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Gök C, Main A, Gao X, Kerekes Z, Plain F, Kuo CW, Robertson AD, Fraser NJ, Fuller W. Insights into the molecular basis of the palmitoylation and depalmitoylation of NCX1. Cell Calcium 2021; 97:102408. [PMID: 33873072 PMCID: PMC8278489 DOI: 10.1016/j.ceca.2021.102408] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 03/30/2021] [Accepted: 04/06/2021] [Indexed: 11/23/2022]
Abstract
Catalyzed by zDHHC-PAT enzymes and reversed by thioesterases, protein palmitoylation is the only post-translational modification recognized to regulate the sodium/calcium exchanger NCX1. NCX1 palmitoylation occurs at a single site at position 739 in its large regulatory intracellular loop. An amphipathic ɑ-helix between residues 740-756 is a critical for NCX1 palmitoylation. Given the rich background of the structural elements involving in NCX1 palmitoylation, the molecular basis of NCX1 palmitoylation is still relatively poorly understood. Here we found that (1) the identity of palmitoylation machinery of NCX1 controls its spatial organization within the cell, (2) the NCX1 amphipathic ɑ-helix directly interacts with zDHHC-PATs, (3) NCX1 is still palmitoylated when it is arrested in either Golgi or ER, indicating that NCX1 is a substrate for multiple zDHHC-PATs, (4) the thioesterase APT1 but not APT2 as a part of NCX1-depalmitoylation machinery governs subcellular organization of NCX1, (5) APT1 catalyzes NCX1 depalmitoylation in the Golgi but not in the ER. We also report that NCX2 and NCX3 are dually palmitoylated, with important implications for substrate recognition and enzyme catalysis by zDHHC-PATs. Our results could support new molecular or pharmacological strategies targeting the NCX1 palmitoylation and depalmitoylation machinery.
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Affiliation(s)
- Caglar Gök
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - Alice Main
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - Xing Gao
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - Zsombor Kerekes
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - Fiona Plain
- School of Medicine, Ninewells Hospital, University of Dundee, Dundee, DD1 9SY, United Kingdom
| | - Chien-Wen Kuo
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - Alan D Robertson
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom
| | - Niall J Fraser
- School of Medicine, Ninewells Hospital, University of Dundee, Dundee, DD1 9SY, United Kingdom
| | - William Fuller
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, Glasgow, G12 8QQ, United Kingdom.
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Shlosman I, Marinelli F, Faraldo-Gómez JD, Mindell JA. The prokaryotic Na +/Ca 2+ exchanger NCX_Mj transports Na + and Ca 2+ in a 3:1 stoichiometry. J Gen Physiol 2017; 150:51-65. [PMID: 29237756 PMCID: PMC5749117 DOI: 10.1085/jgp.201711897] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 11/17/2017] [Indexed: 12/17/2022] Open
Abstract
Sodium–calcium exchangers contribute to the generation of intracellular Ca2+ signals in numerous physiological processes. Shlosman et al. determine the ion stoichiometry of the only sodium–calcium exchanger of known atomic structure, revealing its functional similarity to mammalian exchangers. Intracellular Ca2+ signals control a wide array of cellular processes. These signals require spatial and temporal regulation of the intracellular Ca2+ concentration, which is achieved in part by a class of ubiquitous membrane proteins known as sodium–calcium exchangers (NCXs). NCXs are secondary-active antiporters that power the translocation of Ca2+ across the cell membrane by coupling it to the flux of Na+ in the opposite direction, down an electrochemical gradient. Na+ and Ca2+ are translocated in separate steps of the antiport cycle, each of which is thought to entail a mechanism whereby ion-binding sites within the protein become alternately exposed to either side of the membrane. The prokaryotic exchanger NCX_Mj, the only member of this family with known structure, has been proposed to be a good functional and structural model of mammalian NCXs; yet our understanding of the functional properties of this protein remains incomplete. Here, we study purified NCX_Mj reconstituted into liposomes under well-controlled experimental conditions and demonstrate that this homologue indeed shares key functional features of the NCX family. Transport assays and reversal-potential measurements enable us to delineate the essential characteristics of this antiporter and establish that its ion-exchange stoichiometry is 3Na+:1Ca2+. Together with previous studies, this work confirms that NCX_Mj is a valid model system to investigate the mechanism of ion recognition and membrane transport in sodium–calcium exchangers.
