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Siri-Angkul N, Kamp TJ. Cardiac L-type calcium channel regulation by Leucine-Rich Repeat-Containing Protein 10. Channels (Austin) 2024; 18:2355121. [PMID: 38762910 PMCID: PMC11110685 DOI: 10.1080/19336950.2024.2355121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 05/10/2024] [Indexed: 05/21/2024] Open
Abstract
L-type calcium channels (LTCCs), the major portal for Ca2+ entry into cardiomyocytes, are essential for excitation-contraction coupling and thus play a central role in regulating overall cardiac function. LTCC function is finely tuned by multiple signaling pathways and accessory proteins. Leucine-rich repeat-containing protein 10 (LRRC10) is a little studied cardiomyocyte-specific protein recently identified as a modulator of LTCCs. LRRC10 exerts a remarkable effect on LTCC function, more than doubling L-type Ca2+ current (ICa,L) amplitude in a heterologous expression system by altering the gating of the channels without changing their surface membrane expression. Genetic ablation of LRRC10 expression in mouse and zebrafish hearts leads to a significant reduction in ICa,L density and a slowly progressive dilated cardiomyopathy in mice. Rare sequence variants of LRRC10 have been identified in dilated cardiomyopathy and sudden unexplained nocturnal cardiac death syndrome, but these variants have not been clearly linked to disease. Nevertheless, the DCM-associated variant, I195T, converted LRRC10 from a ICa,L potentiator to a ICa,L suppressor, thus illustrating the wide dynamic range of LRRC10-mediated ICa,L regulation. This review focuses on the contemporary knowledge of LTCC modulation by LRRC10 and discusses potential directions for future investigations.
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Affiliation(s)
- Natthaphat Siri-Angkul
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin - Madison, Madison, WI, USA
| | - Timothy J Kamp
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin - Madison, Madison, WI, USA
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin - Madison, Madison, WI, USA
- Stem Cell and Regenerative Medicine Center, University of Wisconsin - Madison, Madison, WI, USA
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2
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He LS, Qi Y, Allard CAH, Valencia-Montoya WA, Krueger SP, Weir K, Seminara A, Bellono NW. Molecular tuning of sea anemone stinging. eLife 2023; 12:RP88900. [PMID: 37906220 PMCID: PMC10617991 DOI: 10.7554/elife.88900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023] Open
Abstract
Jellyfish and sea anemones fire single-use, venom-covered barbs to immobilize prey or predators. We previously showed that the anemone Nematostella vectensis uses a specialized voltage-gated calcium (CaV) channel to trigger stinging in response to synergistic prey-derived chemicals and touch (Weir et al., 2020). Here, we use experiments and theory to find that stinging behavior is suited to distinct ecological niches. We find that the burrowing anemone Nematostella uses uniquely strong CaV inactivation for precise control of predatory stinging. In contrast, the related anemone Exaiptasia diaphana inhabits exposed environments to support photosynthetic endosymbionts. Consistent with its niche, Exaiptasia indiscriminately stings for defense and expresses a CaV splice variant that confers weak inactivation. Chimeric analyses reveal that CaVβ subunit adaptations regulate inactivation, suggesting an evolutionary tuning mechanism for stinging behavior. These findings demonstrate how functional specialization of ion channel structure contributes to distinct organismal behavior.
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Affiliation(s)
- Lily S He
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Yujia Qi
- Machine Learning Center Genoa (MalGa), Department of Civil, Chemical and Environmental Engineering (DICCA), University of GenoaGenoaItaly
| | - Corey AH Allard
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Wendy A Valencia-Montoya
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard UniversityCambridgeUnited States
| | - Stephanie P Krueger
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Keiko Weir
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Agnese Seminara
- Machine Learning Center Genoa (MalGa), Department of Civil, Chemical and Environmental Engineering (DICCA), University of GenoaGenoaItaly
| | - Nicholas W Bellono
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
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3
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He LS, Qi Y, Allard CAH, Valencia-Montoya WA, Krueger SP, Weir K, Seminara A, Bellono NW. Molecular tuning of sea anemone stinging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.15.545144. [PMID: 37577638 PMCID: PMC10418081 DOI: 10.1101/2023.06.15.545144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Jellyfish and sea anemones fire single-use, venom-covered barbs to immobilize prey or predators. We previously showed that the anemone Nematostella vectensis uses a specialized voltage-gated calcium (CaV) channel to trigger stinging in response to synergistic prey-derived chemicals and touch (Weir et al., 2020). Here we use experiments and theory to find that stinging behavior is suited to distinct ecological niches. We find that the burrowing anemone Nematostella uses uniquely strong CaV inactivation for precise control of predatory stinging. In contrast, the related anemone Exaiptasia diaphana inhabits exposed environments to support photosynthetic endosymbionts. Consistent with its niche, Exaiptasia indiscriminately stings for defense and expresses a CaV splice variant that confers weak inactivation. Chimeric analyses reveal that CaVβ subunit adaptations regulate inactivation, suggesting an evolutionary tuning mechanism for stinging behavior. These findings demonstrate how functional specialization of ion channel structure contributes to distinct organismal behavior.
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Affiliation(s)
- Lily S He
- Department of Molecular and Cellular Biology, Harvard University, Cambridge MA 02138 USA
| | - Yujia Qi
- Machine Learning Center Genoa (MalGa), Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genoa, Via Montallegro 1, 16145 Genoa, Italy
| | - Corey AH Allard
- Department of Molecular and Cellular Biology, Harvard University, Cambridge MA 02138 USA
| | - Wendy A Valencia-Montoya
- Department of Molecular and Cellular Biology, Harvard University, Cambridge MA 02138 USA
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA
| | - Stephanie P Krueger
- Department of Molecular and Cellular Biology, Harvard University, Cambridge MA 02138 USA
| | - Keiko Weir
- Department of Molecular and Cellular Biology, Harvard University, Cambridge MA 02138 USA
| | - Agnese Seminara
- Machine Learning Center Genoa (MalGa), Department of Civil, Chemical and Environmental Engineering (DICCA), University of Genoa, Via Montallegro 1, 16145 Genoa, Italy
| | - Nicholas W Bellono
- Department of Molecular and Cellular Biology, Harvard University, Cambridge MA 02138 USA
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Vergnol A, Traoré M, Pietri-Rouxel F, Falcone S. New Insights in CaVβ Subunits: Role in the Regulation of Gene Expression and Cellular Homeostasis. Front Cell Dev Biol 2022; 10:880441. [PMID: 35465309 PMCID: PMC9019481 DOI: 10.3389/fcell.2022.880441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 03/16/2022] [Indexed: 11/23/2022] Open
Abstract
The voltage-gated calcium channels (CaVs or VGCCs) are fundamental regulators of intracellular calcium homeostasis. When electrical activity induces their activation, the influx of calcium that they mediate or their interaction with intracellular players leads to changes in intracellular Ca2+ levels which regulate many processes such as contraction, secretion and gene expression, depending on the cell type. The essential component of the pore channel is the CaVα1 subunit. However, the fine-tuning of Ca2+-dependent signals is guaranteed by the modulatory role of the auxiliary subunits β, α2δ, and γ of the CaVs. In particular, four different CaVβ proteins (CaVβ1, CaVβ2, CaVβ3, and CaVβ4) are encoded by four different genes in mammalians, each of them displaying several splice variants. Some of these isoforms have been described in regulating CaVα1 docking and stability at the membrane and controlling the channel complex’s conformational changes. In addition, emerging evidences have highlighted other properties of the CaVβ subunits, independently of α1 and non-correlated to its channel or voltage sensing functions. This review summarizes the recent findings reporting novel roles of the auxiliary CaVβ subunits and in particular their direct or indirect implication in regulating gene expression in different cellular contexts.
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Poberezhnyi V, Marchuk O, Katilov O, Shvydiuk O, Lohvinov O. Basic concepts and physical-chemical phenomena, that have conceptual meaning for the formation of systemic clinical thinking and formalization of the knowledge of systemic structural-functional organization of the human’s organism. PAIN MEDICINE 2020. [DOI: 10.31636/pmjua.v5i2.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
From the point of view of perception and generalization processes there are complex, logic and conceptual forms of thinking. Its conceptual form is the highest result of interaction between thinking and speech. While realizing it, human uses the concept, which are logically formed thoughts, that are the meaning of representation in thinking of unity of meaningful features, relations of subjects or phenomena of objective reality. Special concepts, that are used in the science and technique are called terms. They perform a function of corresponding, special, precise marking of subjects and phenomena, their features and interactions. Scientific knowledge are in that way an objective representation of material duality in our consciousness. Certain complex of terms forms a terminological system, that lies in the basis of corresponding sphere of scientific knowledge and conditions a corresponding form and way of thinking. Clinical thinking is a conceptual form, that manifests and represents by the specialized internal speech with gnostic motivation lying in its basis. Its structural elements are corresponding definitions, terms and concepts. Cardinal features of clinical systems are consistency, criticality, justification and substantiation. Principles of perception and main concepts are represented in the article along with short descriptions of physical and chemical phenomena, that have conceptual meaning for the formation of systematic clinical thinking and formalization of systemic structural-functional organization of the human’s organism
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Ca 2+ currents in cardiomyocytes: How to improve interpretation of patch clamp data? PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 157:33-39. [PMID: 32439316 DOI: 10.1016/j.pbiomolbio.2020.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 04/29/2020] [Accepted: 05/13/2020] [Indexed: 11/22/2022]
Abstract
OBJECTIVES Variability of ion currents is major issue when used for significance testing. One of the simplest approach to reduce variability is normalization to cell membrane size. However, efficacy of Ca2+ currents (ICa) normalization is unknown. Beside absolute variability, the type of distribution since non-Gaussian distribution makes application of nonparametric test necessary. METHODS We retrospectively analyzed individual ICa amplitudes measured in ventricular cardiomyocytes from mice, rats and humans and in atrial cardiomyocytes from humans in sinus rhythm and in atrial fibrillation. ICa was normalized to cell membrane size, estimated from capacitance transients. In addition, data were Log transformed to reach Gaussian distribution. Normalized and transformed data were analyzed for variability and applicability of parametric vs. nonparametric tests. RESULTS There was strong correlation between ICa and cell membrane size. However, correlation coefficient was rather low. Normalizing ICa had an inconsistent effect on variability. Variability of ICa in cells from the same patient/animal was not different cardiomyocytes from humans, rat and mice. Calculation of mean values based on mean values of cells from individuals (patients or animals) vs. mean values calculated for all cells drastically reduces statistical power to detect differences between the groups. Log transformation of ICa allowed application of much higher sensitive parametric testing, compensating loss of power. CONCLUSION Impact of cell membrane size to ICa is low and may limit efficacy of normalization of ICa to reduce variability. In contrast, Log transformation of ICa data reduces variability and can increase statistical power to detect difference between ICa datasets.
