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Loh KWZ, Liu C, Soong TW, Hu Z. β subunits of voltage-gated calcium channels in cardiovascular diseases. Front Cardiovasc Med 2023; 10:1119729. [PMID: 36818347 PMCID: PMC9931737 DOI: 10.3389/fcvm.2023.1119729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 01/16/2023] [Indexed: 02/05/2023] Open
Abstract
Calcium signaling is required in bodily functions essential for survival, such as muscle contractions and neuronal communications. Of note, the voltage-gated calcium channels (VGCCs) expressed on muscle and neuronal cells, as well as some endocrine cells, are transmembrane protein complexes that allow for the selective entry of calcium ions into the cells. The α1 subunit constitutes the main pore-forming subunit that opens in response to membrane depolarization, and its biophysical functions are regulated by various auxiliary subunits-β, α2δ, and γ subunits. Within the cardiovascular system, the γ-subunit is not expressed and is therefore not discussed in this review. Because the α1 subunit is the pore-forming subunit, it is a prominent druggable target and the focus of many studies investigating potential therapeutic interventions for cardiovascular diseases. While this may be true, it should be noted that the direct inhibition of the α1 subunit may result in limited long-term cardiovascular benefits coupled with undesirable side effects, and that its expression and biophysical properties may depend largely on its auxiliary subunits. Indeed, the α2δ subunit has been reported to be essential for the membrane trafficking and expression of the α1 subunit. Furthermore, the β subunit not only prevents proteasomal degradation of the α1 subunit, but also directly modulates the biophysical properties of the α1 subunit, such as its voltage-dependent activities and open probabilities. More importantly, various isoforms of the β subunit have been found to differentially modulate the α1 subunit, and post-translational modifications of the β subunits further add to this complexity. These data suggest the possibility of the β subunit as a therapeutic target in cardiovascular diseases. However, emerging studies have reported the presence of cardiomyocyte membrane α1 subunit trafficking and expression in a β subunit-independent manner, which would undermine the efficacy of β subunit-targeting drugs. Nevertheless, a better understanding of the auxiliary β subunit would provide a more holistic approach when targeting the calcium channel complexes in treating cardiovascular diseases. Therefore, this review focuses on the post-translational modifications of the β subunit, as well as its role as an auxiliary subunit in modulating the calcium channel complexes.
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Affiliation(s)
- Kelvin Wei Zhern Loh
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Cong Liu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Tuck Wah Soong
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,NUS Graduate School for Integrative Sciences and Engineering, Singapore, Singapore,Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,*Correspondence: Tuck Wah Soong,
| | - Zhenyu Hu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Cardiovascular Disease Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore,Zhenyu Hu,
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2
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Nguyen H, Zhu W, Baltan S. Casein Kinase 2 Signaling in White Matter Stroke. Front Mol Biosci 2022; 9:908521. [PMID: 35911974 PMCID: PMC9325966 DOI: 10.3389/fmolb.2022.908521] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/21/2022] [Indexed: 11/27/2022] Open
Abstract
The growth of the aging population, together with improved stroke care, has resulted in an increase in stroke survivors and a rise in recurrent events. Axonal injury and white matter (WM) dysfunction are responsible for much of the disability observed after stroke. The mechanisms of WM injury are distinct compared to gray matter and change with age. Therefore, an ideal stroke therapeutic must restore neuronal and axonal function when applied before or after a stroke, and it must also protect across age groups. Casein kinase 2 (CK2), is expressed in the brain, including WM, and is regulated during the development and numerous disease conditions such as cancer and ischemia. CK2 activation in WM mediates ischemic injury by activating the Cdk5 and AKT/GSK3β signaling pathways. Consequently, CK2 inhibition using the small molecule inhibitor CX-4945 (Silmitasertib) correlates with preservation of oligodendrocytes, conservation of axon structure, and axonal mitochondria, leading to improved functional recovery. Remarkably, CK2 inhibition promotes WM function when applied after ischemic injury by specifically regulating the AKT/GSK3β pathways. The blockade of the active conformation of AKT confers post-ischemic protection to young and old WM by preserving mitochondria, implying AKT as a common therapeutic target across age groups. Using a NanoString nCounter miRNA expression profiling, comparative analyses of ischemic WM with or without CX-4945 treatment reveal that miRNAs are expressed at high levels in WM after ischemia, and CX-4945 differentially regulates some of these miRNAs. Therefore, we propose that miRNA regulation may be one of the protective actions of CX-4945 against WM ischemic injury. Silmitasertib is FDA approved and currently in use for cancer and Covid patients; therefore, it is plausible to repurpose CK2 inhibitors for stroke patients.