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Affiliation(s)
- Irina Shlosman
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD.,Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Fabrizio Marinelli
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - José D Faraldo-Gómez
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Joseph A Mindell
- Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
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3
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Sodium recognition by the Na+/Ca2+ exchanger in the outward-facing conformation. Proc Natl Acad Sci U S A 2014; 111:E5354-62. [PMID: 25468964 DOI: 10.1073/pnas.1415751111] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Na(+)/Ca(2+) exchangers (NCXs) are ubiquitous membrane transporters with a key role in Ca(2+) homeostasis and signaling. NCXs mediate the bidirectional translocation of either Na(+) or Ca(2+), and thus can catalyze uphill Ca(2+) transport driven by a Na(+) gradient, or vice versa. In a major breakthrough, a prokaryotic NCX homolog (NCX_Mj) was recently isolated and its crystal structure determined at atomic resolution. The structure revealed an intriguing architecture consisting of two inverted-topology repeats, each comprising five transmembrane helices. These repeats adopt asymmetric conformations, yielding an outward-facing occluded state. The crystal structure also revealed four putative ion-binding sites, but the occupancy and specificity thereof could not be conclusively established. Here, we use molecular-dynamics simulations and free-energy calculations to identify the ion configuration that best corresponds to the crystallographic data and that is also thermodynamically optimal. In this most probable configuration, three Na(+) ions occupy the so-called Sext, SCa, and Sint sites, whereas the Smid site is occupied by one water molecule and one H(+), which protonates an adjacent aspartate side chain (D240). Experimental measurements of Na(+)/Ca(2+) and Ca(2+)/Ca(2+) exchange by wild-type and mutagenized NCX_Mj confirm that transport of both Na(+) and Ca(2+) requires protonation of D240, and that this side chain does not coordinate either ion at Smid. These results imply that the ion exchange stoichiometry of NCX_Mj is 3:1 and that translocation of Na(+) across the membrane is electrogenic, whereas transport of Ca(2+) is not. Altogether, these findings provide the basis for further experimental and computational studies of the conformational mechanism of this exchanger.
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Shen JB, Yang R, Pappano A, Liang BT. Cardiac P2X purinergic receptors as a new pathway for increasing Na⁺ entry in cardiac myocytes. Am J Physiol Heart Circ Physiol 2014; 307:H1469-77. [PMID: 25239801 DOI: 10.1152/ajpheart.00553.2014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
P2X4 receptors (P2X4Rs) are ligand-gated ion channels capable of conducting cations such as Na(+). Endogenous cardiac P2X4R can mediate ATP-activated current in adult murine cardiomyocytes. In the present study, we tested the hypothesis that cardiac P2X receptors can induce Na(+) entry and modulate Na(+) handling. We further determined whether P2X receptor-induced stimulation of the Na(+)/Ca(2+) exchanger (NCX) has a role in modulating the cardiac contractile state. Changes in Na(+)-K(+)-ATPase current (Ip) and NCX current (INCX) after agonist stimulation were measured in ventricular myocytes of P2X4 transgenic mice using whole cell patch-clamp techniques. The agonist 2-methylthio-ATP (2-meSATP) increased peak Ip from a basal level of 0.52 ± 0.02 to 0.58 ± 0.03 pA/pF. 2-meSATP also increased the Ca(2+) entry mode of INCX (0.55 ± 0.09 pA/pF under control conditions vs. 0.82 ± 0.14 pA/pF with 2-meSATP) at a membrane potential of +50 mV. 2-meSATP shifted the reversal potential of INCX from -14 ± 2.3 to -25 ± 4.1 mV, causing an estimated intracellular Na(+) concentration increase of 1.28 ± 0.42 mM. These experimental results were closely mimicked by mathematical simulations based on previously established models. KB-R7943 or a structurally different agent preferentially opposing the Ca(2+) entry mode of NCX, YM-244769, could inhibit the 2-meSATP-induced increase in cell shortening in transgenic myocytes. Thus, the Ca(2+) entry mode of INCX participates in P2X agonist-stimulated contractions. In ventricular myocytes from wild-type mice, the P2X agonist could increase INCX, and KB-R7943 was able to inhibit the contractile effect of endogenous P2X4Rs, indicating a physiological role of these receptors in wild-type cells. The data demonstrate a novel Na(+) entry pathway through ligand-gated P2X4Rs in cardiomyocytes.
