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Tauber M, Ben-Chaim Y. Voltage Sensors Embedded in G Protein-Coupled Receptors. Int J Mol Sci 2024; 25:5295. [PMID: 38791333 PMCID: PMC11120775 DOI: 10.3390/ijms25105295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 05/08/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
Some signaling processes mediated by G protein-coupled receptors (GPCRs) are modulated by membrane potential. In recent years, increasing evidence that GPCRs are intrinsically voltage-dependent has accumulated. A recent publication challenged the view that voltage sensors are embedded in muscarinic receptors. Herein, we briefly discuss the evidence that supports the notion that GPCRs themselves are voltage-sensitive proteins and an alternative mechanism that suggests that voltage-gated sodium channels are the voltage-sensing molecules involved in such processes.
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Affiliation(s)
| | - Yair Ben-Chaim
- Department of Natural Sciences, The Open University of Israel, Ra’anana 4353701, Israel
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2
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Cohen-Armon M. Are Voltage Sensors Really Embedded in Muscarinic Receptors? Int J Mol Sci 2023; 24:ijms24087538. [PMID: 37108699 PMCID: PMC10142193 DOI: 10.3390/ijms24087538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 04/16/2023] [Accepted: 04/18/2023] [Indexed: 04/29/2023] Open
Abstract
Unexpectedly, the affinity of the seven-transmembrane muscarinic acetylcholine receptors for their agonists is modulated by membrane depolarization. Recent reports attribute this characteristic to an embedded charge movement in the muscarinic receptor, acting as a voltage sensor. However, this explanation is inconsistent with the results of experiments measuring acetylcholine binding to muscarinic receptors in brain synaptoneurosomes. According to these results, the gating of the voltage-dependent sodium channel (VDSC) acts as the voltage sensor, generating activation of Go-proteins in response to membrane depolarization, and this modulates the affinity of muscarinic receptors for their cholinergic agonists.
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Affiliation(s)
- Malka Cohen-Armon
- The Sackler School of Medicine, Department of Physiology and Pharmacology, and Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv 69978, Israel
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3
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Visochek L, Castiel A, Mittelman L, Elkin M, Atias D, Golan T, Izraeli S, Peretz T, Cohen-Armon M. Exclusive destruction of mitotic spindles in human cancer cells. Oncotarget 2017; 8:20813-20824. [PMID: 28209915 PMCID: PMC5400547 DOI: 10.18632/oncotarget.15343] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 01/31/2017] [Indexed: 12/15/2022] Open
Abstract
We identified target proteins modified by phenanthrenes that cause exclusive eradication of human cancer cells. The cytotoxic activity of the phenanthrenes in a variety of human cancer cells is attributed by these findings to post translational modifications of NuMA and kinesins HSET/kifC1 and kif18A. Their activity prevented the binding of NuMA to α-tubulin and kinesins in human cancer cells, and caused aberrant spindles. The most efficient cytotoxic activity of the phenanthridine PJ34, caused significantly smaller aberrant spindles with disrupted spindle poles and scattered extra-centrosomes and chromosomes. Concomitantly, PJ34 induced tumor growth arrest of human malignant tumors developed in athymic nude mice, indicating the relevance of its activity for cancer therapy.
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Affiliation(s)
- Leonid Visochek
- The Neufeld Cardiac Research Institute, Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Asher Castiel
- Cancer Research Center, Sheba Medical Center, Ramat Gan 53621, Israel
| | - Leonid Mittelman
- The Imaging Unit, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Michael Elkin
- Sharett Oncology Institute, Hadassah Medical Center, Ein-Kerem, Jerusalem 91120, Israel
| | - Dikla Atias
- Cancer Research Center, Sheba Medical Center, Ramat Gan 53621, Israel
| | - Talia Golan
- Cancer Research Center, Sheba Medical Center, Ramat Gan 53621, Israel
| | - Shai Izraeli
- Cancer Research Center, Sheba Medical Center, Ramat Gan 53621, Israel.,The Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Tamar Peretz
- Sharett Oncology Institute, Hadassah Medical Center, Ein-Kerem, Jerusalem 91120, Israel
| | - Malka Cohen-Armon
- The Neufeld Cardiac Research Institute, Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel.,Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv 69978, Israel
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4
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Jiang M, Bajpayee NS. Molecular mechanisms of go signaling. Neurosignals 2009; 17:23-41. [PMID: 19212138 DOI: 10.1159/000186688] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 04/09/2008] [Indexed: 12/26/2022] Open
Abstract
Go is the most abundant G protein in the central nervous system, where it comprises about 1% of membrane protein in mammalian brains. It functions to couple cell surface receptors to intercellular effectors, which is a critical process for cells to receive, interpret and respond to extracellular signals. Go protein belongs to the pertussis toxin-sensitive Gi/Go subfamily of G proteins. A number of G-protein-coupled receptors transmit stimuli to intercellular effectors through Go. Go regulates several cellular effectors, including ion channels, enzymes, and even small GTPases to modulate cellular function. This review summarizes some of the advances in Go research and proposes areas to be further addressed in exploring the functional role of Go.