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7
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New aspects in cardiac L-type Ca2+ channel regulation. Biochem Soc Trans 2020; 48:39-49. [PMID: 32065210 DOI: 10.1042/bst20190229] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 01/24/2020] [Accepted: 01/24/2020] [Indexed: 12/23/2022]
Abstract
Cardiac excitation-contraction coupling is initiated with the influx of Ca2+ ions across the plasma membrane through voltage-gated L-type calcium channels. This process is tightly regulated by modulation of the channel open probability and channel localization. Protein kinase A (PKA) is found in close association with the channel and is one of the main regulators of its function. Whether this kinase is modulating the channel open probability by phosphorylation of key residues or via alternative mechanisms is unclear. This review summarizes recent findings regarding the PKA-mediated channel modulation and will highlight recently discovered regulatory mechanisms that are independent of PKA activity and involve protein-protein interactions and channel localization.
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Binas S, Knyrim M, Hupfeld J, Kloeckner U, Rabe S, Mildenberger S, Quarch K, Strätz N, Misiak D, Gekle M, Grossmann C, Schreier B. miR-221 and -222 target CACNA1C and KCNJ5 leading to altered cardiac ion channel expression and current density. Cell Mol Life Sci 2020; 77:903-918. [PMID: 31312877 PMCID: PMC7058603 DOI: 10.1007/s00018-019-03217-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 06/14/2019] [Accepted: 07/02/2019] [Indexed: 12/26/2022]
Abstract
MicroRNAs (miRs) contribute to different aspects of cardiovascular pathology, among others cardiac hypertrophy and atrial fibrillation. The aim of our study was to evaluate the impact of miR-221/222 on cardiac electrical remodeling. Cardiac miR expression was analyzed in a mouse model with altered electrocardiography parameters and severe heart hypertrophy. Next generation sequencing revealed 14 differentially expressed miRs in hypertrophic hearts, with miR-221 and -222 being the strongest regulated miR-cluster. This increase was restricted to cardiomyocytes and not observed in cardiac fibroblasts. Additionally, we evaluated the change of miR-221/222 in vivo in two models of pharmacologically induced heart hypertrophy (angiotensin II, isoprenaline), thereby demonstrating a stimulus-induced increase in miR-221/222 in vivo by angiotensin II but not by isoprenaline. Whole transcriptome analysis by RNA-seq and qRT-PCR validation revealed an enriched number of downregulated mRNAs coding for proteins located in the T-tubule, which are also predicted targets for miR-221/222. Among those, mRNAs were the L-type Ca2+ channel subunits as well as potassium channel subunits. We confirmed that both miRs target the 3'-untranslated regions of Cacna1c and Kcnj5. Furthermore, enhanced expression of these miRs reduced L-type Ca2+ channel and Kcnj5 channel abundance and function, which was analyzed by whole-cell patch clamp recordings or Western blot and flux measurements, respectively. miR-221 and -222 contribute to the regulation of L-type Ca2+ channels as well as Kcnj5 channels and, therefore, potentially contribute to disturbed cardiac excitation generation and propagation. Future studies will have to evaluate the pathophysiological and clinical relevance of aberrant miR-221/222 expression for electrical remodeling.
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Affiliation(s)
- Stephanie Binas
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Maria Knyrim
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Julia Hupfeld
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Udo Kloeckner
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Sindy Rabe
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Sigrid Mildenberger
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Katja Quarch
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Nicole Strätz
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Danny Misiak
- Institute of Molecular Medicine, Martin-Luther-University Halle-Wittenberg, Heinrich-Damerow-Str. 1, 06120, Halle/Saale, Germany
| | - Michael Gekle
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Claudia Grossmann
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany
| | - Barbara Schreier
- Julius-Bernstein-Institute of Physiology, Martin Luther University Halle-Wittenberg, Magdeburger Str. 6, 06110, Halle/Saale, Germany.
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9
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Ortner NJ, Pinggera A, Hofer NT, Siller A, Brandt N, Raffeiner A, Vilusic K, Lang I, Blum K, Obermair GJ, Stefan E, Engel J, Striessnig J. RBP2 stabilizes slow Cav1.3 Ca 2+ channel inactivation properties of cochlear inner hair cells. Pflugers Arch 2019; 472:3-25. [PMID: 31848688 PMCID: PMC6960213 DOI: 10.1007/s00424-019-02338-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 10/18/2019] [Accepted: 12/04/2019] [Indexed: 01/31/2023]
Abstract
Cav1.3 L-type Ca2+ channels (LTCCs) in cochlear inner hair cells (IHCs) are essential for hearing as they convert sound-induced graded receptor potentials into tonic postsynaptic glutamate release. To enable fast and indefatigable presynaptic Ca2+ signaling, IHC Cav1.3 channels exhibit a negative activation voltage range and uniquely slow inactivation kinetics. Interaction with CaM-like Ca2+-binding proteins inhibits Ca2+-dependent inactivation, while the mechanisms underlying slow voltage-dependent inactivation (VDI) are not completely understood. Here we studied if the complex formation of Cav1.3 LTCCs with the presynaptic active zone proteins RIM2α and RIM-binding protein 2 (RBP2) can stabilize slow VDI. We detected both RIM2α and RBP isoforms in adult mouse IHCs, where they co-localized with Cav1.3 and synaptic ribbons. Using whole-cell patch-clamp recordings (tsA-201 cells), we assessed their effect on the VDI of the C-terminal full-length Cav1.3 (Cav1.3L) and a short splice variant (Cav1.342A) that lacks the C-terminal RBP2 interaction site. When co-expressed with the auxiliary β3 subunit, RIM2α alone (Cav1.342A) or RIM2α/RBP2 (Cav1.3L) reduced Cav1.3 VDI to a similar extent as observed in IHCs. Membrane-anchored β2 variants (β2a, β2e) that inhibit inactivation on their own allowed no further modulation of inactivation kinetics by RIM2α/RBP2. Moreover, association with RIM2α and/or RBP2 consolidated the negative Cav1.3 voltage operating range by shifting the channel's activation threshold toward more hyperpolarized potentials. Taken together, the association with "slow" β subunits (β2a, β2e) or presynaptic scaffolding proteins such as RIM2α and RBP2 stabilizes physiological gating properties of IHC Cav1.3 LTCCs in a splice variant-dependent manner ensuring proper IHC function.
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Affiliation(s)
- Nadine J Ortner
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
| | - Alexandra Pinggera
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Nadja T Hofer
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Anita Siller
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Niels Brandt
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Andrea Raffeiner
- Institute of Biochemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Kristina Vilusic
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Isabelle Lang
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Kerstin Blum
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Gerald J Obermair
- Division of Physiology, Medical University Innsbruck, Innsbruck, Austria.,Division Physiology, Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Eduard Stefan
- Institute of Biochemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Jutta Engel
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
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Tyan L, Foell JD, Vincent KP, Woon MT, Mesquitta WT, Lang D, Best JM, Ackerman MJ, McCulloch AD, Glukhov AV, Balijepalli RC, Kamp TJ. Long QT syndrome caveolin-3 mutations differentially modulate K v 4 and Ca v 1.2 channels to contribute to action potential prolongation. J Physiol 2019; 597:1531-1551. [PMID: 30588629 DOI: 10.1113/jp276014] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 12/14/2018] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS Mutations in the caveolae scaffolding protein, caveolin-3 (Cav3), have been linked to the long QT type 9 inherited arrhythmia syndrome (LQT9) and the cause of underlying action potential duration prolongation is incompletely understood. In the present study, we show that LQT9 Cav3 mutations, F97C and S141R, cause mutation-specific gain of function effects on Cav 1.2-encoded L-type Ca2+ channels responsible for ICa,L and also cause loss of function effects on heterologously expressed Kv 4.2 and Kv 4.3 channels responsible for Ito . A computational model of the human ventricular myocyte action potential suggests that the major ionic current change causing action potential duration prolongation in the presence of Cav3-F97C is the slowly inactivating ICa,L but, for Cav3-S141R, both increased ICa,L and increased late Na+ current contribute equally to action potential duration prolongation. Overall, the LQT9 Cav3-F97C and Cav3-S141R mutations differentially impact multiple ionic currents, highlighting the complexity of Cav3 regulation of cardiac excitability and suggesting mutation-specific therapeutic approaches. ABSTRACT Mutations in the CAV3 gene encoding caveolin-3 (Cav3), a scaffolding protein integral to caveolae in cardiomyocytes, have been associated with the congenital long-QT syndrome (LQT9). Initial studies demonstrated that LQT9-associated Cav3 mutations, F97C and S141R, increase late sodium current as a potential mechanism to prolong action potential duration (APD) and cause LQT9. Whether these Cav3 LQT9 mutations impact other caveolae related ion channels remains unknown. We used the whole-cell, patch clamp technique to characterize the effect of Cav3-F97C and Cav3-S141R mutations on heterologously expressed Cav 1.2+Cav β2cN4 channels, as well as Kv 4.2 and Kv 4.3 channels, in HEK 293 cells. Expression of Cav3-S141R increased ICa,L density without changes in gating properties, whereas expression of Cav3-F97C reduced Ca2+ -dependent inactivation of ICa,L without changing current density. The Cav3-F97C mutation reduced current density and altered the kinetics of IKv4.2 and IKv4.3 and also slowed recovery from inactivation. Cav3-S141R decreased current density and also slowed activation kinetics and recovery from inactivation of IKv4.2 but had no effect on IKv4.3 . Using the O'Hara-Rudy computational model of the human ventricular myocyte action potential, the Cav3 mutation-induced changes in Ito are predicted to have negligible effect on APD, whereas blunted Ca2+ -dependent inactivation of ICa,L by Cav3-F97C is predicted to be primarily responsible for APD prolongation, although increased ICa,L and late INa by Cav3-S141R contribute equally to APD prolongation. Thus, LQT9 Cav3-associated mutations, F97C and S141R, produce mutation-specific changes in multiple ionic currents leading to different primary causes of APD prolongation, which suggests the use of mutation-specific therapeutic approaches in the future.
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Affiliation(s)
- Leonid Tyan
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Jason D Foell
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Kevin P Vincent
- Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
| | - Marites T Woon
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Walatta T Mesquitta
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Di Lang
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Jabe M Best
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Michael J Ackerman
- Departments of Cardiovascular Medicine, Pediatric and Adolescent Medicine and Molecular Pharmacology & Experimental Therapeutics, Divisions of Heart Rhythm Services and Pediatric Cardiology, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, 200 First Street SW, Rochester, MN, USA
| | - Andrew D McCulloch
- Department of Bioengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA.,Department of Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, USA
| | - Alexey V Glukhov
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Ravi C Balijepalli
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
| | - Timothy J Kamp
- Department of Medicine, Division of Cardiovascular Medicine, University of Wisconsin-Madison, 1111, Highland Ave, Madison, WI, USA
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11
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Ahern BM, Satin J. The L-type calcium channel current modulation mechanism: the plot thickens and fogs. J Clin Invest 2019; 129:496-498. [PMID: 30614816 DOI: 10.1172/jci125958] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Stressful situations provoke the fight-or-flight response, incurring rapid elevation of cardiac output via activation of protein kinase A (PKA). In this issue of the JCI, Yang et al. focus on the L-type calcium channel complex (LTCC), and their findings require reexamination of dogmatic principles. LTCC phosphorylation sites identified and studied to date are dispensable for PKA modulation of LTCC; however, a CaVβ2-CaV1.2 calcium channel interaction is now shown to be required. Yang et al. suggest a new hypothesis that LTCC modulation involves rearrangement of auxiliary proteins within the LTCC. However, we still do not know the targets of PKA that mediate LTCC modulation.