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Affiliation(s)
- Jian-Bing Shen
- Pat and Jim Calhoun Cardiology Center, University of Connecticut Medical Center, Farmington, Connecticut
| | - Ronghua Yang
- Pat and Jim Calhoun Cardiology Center, University of Connecticut Medical Center, Farmington, Connecticut
| | - Achilles Pappano
- Pat and Jim Calhoun Cardiology Center, University of Connecticut Medical Center, Farmington, Connecticut
| | - Bruce T Liang
- Pat and Jim Calhoun Cardiology Center, University of Connecticut Medical Center, Farmington, Connecticut
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Ahn HS, Vasylyev DV, Estacion M, Macala LJ, Shah P, Faber CG, Merkies IS, Dib-Hajj SD, Waxman SG. Differential effect of D623N variant and wild-type Nav1.7 sodium channels on resting potential and interspike membrane potential of dorsal root ganglion neurons. Brain Res 2013; 1529:165-77. [DOI: 10.1016/j.brainres.2013.07.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/02/2013] [Accepted: 07/03/2013] [Indexed: 12/15/2022]
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Roberts DE, Matsuda T, Bose R. Molecular and functional characterization of the human platelet Na(+) /Ca(2+) exchangers. Br J Pharmacol 2012; 165:922-36. [PMID: 21790537 DOI: 10.1111/j.1476-5381.2011.01600.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The Na(+) /Ca(2+) exchanger is a bi-directional transporter that plays an important role in maintaining the concentration of cytosolic Ca(2+) ([Ca(2+) ](i) ) of quiescent platelets and increasing it during activation with some, but not all, agonists. There are two classes of Na(+) /Ca(2+) exchangers: K(+) -independent Na(+) /Ca(2+) exchanger (NCX) and K(+) -dependent Na(+) /Ca(2+) exchanger (NCKX). Platelets have previously been shown to express NCKX1. However, initial studies from our laboratory suggest that NCX may also play a role in platelet activation. The objective of this study was to determine if the human platelet expresses functional NCXs. EXPERIMENTAL APPROACH RT-PCR, DNA sequencing and Western blot analysis were utilized to characterize the human platelet Na(+) /Ca(2+) exchangers. Their function during quiescence and collagen-induced activation was determined by measuring [Ca(2+) ](i) with calcium-green/fura-red in response to: changes in the Na(+) and K(+) gradient, NCX pharmacological inhibitors (CBDMB, KB-R7943 and SEA0400) and antibodies specific to extracellular epitopes of the exchangers. KEY RESULTS Human platelets express NCX1.3, NCX3.2 and NCX3.4. The NCXs operate in the Ca(2+) efflux mode in resting platelets and also during their activation with thrombin but not collagen. Collagen-induced increase in [Ca(2+) ](i) was reduced with the pharmacological inhibitors of NCX (CBDMB, KB-R7943 or SEA0400), anti-NCX1 and anti-NCX3. In contrast, anti-NCKX1 enhanced the collagen-induced increase in [Ca(2+) ](i) . CONCLUSIONS AND IMPLICATIONS Human platelets express K(+) -independent Na(+) /Ca(2+) exchangers NCX1.3, NCX3.2 and NCX3.4. During collagen activation, NCX1 and NCX3 transiently reverse to promote Ca(2+) influx, whereas NCKX1 continues to operate in the Ca(2+) efflux mode to reduce [Ca(2+) ](i) .