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Affiliation(s)
- Meisheng Jiang
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
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Majumdar S, Sikdar SK. G-protein activation modulates pseudo-periodic oscillation of Na channel. Biochem Biophys Res Commun 2006; 347:444-51. [PMID: 16831405 DOI: 10.1016/j.bbrc.2006.06.104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Accepted: 06/17/2006] [Indexed: 10/24/2022]
Abstract
We have shown before that the duration and amplitude of both prolonged (1-160 s) and short (100-1000 ms) depolarizing prepulse altered all the steady-state and kinetic parameters of rNav1.2a voltage-gated sodium channel in a pseudo-oscillatory fashion with variable time period and amplitude, often superimposed on a linear trend. In this study, we have examined the effect of G-protein activation on pseudo-oscillatory properties of the rNav1.2a sodium channel alpha subunit, heterologously expressed in Chinese hamster ovary cells. G-protein modification caused insignificant changes in the slow pseudo-periodic oscillation of the activation properties of sodium channel; only the time period of the oscillation was altered from approximately 30 to 21s. In contrast, G-protein activation abolished the faster component of pseudo-periodic oscillation in steady-state inactivation properties of sodium channel; the conditioning duration dependence of steady-state inactivation becomes monotonic in nature.
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Affiliation(s)
- Sriparna Majumdar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
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Eltit JM, García AA, Hidalgo J, Liberona JL, Chiong M, Lavandero S, Maldonado E, Jaimovich E. Membrane electrical activity elicits inositol 1,4,5-trisphosphate-dependent slow Ca2+ signals through a Gbetagamma/phosphatidylinositol 3-kinase gamma pathway in skeletal myotubes. J Biol Chem 2006; 281:12143-54. [PMID: 16513646 DOI: 10.1074/jbc.m511218200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Tetanic electrical stimulation of myotubes evokes a ryanodine receptor-related fast calcium signal, during the stimulation, followed by a phospholipase C/inositol 1,4,5-trisphosphate-dependent slow calcium signal few seconds after stimulus end. L-type calcium channels (Cav 1.1, dihydropyridine receptors) acting as voltage sensors activate an unknown signaling pathway involved in phospholipase C activation. We demonstrated that both G protein and phosphatidylinositol 3-kinase were activated by electrical stimulation, and both the inositol 1,4,5-trisphosphate rise and slow calcium signal induced by electrical stimulation were blocked by pertussis toxin, by a Gbetagamma scavenger peptide, and by phosphatidylinositol 3-kinase inhibitors. Immunofluorescence using anti-phosphatidylinositol 3-kinase gamma antibodies showed a clear location in striations within the cytoplasm, consistent with a position near the I band region of the sarcomere. The time course of phosphatidylinositol 3-kinase activation, monitored in single living cells using a pleckstrin homology domain fused to green fluorescent protein, was compatible with sequential phospholipase Cgamma1 activation as confirmed by phosphorylation assays for the enzyme. Co-transfection of a dominant negative form of phosphatidylinositol 3-kinase gamma inhibited the phosphatidylinositol 3-kinase activity as well as the slow calcium signal. We conclude that Gbetagamma/phosphatidylinositol 3-kinase gamma signaling pathway is involved in phospholipase C activation and the generation of the slow calcium signal induced by tetanic stimulation. We postulate that membrane potential fluctuations in skeletal muscle cells can activate a pertussis toxin-sensitive G protein, phosphatidylinositol 3-kinase, phospholipase C pathway toward modulation of long term, activity-dependent plastic changes.