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Affiliation(s)
| | | | - Selva Baltan
- Anesthesiology and Peri-Operative Medicine (APOM), Oregon Health and Science University, Portland, OR, United States
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3
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Lertwanakarn T, Suntravat M, Sánchez EE, Wolska BM, Solaro RJ, de Tombe PP, Tachampa K. Negative inotropic mechanisms of β-cardiotoxin in cardiomyocytes by depression of myofilament ATPase activity without activation of the classical β-adrenergic pathway. Sci Rep 2021; 11:21154. [PMID: 34707114 PMCID: PMC8551325 DOI: 10.1038/s41598-021-00282-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 10/06/2021] [Indexed: 11/09/2022] Open
Abstract
Beta-cardiotoxin (β-CTX) from the king cobra venom (Ophiophagus hannah) was previously proposed as a novel β-adrenergic blocker. However, the involvement of β-adrenergic signaling by this compound has never been elucidated. The objectives of this study were to investigate the underlying mechanisms of β-CTX as a β-blocker and its association with the β-adrenergic pathway. The effects of β-CTX on isolated cardiac myocyte functions, calcium homeostasis, the phosphorylation level of targeted proteins, and the myofibrillar ATPase activity were studied. Healthy Sprague Dawley rats were used for cardiomyocytes isolation. Like propranolol, β-CTX attenuated the cardiomyocyte inotropy and calcium transient alterations as induced by isoproterenol stimulation. In contrast, these effects were not observed in forskolin-treated cells. Interestingly, cardiomyocytes treated with β-CTX showed no changes in phosphorylation level at any PKA-targeted sites in the myofilaments as demonstrated in Western blot analysis. The skinned fibers study revealed no change in myofilament kinetics by β-CTX. However, this protein exhibited the direct inhibition of myofibrillar ATPase activity with calcium de-sensitization of the enzyme. In summary, the negative inotropic mechanism of β-CTX was discovered. β-CTX exhibits an atypical β-blocker mechanism. These properties of β-CTX may benefit in developing a novel agent aid to treat hypertrophic cardiomyopathy.
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Affiliation(s)
- Tuchakorn Lertwanakarn
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand
| | - Montamas Suntravat
- National Natural Toxins Research Center, Texas-A&M University-Kingsville, Kingsville, TX, USA.,Department of Chemistry, Texas A&M University-Kingsville, Kingsville, TX, USA
| | - Elda E Sánchez
- National Natural Toxins Research Center, Texas-A&M University-Kingsville, Kingsville, TX, USA.,Department of Chemistry, Texas A&M University-Kingsville, Kingsville, TX, USA
| | - Beata M Wolska
- Department of Physiology and Biophysics, the University of Illinois at Chicago, Chicago, IL, USA.,Department of Medicine, the University of Illinois at Chicago, Chicago, IL, USA
| | - R John Solaro
- Department of Physiology and Biophysics, the University of Illinois at Chicago, Chicago, IL, USA
| | - Pieter P de Tombe
- Department of Physiology and Biophysics, the University of Illinois at Chicago, Chicago, IL, USA.,Phymedexp, Université de Montpellier, Inserm, CNRS, Montpellier, France
| | - Kittipong Tachampa
- Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.