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Affiliation(s)
- Diane E Roberts
- Department of Pharmacology and Therapeutics; University of Manitoba, Winnipeg, Manitoba, Canada
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7
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Barman P, Choisy SCM, Hancox JC, James AF. β-Adrenoceptor/PKA-stimulation, Na(+)-Ca(2+) exchange and PKA-activated Cl(-) currents in rabbit cardiomyocytes: a conundrum. Cell Calcium 2011; 49:233-9. [PMID: 21439639 PMCID: PMC3092849 DOI: 10.1016/j.ceca.2011.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Investigations into the functional modulation of the cardiac Na(+)-Ca(2+) exchanger (NCX) by acute β-adrenoceptor/PKA stimulation have produced conflicting results. Here, we investigated (i) whether or not β-adrenoceptor activation/PKA stimulation activates current in rabbit cardiac myocytes under NCX-'selective' conditions and (ii) if so, whether a PKA-activated Cl(-)-current may contribute to the apparent modulation of NCX current (I(NCX)). Whole-cell voltage-clamp experiments were conducted at 37°C on rabbit ventricular and atrial myocytes. The β-adrenoceptor-activated currents both in NCX-'selective' and Cl(-)-selective recording conditions were found to be sensitive to 10mM Ni(2+). In contrast, the PKA-activated Cl(-) current was not sensitive to Ni(2+), when it was activated downstream to the β-adrenoceptors using 10μM forskolin (an adenylyl cyclase activator). When 10μM forskolin was applied under NCX-selective recording conditions, the Ni(2+)-sensitive current did not differ between control and forskolin. These findings suggest that in rabbit myocytes: (a) a PKA-activated Cl(-) current contributes to the Ni(2+)-sensitive current activated via β-adrenoceptor stimulation under recording conditions previously considered selective for I(NCX); (b) downstream activation of PKA does not augment Ni(2+)-sensitive I(NCX), when this is measured under conditions where the Ni(2+)-sensitive PKA-activated Cl(-) current is not present.
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Affiliation(s)
- Palash Barman
- Bristol Heart Institute, Cardiovascular Research Laboratories, School of Physiology & Pharmacology, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
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8
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Andrade AL, Rossi DJ. Simulated ischaemia induces Ca2+-independent glutamatergic vesicle release through actin filament depolymerization in area CA1 of the hippocampus. J Physiol 2010; 588:1499-514. [PMID: 20211977 DOI: 10.1113/jphysiol.2010.187609] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Transient, non-catastrophic brain ischaemia can induce either a protected state against subsequent episodes of ischaemia (ischaemic preconditioning) or delayed, selective neuronal death. Altered glutamatergic signalling and altered Ca(2+) homeostasis have been implicated in both processes. Here we use simultaneous patch-clamp recording and Ca(2+) imaging to monitor early changes in glutamate release and cytoplasmic [Ca(2+)] ([Ca(2+)](c)) in an in vitro slice model of hippocampal ischaemia. In slices loaded with the Ca(2+)-sensitive dye Fura-2, ischaemia leads to an early increase in [Ca(2+)](c) that precedes the severe ischaemic depolarization (ID) associated with pan necrosis. The early increase in [Ca(2+)](c) is mediated by influx through the plasma membrane and release from internal stores, and parallels an early increase in vesicular glutamate release that manifests as a fourfold increase in the frequency of miniature excitatory postsynaptic currents (mEPSCs). However, the increase in mEPSC frequency is not prevented by blocking the increase in [Ca(2+)](c), and the early rise in [Ca(2+)](c) is not affected by blocking ionotropic and metabotropic glutamate receptors. Thus, the increase in [Ca(2+)](c) and the increase in glutamate release are independent of each other. Stabilizing actin filaments with jaspamide or phalloidin prevented vesicle release induced by ischaemia. Our results identify several early cellular cascades triggered by ischaemia: Ca(2+) influx, Ca(2+) release from intracellular stores, actin filament depolymerization, and vesicular release of glutamate that depends on actin dynamics but not [Ca(2+)](c). All of these processes precede the catastrophic ID by several minutes, and thus represent potential target mechanisms to influence the outcome of an ischaemic episode.
