOI: 10.4149/gpb_2014037] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 11/06/2014] [Indexed: 11/08/2022]
Abstract
In nerve cells the ubiquitous second messenger calcium regulates a variety of vitally important functions including neurotransmitter release, gene regulation, and neuronal plasticity. The entry of calcium into cells is tightly regulated by voltage-gated calcium channels, which consist of a heteromultimeric complex of a pore forming α₁, and the auxiliary β and α₂δ subunits. Four genes (Cacna2d1-4) encode for the extracellular membrane-attached α₂δ subunits (α₂δ-1 to α₂δ-4), out of which three isoforms (α₂δ-1 to -3) are strongly expressed in the central nervous system. Over the years a wealth of studies has demonstrated the classical role of α₂δ subunits in channel trafficking and calcium current modulation. Recent studies in specialized neuronal cell systems propose roles of α₂δ subunits beyond the classical view and implicate α₂δ subunits as important regulators of synapse formation. These findings are supported by the identification of novel human disease mutations associated with α₂δ subunits and by the fact that α₂δ subunits are the target of the anti-epileptic and anti-allodynic drugs gabapentin and pregabalin. Here we review the recently emerging evidence for specific as well as redundant neuronal roles of α₂δ subunits and discuss the mechanisms for establishing and maintaining specificity.
Collapse
Affiliation(s)
- Stefanie Geisler
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Clemens L Schöpf
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Gerald J Obermair
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| |
Collapse
|
89
|
Simms BA, Zamponi GW. Neuronal voltage-gated calcium channels: structure, function, and dysfunction. Neuron 2014; 82:24-45. [PMID: 24698266 DOI: 10.1016/j.neuron.2014.03.016] [Citation(s) in RCA: 413] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Voltage-gated calcium channels are the primary mediators of depolarization-induced calcium entry into neurons. There is great diversity of calcium channel subtypes due to multiple genes that encode calcium channel α1 subunits, coassembly with a variety of ancillary calcium channel subunits, and alternative splicing. This allows these channels to fulfill highly specialized roles in specific neuronal subtypes and at particular subcellular loci. While calcium channels are of critical importance to brain function, their inappropriate expression or dysfunction gives rise to a variety of neurological disorders, including, pain, epilepsy, migraine, and ataxia. This Review discusses salient aspects of voltage-gated calcium channel function, physiology, and pathophysiology.
Collapse
Affiliation(s)
- Brett A Simms
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada.
| |
Collapse
|
90
|
α2δ3 is essential for normal structure and function of auditory nerve synapses and is a novel candidate for auditory processing disorders. J Neurosci 2014; 34:434-45. [PMID: 24403143 DOI: 10.1523/jneurosci.3085-13.2014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The auxiliary subunit α2δ3 modulates the expression and function of voltage-gated calcium channels. Here we show that α2δ3 mRNA is expressed in spiral ganglion neurons and auditory brainstem nuclei and that the protein is required for normal acoustic responses. Genetic deletion of α2δ3 led to impaired auditory processing, with reduced acoustic startle and distorted auditory brainstem responses. α2δ3(-/-) mice learned to discriminate pure tones, but they failed to discriminate temporally structured amplitude-modulated tones. Light and electron microscopy analyses revealed reduced levels of presynaptic Ca(2+) channels and smaller auditory nerve fiber terminals contacting cochlear nucleus bushy cells. Juxtacellular in vivo recordings of sound-evoked activity in α2δ3(-/-) mice demonstrated impaired transmission at these synapses. Together, our results identify a novel role for the α2δ3 auxiliary subunit in the structure and function of specific synapses in the mammalian auditory pathway and in auditory processing disorders.