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Affiliation(s)
- José M Eltit
- Centro de Estudios Moleculares de la Célula, Instituto de Ciencias Biomédicas, Facultades de Medicina y Ciencias Químicas y Farmacéuticas, Universidad de Chile, Independecia 1027, Santiago 7, Chile
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Majumdar S, Foster G, Sikdar SK. Induction of pseudo-periodic oscillation in voltage-gated sodium channel properties is dependent on the duration of prolonged depolarization. Eur J Neurosci 2004; 20:127-43. [PMID: 15245486 DOI: 10.1111/j.1460-9568.2004.03466.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The neuronal voltage-gated sodium channels play a vital role in the action potential waveform shaping and propagation. Here, we report the effects of prolonged depolarization (1-160 s) on the detailed kinetics of activation, fast inactivation and recovery from slow inactivation in the rNa(v)1.2a voltage-gated sodium channel alpha-subunit expressed in Chinese hamster ovary (CHO) cells. Wavelet analysis revealed that the duration and amplitude of a prolonged sustained depolarization altered all the steady state and kinetic parameters of the channel in a pseudo-oscillatory fashion with time-variable period and amplitude, often superimposed on a linear trend. The half steady state activation potential showed a reversible depolarizing shift of 5-10 mV with duration of prolonged depolarization, while half steady state inactivation potential showed a hyperpolarizing shift of 43-55 mV. The time periods for most of the parameters relating to activation and fast and slow inactivation, lie close to 28-30 s, suggesting coupling of these kinetic processes through an oscillatory mechanism. Co-expression of the beta1-subunit affected the time periods of oscillation (close to 22 s for alpha + beta1) in steady state activation parameters. Application of a pulse protocol that mimicked paroxysmal depolarizing shift (PDS), a kind of depolarization seen in epileptic discharges, instead of a sustained depolarization, also caused oscillatory behaviour in the rNav1.2a alpha-subunit. This inherent pseudo-oscillatory mechanism may regulate excitability of the neurons, account for the epileptic discharges and subthreshold membrane potential oscillation and offer a molecular memory mechanism intrinsic to the neurons, independent of synaptic plasticity.
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Affiliation(s)
- Sriparna Majumdar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore-560012, India
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8
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Dekel N, Visochek L, Anis Y, Cohen-Armon M. Stimulation-induced modifications in Go proteins examined in giant fused synaptosomes. J Mol Neurosci 2003; 20:73-80. [PMID: 12663937 DOI: 10.1385/jmn:20:1:73] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Synaptoneurosomes (1-3 microm in diameter), prepared from rat brain stem or brain cortex, were fused with liposomes, producing a high yield of giant synaptosomes (10-60 microm in diameter). Single channel currents were measured by using the cell-attach patch-clamp technique. The membrane of the majority of these giant synaptosomes retained the cell membrane selective permeability. However, nonpermeating molecules, such as guanine nucleotides and antibodies directed against GTP-binding region in the alpha-subunit of trimeric GTP-binding proteins, were trapped in the giant synaptosomes during their preparation. Activation of Go proteins was assayed in high [K(+)]-depolarized giant synaptosomes, indicating the advantage of this preparation for tracing signal-transduction mechanisms in stimulated synaptic membranes. Stimulation-induced interactions between membrane proteins, either native or reconstituted, can be studied in the giant synaptosomes.
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Affiliation(s)
- Noya Dekel
- The Neufeld Cardiac Research Institute, Sackler School of Medicine, Tel-Aviv University, 69978 Tel-Aviv, Israel
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Perroy J, Richard S, Nargeot J, Bockaert J, Fagni L. Permissive effect of voltage on mGlu 7 receptor subtype signaling in neurons. J Biol Chem 2002; 277:1223-8. [PMID: 11706005 DOI: 10.1074/jbc.m109141200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors mobilize neuronal signaling cascades which until now have not been shown to depend on the state of membrane depolarization. Thus we have previously shown that the metabotropic glutamate receptor type 7 (mGlu7 receptor) blocks P/Q-type Ca(2+) channels via activation of a G(o) protein and PKC, in cerebellar granule cells. We show here that the transient depolarizations used to evoke the studied Ca(2+) current were indeed permissive to activate this pathway by a mGlu7 receptor agonist. Indeed, sustained depolarization to 0 mV was sufficient to inhibit P/Q-type Ca(2+) channels. This effect involved a conformational change in voltage-gated sodium channel independently of Na(+) flux, activation of a pertussis toxin-sensitive G-protein, inositol trisphosphate formation, intracellular Ca(2+) release, and PKC activity. Subliminal sustained membrane depolarization became efficient in inducing inositol trisphosphate formation, release of intracellular Ca(2+) and in blocking Ca(2+) channels, when applied concomitantly with the mGlu7a receptor agonist, d,l-aminophosphonobutyrate. This synergistic effect of membrane depolarization and mGlu7 receptor activation provides a mechanism by which neuronal excitation could control action of the mGlu7 receptor in neurons.