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12
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Tammineni ER, Carrillo ED, Soto-Acosta R, Angel-Ambrocio AH, García MC, Bautista-Carbajal P, del Angel RM, Sánchez JA. The β
4
subunit of Ca
v
1.2 channels is required for an optimal interferon response in cardiac muscle cells. Sci Signal 2018; 11:11/560/eaaj1676. [DOI: 10.1126/scisignal.aaj1676] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Eshwar R. Tammineni
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Elba D. Carrillo
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Rubén Soto-Acosta
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Antonio H. Angel-Ambrocio
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - María C. García
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Patricia Bautista-Carbajal
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Rosa M. del Angel
- Departamento de Infectómica y Patogénesis Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Jorge A. Sánchez
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
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13
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Lang D, Glukhov AV. Functional Microdomains in Heart's Pacemaker: A Step Beyond Classical Electrophysiology and Remodeling. Front Physiol 2018; 9:1686. [PMID: 30538641 PMCID: PMC6277479 DOI: 10.3389/fphys.2018.01686] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/09/2018] [Indexed: 12/12/2022] Open
Abstract
Spontaneous beating of the sinoatrial node (SAN), the primary pacemaker of the heart, is initiated, sustained, and regulated by a complex system that integrates ion channels and transporters on the cell membrane surface (often referred to as "membrane clock") with subcellular calcium handling machinery (by parity of reasoning referred to as an intracellular "Ca2+ clock"). Stable, rhythmic beating of the SAN is ensured by a rigorous synchronization between these two clocks highlighted in the coupled-clock system concept of SAN timekeeping. The emerging results demonstrate that such synchronization of the complex pacemaking machinery at the cellular level depends on tightly regulated spatiotemporal signals which are restricted to precise sub-cellular microdomains and associated with discrete clusters of different ion channels, transporters, and regulatory receptors. It has recently become evident that within the microdomains, various proteins form an interacting network and work together as a part of a macromolecular signaling complex. These protein-protein interactions are tightly controlled and regulated by a variety of neurohormonal signaling pathways and the diversity of cellular responses achieved with a limited pool of second messengers is made possible through the organization of essential signal components in particular microdomains. In this review, we highlight the emerging understanding of the functionality of distinct subcellular microdomains in SAN myocytes and their functional role in the accumulation and neurohormonal regulation of proteins involved in cardiac pacemaking. We also demonstrate how changes in scaffolding proteins may lead to microdomain-targeted remodeling and regulation of pacemaker proteins contributing to SAN dysfunction.
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Affiliation(s)
- Di Lang
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Alexey V Glukhov
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
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14
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Basheer WA, Shaw RM. Connexin 43 and CaV1.2 Ion Channel Trafficking in Healthy and Diseased Myocardium. Circ Arrhythm Electrophysiol 2018; 9:e001357. [PMID: 27266274 DOI: 10.1161/circep.115.001357] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 04/29/2016] [Indexed: 11/16/2022]
Affiliation(s)
- Wassim A Basheer
- From the Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (W.A.B., R.M.S.); and Department of Medicine, University of California Los Angeles (R.M.S.)
| | - Robin M Shaw
- From the Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (W.A.B., R.M.S.); and Department of Medicine, University of California Los Angeles (R.M.S.).
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15
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Xu H, Dorn GW, Shetty A, Parihar A, Dave T, Robinson SW, Gottlieb SS, Donahue MP, Tomaselli GF, Kraus WE, Mitchell BD, Liggett SB. A Genome-Wide Association Study of Idiopathic Dilated Cardiomyopathy in African Americans. J Pers Med 2018; 8:E11. [PMID: 29495422 PMCID: PMC5872085 DOI: 10.3390/jpm8010011] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 02/17/2018] [Accepted: 02/21/2018] [Indexed: 01/03/2023] Open
Abstract
Idiopathic dilated cardiomyopathy (IDC) is the most common form of non-ischemic chronic heart failure. Despite the higher prevalence of IDC in African Americans, the genetics of IDC have been relatively understudied in this ethnic group. We performed a genome-wide association study to identify susceptibility genes for IDC in African Americans recruited from five sites in the U.S. (662 unrelated cases and 1167 controls). The heritability of IDC was calculated to be 33% (95% confidence interval: 19-47%; p = 6.4 × 10-7). We detected association of a variant in a novel intronic locus in the CACNB4 gene meeting genome-wide levels of significance (p = 4.1 × 10-8). The CACNB4 gene encodes a calcium channel subunit expressed in the heart that is important for cardiac muscle contraction. This variant has not previously been associated with IDC in any racial group. Pathway analysis, based on the 1000 genes most strongly associated with IDC, showed an enrichment for genes related to calcium signaling, growth factor signaling, neuronal/neuromuscular signaling, and various types of cellular level signaling, including gap junction and cAMP signaling. Our results suggest a novel locus for IDC in African Americans and provide additional insights into the genetic architecture and etiology.
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Affiliation(s)
- Huichun Xu
- Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Gerald W Dorn
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Amol Shetty
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Ankita Parihar
- Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Tushar Dave
- Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Shawn W Robinson
- Division of Cardiovascular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Stephen S Gottlieb
- Division of Cardiovascular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| | - Mark P Donahue
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, NC 27708, USA.
| | - Gordon F Tomaselli
- Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21218, USA.
| | - William E Kraus
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, NC 27708, USA.
- Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC 27701, USA.
| | - Braxton D Mitchell
- Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
- Geriatrics Research and Education Clinical Center, Baltimore Veterans Administration Medical Center, Baltimore, MD 21201, USA.
| | - Stephen B Liggett
- Department of Internal Medicine and Molecular Pharmacology and Physiology, and the Center for Personalized Medicine and Genomics, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA.
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16
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Woon MT, Long PA, Reilly L, Evans JM, Keefe AM, Lea MR, Beglinger CJ, Balijepalli RC, Lee Y, Olson TM, Kamp TJ. Pediatric Dilated Cardiomyopathy-Associated LRRC10 (Leucine-Rich Repeat-Containing 10) Variant Reveals LRRC10 as an Auxiliary Subunit of Cardiac L-Type Ca 2+ Channels. J Am Heart Assoc 2018; 7:e006428. [PMID: 29431102 PMCID: PMC5850229 DOI: 10.1161/jaha.117.006428] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Accepted: 11/10/2017] [Indexed: 12/30/2022]
Abstract
BACKGROUND Genetic causes of dilated cardiomyopathy (DCM) are incompletely understood. LRRC10 (leucine-rich repeat-containing 10) is a cardiac-specific protein of unknown function. Heterozygous mutations in LRRC10 have been suggested to cause DCM, and deletion of Lrrc10 in mice results in DCM. METHODS AND RESULTS Whole-exome sequencing was carried out on a patient who presented at 6 weeks of age with DCM and her unaffected parents, filtering for rare, deleterious, recessive, and de novo variants. Whole-exome sequencing followed by trio-based filtering identified a homozygous recessive variant in LRRC10, I195T. Coexpression of I195T LRRC10 with the L-type Ca2+ channel (Cav1.2, β2CN2, and α2δ subunits) in HEK293 cells resulted in a significant ≈0.5-fold decrease in ICa,L at 0 mV, in contrast to the ≈1.4-fold increase in ICa,L by coexpression of LRRC10 (n=9-12, P<0.05). Coexpression of LRRC10 or I195T LRRC10 did not alter the surface membrane expression of Cav1.2. LRRC10 coexpression with Cav1.2 in the absence of auxiliary β2CN2 and α2δ subunits revealed coassociation of Cav1.2 and LRRC10 and a hyperpolarizing shift in the voltage dependence of activation (n=6-9, P<0.05). Ventricular myocytes from Lrrc10-/- mice had significantly smaller ICa,L, and coimmunoprecipitation experiments confirmed association between LRRC10 and the Cav1.2 subunit in mouse hearts. CONCLUSIONS Examination of a patient with DCM revealed homozygosity for a previously unreported LRRC10 variant: I195T. Wild-type and I195T LRRC10 function as cardiac-specific subunits of L-type Ca2+ channels and exert dramatically different effects on channel gating, providing a potential link to DCM.
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Affiliation(s)
- Marites T Woon
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Pamela A Long
- Mayo Graduate School, Molecular Pharmacology and Experimental Therapeutics Track, Mayo Clinic, Rochester, MN
| | - Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Jared M Evans
- Division of Biomedical Statistics and Informatics, Department of Health Sciences Research, Mayo Clinic, Rochester, MN
| | - Alexis M Keefe
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Martin R Lea
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Carl J Beglinger
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Ravi C Balijepalli
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
| | - Youngsook Lee
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI
| | - Timothy M Olson
- Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
- Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic, Rochester, MN
| | - Timothy J Kamp
- Cellular and Molecular Arrhythmia Research Program, University of Wisconsin-Madison, Madison, WI
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI
- Department of Medicine, University of Wisconsin-Madison, Madison, WI
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17
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Alternative Splicing of L-type Ca V1.2 Calcium Channels: Implications in Cardiovascular Diseases. Genes (Basel) 2017; 8:genes8120344. [PMID: 29186814 PMCID: PMC5748662 DOI: 10.3390/genes8120344] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 11/09/2017] [Accepted: 11/21/2017] [Indexed: 01/28/2023] Open
Abstract
L-type CaV1.2 calcium channels are the major pathway for Ca2+ influx to initiate the contraction of smooth and cardiac muscles. Alteration of CaV1.2 channel function has been implicated in multiple cardiovascular diseases, such as hypertension and cardiac hypertrophy. Alternative splicing is a post-transcriptional mechanism that expands CaV1.2 channel structures to modify function, pharmacological and biophysical property such as calcium/voltage-dependent inactivation (C/VDI), or to influence its post-translational modulation by interacting proteins such as Galectin-1. Alternative splicing has generated functionally diverse CaV1.2 isoforms that can be developmentally regulated in the heart, or under pathophysiological conditions such as in heart failure. More importantly, alternative splicing of certain exons of CaV1.2 has been reported to be regulated by splicing factors such as RNA-binding Fox-1 homolog 1/2 (Rbfox 1/2), polypyrimidine tract-binding protein (PTBP1) and RNA-binding motif protein 20 (RBM20). Understanding how CaV1.2 channel function is remodelled in disease will provide better information to guide the development of more targeted approaches to discover therapeutic agents for cardiovascular diseases.