Collapse
|
91
|
Hofmann F, Flockerzi V, Kahl S, Wegener JW. L-type CaV1.2 calcium channels: from in vitro findings to in vivo function. Physiol Rev 2014; 94:303-26. [PMID: 24382889 DOI: 10.1152/physrev.00016.2013] [Citation(s) in RCA: 233] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The L-type Cav1.2 calcium channel is present throughout the animal kingdom and is essential for some aspects of CNS function, cardiac and smooth muscle contractility, neuroendocrine regulation, and multiple other processes. The L-type CaV1.2 channel is built by up to four subunits; all subunits exist in various splice variants that potentially affect the biophysical and biological functions of the channel. Many of the CaV1.2 channel properties have been analyzed in heterologous expression systems including regulation of the L-type CaV1.2 channel by Ca(2+) itself and protein kinases. However, targeted mutations of the calcium channel genes confirmed only some of these in vitro findings. Substitution of the respective serines by alanine showed that β-adrenergic upregulation of the cardiac CaV1.2 channel did not depend on the phosphorylation of the in vitro specified amino acids. Moreover, well-established in vitro phosphorylation sites of the CaVβ2 subunit of the cardiac L-type CaV1.2 channel were found to be irrelevant for the in vivo regulation of the channel. However, the molecular basis of some kinetic properties, such as Ca(2+)-dependent inactivation and facilitation, has been approved by in vivo mutagenesis of the CaV1.2α1 gene. This article summarizes recent findings on the in vivo relevance of well-established in vitro results.
Collapse
|
92
|
De Sevilla Müller LP, Liu J, Solomon A, Rodriguez A, Brecha NC. Expression of voltage-gated calcium channel α(2)δ(4) subunits in the mouse and rat retina. J Comp Neurol 2014; 521:2486-501. [PMID: 23296739 DOI: 10.1002/cne.23294] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 12/12/2012] [Accepted: 12/27/2012] [Indexed: 01/18/2023]
Abstract
High-voltage activated Ca channels participate in multiple cellular functions, including transmitter release, excitation, and gene transcription. Ca channels are heteromeric proteins consisting of a pore-forming α(1) subunit and auxiliary α(2)δ and β subunits. Although there are reports of α(2)δ(4) subunit mRNA in the mouse retina and localization of the α(2)δ(4) subunit immunoreactivity to salamander photoreceptor terminals, there is a limited overall understanding of its expression and localization in the retina. α(2)δ(4) subunit expression and distribution in the mouse and rat retina were evaluated by using reverse transcriptase polymerase chain reaction, western blot, and immunohistochemistry with specific primers and a well-characterized antibody to the α(2)δ(4) subunit. α(2)δ(4) subunit mRNA and protein are present in mouse and rat retina, brain, and liver homogenates. Immunostaining for the α(2)δ(4) subunit is mainly localized to Müller cell processes and endfeet, photoreceptor terminals, and photoreceptor outer segments. This subunit is also expressed in a few displaced ganglion cells and bipolar cell dendrites. These findings suggest that the α(2)δ(4) subunit participates in the modulation of L-type Ca(2+) current regulating neurotransmitter release from photoreceptor terminals and Ca(2+)-dependent signaling pathways in bipolar and Müller cells.
Collapse
Affiliation(s)
- Luis Pérez De Sevilla Müller
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California 90095, USA.
| | | | | | | | | |
Collapse
|
93
|
α2δ-1 gene deletion affects somatosensory neuron function and delays mechanical hypersensitivity in response to peripheral nerve damage. J Neurosci 2013; 33:16412-26. [PMID: 24133248 DOI: 10.1523/jneurosci.1026-13.2013] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The α2δ-1 subunit of voltage-gated calcium channels is upregulated after sensory nerve injury and is also the therapeutic target of gabapentinoid drugs. It is therefore likely to play a key role in the development of neuropathic pain. In this study, we have examined mice in which α2δ-1 gene expression is disrupted, to determine whether α2δ-1 is involved in various modalities of nociception, and for the development of behavioral hypersensitivity after partial sciatic nerve ligation (PSNL). We find that naive α2δ-1(-/-) mice show a marked behavioral deficit in mechanical and cold sensitivity, but no change in thermal nociception threshold. The lower mechanical sensitivity is mirrored by a reduced in vivo electrophysiological response of dorsal horn wide dynamic range neurons. The CaV2.2 level is reduced in brain and spinal cord synaptosomes from α2δ-1(-/-) mice, and α2δ-1(-/-) DRG neurons exhibit lower calcium channel current density. Furthermore, a significantly smaller number of DRG neurons respond to the TRPM8 agonist menthol. After PSNL, α2δ-1(-/-) mice show delayed mechanical hypersensitivity, which only develops at 11 d after surgery, whereas in wild-type littermates it is maximal at the earliest time point measured (3 d). There is no compensatory upregulation of α2δ-2 or α2δ-3 after PSNL in α2δ-1(-/-) mice, and other transcripts, including neuropeptide Y and activating transcription factor-3, are upregulated normally. Furthermore, the ability of pregabalin to alleviate mechanical hypersensitivity is lost in PSNL α2δ-1(-/-) mice. Thus, α2δ-1 is essential for rapid development of mechanical hypersensitivity in a nerve injury model of neuropathic pain.