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Affiliation(s)
- Julie Perroy
- CNRS-UPR 9023 CCIPE and CNRS-UPR 1142 IGH, 141 Rue de la Cardonille, 34094 Montpellier, Cedex 05, France
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10
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Marin P, Fagni L, Torrens Y, Alcaraz G, Couraud F, Bockaert J, Glowinski J, Prémont J. AMPA receptor activation induces association of G-beta protein with the alpha subunit of the sodium channel in neurons. Eur J Neurosci 2001; 14:1953-60. [PMID: 11860490 DOI: 10.1046/j.0953-816x.2001.01827.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutamatergic transmission is mediated by ionotropic receptors that directly gate cationic channels and metabotropic receptors that are coupled to second messenger generating systems and to ionic channels via heterotrimeric guanine-nucleotide binding- (G) proteins. This distinction cannot be made for the ionotropic receptor subclass activated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), which has been shown to be physically associated with the alpha-subunit of Gi1 protein and activates this G-protein. Here, we report that, in addition to a Ca2+ influx, AMPA induces the mobilization of Ca2+ from the mitochondrial pool by reversing the mitochondrial Na+/Ca2+ exchanger in mouse neurons in primary culture. Both processes required the activation of tetrodotoxin-sensitive Na+ channels. AMPA receptor activation modified the gating properties of the Na+ channel, independently of the AMPA current, suggesting a G-protein-mediated process. Indeed, co-immunoprecipitation experiments indicated that AMPA receptor activation induced the association of Gbeta with the alpha-subunit of the Na+ channel. These results suggest that, in addition to its ionic channel function, the AMPA receptor is coupled to Na+ channels through G-proteins and that this novel metabotropic function is involved in the control of neuronal excitability.
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Affiliation(s)
- P Marin
- INSERM U114, Collège de France, 11, Place Marcelin Berthelot, 75231 Paris Cedex 05, France
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11
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Kim JA, Kang YS, Lee SH, Lee EH, Lee YS. Role of pertussis toxin-sensitive G-proteins in intracellular Ca2+ release and apoptosis induced by inhibiting cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels in HepG2 human hepatoblastoma cells. J Cell Biochem 2001; 81:93-101. [PMID: 11180400 DOI: 10.1002/1097-4644(20010401)81:1<93::aid-jcb1026>3.0.co;2-i] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Previously, we have reported that inhibition of cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels by glibenclamide induced intracellular Ca2+ release from IP(3)-sensitive stores and apoptosis in HepG2 human hepatoblastoma cells (Kim JA, Kang YS, Lee SH, Lee EH, Yoo BH, Lee YS. 1999. Biochem Biophys Res Commun 261:682-688). In this study we investigated the upstream signals involved in the mechanism of these actions of glibenclamide. Treatment with glibenclamide initiated production of inositol 1,4,5-trisphosphate (IP(3)) in a dose- and time-dependent manner. The glibenclamide-induced formation of IP(3) was significantly inhibited by CFTR activators (levamisole and bromotetramisole). The intracellular Ca2+ release and apoptosis induced by glibenclamide were significantly suppressed by treatment with phospholipase C (PLC) inhibitors (U-73122 and manoalide) or by pretreatment with pertussis toxin (PTx). In addition, PTx-catalyzed ADP-ribosylation of GTP-binding proteins (G-proteins) was markedly enhanced by treatment with glibenclamide in a time-dependent manner. Taken together, these results suggest that PTx-sensitive G-proteins coupled to PLCbeta may mediate the intracellular Ca2+ release and apoptosis induced by inhibiting CFTR Cl- channels in HepG2 cells. These results further suggest that the PTx-sensitive G-proteins may be a valuable target for the therapeutic intervention of human hepatomas.