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4
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Ednie AR, Bennett ES. Intracellular O-linked glycosylation directly regulates cardiomyocyte L-type Ca 2+ channel activity and excitation-contraction coupling. Basic Res Cardiol 2020; 115:59. [PMID: 32910282 DOI: 10.1007/s00395-020-00820-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 08/17/2020] [Indexed: 12/20/2022]
Abstract
Cardiomyocyte L-type Ca2+ channels (Cavs) are targets of signaling pathways that modulate channel activity in response to physiologic stimuli. Cav regulation is typically transient and beneficial but chronic stimulation can become pathologic; therefore, gaining a more complete understanding of Cav regulation is of critical importance. Intracellular O-linked glycosylation (O-GlcNAcylation), which is the result of two enzymes that dynamically add and remove single N-acetylglucosamines to and from intracellular serine/threonine residues (OGT and OGA respectively), has proven to be an increasingly important post-translational modification that contributes to the regulation of many physiologic processes. However, there is currently no known role for O-GlcNAcylation in the direct regulation of Cav activity nor is its contribution to cardiac electrical signaling and EC coupling well understood. Here we aimed to delineate the role of O-GlcNAcylation in regulating cardiomyocyte L-type Cav activity and its subsequent effect on EC coupling by utilizing a mouse strain possessing an inducible cardiomyocyte-specific OGT-null-transgene. Ablation of the OGT-gene in adult cardiomyocytes (OGTKO) reduced OGT expression and O-GlcNAcylation by > 90%. Voltage clamp recordings indicated an ~ 40% reduction in OGTKO Cav current (ICa), but with increased efficacy of adrenergic stimulation, and Cav steady-state gating and window current were significantly depolarized. Consistently, OGTKO cardiomyocyte intracellular Ca2+ release and contractility were diminished and demonstrated greater beat-to-beat variability. Additionally, we show that the Cav α1 and β2 subunits are O-GlcNAcylated while α2δ1 is not. Echocardiographic analyses indicated that the reductions in OGTKO cardiomyocyte Ca2+ handling and contractility were conserved at the whole-heart level as evidenced by significantly reduced left-ventricular contractility in the absence of hypertrophy. The data indicate, for the first time, that O-GlcNAc signaling is a critical and direct regulator of cardiomyocyte ICa achieved through altered Cav expression, gating, and response to adrenergic stimulation; these mechanisms have significant implications for understanding how EC coupling is regulated in health and disease.
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Affiliation(s)
- Andrew R Ednie
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, 143 Biological Sciences II, 3640 Colonel Glenn Hwy, Dayton, OH, 45435, USA.
| | - Eric S Bennett
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, 143 Biological Sciences II, 3640 Colonel Glenn Hwy, Dayton, OH, 45435, USA
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Scheuer R, Philipp SE, Becker A, Nalbach L, Ampofo E, Montenarh M, Götz C. Protein Kinase CK2 Controls Ca V2.1-Dependent Calcium Currents and Insulin Release in Pancreatic β-Cells. Int J Mol Sci 2020; 21:ijms21134668. [PMID: 32630015 PMCID: PMC7370021 DOI: 10.3390/ijms21134668] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/18/2020] [Accepted: 06/26/2020] [Indexed: 12/21/2022] Open
Abstract
The regulation of insulin biosynthesis and secretion in pancreatic β-cells is essential for glucose homeostasis in humans. Previous findings point to the highly conserved, ubiquitously expressed serine/threonine kinase CK2 as having a negative regulatory impact on this regulation. In the cell culture model of rat pancreatic β-cells INS-1, insulin secretion is enhanced after CK2 inhibition. This enhancement is preceded by a rise in the cytosolic Ca2+ concentration. Here, we identified the serine residues S2362 and S2364 of the voltage-dependent calcium channel CaV2.1 as targets of CK2 phosphorylation. Furthermore, co-immunoprecipitation experiments revealed that CaV2.1 binds to CK2 in vitro and in vivo. CaV2.1 knockdown experiments showed that the increase in the intracellular Ca2+ concentration, followed by an enhanced insulin secretion upon CK2 inhibition, is due to a Ca2+ influx through CaV2.1 channels. In summary, our results point to a modulating role of CK2 in the CaV2.1-mediated exocytosis of insulin.