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18
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Qian H, Patriarchi T, Price JL, Matt L, Lee B, Nieves-Cintrón M, Buonarati OR, Chowdhury D, Nanou E, Nystoriak MA, Catterall WA, Poomvanicha M, Hofmann F, Navedo MF, Hell JW. Phosphorylation of Ser1928 mediates the enhanced activity of the L-type Ca2+ channel Cav1.2 by the β2-adrenergic receptor in neurons. Sci Signal 2017; 10:10/463/eaaf9659. [PMID: 28119465 DOI: 10.1126/scisignal.aaf9659] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The L-type Ca2+ channel Cav1.2 controls multiple functions throughout the body including heart rate and neuronal excitability. It is a key mediator of fight-or-flight stress responses triggered by a signaling pathway involving β-adrenergic receptors (βARs), cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA). PKA readily phosphorylates Ser1928 in Cav1.2 in vitro and in vivo, including in rodents and humans. However, S1928A knock-in (KI) mice have normal PKA-mediated L-type channel regulation in the heart, indicating that Ser1928 is not required for regulation of cardiac Cav1.2 by PKA in this tissue. We report that augmentation of L-type currents by PKA in neurons was absent in S1928A KI mice. Furthermore, S1928A KI mice failed to induce long-term potentiation in response to prolonged theta-tetanus (PTT-LTP), a form of synaptic plasticity that requires Cav1.2 and enhancement of its activity by the β2-adrenergic receptor (β2AR)-cAMP-PKA cascade. Thus, there is an unexpected dichotomy in the control of Cav1.2 by PKA in cardiomyocytes and hippocampal neurons.
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Affiliation(s)
- Hai Qian
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Tommaso Patriarchi
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | - Jennifer L Price
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | - Lucas Matt
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | - Boram Lee
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | | | - Olivia R Buonarati
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | | | - Evanthia Nanou
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - Matthew A Nystoriak
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - Montatip Poomvanicha
- Department of Pharmacology and Toxicology, Technical University of Munich, D-80802 Munich, Germany
| | - Franz Hofmann
- Department of Pharmacology and Toxicology, Technical University of Munich, D-80802 Munich, Germany
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA 95616-8636, USA.
| | - Johannes W Hell
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242-1109, USA. .,Department of Pharmacology, University of California, Davis, CA 95616-8636, USA
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19
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Markandeya YS, Kamp TJ. Rational strategy to stop arrhythmias: Early afterdepolarizations and L-type Ca2+ current. ACTA ACUST UNITED AC 2016; 145:475-9. [PMID: 26009542 PMCID: PMC4442792 DOI: 10.1085/jgp.201511429] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Yogananda S Markandeya
- Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705 Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705
| | - Timothy J Kamp
- Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705 Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705
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20
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Sanoudou D, Kolokathis F, Arvanitis D, Al-Shafai K, Krishnamoorthy N, Buchan RJ, Walsh R, Tsiapras D, Barton PJ, Cook SA, Kremastinos D, Yacoub M. Genetic modifiers to the PLN L39X mutation in a patient with DCM and sustained ventricular tachycardia? Glob Cardiol Sci Pract 2015; 2015:29. [PMID: 26535225 PMCID: PMC4614339 DOI: 10.5339/gcsp.2015.29] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 04/30/2015] [Indexed: 11/03/2022] Open
Affiliation(s)
- Despina Sanoudou
- 4 Dept. of Internal Medicine, Medical School, University of Athens, Greece. ; Biomedical Research Foundation of the Academy of Athens, Greece
| | | | | | - Kholoud Al-Shafai
- Qatar Cardiovascular Research Center (QCRC), Qatar Foundation, Doha, Qatar
| | | | - Rachel J Buchan
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, UK. ; National Heart & Lung Institute, Imperial College London, London, UK
| | - Roddy Walsh
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, UK. ; National Heart & Lung Institute, Imperial College London, London, UK
| | | | - Paul Jr Barton
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, UK. ; National Heart & Lung Institute, Imperial College London, London, UK
| | - Stuart A Cook
- NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, UK. ; National Heart & Lung Institute, Imperial College London, London, UK. ; NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, UK
| | | | - Magdi Yacoub
- Qatar Cardiovascular Research Center (QCRC), Qatar Foundation, Doha, Qatar. ; NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London, UK
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21
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Moreno C, Hermosilla T, Morales D, Encina M, Torres-Díaz L, Díaz P, Sarmiento D, Simon F, Varela D. Cavβ2 transcription start site variants modulate calcium handling in newborn rat cardiomyocytes. Pflugers Arch 2015; 467:2473-84. [PMID: 26265381 DOI: 10.1007/s00424-015-1723-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 07/17/2015] [Indexed: 12/21/2022]
Abstract
In the heart, the main pathway for calcium influx is mediated by L-type calcium channels, a multi-subunit complex composed of the pore-forming subunit CaV1.2 and the auxiliary subunits CaVα2δ1 and CaVβ2. To date, five distinct CaVβ2 transcriptional start site (TSS) variants (CaVβ2a-e) varying only in the composition and length of the N-terminal domain have been described, each of them granting distinct biophysical properties to the L-type current. However, the physiological role of these variants in Ca(2+) handling in the native tissue has not been explored. Our results show that four of these variants are present in neonatal rat cardiomyocytes. The contribution of those CaVβ2 TSS variants on endogenous L-type current and Ca(2+) handling was explored by adenoviral-mediated overexpression of each CaVβ2 variant in cultured newborn rat cardiomyocytes. As expected, all CaVβ2 TSS variants increased L-type current density and produced distinctive changes on L-type calcium channel (LTCC) current activation and inactivation kinetics. The characteristics of the induced calcium transients were dependent on the TSS variant overexpressed. Moreover, the amplitude of the calcium transients varied depending on the subunit involved, being higher in cardiomyocytes transduced with CaVβ2a and smaller in CaVβ2d. Interestingly, the contribution of Ca(2+) influx and Ca(2+) release on total calcium transients, as well as the sarcoplasmic calcium content, was found to be TSS-variant-dependent. Remarkably, determination of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) messenger RNA (mRNA) abundance and cell size change indicates that CaVβ2 TSS variants modulate the cardiomyocyte hypertrophic state. In summary, we demonstrate that expression of individual CaVβ2 TSS variants regulates calcium handling in cardiomyocytes and, consequently, has significant repercussion in the development of hypertrophy.
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Affiliation(s)
- Cristian Moreno
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Tamara Hermosilla
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Danna Morales
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Matías Encina
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Leandro Torres-Díaz
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Pablo Díaz
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile
| | - Daniela Sarmiento
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, Santiago, Chile
| | - Felipe Simon
- Departamento de Ciencias Biologicas, Facultad de Ciencias Biologicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, Santiago, Chile.,Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
| | - Diego Varela
- Centro de Estudios Moleculares de la Célula (CEMC), Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
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Intramolecular ex vivo Fluorescence Resonance Energy Transfer (FRET) of Dihydropyridine Receptor (DHPR) β1a Subunit Reveals Conformational Change Induced by RYR1 in Mouse Skeletal Myotubes. PLoS One 2015; 10:e0131399. [PMID: 26114725 PMCID: PMC4482598 DOI: 10.1371/journal.pone.0131399] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 06/02/2015] [Indexed: 11/29/2022] Open
Abstract
The dihydropyridine receptor (DHPR) β1a subunit is essential for skeletal muscle excitation-contraction coupling, but the structural organization of β1a as part of the macromolecular DHPR-ryanodine receptor type I (RyR1) complex is still debatable. We used fluorescence resonance energy transfer (FRET) to probe proximity relationships within the β1a subunit in cultured skeletal myotubes lacking or expressing RyR1. The fluorescein biarsenical reagent FlAsH was used as the FRET acceptor, which exhibits fluorescence upon binding to specific tetracysteine motifs, and enhanced cyan fluorescent protein (CFP) was used as the FRET donor. Ten β1a reporter constructs were generated by inserting the CCPGCC FlAsH binding motif into five positions probing the five domains of β1a with either carboxyl or amino terminal fused CFP. FRET efficiency was largest when CCPGCC was positioned next to CFP, and significant intramolecular FRET was observed for all constructs suggesting that in situ the β1a subunit has a relatively compact conformation in which the carboxyl and amino termini are not extended. Comparison of the FRET efficiency in wild type to that in dyspedic (lacking RyR1) myotubes revealed that in only one construct (H458 CCPGCC β1a -CFP) FRET efficiency was specifically altered by the presence of RyR1. The present study reveals that the C-terminal of the β1a subunit changes conformation in the presence of RyR1 consistent with an interaction between the C-terminal of β1a and RyR1 in resting myotubes.
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23
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Balycheva M, Faggian G, Glukhov AV, Gorelik J. Microdomain-specific localization of functional ion channels in cardiomyocytes: an emerging concept of local regulation and remodelling. Biophys Rev 2015; 7:43-62. [PMID: 28509981 PMCID: PMC5425752 DOI: 10.1007/s12551-014-0159-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/18/2014] [Indexed: 12/26/2022] Open
Abstract
Cardiac excitation involves the generation of action potential by individual cells and the subsequent conduction of the action potential from cell to cell through intercellular gap junctions. Excitation of the cellular membrane results in opening of the voltage-gated L-type calcium ion (Ca2+) channels, thereby allowing a small amount of Ca2+ to enter the cell, which in turn triggers the release of a much greater amount of Ca2+ from the sarcoplasmic reticulum, the intracellular Ca2+ store, and gives rise to the systolic Ca2+ transient and contraction. These processes are highly regulated by the autonomic nervous system, which ensures the acute and reliable contractile function of the heart and the short-term modulation of this function upon changes in heart rate or workload. It has recently become evident that discrete clusters of different ion channels and regulatory receptors are present in the sarcolemma, where they form an interacting network and work together as a part of a macro-molecular signalling complex which in turn allows the specificity, reliability and accuracy of the autonomic modulation of the excitation-contraction processes by a variety of neurohormonal pathways. Disruption in subcellular targeting of ion channels and associated signalling proteins may contribute to the pathophysiology of a variety of cardiac diseases, including heart failure and certain arrhythmias. Recent methodological advances have made it possible to routinely image the topography of live cardiomyocytes, allowing the study of clustering functional ion channels and receptors as well as their coupling within a specific microdomain. In this review we highlight the emerging understanding of the functionality of distinct subcellular microdomains in cardiac myocytes (e.g. T-tubules, lipid rafts/caveolae, costameres and intercalated discs) and their functional role in the accumulation and regulation of different subcellular populations of sodium, Ca2+ and potassium ion channels and their contributions to cellular signalling and cardiac pathology.
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Affiliation(s)
- Marina Balycheva
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK
- Cardiosurgery Department, University of Verona School of Medicine, Verona, Italy
| | - Giuseppe Faggian
- Cardiosurgery Department, University of Verona School of Medicine, Verona, Italy
| | - Alexey V Glukhov
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
| | - Julia Gorelik
- Department of Cardiovascular Sciences, National Heart and Lung Institute, Imperial Centre for Translational and Experimental Medicine, Imperial College London, 4th Floor National Heart and Lung Institute, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
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24
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Stölting G, de Oliveira RC, Guzman RE, Miranda-Laferte E, Conrad R, Jordan N, Schmidt S, Hendriks J, Gensch T, Hidalgo P. Direct interaction of CaVβ with actin up-regulates L-type calcium currents in HL-1 cardiomyocytes. J Biol Chem 2015; 290:4561-4572. [PMID: 25533460 PMCID: PMC4335199 DOI: 10.1074/jbc.m114.573956] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 12/05/2014] [Indexed: 12/14/2022] Open
Abstract
Expression of the β-subunit (CaVβ) is required for normal function of cardiac L-type calcium channels, and its up-regulation is associated with heart failure. CaVβ binds to the α1 pore-forming subunit of L-type channels and augments calcium current density by facilitating channel opening and increasing the number of channels in the plasma membrane, by a poorly understood mechanism. Actin, a key component of the intracellular trafficking machinery, interacts with Src homology 3 domains in different proteins. Although CaVβ encompasses a highly conserved Src homology 3 domain, association with actin has not yet been explored. Here, using co-sedimentation assays and FRET experiments, we uncover a direct interaction between CaVβ and actin filaments. Consistently, single-molecule localization analysis reveals streaklike structures composed by CaVβ2 that distribute over several micrometers along actin filaments in HL-1 cardiomyocytes. Overexpression of CaVβ2-N3 in HL-1 cells induces an increase in L-type current without altering voltage-dependent activation, thus reflecting an increased number of channels in the plasma membrane. CaVβ mediated L-type up-regulation, and CaVβ-actin association is prevented by disruption of the actin cytoskeleton with cytochalasin D. Our study reveals for the first time an interacting partner of CaVβ that is directly involved in vesicular trafficking. We propose a model in which CaVβ promotes anterograde trafficking of the L-type channels by anchoring them to actin filaments in their itinerary to the plasma membrane.