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Affiliation(s)
- Adriana L Andrade
- Department of Behavioral Neuroscience, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA
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9
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Sakamoto K, Owada Y, Shikama Y, Wada I, Waguri S, Iwamoto T, Kimura J. Involvement of Na+/Ca2+ exchanger in migration and contraction of rat cultured tendon fibroblasts. J Physiol 2009; 587:5345-59. [PMID: 19770194 DOI: 10.1113/jphysiol.2009.172080] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In response to injury and inflammation of tendons, tendon fibroblasts are activated, migrate to the wound, and eventually induce contraction of the extracellular matrices to repair the tissue. Under such conditions, Ca(2+) signalling is involved in motility and contractility of tendon fibroblasts. Using cultured tendon fibroblasts isolated from rat Achilles tendons, we investigated functional expression of Na(+)/Ca(2+) exchangers (NCX). The fluorometric study showed that the intracellular Ca(2+) concentration ([Ca(2+)](i)) was increased by reducing extracellular Na(+) concentration ([Na(+)](o)) in tendon fibroblasts. Selective NCX inhibitors, KB-R7943 and SEA0400, both attenuated [Na(+)](o)-dependent [Ca(2+)](i) elevation and the resting [Ca(2+)](i) in tendon fibroblasts. RT-PCR, Western blots and sequence analyses revealed that NCX1.3 and NCX1.7 were expressed in cultured tendon fibroblasts. NCX2 mRNA was undetected. NCX3 expression was negligibly low. Immunofluorescence microscopy indicated that NCX1 protein localized in the plasma membrane especially at the microspikes of tendon fibroblasts. In the wound-healing scratch assay, the cells migrated toward the space created by a scratch and almost completely filled the space within 48 h. This phenomenon was significantly suppressed by KB-R7943 and SEA0400. Furthermore, the NCX inhibitors abrogated the tendon fibroblast-mediated collagen-matrix contractions. Two types of siRNAs for NCX1 also suppressed the migration and contraction of tendon fibroblasts. We conclude that NCX is expressed and mediates Ca(2+) influx in cultured tendon fibroblasts. Since the pharmacological inhibitors and siRNA for NCX1 suppressed motility and contractility of tendon fibroblasts, NCX may play an important role in the function of tendon fibroblasts in the wound healing.
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Affiliation(s)
- Kazuho Sakamoto
- Department of Pharmacology, Fukushima Medical University, School of Medicine, Hikarigaoka, Fukushima, Japan.
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Ren X, Nicoll DA, Galang G, Philipson KD. Intermolecular Cross-Linking of Na+−Ca2+ Exchanger Proteins: Evidence for Dimer Formation. Biochemistry 2008; 47:6081-7. [DOI: 10.1021/bi800177t] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiaoyan Ren
- Departments of Physiology and Medicine and the Cardiovascular Research Laboratories, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1760
| | - Debora A. Nicoll
- Departments of Physiology and Medicine and the Cardiovascular Research Laboratories, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1760
| | - Giselle Galang
- Departments of Physiology and Medicine and the Cardiovascular Research Laboratories, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1760
| | - Kenneth D. Philipson
- Departments of Physiology and Medicine and the Cardiovascular Research Laboratories, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-1760
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11
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Bers DM, Ginsburg KS. Na:Ca Stoichiometry and Cytosolic Ca-Dependent Activation of NCX in Intact Cardiomyocytes. Ann N Y Acad Sci 2007; 1099:326-38. [PMID: 17303827 DOI: 10.1196/annals.1387.060] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We are studying both Na:Ca exchange stoichiometry and cytosolic [Ca] ([Ca]i)-dependent regulation of Na-Ca exchange (NCX) in intact rabbit ventricular myocytes. Analysis of NCX fluxes in subcellular systems strongly supports a dominant 3Na:1Ca exchange, and our measurements in intact cells confirm this. However, in intact native cells, local ion gradients and other factors complicate the process of inferring stoichiometry. From a functional viewpoint, NCX stoichiometry is near 3:1 but is affected by ion accumulation/depletion as well as non-NCX fluxes. We and others have viewed [Ca]i-dependent NCX regulation as a static process (dependent on instantaneous local [Ca]i). However, evidence from subcellular and expression systems shows the process to be dynamic, and our observations confirm this to be the case in intact cardiac cells as well.
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Affiliation(s)
- Donald M Bers
- Department of Physiology, Loyola University Chicago, Stritch School of Medicine, 2160 South First Avenue, Maywood, IL 60153, USA.