Collapse
|
94
|
The α2δ subunits of voltage-gated calcium channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013. [DOI: 10.1016/j.bbamem.2012.11.019] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
95
|
Dayal A, Bhat V, Franzini-Armstrong C, Grabner M. Domain cooperativity in the β1a subunit is essential for dihydropyridine receptor voltage sensing in skeletal muscle. Proc Natl Acad Sci U S A 2013; 110:7488-93. [PMID: 23589859 PMCID: PMC3645543 DOI: 10.1073/pnas.1301087110] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The dihydropyridine receptor (DHPR) β1a subunit is crucial for enhancement of DHPR triad expression, assembly of DHPRs in tetrads, and elicitation of DHPRα1S charge movement--the three prerequisites of skeletal muscle excitation-contraction coupling. Despite the ability to fully target α1S into triadic junctions and tetradic arrays, the neuronal isoform β3 was unable to restore considerable charge movement (measure of α1S voltage sensing) upon expression in β1-null zebrafish relaxed myotubes, unlike the other three vertebrate β-isoforms (β1a, β2a, and β4). Thus, we used β3 for chimerization with β1a to investigate whether any of the five distinct molecular regions of β1a is dominantly involved in inducing the voltage-sensing function of α1S. Surprisingly, systematic domain swapping between β1a and β3 revealed a pivotal role of the src homology 3 (SH3) domain and C terminus of β1a in charge movement restoration. More interestingly, β1a SH3 domain and C terminus, when simultaneously engineered into β3 sequence background, were able to fully restore charge movement together with proper intracellular Ca(2+) release, suggesting cooperativity of these two domains in induction of the α1S voltage-sensing function in skeletal muscle excitation-contraction coupling. Furthermore, substitution of a proline by alanine in the putative SH3-binding polyproline motif in the proximal C terminus of β1a (also of β2a and β4) fully obstructed α1S charge movement. Consequently, we postulate a model according to which β subunits, probably via the SH3-C-terminal polyproline interaction, adapt a discrete conformation required to modify the α1S conformation apt for voltage sensing in skeletal muscle.