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Affiliation(s)
- Gabriel Stölting
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | | | - Raul E Guzman
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Erick Miranda-Laferte
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Rachel Conrad
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Nadine Jordan
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Silke Schmidt
- the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Johnny Hendriks
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Thomas Gensch
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and
| | - Patricia Hidalgo
- From the Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany and.
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25
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Neely A, Hidalgo P. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels. Front Physiol 2014; 5:209. [PMID: 24917826 PMCID: PMC4042065 DOI: 10.3389/fphys.2014.00209] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 05/15/2014] [Indexed: 11/13/2022] Open
Abstract
Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels.
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Affiliation(s)
- Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso and Facultad de Ciencias, Universidad de Valparaíso Valparaíso, Chile
| | - Patricia Hidalgo
- Forschungszentrum Jülich, Institute of Complex Systems 4, Zelluläre Biophysik Jülich, Germany
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26
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Breitenkamp AFS, Matthes J, Nass RD, Sinzig J, Lehmkuhl G, Nürnberg P, Herzig S. Rare mutations of CACNB2 found in autism spectrum disease-affected families alter calcium channel function. PLoS One 2014; 9:e95579. [PMID: 24752249 PMCID: PMC3994086 DOI: 10.1371/journal.pone.0095579] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 03/27/2014] [Indexed: 01/06/2023] Open
Abstract
Autism Spectrum Disorders (ASD) are complex neurodevelopmental diseases clinically defined by dysfunction of social interaction. Dysregulation of cellular calcium homeostasis might be involved in ASD pathogenesis, and genes coding for the L-type calcium channel subunits CaV1.2 (CACNA1C) and CaVβ2 (CACNB2) were recently identified as risk loci for psychiatric diseases. Here, we present three rare missense mutations of CACNB2 (G167S, S197F, and F240L) found in ASD-affected families, two of them described here for the first time (G167S and F240L). All these mutations affect highly conserved regions while being absent in a sample of ethnically matched controls. We suggest the mutations to be of physiological relevance since they modulate whole-cell Ba2+ currents through calcium channels when expressed in a recombinant system (HEK-293 cells). Two mutations displayed significantly decelerated time-dependent inactivation as well as increased sensitivity of voltage-dependent inactivation. In contrast, the third mutation (F240L) showed significantly accelerated time-dependent inactivation. By altering the kinetic parameters, the mutations are reminiscent of the CACNA1C mutation causing Timothy Syndrome, a Mendelian disease presenting with ASD. In conclusion, the results of our first-time biophysical characterization of these three rare CACNB2 missense mutations identified in ASD patients support the hypothesis that calcium channel dysfunction may contribute to autism.
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Affiliation(s)
| | - Jan Matthes
- Department of Pharmacology, University of Cologne, Cologne, Germany
| | | | - Judith Sinzig
- Department of Child and Adolescent Psychiatry and Psychotherapy, LVR-Klinik Bonn, Bonn, Germany
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Cologne, Cologne, Germany
| | - Gerd Lehmkuhl
- Department of Child and Adolescent Psychiatry and Psychotherapy, University of Cologne, Cologne, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Stefan Herzig
- Department of Pharmacology, University of Cologne, Cologne, Germany
- Center for Molecular Medicine, University of Cologne, Cologne, Germany
- * E-mail:
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27
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Dawson TF, Boone AN, Senatore A, Piticaru J, Thiyagalingam S, Jackson D, Davison A, Spafford JD. Gene splicing of an invertebrate beta subunit (LCavβ) in the N-terminal and HOOK domains and its regulation of LCav1 and LCav2 calcium channels. PLoS One 2014; 9:e92941. [PMID: 24690951 PMCID: PMC3972191 DOI: 10.1371/journal.pone.0092941] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 02/27/2014] [Indexed: 01/31/2023] Open
Abstract
The accessory beta subunit (Ca(v)β) of calcium channels first appear in the same genome as Ca(v)1 L-type calcium channels in single-celled coanoflagellates. The complexity of this relationship expanded in vertebrates to include four different possible Ca(v)β subunits (β1, β2, β3, β4) which associate with four Ca(v)1 channel isoforms (Ca(v)1.1 to Ca(v)1.4) and three Ca(v)2 channel isoforms (Ca(v)2.1 to Ca(v)2.3). Here we assess the fundamentally-shared features of the Ca(v)β subunit in an invertebrate model (pond snail Lymnaea stagnalis) that bears only three homologous genes: (LCa(v)1, LCa(v)2, and LCa(v)β). Invertebrate Ca(v)β subunits (in flatworms, snails, squid and honeybees) slow the inactivation kinetics of Ca(v)2 channels, and they do so with variable N-termini and lacking the canonical palmitoylation residues of the vertebrate β2a subunit. Alternative splicing of exon 7 of the HOOK domain is a primary determinant of a slow inactivation kinetics imparted by the invertebrate LCa(v)β subunit. LCa(v)β will also slow the inactivation kinetics of LCa(v)3 T-type channels, but this is likely not physiologically relevant in vivo. Variable N-termini have little influence on the voltage-dependent inactivation kinetics of differing invertebrate Ca(v)β subunits, but the expression pattern of N-terminal splice isoforms appears to be highly tissue specific. Molluscan LCa(v)β subunits have an N-terminal "A" isoform (coded by exons: 1a and 1b) that structurally resembles the muscle specific variant of vertebrate β1a subunit, and has a broad mRNA expression profile in brain, heart, muscle and glands. A more variable "B" N-terminus (exon 2) in the exon position of mammalian β3 and has a more brain-centric mRNA expression pattern. Lastly, we suggest that the facilitation of closed-state inactivation (e.g. observed in Ca(v)2.2 and Ca(v)β3 subunit combinations) is a specialization in vertebrates, because neither snail subunit (LCa(v)2 nor LCa(v)β) appears to be compatible with this observed property.
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Affiliation(s)
- Taylor F. Dawson
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Adrienne N. Boone
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Adriano Senatore
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Joshua Piticaru
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | | | - Daniel Jackson
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - Angus Davison
- Institute of Genetics, School of Biology, University of Nottingham, Nottingham, United Kingdom
| | - J. David Spafford
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
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28
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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.
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29
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Manning JR, Yin G, Kaminski CN, Magyar J, Feng H, Penn J, Sievert G, Thompson K, Jin J, Andres DA, Satin J. Rad GTPase deletion increases L-type calcium channel current leading to increased cardiac contraction. J Am Heart Assoc 2013; 2:e000459. [PMID: 24334906 PMCID: PMC3886777 DOI: 10.1161/jaha.113.000459] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND The small GTPase Rad is a negative regulator of voltage-dependent L-type calcium channel current (ICaL); however, the effects of Rad ablation on cardiomyocyte function are unknown. The objective of this study is to test the hypothesis that Rad-depletion causes positive inotropic effects without inducing cardiac hypertrophy. METHODS AND RESULTS Ventricular myocytes from adult Rad(-/-) mice were isolated and evaluated by patch-clamp recordings for I(Ca,L) and action potentials, Ca(2+) transients, and sarcomere shortening. Maximum I(CaL) is elevated in Rad(-/-) (maximal conductance 0.35 ± 0.04 picoSiemens/picoFarad (pS/pF) wild-type; 0.61 ± 0.14 pS/pF Rad(-/-)), decay kinetics are faster, and I(Ca,L) activates at lower voltages (activation midpoint -7.2 ± 0.6 wild-type; -11.7 ± 0.9 Rad(-/-)) mimicking effects of β-adrenergic receptor stimulation. Diastolic and twitch calcium are elevated in Rad(-/-) (F340/380: 1.03 diastolic and 0.35 twitch for wild-type; 1.47 diastolic and 0.736 twitch for Rad(-/-)) and sarcomere shortening is enhanced (4.31% wild-type; 14.13% Rad(-/-)) at lower pacing frequencies. Consequentially, frequency-dependence of Ca(2+) transients is less in Rad(-/-), and the frequency dependence of relaxation is also blunted. In isolated working hearts, similar results were obtained; chiefly, +dP/dt was elevated at baseline and developed pressure was relatively nonresponsive to acute β-adrenergic receptor stimulation. In single cells, at subphysiological frequencies, nonstimulated calmodulin-dependent protein kinase-sensitive calcium release is observed. Remarkably, Rad(-/-) hearts did not show hypertrophic growth despite elevated levels of diastolic calcium. CONCLUSIONS This study demonstrates that the depletion of Rad GTPase is equivalent to sympathomimetic β-adrenergic receptor, without stimulating cardiac hypertrophy. Thus, targeting Rad GTPase is a novel potential therapeutic target for Ca(2+)-homeostasis-driven positive inotropic support of the heart.
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Affiliation(s)
- Janet R. Manning
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY (J.R.M., G.Y., J.M., J.P., G.S., J.S.)
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY (J.R.M., C.N.K., D.A.A.)
| | - Guo Yin
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY (J.R.M., G.Y., J.M., J.P., G.S., J.S.)
| | - Catherine N. Kaminski
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY (J.R.M., C.N.K., D.A.A.)
| | - Janos Magyar
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY (J.R.M., G.Y., J.M., J.P., G.S., J.S.)
- Department of Physiology, University of Debrecen, Hungary (J.M.)
| | - Han‐Zhong Feng
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI (H.Z.F., J.)
| | - John Penn
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY (J.R.M., G.Y., J.M., J.P., G.S., J.S.)
| | - Gail Sievert
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY (J.R.M., G.Y., J.M., J.P., G.S., J.S.)
| | - Katherine Thompson
- Department of Statistics, University of Kentucky College of Medicine, Lexington, KY (K.T.)
| | - J.‐P. Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI (H.Z.F., J.)
| | - Douglas A. Andres
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY (J.R.M., C.N.K., D.A.A.)
| | - Jonathan Satin
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY (J.R.M., G.Y., J.M., J.P., G.S., J.S.)