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Affiliation(s)
- Rebecca Scheuer
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Kirrberger Str., bldg. 44, D-66424 Homburg, Germany; (R.S.); (M.M.)
| | - Stephan Ernst Philipp
- Department of Experimental and Clinical Pharmacology and Toxicology, Saarland University Kirrberger Str., bldg. 45-46, D-66424 Homburg, Germany; (S.E.P.); (A.B.)
| | - Alexander Becker
- Department of Experimental and Clinical Pharmacology and Toxicology, Saarland University Kirrberger Str., bldg. 45-46, D-66424 Homburg, Germany; (S.E.P.); (A.B.)
| | - Lisa Nalbach
- Institute for Clinical & Experimental Surgery, Saarland University Kirrberger Str., bldg. 65, D-66424 Homburg, Germany; (L.N.); (E.A.)
| | - Emmanuel Ampofo
- Institute for Clinical & Experimental Surgery, Saarland University Kirrberger Str., bldg. 65, D-66424 Homburg, Germany; (L.N.); (E.A.)
| | - Mathias Montenarh
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Kirrberger Str., bldg. 44, D-66424 Homburg, Germany; (R.S.); (M.M.)
| | - Claudia Götz
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Kirrberger Str., bldg. 44, D-66424 Homburg, Germany; (R.S.); (M.M.)
- Correspondence:
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Autism-associated mutations in the CaVβ2 calcium-channel subunit increase Ba2+-currents and lead to differential modulation by the RGK-protein Gem. Neurobiol Dis 2020; 136:104721. [DOI: 10.1016/j.nbd.2019.104721] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/06/2019] [Accepted: 12/26/2019] [Indexed: 12/26/2022] Open
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Bastian C, Quinn J, Tripathi A, Aquila D, McCray A, Dutta R, Baltan S, Brunet S. CK2 inhibition confers functional protection to young and aging axons against ischemia by differentially regulating the CDK5 and AKT signaling pathways. Neurobiol Dis 2018; 126:47-61. [PMID: 29944965 DOI: 10.1016/j.nbd.2018.05.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 05/08/2018] [Accepted: 05/21/2018] [Indexed: 12/25/2022] Open
Abstract
White matter (WM) is injured in most strokes, which contributes to functional deficits during recovery. Casein kinase 2 (CK2) is a protein kinase that is expressed in brain, including WM. To assess the impact of CK2 inhibition on axon recovery following oxygen glucose deprivation (OGD), mouse optic nerves (MONs), which are pure WM tracts, were subjected to OGD with or without the selective CK2 inhibitor CX-4945. CX-4945 application preserved axon function during OGD and promoted axon function recovery when applied before or after OGD. This protective effect of CK2 inhibition correlated with preservation of oligodendrocytes and conservation of axon structure and axonal mitochondria. To investigate the pertinent downstream signaling pathways, siRNA targeting the CK2α subunit identified CDK5 and AKT as downstream molecules. Consequently, MK-2206 and roscovitine, which are selective AKT and CDK5 inhibitors, respectively, protected young and aging WM function only when applied before OGD. However, a novel pan-AKT allosteric inhibitor, ARQ-092, which targets both the inactive and active conformations of AKT, conferred protection to young and aging axons when applied before or after OGD. These results suggest that AKT and CDK5 signaling contribute to the WM functional protection conferred by CK2 inhibition during ischemia, while inhibition of activated AKT signaling plays the primary role in post-ischemic protection conferred by CK2 inhibition in WM independent of age. CK2 inhibitors are currently being used in clinical trials for cancer patients; therefore, our results will provide rationale for repurposing these drugs as therapeutic options for stroke patients by adding novel targets.
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Affiliation(s)
- Chinthasagar Bastian
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America
| | - John Quinn
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America
| | - Ajai Tripathi
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America
| | - Danielle Aquila
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America
| | - Andrew McCray
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America
| | - Ranjan Dutta
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America
| | - Selva Baltan
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America.
| | - Sylvain Brunet
- Departments of Neurosciences, Cleveland Clinic, Cleveland, OH 44195, United States of America.