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Affiliation(s)
- J A Kim
- College of Pharmacy, Yeungnam University, Korea
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13
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Willard FS, Crouch MF. Nuclear and cytoskeletal translocation and localization of heterotrimeric G-proteins. Immunol Cell Biol 2000; 78:387-94. [PMID: 10947863 DOI: 10.1046/j.1440-1711.2000.00927.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Heterotrimeric GTP-binding proteins (G-proteins) are involved in a diverse array of signalling pathways. They are generally thought to be membrane-bound proteins, which disassociate on receptor activation and binding of GTP. A model to explain this has been proposed, which is often described as 'the G-protein cycle'. The 'G-protein cycle' is discussed in the present paper in relation to evidence that now exists regarding the non- membranous localization of G-proteins. Specifically, the experimental evidence demonstrating association of G-proteins with the cytoskeleton and the nucleus, and the mechanisms by which G-proteins translocate to these sites are reviewed. Furthermore, the possible effector pathways and the physiological function of G-proteins at these sites are discussed.
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Affiliation(s)
- F S Willard
- Molecular Signalling Group, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
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Homburg S, Visochek L, Moran N, Dantzer F, Priel E, Asculai E, Schwartz D, Rotter V, Dekel N, Cohen-Armon M. A fast signal-induced activation of Poly(ADP-ribose) polymerase: a novel downstream target of phospholipase c. J Cell Biol 2000; 150:293-307. [PMID: 10908573 PMCID: PMC2180227 DOI: 10.1083/jcb.150.2.293] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2000] [Accepted: 06/08/2000] [Indexed: 11/24/2022] Open
Abstract
We present the first evidence for a fast activation of the nuclear protein poly(ADP-ribose) polymerase (PARP) by signals evoked in the cell membrane, constituting a novel mode of signaling to the cell nucleus. PARP, an abundant, highly conserved, chromatin-bound protein found only in eukaryotes, exclusively catalyzes polyADP-ribosylation of DNA-binding proteins, thereby modulating their activity. Activation of PARP, reportedly induced by formation of DNA breaks, is involved in DNA transcription, replication, and repair. Our findings demonstrate an alternative mechanism: a fast activation of PARP, evoked by inositol 1,4,5,-trisphosphate-Ca(2+) mobilization, that does not involve DNA breaks. These findings identify PARP as a novel downstream target of phospholipase C, and unveil a novel fast signal-induced modification of DNA-binding proteins by polyADP-ribosylation.
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Affiliation(s)
- S. Homburg
- The Neufeld Cardiac Research Institute, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - L. Visochek
- The Neufeld Cardiac Research Institute, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - N. Moran
- Department of Agricultural Botany, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - F. Dantzer
- Laboratory of Molecular and Structural Biology, Ecole Superieure de Biotechnologie de Strasbourg, F-67400 Illkirch-Graffenstaden, France
| | - E. Priel
- Department of Microbiology and Immunology, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva 84105, Israel
| | - E. Asculai
- Department of Microbiology and Immunology, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva 84105, Israel
| | - D. Schwartz
- Department of Molecular and Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - V. Rotter
- Department of Molecular and Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - N. Dekel
- The Neufeld Cardiac Research Institute, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - M. Cohen-Armon
- The Neufeld Cardiac Research Institute, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
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Nakahari T, Yoshida H, Imai Y, Fujiwara S, Ohnishi A, Shimamoto C, Katsu KI. Inhibition of Ca(2+) entry caused by depolarization in acetylcholine-stimulated antral mucous cells of guinea pig: G protein regulation of Ca(2+) permeable channels. THE JAPANESE JOURNAL OF PHYSIOLOGY 1999; 49:545-50. [PMID: 10603441 DOI: 10.2170/jjphysiol.49.545] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The effects of depolarizing conditions resulting from increasing extracellular K(+) concentration or nystatin treatment on intracellular Ca(2+) concentration ([Ca(2+)](i)) were studied in guinea pig antral mucous cells following acetylcholine (ACh) stimulation. ACh stimulation evoked a biphasic increase in [Ca(2+)](i), that is, an initial transient increase followed by a plateau. Depolarizing conditions reduced the [Ca(2+)](i) in the plateau phase during ACh stimulation. However, pertussis toxin (PTX, a G protein inhibitor) treatment caused [Ca(2+)](i) in the ACh-evoked plateau phase to increase under depolarizing conditions, while it had no effect on [Ca(2+)](i) under hyperpolarized conditions. Based on these observations, Ca(2+) permeable channels are regulated by a G protein which is activated by depolarized conditions and inhibited by hyperpolarized conditions and PTX; activation of the G protein (depolarization) causes Ca(2+) permeable channels to inhibit, and in turn, inhibition of the G protein (hyperpolarization) causes them to activate.
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Affiliation(s)
- T Nakahari
- Department of Physiology, Osaka Medical College, Takatsuki, 569-8686, Japan.
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