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30
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Felix R, Calderón-Rivera A, Andrade A. Regulation of high-voltage-activated Ca 2+ channel function, trafficking, and membrane stability by auxiliary subunits. ACTA ACUST UNITED AC 2013; 2:207-220. [PMID: 24949251 DOI: 10.1002/wmts.93] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Voltage-gated Ca2+ (CaV) channels mediate Ca2+ ions influx into cells in response to depolarization of the plasma membrane. They are responsible for initiation of excitation-contraction and excitation-secretion coupling, and the Ca2+ that enters cells through this pathway is also important in the regulation of protein phosphorylation, gene transcription, and many other intracellular events. Initial electrophysiological studies divided CaV channels into low-voltage-activated (LVA) and high-voltage-activated (HVA) channels. The HVA CaV channels were further subdivided into L, N, P/Q, and R-types which are oligomeric protein complexes composed of an ion-conducting CaVα1 subunit and auxiliary CaVα2δ, CaVβ, and CaVγ subunits. The functional consequences of the auxiliary subunits include altered functional and pharmacological properties of the channels as well as increased current densities. The latter observation suggests an important role of the auxiliary subunits in membrane trafficking of the CaVα1 subunit. This includes the mechanisms by which CaV channels are targeted to the plasma membrane and to appropriate regions within a given cell. Likewise, the auxiliary subunits seem to participate in the mechanisms that remove CaV channels from the plasma membrane for recycling and/or degradation. Diverse studies have provided important clues to the molecular mechanisms involved in the regulation of CaV channels by the auxiliary subunits, and the roles that these proteins could possibly play in channel targeting and membrane Stabilization.
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Affiliation(s)
- Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico
| | - Aida Calderón-Rivera
- Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico
| | - Arturo Andrade
- Department of Neuroscience, Brown University, Providence, RI, USA
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31
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Ca2+ channel and Na+/Ca2+ exchange localization in cardiac myocytes. J Mol Cell Cardiol 2013; 58:22-31. [DOI: 10.1016/j.yjmcc.2012.11.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/20/2012] [Accepted: 11/28/2012] [Indexed: 01/01/2023]
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32
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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.
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Affiliation(s)
- Robin M Shaw
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, CA 94143, USA
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33
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Harvey RD, Hell JW. CaV1.2 signaling complexes in the heart. J Mol Cell Cardiol 2012; 58:143-52. [PMID: 23266596 DOI: 10.1016/j.yjmcc.2012.12.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/07/2012] [Accepted: 12/10/2012] [Indexed: 01/08/2023]
Abstract
L-type Ca(2+) channels (LTCCs) are essential for generation of the electrical and mechanical properties of cardiac muscle. Furthermore, regulation of LTCC activity plays a central role in mediating the effects of sympathetic stimulation on the heart. The primary mechanism responsible for this regulation involves β-adrenergic receptor (βAR) stimulation of cAMP production and subsequent activation of protein kinase A (PKA). Although it is well established that PKA-dependent phosphorylation regulates LTCC function, there is still much we do not understand. However, it has recently become clear that the interaction of the various signaling proteins involved is not left to completely stochastic events due to random diffusion. The primary LTCC expressed in cardiac muscle, CaV1.2, forms a supramolecular signaling complex that includes the β2AR, G proteins, adenylyl cyclases, phosphodiesterases, PKA, and protein phosphatases. In some cases, the protein interactions with CaV1.2 appear to be direct, in other cases they involve scaffolding proteins such as A kinase anchoring proteins and caveolin-3. Functional evidence also suggests that the targeting of these signaling proteins to specific membrane domains plays a critical role in maintaining the fidelity of receptor mediated LTCC regulation. This information helps explain the phenomenon of compartmentation, whereby different receptors, all linked to the production of a common diffusible second messenger, can vary in their ability to regulate LTCC activity. The purpose of this review is to examine our current understanding of the signaling complexes involved in cardiac LTCC regulation.
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Affiliation(s)
- Robert D Harvey
- Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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34
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Buraei Z, Yang J. Structure and function of the β subunit of voltage-gated Ca²⁺ channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1828:1530-40. [PMID: 22981275 DOI: 10.1016/j.bbamem.2012.08.028] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 08/22/2012] [Accepted: 08/25/2012] [Indexed: 12/31/2022]
Abstract
The voltage-gated Ca²⁺ channel β subunit (Ca(v)β) is a cytosolic auxiliary subunit that plays an essential role in regulating the surface expression and gating properties of high-voltage activated (HVA) Ca²⁺ channels. It is also crucial for the modulation of HVA Ca²⁺ channels by G proteins, kinases, Ras-related RGK GTPases, and other proteins. There are indications that Ca(v)β may carry out Ca²⁺ channel-independent functions. Ca(v)β knockouts are either non-viable or result in a severe pathophysiology, and mutations in Ca(v)β have been implicated in disease. In this article, we review the structure and various biological functions of Ca(v)β, as well as recent advances. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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35
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Juhola J, Oikonen M, Magnussen CG, Mikkilä V, Siitonen N, Jokinen E, Laitinen T, Würtz P, Gidding SS, Taittonen L, Seppälä I, Jula A, Kähönen M, Hutri-Kähönen N, Lehtimäki T, Viikari JS, Juonala M, Raitakari OT. Childhood Physical, Environmental, and Genetic Predictors of Adult Hypertension. Circulation 2012; 126:402-9. [DOI: 10.1161/circulationaha.111.085977] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Background—
Hypertension is a major modifiable cardiovascular risk factor. The present longitudinal study aimed to examine the best combination of childhood physical and environmental factors to predict adult hypertension and furthermore whether newly identified genetic variants for blood pressure increase the prediction of adult hypertension.
Methods and Results—
The study cohort included 2625 individuals from the Cardiovascular Risk in Young Finns Study who were followed up for 21 to 27 years since baseline (1980; age, 3–18 years). In addition to dietary factors and biomarkers related to blood pressure, we examined whether a genetic risk score based on 29 newly identified single-nucleotide polymorphisms enhances the prediction of adult hypertension. Hypertension in adulthood was defined as systolic blood pressure ≥130 mm Hg and/or diastolic blood pressure ≥85 mm Hg or medication for the condition. Independent childhood risk factors for adult hypertension included the individual's own blood pressure (
P
<0.0001), parental hypertension (
P
<0.0001), childhood overweight/obesity (
P
=0.005), low parental occupational status (
P
=0.003), and high genetic risk score (
P
<0.0001). Risk assessment based on childhood overweight/obesity status, parental hypertension, and parental occupational status was superior in predicting hypertension compared with the approach using only data on childhood blood pressure levels (C statistics, 0.718 versus 0.733;
P
=0.0007). Inclusion of both parental hypertension history and data on novel genetic variants for hypertension further improved the C statistics (0.742;
P
=0.015).
Conclusions—
Prediction of adult hypertension was enhanced by taking into account known physical and environmental childhood risk factors, family history of hypertension, and novel genetic variants. A multifactorial approach may be useful in identifying children at high risk for adult hypertension.
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Affiliation(s)
- Jonna Juhola
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Mervi Oikonen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Costan G. Magnussen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Vera Mikkilä
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Niina Siitonen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Eero Jokinen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Tomi Laitinen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Peter Würtz
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Samuel S. Gidding
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Leena Taittonen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Ilkka Seppälä
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Antti Jula
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Mika Kähönen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Nina Hutri-Kähönen
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Terho Lehtimäki
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Jorma S.A. Viikari
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Markus Juonala
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
| | - Olli T. Raitakari
- From the Research Center of Applied and Preventive Cardiovascular Medicine (J.J., M.O., C.G.M., N.S., M.J., O.T.R.), Department of Clinical Physiology (O.T.R.), and Department of Medicine (J.S.A.V., M.J.), University of Turku and Turku University Hospital, Turku, Finland; Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia (C.G.M.); Division of Nutrition, Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland (V.M.); Children's Hospital,
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Lin YC, Huang J, Kan H, Castranova V, Frisbee JC, Yu HG. Defective calcium inactivation causes long QT in obese insulin-resistant rat. Am J Physiol Heart Circ Physiol 2011; 302:H1013-22. [PMID: 22198168 DOI: 10.1152/ajpheart.00837.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The majority of diabetic patients who are overweight or obese die of heart disease. We suspect that the obesity-induced insulin resistance may lead to abnormal cardiac electrophysiology. We tested this hypothesis by studying an obese insulin-resistant rat model, the obese Zucker rat (OZR). Compared with the age-matched control, lean Zucker rat (LZR), OZR of 16-17 wk old exhibited an increase in QTc interval, action potential duration, and cell capacitance. Furthermore, the L-type calcium current (I(CaL)) in OZR exhibited defective inactivation and lost the complete inactivation back to the closed state, leading to increased Ca(2+) influx. The current density of I(CaL) was reduced in OZR, whereas the threshold activation and the current-voltage relationship of I(CaL) were not significantly altered. L-type Ba(2+) current (I(BaL)) in OZR also exhibited defective inactivation, and steady-state inactivation was not significantly altered. However, the current-voltage relationship and activation threshold of I(BaL) in OZR exhibited a depolarized shift compared with LZR. The total and membrane protein expression levels of Cav1.2 [pore-forming subunit of L-type calcium channels (LTCC)], but not the insulin receptors, were decreased in OZR. The insulin receptor was found to be associated with the Cav1.2, which was weakened in OZR. The total protein expression of calmodulin was reduced, but that of Cavβ2 subunit was not altered in OZR. Together, these results suggested that the 16- to 17-wk-old OZR has 1) developed cardiac hypertrophy, 2) exhibited altered electrophysiology manifested by the prolonged QTc interval, 3) increased duration of action potential in isolated ventricular myocytes, 4) defective inactivation of I(CaL) and I(BaL), 5) weakened the association of LTCC with the insulin receptor, and 6) decreased protein expression of Cav1.2 and calmodulin. These results also provided mechanistic insights into a remodeled cardiac electrophysiology under the condition of insulin resistance, enhancing our understanding of long QT associated with obese type 2 diabetic patients.
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Affiliation(s)
- Yen-Chang Lin
- Center for Cardiovascular and Respiratory Sciences, Department of Physiology and Pharmacology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26056, USA.
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37
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Different subcellular populations of L-type Ca2+ channels exhibit unique regulation and functional roles in cardiomyocytes. J Mol Cell Cardiol 2011; 52:376-87. [PMID: 21888911 DOI: 10.1016/j.yjmcc.2011.08.014] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 07/11/2011] [Accepted: 08/17/2011] [Indexed: 11/23/2022]
Abstract
Influx of Ca(2+) through L-type Ca(2+) channels (LTCCs) contributes to numerous cellular processes in cardiomyocytes including excitation-contraction (EC) coupling, membrane excitability, and transcriptional regulation. Distinct subpopulations of LTCCs have been identified in cardiac myocytes, including those at dyadic junctions and within different plasma membrane microdomains such as lipid rafts and caveolae. These subpopulations of LTCCs exhibit regionally distinct functional properties and regulation, affording precise spatiotemporal modulation of L-type Ca(2+) current (I(Ca,L)). Different subcellular LTCC populations demonstrate variable rates of Ca(2+)-dependent inactivation and sometimes coupled gating of neighboring channels, which can lead to focal, persistent I(Ca,L). In addition, the assembly of spatially defined macromolecular signaling complexes permits compartmentalized regulation of I(Ca,L) by a variety of neurohormonal pathways. For example, β-adrenergic receptor subtypes signal to different LTCC subpopulations, with β(2)-adrenergic activation leading to enhanced I(Ca,L) through caveolar LTCCs and β(1)-adrenergic stimulation modulating LTCCs outside of caveolae. Disruptions in the normal subcellular targeting of LTCCs and associated signaling proteins may contribute to the pathophysiology of a variety of cardiac diseases including heart failure and certain arrhythmias. Further identifying the characteristic functional properties and array of regulatory molecules associated with specific LTCC subpopulations will provide a mechanistic framework to understand how LTCCs contribute to diverse cellular processes in normal and diseased myocardium. This article is part of a Special Issue entitled "Local Signaling in Myocytes".