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12
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Medina DC, Kirkland DM, Tavazoie MF, Springer CS, Anderson SE. Na+/Ca2+-exchanger-mediated Mn2+-enhanced1H2O MRI in hypoxic, perfused rat myocardium. CONTRAST MEDIA & MOLECULAR IMAGING 2007; 2:248-57. [DOI: 10.1002/cmmi.151] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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Riedel MJ, Baczkó I, Searle GJ, Webster N, Fercho M, Jones L, Lang J, Lytton J, Dyck JRB, Light PE. Metabolic regulation of sodium-calcium exchange by intracellular acyl CoAs. EMBO J 2006; 25:4605-14. [PMID: 16977318 PMCID: PMC1589979 DOI: 10.1038/sj.emboj.7601321] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Accepted: 08/09/2006] [Indexed: 11/09/2022] Open
Abstract
The sodium-calcium exchanger (NCX) is a critical mediator of calcium homeostasis. In the heart, NCX1 predominantly operates in forward mode to extrude Ca(2+); however, reverse-mode NCX1 activity during ischemia/reperfusion (IR) contributes to Ca(2+) loading and electrical and contractile dysfunction. IR injury has also been associated with altered fat metabolism and accumulation of long-chain acyl CoA esters. Here, we show that acyl CoAs are novel, endogenous activators of reverse-mode NCX1 activity, exhibiting chain length and saturation dependence, with longer chain saturated acyl moieties being the most effective NCX1 activators. These results implicate dietary fat composition as a plausible determinant of IR injury. We further show that acyl CoAs may interact directly with the XIP (exchanger inhibitory peptide) sequence, a known region of anionic lipid modulation, to dynamically regulate NCX1 activity and Ca(2+) homeostasis. Additionally, our findings have broad implications for the coupling of Ca(2+) homeostasis to fat metabolism in a variety of tissues.
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Affiliation(s)
- Michael J Riedel
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - István Baczkó
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical Center, University of Szeged, Szeged, Hungary
| | - Gavin J Searle
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Nicola Webster
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Matthew Fercho
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Lynn Jones
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Jessica Lang
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Jonathan Lytton
- Departments of Biochemistry & Molecular Biology and Physiology & Biophysics, University of Calgary, Alberta, Canada
| | - Jason R B Dyck
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E Light
- Departments of Pharmacology and Pediatrics, University of Alberta, Edmonton, Alberta, Canada
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, 9-58 Medical Sciences Bldg, Edmonton, Edmonton, Alberta, Canada T6G 2H7. Tel.: +1 780 492 0638; Fax: +1 780 492 4325; E-mail:
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14
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Hille C, Walz B. Dopamine-induced graded intracellular Ca2+ elevation via the Na+Ca2+ exchanger operating in the Ca2+-entry mode in cockroach salivary ducts. Cell Calcium 2006; 39:305-11. [PMID: 16423391 DOI: 10.1016/j.ceca.2005.11.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2005] [Revised: 11/22/2005] [Accepted: 11/28/2005] [Indexed: 10/25/2022]
Abstract
Stimulation with the neurotransmitter dopamine causes an amplitude-modulated increase in the intracellular Ca(2+) concentration ([Ca(2+)](i)) in epithelial cells of the ducts of cockroach salivary glands. This is completely attributable to a Ca(2+) influx from the extracellular space. Additionally, dopamine induces a massive [Na(+)](i) elevation via the Na(+)K(+)2Cl(-) cotransporter (NKCC). We have reasoned that Ca(2+)-entry is mediated by the Na(+)Ca(2+) exchanger (NCE) operating in the Ca(2+)-entry mode. To test this hypothesis, [Ca(2+)](i) and [Na(+)](i) were measured by using the fluorescent dyes Fura-2, Fluo-3, and SBFI. Inhibition of Na(+)-entry from the extracellular space by removal of extracellular Na(+) or inhibition of the NKCC by 10 microM bumetanide did not influence resting [Ca(2+)](i) but completely abolished the dopamine-induced [Ca(2+)](i) elevation. Simultaneous recordings of [Ca(2+)](i) and [Na(+)](i) revealed that the dopamine-induced [Na(+)](i) elevation preceded the [Ca(2+)](i) elevation. During dopamine stimulation, the generation of an outward Na(+) concentration gradient by removal of extracellular Na(+) boosted the [Ca(2+)](i) elevation. Furthermore, prolonging the dopamine-induced [Na(+)](i) rise by blocking the Na(+)/K(+)-ATPase reduced the recovery from [Ca(2+)](i) elevation. These results indicate that dopamine induces a massive NKCC-mediated elevation in [Na(+)](i), which reverses the NCE activity into the reverse mode causing a graded [Ca(2+)](i) elevation in the duct cells.