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Rosa N, Triffaux E, Robert V, Mars M, Klein M, Bouchaud G, Canivet A, Magnan A, Guéry JC, Pelletier L, Savignac M. The β and α2δ auxiliary subunits of voltage-gated calcium channel 1 (Ca v1) are required for T H2 lymphocyte function and acute allergic airway inflammation. J Allergy Clin Immunol 2017; 142:892-903.e8. [PMID: 29129580 DOI: 10.1016/j.jaci.2017.09.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 08/04/2017] [Accepted: 09/08/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND T lymphocytes express not only cell membrane ORAI calcium release-activated calcium modulator 1 but also voltage-gated calcium channel (Cav) 1 channels. In excitable cells these channels are composed of the ion-forming pore α1 and auxiliary subunits (β and α2δ) needed for proper trafficking and activation of the channel. Previously, we disclosed the role of Cav1.2 α1 in mouse and human TH2 but not TH1 cell functions and showed that knocking down Cav1 α1 prevents experimental asthma. OBJECTIVE We investigated the role of β and α2δ auxiliary subunits on Cav1 α1 function in TH2 lymphocytes and on the development of acute allergic airway inflammation. METHODS We used Cavβ antisense oligonucleotides to knock down Cavβ and gabapentin, a drug that binds to and inhibits α2δ1 and α2δ2, to test their effects on TH2 functions and their capacity to reduce allergic airway inflammation. RESULTS Mouse and human TH2 cells express mainly Cavβ1, β3, and α2δ2 subunits. Cavβ antisense reduces T-cell receptor-driven calcium responses and cytokine production by mouse and human TH2 cells with no effect on TH1 cells. Cavβ is mainly involved in restraining Cav1.2 α1 degradation through the proteasome because a proteasome inhibitor partially restores the α1 protein level. Gabapentin impairs the T-cell receptor-driven calcium response and cytokine production associated with the loss of α2δ2 protein in TH2 cells. CONCLUSIONS These results stress the role of Cavβ and α2δ2 auxiliary subunits in the stability and activation of Cav1.2 channels in TH2 lymphocytes both in vitro and in vivo, as demonstrated by the beneficial effect of Cavβ antisense and gabapentin in allergic airway inflammation.
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Affiliation(s)
- Nicolas Rosa
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Emily Triffaux
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Virginie Robert
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Marion Mars
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Martin Klein
- Institut du Thorax, INSERM CNRS, UNIV Nantes, France
| | | | - Astrid Canivet
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Antoine Magnan
- Institut du Thorax, INSERM CNRS, UNIV Nantes, France; Centre Hospitalier Universitaire de Nantes, Service de Pneumologie, Nantes, France
| | - Jean-Charles Guéry
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France
| | - Lucette Pelletier
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France.
| | - Magali Savignac
- Center of Physiopathology Toulouse Purpan, University Paul Sabatier Toulouse III, INSERM U1043, CNRS UMR 5282, Toulouse, France.
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Park CG, Park Y, Suh BC. The HOOK region of voltage-gated Ca2+ channel β subunits senses and transmits PIP2 signals to the gate. J Gen Physiol 2017; 149:261-276. [PMID: 28087621 PMCID: PMC5299622 DOI: 10.1085/jgp.201611677] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 12/12/2016] [Accepted: 12/22/2016] [Indexed: 12/12/2022] Open
Abstract
The β subunit of voltage-gated Ca2+ (CaV) channels plays an important role in regulating gating of the α1 pore-forming subunit and its regulation by phosphatidylinositol 4,5-bisphosphate (PIP2). Subcellular localization of the CaV β subunit is critical for this effect; N-terminal-dependent membrane targeting of the β subunit slows inactivation and decreases PIP2 sensitivity. Here, we provide evidence that the HOOK region of the β subunit plays an important role in the regulation of CaV biophysics. Based on amino acid composition, we broadly divide the HOOK region into three domains: S (polyserine), A (polyacidic), and B (polybasic). We show that a β subunit containing only its A domain in the HOOK region increases inactivation kinetics and channel inhibition by PIP2 depletion, whereas a β subunit with only a B domain decreases these responses. When both the A and B domains are deleted, or when the entire HOOK region is deleted, the responses are elevated. Using a peptide-to-liposome binding assay and confocal microscopy, we find that the B domain of the HOOK region directly interacts with anionic phospholipids via polybasic and two hydrophobic Phe residues. The β2c-short subunit, which lacks an A domain and contains fewer basic amino acids and no Phe residues in the B domain, neither associates with phospholipids nor affects channel gating dynamically. Together, our data suggest that the flexible HOOK region of the β subunit acts as an important regulator of CaV channel gating via dynamic electrostatic and hydrophobic interaction with the plasma membrane.
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Affiliation(s)
- Cheon-Gyu Park
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea
| | - Yongsoo Park
- Izmir International Biomedicine and Genome Institute (iBG-izmir), Dokuz Eylul University, 35340 Balcova, Izmir, Turkey
| | - Byung-Chang Suh
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Korea
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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.
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