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Tester DJ, Tan BH, Medeiros-Domingo A, Song C, Makielski JC, Ackerman MJ. Loss-of-function mutations in the KCNJ8-encoded Kir6.1 K(ATP) channel and sudden infant death syndrome. ACTA ACUST UNITED AC 2011; 4:510-5. [PMID: 21836131 DOI: 10.1161/circgenetics.111.960195] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Approximately 10% of sudden infant death syndrome (SIDS) may stem from cardiac channelopathies. The KCNJ8-encoded Kir6.1 (K(ATP)) channel critically regulates vascular tone and cardiac adaptive response to systemic metabolic stressors, including sepsis. KCNJ8-deficient mice are prone to premature sudden death, particularly with infection. We determined the spectrum, prevalence, and function of KCNJ8 mutations in a large SIDS cohort. METHODS AND RESULTS Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing, comprehensive open reading frame/splice-site mutational analysis of KCNJ8 was performed on genomic DNA isolated from necropsy tissue on 292 unrelated SIDS cases (178 males, 204 white; age, 2.9±1.9 months). KCNJ8 mutations were coexpressed heterologously with SUR2A in COS-1 cells and characterized using whole-cell patch-clamp. Two novel KCNJ8 mutations were identified. A 5-month-old white male had an in-frame deletion (E332del) and a 2-month-old black female had a missense mutation (V346I). Both mutations localized to Kir6.1's C-terminus, involved conserved residues and were absent in 400 and 200 ethnic-matched reference alleles respectively. Both cases were negative for mutations in established channelopathic genes. Compared with WT, the pinacidil-activated K(ATP) current was decreased 45% to 68% for Kir6.1-E332del and 40% to 57% for V346I between -20 mV and 40 mV. CONCLUSIONS Molecular and functional evidence implicated loss-of-function KCNJ8 mutations as a novel pathogenic mechanism in SIDS, possibly by predisposition of a maladaptive cardiac response to systemic metabolic stressors akin to the mouse models of KCNJ8 deficiency.
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Affiliation(s)
- David J Tester
- Department of Medicine, Division of Cardiovascular Diseases, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN 55905, USA
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Larson MH, Landick R, Block SM. Single-molecule studies of RNA polymerase: one singular sensation, every little step it takes. Mol Cell 2011; 41:249-62. [PMID: 21292158 DOI: 10.1016/j.molcel.2011.01.008] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 12/09/2010] [Accepted: 01/05/2011] [Indexed: 11/17/2022]
Abstract
Transcription is the first of many biochemical steps that turn the genetic information found in DNA into the proteins responsible for driving cellular processes. In this review, we highlight certain advantages of single-molecule techniques in the study of prokaryotic and eukaryotic transcription, and the specific ways in which these techniques complement conventional, ensemble-based biochemistry. We focus on recent literature, highlighting examples where single-molecule methods have provided fresh insights into mechanism. We also present recent technological advances and outline future directions in the field.
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Affiliation(s)
- Matthew H Larson
- Biophysics Program, Stanford University, Stanford, CA 94305, USA
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40
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Meissner M, Weissgerber P, Londoño JEC, Prenen J, Link S, Ruppenthal S, Molkentin JD, Lipp P, Nilius B, Freichel M, Flockerzi V. Moderate calcium channel dysfunction in adult mice with inducible cardiomyocyte-specific excision of the cacnb2 gene. J Biol Chem 2011; 286:15875-82. [PMID: 21357697 DOI: 10.1074/jbc.m111.227819] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The major L-type voltage-gated calcium channels in heart consist of an α1C (Ca(V)1.2) subunit usually associated with an auxiliary β subunit (Ca(V)β2). In embryonic cardiomyocytes, both the complete and the cardiac myocyte-specific null mutant of Ca(V)β2 resulted in reduction of L-type calcium currents by up to 75%, compromising heart function and causing defective remodeling of intra- and extra-embryonic blood vessels followed by embryonic death. Here we conditionally excised the Ca(V)β2 gene (cacnb2) specifically in cardiac myocytes of adult mice (KO). Upon gene deletion, Ca(V)β2 protein expression declined by >96% in isolated cardiac myocytes and by >74% in protein fractions from heart. These latter protein fractions include Ca(V)β2 proteins expressed in cardiac fibroblasts. Surprisingly, mice did not show any obvious impairment, although cacnb2 excision was not compensated by expression of other Ca(V)β proteins or changes of Ca(V)1.2 protein levels. Calcium currents were still dihydropyridine-sensitive, but current density at 0 mV was reduced by <29%. The voltage for half-maximal activation was slightly shifted to more depolarized potentials in KO cardiomyocytes when compared with control cells, but the difference was not significant. In summary, Ca(V)β2 appears to be a much stronger modulator of L-type calcium currents in embryonic than in adult cardiomyocytes. Although essential for embryonic survival, Ca(V)β2 down-regulation in cardiomyocytes is well tolerated by the adult mice.
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Affiliation(s)
- Marcel Meissner
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg, Germany
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Best JM, Foell JD, Buss CR, Delisle BP, Balijepalli RC, January CT, Kamp TJ. Small GTPase Rab11b regulates degradation of surface membrane L-type Cav1.2 channels. Am J Physiol Cell Physiol 2011; 300:C1023-33. [PMID: 21248079 DOI: 10.1152/ajpcell.00288.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
L-type Ca(2+) channels (LTCCs) play a critical role in Ca(2+)-dependent signaling processes in a variety of cell types. The number of functional LTCCs at the plasma membrane strongly influences the strength and duration of Ca(2+) signals. Recent studies demonstrated that endosomal trafficking provides a mechanism for dynamic changes in LTCC surface membrane density. The purpose of the current study was to determine whether the small GTPase Rab11b, a known regulator of endosomal recycling, impacts plasmalemmal expression of Ca(v)1.2 LTCCs. Disruption of endogenous Rab11b function with a dominant negative Rab11b S25N mutant led to a significant 64% increase in peak L-type Ba(2+) current (I(Ba,L)) in human embryonic kidney (HEK)293 cells. Short-hairpin RNA (shRNA)-mediated knockdown of Rab11b also significantly increased peak I(Ba,L) by 66% compared when with cells transfected with control shRNA, whereas knockdown of Rab11a did not impact I(Ba,L). Rab11b S25N led to a 1.7-fold increase in plasma membrane density of hemagglutinin epitope-tagged Ca(v)1.2 expressed in HEK293 cells. Cell surface biotinylation experiments demonstrated that Rab11b S25N does not significantly impact anterograde trafficking of LTCCs to the surface membrane but rather slows degradation of plasmalemmal Ca(v)1.2 channels. We further demonstrated Rab11b expression in ventricular myocardium and showed that Rab11b S25N significantly increases peak I(Ba,L) by 98% in neonatal mouse cardiac myocytes. These findings reveal a novel role for Rab11b in limiting, rather than promoting, the plasma membrane expression of Ca(v)1.2 LTCCs in contrast to its effects on other ion channels including human ether-a-go-go-related gene (hERG) K(+) channels and cystic fibrosis transmembrane conductance regulator. This suggests Rab11b differentially regulates the trafficking of distinct cargo and extends our understanding of how endosomal transport impacts the functional expression of LTCCs.
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Affiliation(s)
- Jabe M Best
- University of Wisconsin School of Medicine and Public Health, H6/370 Clinical Science Center, 600 Highland Ave., Madison, WI 53792-3248, USA
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Xu X, Lee YJ, Holm JB, Terry MD, Oswald RE, Horne WA. The Ca2+ channel beta4c subunit interacts with heterochromatin protein 1 via a PXVXL binding motif. J Biol Chem 2011; 286:9677-87. [PMID: 21220418 DOI: 10.1074/jbc.m110.187864] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The β subunits of voltage-gated Ca(2+) channels are best known for their roles in regulating surface expression and gating of voltage-gated Ca(2+) channel α(1) subunits. Recent evidence, however, indicates that these proteins have a variety of Ca(2+) channel-independent functions. For example, on the molecular level, they regulate gene expression, and on the whole animal level, they regulate early cell movements in zebrafish development. In the present study, an alternatively spliced, truncated β4 subunit (β4c) is identified in the human brain and shown to be highly expressed in nuclei of vestibular neurons. Pull-down assays, nuclear magnetic resonance, and isothermal titration calorimetry demonstrate that the protein interacts with the chromo shadow domain (CSD) of heterochromatin protein 1γ. Site-directed mutagenesis reveals that the primary CSD interaction occurs through a β4c C-terminal PXVXL consensus motif, adding the β4c subunit to a growing PXVXL protein family with epigenetic responsibilities. These proteins have multiple nuclear functions, including transcription regulation (TIF1α) and nucleosome assembly (CAF1). An NMR-based two-site docking model of β4c in complex with dimerized CSD is presented. Possible roles for the interaction are discussed.
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Affiliation(s)
- Xingfu Xu
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA
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43
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Yang L, Katchman A, Morrow JP, Doshi D, Marx SO. Cardiac L-type calcium channel (Cav1.2) associates with gamma subunits. FASEB J 2010; 25:928-36. [PMID: 21127204 DOI: 10.1096/fj.10-172353] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The cardiac voltage-gated Ca(2+) channel, Ca(v)1.2, mediates excitation-contraction coupling in the heart. The molecular composition of the channel includes the pore-forming α1 subunit and auxiliary α2/δ-1 and β subunits. Ca(2+) channel γ subunits, of which there are 8 isoforms, consist of 4 transmembrane domains with intracellular N- and C-terminal ends. The γ1 subunit was initially detected in the skeletal muscle Ca(v)1.1 channel complex, modulating current amplitude and activation and inactivation properties. The γ1 subunit also shifts the steady-state inactivation to more negative membrane potentials, accelerates current inactivation, and increases peak currents, when coexpressed with the cardiac α1c subunit in Xenopus oocytes and human embryonic kidney (HEK) 293 cells. The γ1 subunit is not expressed, however, in cardiac muscle. We sought to determine whether γ subunits that are expressed in cardiac tissue physically associate with and modulate Ca(v)1.2 function. We now demonstrate that γ4, γ6, γ7, and γ8 subunits physically interact with the Ca(v)1.2 complex. The γ subunits differentially modulate Ca(2+) channel function when coexpressed with the β1b and α2/δ-1 subunits in HEK cells, altering both activation and inactivation properties. The effects of γ on Ca(v)1.2 function are dependent on the subtype of β subunit. Our results identify new members of the cardiac Ca(v)1.2 macromolecular complex and identify a mechanism by which to increase the functional diversity of Ca(v)1.2 channels.