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Affiliation(s)
- Carsten Hille
- Institute of Biochemistry and Biology, Department of Animal Physiology, University of Potsdam, Germany
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15
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Abstract
Ca(2+) is a central player in the excitation-contraction coupling of cardiac myocytes, the process that enables the heart to contract and relax. Mishandling of Ca(2+) is a central cause of both contractile dysfunction and arrhythmias in pathophysiological conditions such as heart failure (HF). Upon electrical excitation, Ca(2+) enters the myocytes via voltage-gated Ca(2+) channels and induces further Ca(2+) release from the sarcoplasmic reticulum (SR). This raises the free intracellular Ca(2+) concentration ([Ca(2+)](i)), activating contraction. Relaxation is driven by [Ca(2+)](i) decline, mainly due to re-uptake into the SR via SR Ca(2+)-ATPase and extrusion via the sarcolemmal Na(+)/Ca(2+) exchange, NCX. Intracellular Na(+) concentration ([Na(+)](i)) is a main regulator of NCX, and thus [Na(+)](i) plays an important role in controlling the cytosolic and SR [Ca(2+)]. [Na(+)](i) may have an even more important role in HF because NCX is generally upregulated. There are several pathways for Na(+) entry into the cells, whereas the Na(+)/K(+) pump (NKA) is the main Na(+) extrusion pathway and therefore is essential in maintaining the transmembrane Na(+) gradient. Phospholemman is an important regulator of NKA function (decreasing [Na(+)](i) affinity unless it is phosphorylated). Here we discuss the interplay between Ca(2+) and Na(+) in myocytes from normal and failing hearts.
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Affiliation(s)
- Donald M Bers
- Department of Physiology, Loyola University Chicago, Stritch School of Medicine, Maywood, IL 60153, USA.
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Boyden PA, ter Keurs H. Would modulation of intracellular Ca2+ be antiarrhythmic? Pharmacol Ther 2005; 108:149-79. [PMID: 16038982 DOI: 10.1016/j.pharmthera.2005.03.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Accepted: 03/22/2005] [Indexed: 01/10/2023]
Abstract
Under several types of conditions, reversal of steps of excitation-contraction coupling (RECC) can give rise to nondriven electrical activity. In this review we explore those conditions for several cardiac cell types (SA, atrial, Purkinje, ventricular cells). We find that abnormal spontaneous Ca2+ release from intracellular Ca2+ stores, aberrant Ca2+ influx from sarcolemmal channels or abnormal Ca2+ surges in nonuniform muscle can be the initiators of the RECC. Often, with such increases in Ca2+, spontaneous Ca2+ waves occur and lead to membrane depolarizations. Because the change in membrane voltage is produced by Ca2+-dependent changes in ion channel function, we also review here what is known about the molecular interaction of Ca2+ and several Ca2+-dependent processes, including the intracellular Ca2+ release channels implicated in the genetic basis of some forms of human arrhythmias. Finally, we review what is known about the effectiveness of several agents in modifying such Ca2+-dependent arrhythmias.
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Affiliation(s)
- Penelope A Boyden
- Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, NY 10032, USA.
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Eder P, Poteser M, Romanin C, Groschner K. Na(+) entry and modulation of Na(+)/Ca(2+) exchange as a key mechanism of TRPC signaling. Pflugers Arch 2005; 451:99-104. [PMID: 15924237 DOI: 10.1007/s00424-005-1434-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 04/08/2005] [Indexed: 10/25/2022]
Abstract
Ion channels formed by canonical transient receptor potential (TRPC) proteins are considered to be key players in cellular Ca(2+) homeostasis. As permeation of Ca(2+) through TRPC homo- and/or heteromeric channels has been repeatedly demonstrated, analysis of the physiological role of TRPC proteins was so far based on the concept that these proteins form regulated Ca(2+) entry channels. The well-recognized lack of cation selectivity of TRPC channels and the ability to generate substantial monovalent conductances that govern membrane potential and cation gradients were barely appreciated as a physiologically relevant issue. Nonetheless, recent studies suggest monovalent, specifically Na(+) permeation through TRPC cation channels as an important event in TRPC signaling. TRPC-mediated Na(+) entry may be converted into a distinct pattern of cellular Ca(2+) signals by interaction with Na(+)/Ca(2+) exchanger proteins. This review discusses current concepts regarding the link between Na(+) entry through TRPC channels and cellular Ca(2+) signaling.
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Affiliation(s)
- Petra Eder
- Institute of Pharmaceutical Sciences, Pharmacology and Toxicology, Karl-Franzens-University of Graz, Universitaetsplatz 2, 8010 Graz, Austria
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