Collapse
Affiliation(s)
- Anamika Dayal
- Department of Medical Genetics, Molecular, and Clinical Pharmacology, Innsbruck Medical University, A-6020 Innsbruck, Austria; and
| | - Vinayakumar Bhat
- Department of Medical Genetics, Molecular, and Clinical Pharmacology, Innsbruck Medical University, A-6020 Innsbruck, Austria; and
| | - Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104
| | - Manfred Grabner
- Department of Medical Genetics, Molecular, and Clinical Pharmacology, Innsbruck Medical University, A-6020 Innsbruck, Austria; and
| |
Collapse
|
96
|
Shaw RM, Colecraft HM. L-type calcium channel targeting and local signalling in cardiac myocytes. Cardiovasc Res 2013; 98:177-86. [PMID: 23417040 DOI: 10.1093/cvr/cvt021] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In the heart, Ca(2+) influx via Ca(V)1.2 L-type calcium channels (LTCCs) is a multi-functional signal that triggers muscle contraction, controls action potential duration, and regulates gene expression. The use of LTCC Ca(2+) as a multi-dimensional signalling molecule in the heart is complicated by several aspects of cardiac physiology. Cytosolic Ca(2+) continuously cycles between ~100 nM and ~1 μM with each heartbeat due to Ca(2+) linked signalling from LTCCs to ryanodine receptors. This rapid cycling raises the question as to how cardiac myocytes distinguish the Ca(2+) fluxes originating through L-type channels that are dedicated to contraction from Ca(2+) fluxes originating from other L-type channels that are used for non-contraction-related signalling. In general, disparate Ca(2+) sources in cardiac myocytes such as current through differently localized LTCCs as well as from IP3 receptors can signal selectively to Ca(2+)-dependent effectors in local microdomains that can be impervious to the cytoplasmic Ca(2+) transients that drive contraction. A particular challenge for diversified signalling via cardiac LTCCs is that they are voltage-gated and, therefore, open and presumably flood their microdomains with Ca(2+) with each action potential. Thus spatial localization of Cav1.2 channels to different types of microdomains of the ventricular cardiomyocyte membrane as well as the existence of particular macromolecular complexes in each Cav1.2 microdomain are important to effect different types of Cav1.2 signalling. In this review we examine aspects of Cav1.2 structure, targeting and signalling in two specialized membrane microdomains--transverse tubules and caveolae.
Collapse
Affiliation(s)
- Robin M Shaw
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, CA 94143, USA
| | | |
Collapse
|
97
|
Isolation and characterization of the 5´-upstream region of the human voltage-gated Ca2+ channel α2δ-1 auxiliary subunit gene: promoter analysis and regulation by transcription factor Sp1. Pflugers Arch 2012; 465:819-28. [DOI: 10.1007/s00424-012-1194-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/07/2012] [Accepted: 11/29/2012] [Indexed: 01/07/2023]
|
98
|
Calcium channel auxiliary α2δ and β subunits: trafficking and one step beyond. Nat Rev Neurosci 2012; 13:542-55. [PMID: 22805911 DOI: 10.1038/nrn3311] [Citation(s) in RCA: 264] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The voltage-gated calcium channel α(2)δ and β subunits are traditionally considered to be auxiliary subunits that enhance channel trafficking, increase the expression of functional calcium channels at the plasma membrane and influence the channels' biophysical properties. Accumulating evidence indicates that these subunits may also have roles in the nervous system that are not directly linked to calcium channel function. For example, β subunits may act as transcriptional regulators, and certain α(2)δ subunits may function in synaptogenesis. The aim of this Review is to examine both the classic and novel roles for these auxiliary subunits in voltage-gated calcium channel function and beyond.
Collapse
|
99
|
Venetucci L, Denegri M, Napolitano C, Priori SG. Inherited calcium channelopathies in the pathophysiology of arrhythmias. Nat Rev Cardiol 2012; 9:561-75. [DOI: 10.1038/nrcardio.2012.93] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
|
100
|
Simms BA, Zamponi GW. Trafficking and stability of voltage-gated calcium channels. Cell Mol Life Sci 2012; 69:843-56. [PMID: 21964928 PMCID: PMC11115007 DOI: 10.1007/s00018-011-0843-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 02/07/2023]
Abstract
Voltage-gated calcium channels are important mediators of calcium influx into electrically excitable cells. The amount of calcium entering through this family of channel proteins is not only determined by the functional properties of channels embedded in the plasma membrane but also by the numbers of channels that are expressed at the cell surface. The trafficking of channels is controlled by numerous processes, including co-assembly with ancillary calcium channel subunits, ubiquitin ligases, and interactions with other membrane proteins such as G protein coupled receptors. Here we provide an overview about the current state of knowledge of calcium channel trafficking to the cell membrane, and of the mechanisms regulating the stability and internalization of this important ion channel family.
Collapse
Affiliation(s)
- Brett A. Simms
- Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1 Canada
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1 Canada
| |
Collapse
|