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Affiliation(s)
- Lin Yang
- Division of Cardiology, Department of Medicine, Columbia University, College of Physicians and Surgeons, 622 W. 168th St., New York, NY 10032, USA
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44
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Lao QZ, Kobrinsky E, Liu Z, Soldatov NM. Oligomerization of Ca vβ subunits is an essential correlate of Ca 2+channel activity. FASEB J 2010. [DOI: 10.1096/fj.10.165381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Qi Zong Lao
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| | - Evgeny Kobrinsky
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| | - Zhuo Liu
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
| | - Nikolai M. Soldatov
- National Institute on Aging, National Institutes of Health Baltimore Maryland USA
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45
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Markandeya YS, Fahey JM, Pluteanu F, Cribbs LL, Balijepalli RC. Caveolin-3 regulates protein kinase A modulation of the Ca(V)3.2 (alpha1H) T-type Ca2+ channels. J Biol Chem 2010; 286:2433-44. [PMID: 21084288 DOI: 10.1074/jbc.m110.182550] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated T-type Ca(2+) channel Ca(v)3.2 (α(1H)) subunit, responsible for T-type Ca(2+) current, is expressed in different tissues and participates in Ca(2+) entry, hormonal secretion, pacemaker activity, and arrhythmia. The precise subcellular localization and regulation of Ca(v)3.2 channels in native cells is unknown. Caveolae containing scaffolding protein caveolin-3 (Cav-3) localize many ion channels, signaling proteins and provide temporal and spatial regulation of intracellular Ca(2+) in different cells. We examined the localization and regulation of the Ca(v)3.2 channels in cardiomyocytes. Immunogold labeling and electron microscopy analysis demonstrated co-localization of the Ca(v)3.2 channel and Cav-3 relative to caveolae in ventricular myocytes. Co-immunoprecipitation from neonatal ventricular myocytes or transiently transfected HEK293 cells demonstrated that Ca(v)3.1 and Ca(v)3.2 channels co-immunoprecipitate with Cav-3. GST pulldown analysis confirmed that the N terminus region of Cav-3 closely interacts with Ca(v)3.2 channels. Whole cell patch clamp analysis demonstrated that co-expression of Cav-3 significantly decreased the peak Ca(v)3.2 current density in HEK293 cells, whereas co-expression of Cav-3 did not alter peak Ca(v)3.1 current density. In neonatal mouse ventricular myocytes, overexpression of Cav-3 inhibited the peak T-type calcium current (I(Ca,T)) and adenovirus (AdCa(v)3.2)-mediated increase in peak Ca(v)3.2 current, but did not affect the L-type current. The protein kinase A-dependent stimulation of I(Ca,T) by 8-Br-cAMP (membrane permeable cAMP analog) was abolished by siRNA directed against Cav-3. Our findings on functional modulation of the Ca(v)3.2 channels by Cav-3 is important for understanding the compartmentalized regulation of Ca(2+) signaling during normal and pathological processes.
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Affiliation(s)
- Yogananda S Markandeya
- Department of Medicine, Cellular and Molecular Arrhythmia Research Program, University of Wisconsin, Madison, Wisconsin 53706, USA
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Abstract
Calcium regulates a wide spectrum of physiological processes such as heartbeat, muscle contraction, neuronal communication, hormone release, cell division, and gene transcription. Major entryways for Ca(2+) in excitable cells are high-voltage activated (HVA) Ca(2+) channels. These are plasma membrane proteins composed of several subunits, including α(1), α(2)δ, β, and γ. Although the principal α(1) subunit (Ca(v)α(1)) contains the channel pore, gating machinery and most drug binding sites, the cytosolic auxiliary β subunit (Ca(v)β) plays an essential role in regulating the surface expression and gating properties of HVA Ca(2+) channels. Ca(v)β is also crucial for the modulation of HVA Ca(2+) channels by G proteins, kinases, and the Ras-related RGK GTPases. New proteins have emerged in recent years that modulate HVA Ca(2+) channels by binding to Ca(v)β. There are also indications that Ca(v)β may carry out Ca(2+) channel-independent functions, including directly regulating gene transcription. All four subtypes of Ca(v)β, encoded by different genes, have a modular organization, consisting of three variable regions, a conserved guanylate kinase (GK) domain, and a conserved Src-homology 3 (SH3) domain, placing them into the membrane-associated guanylate kinase (MAGUK) protein family. Crystal structures of Ca(v)βs reveal how they interact with Ca(v)α(1), open new research avenues, and prompt new inquiries. In this article, we review the structure and various biological functions of Ca(v)β, with both a historical perspective as well as an emphasis on recent advances.
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Affiliation(s)
- Zafir Buraei
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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Mutations in the cardiac L-type calcium channel associated with inherited J-wave syndromes and sudden cardiac death. Heart Rhythm 2010; 7:1872-82. [PMID: 20817017 DOI: 10.1016/j.hrthm.2010.08.026] [Citation(s) in RCA: 258] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 08/30/2010] [Indexed: 12/15/2022]
Abstract
BACKGROUND L-type calcium channel (LTCC) mutations have been associated with Brugada syndrome (BrS), short QT (SQT) syndrome, and Timothy syndrome (LQT8). Little is known about the extent to which LTCC mutations contribute to the J-wave syndromes associated with sudden cardiac death. OBJECTIVE The purpose of this study was to identify mutations in the α1, β2, and α2δ subunits of LTCC (Ca(v)1.2) among 205 probands diagnosed with BrS, idiopathic ventricular fibrillation (IVF), and early repolarization syndrome (ERS). CACNA1C, CACNB2b, and CACNA2D1 genes of 162 probands with BrS and BrS+SQT, 19 with IVF, and 24 with ERS were screened by direct sequencing. METHODS/RESULTS Overall, 23 distinct mutations were identified. A total of 12.3%, 5.2%, and 16% of BrS/BrS+SQT, IVF, and ERS probands displayed mutations in α1, β2, and α2δ subunits of LTCC, respectively. When rare polymorphisms were included, the yield increased to 17.9%, 21%, and 29.1% for BrS/BrS+SQT, IVF, and ERS probands, respectively. Functional expression of two CACNA1C mutations associated with BrS and BrS+SQT led to loss of function in calcium channel current. BrS probands displaying a normal QTc had additional variations known to prolong the QT interval. CONCLUSION The study results indicate that mutations in the LTCCs are detected in a high percentage of probands with J-wave syndromes associated with inherited cardiac arrhythmias, suggesting that genetic screening of Ca(v) genes may be a valuable diagnostic tool in identifying individuals at risk. These results are the first to identify CACNA2D1 as a novel BrS susceptibility gene and CACNA1C, CACNB2, and CACNA2D1 as possible novel ERS susceptibility genes.
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Lao QZ, Kobrinsky E, Liu Z, Soldatov NM. Oligomerization of Cavbeta subunits is an essential correlate of Ca2+ channel activity. FASEB J 2010; 24:5013-23. [PMID: 20732952 DOI: 10.1096/fj.10-165381] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Voltage-gated calcium channels conduct Ca(2+) ions in response to membrane depolarization. The resulting transient increase in cytoplasmic free calcium concentration is a critical trigger for the initiation of such vital responses as muscle contraction and transcription. L-type Ca(v)1.2 calcium channels are complexes of the pore-forming α(1C) subunit associated with cytosolic Ca(v)β subunits. All major Ca(v)βs share a highly homologous membrane associated guanylate kinase-like (MAGUK) domain that binds to α(1C) at the α-interaction domain (AID), a short motif in the linker between transmembrane repeats I and II. In this study we show that Ca(v)β subunits form multimolecular homo- and heterooligomeric complexes in human vascular smooth muscle cells expressing native calcium channels and in Cos7 cells expressing recombinant Ca(v)1.2 channel subunits. Ca(v)βs oligomerize at the α(1C) subunits residing in the plasma membrane and bind to the AID. However, Ca(v)β oligomerization occurs independently on the association with α(1C). Molecular structures responsible for Ca(v)β oligomerization reside in 3 regions of the guanylate kinase subdomain of MAGUK. An augmentation of Ca(v)β homooligomerization significantly increases the calcium current density, while heterooligomerization may also change the voltage-dependence and inactivation kinetics of the channel. Thus, oligomerization of Ca(v)β subunits represents a novel and essential aspect of calcium channel regulation.
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Affiliation(s)
- Qi Zong Lao
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
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Alvarez JL, Petzhold D, Pankonien I, Behlke J, Kouno M, Vassort G, Morano I, Haase H. Ahnak1 modulates L-type Ca2+ channel inactivation of rodent cardiomyocytes. Pflugers Arch 2010; 460:719-30. [DOI: 10.1007/s00424-010-0853-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 05/28/2010] [Accepted: 06/02/2010] [Indexed: 01/21/2023]
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Medeiros-Domingo A, Tan BH, Crotti L, Tester DJ, Eckhardt L, Cuoretti A, Kroboth SL, Song C, Zhou Q, Kopp D, Schwartz PJ, Makielski JC, Ackerman MJ. Gain-of-function mutation S422L in the KCNJ8-encoded cardiac K(ATP) channel Kir6.1 as a pathogenic substrate for J-wave syndromes. Heart Rhythm 2010; 7:1466-71. [PMID: 20558321 DOI: 10.1016/j.hrthm.2010.06.016] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 06/09/2010] [Indexed: 02/07/2023]
Abstract
BACKGROUND J-wave syndromes have emerged conceptually to encompass the pleiotropic expression of J-point abnormalities including Brugada syndrome (BrS) and early repolarization syndrome (ERS). KCNJ8, which encodes the cardiac K(ATP) Kir6.1 channel, recently has been implicated in ERS following identification of the functionally uncharacterized missense mutation S422L. OBJECTIVE The purpose of this study was to further explore KCNJ8 as a novel susceptibility gene for J-wave syndromes. METHODS Using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct DNA sequencing, comprehensive open reading frame/splice site mutational analysis of KCNJ8 was performed in 101 unrelated patients with J-wave syndromes, including 87 with BrS and 14 with ERS. Six hundred healthy individuals were examined to assess the allelic frequency for all variants detected. KCNJ8 mutation(s) was engineered by site-directed mutagenesis and coexpressed heterologously with SUR2A in COS-1 cells. Ion currents were recorded using whole-cell configuration of the patch-clamp technique. RESULTS One BrS case and one ERS case hosted the identical missense mutation S422L, which was reported previously. KCNJ8-S422L involves a highly conserved residue and was absent in 1,200 reference alleles. Both cases were negative for mutations in all known BrS and ERS susceptibility genes. K(ATP) current of the Kir6.1-S422L mutation was increased significantly over the voltage range from 0 to 40 mV compared to Kir6.1-WT channels (n = 16-21; P <.05). CONCLUSION These findings further implicate KCNJ8 as a novel J-wave syndrome susceptibility gene and a marked gain of function in the cardiac K(ATP) Kir6.1 channel secondary to KCNJ8-S422L as a novel pathogenic mechanism for the phenotypic expression of both BrS and ERS.
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Affiliation(s)
- Argelia Medeiros-Domingo
- Department of Medicine (Division of Cardiovascular Diseases), Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota 55905, USA
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