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Sarcoplasmic reticulum and calcium signaling in muscle cells: Homeostasis and disease. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 350:197-264. [PMID: 32138900 DOI: 10.1016/bs.ircmb.2019.12.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The sarco/endoplasmic reticulum is an extensive, dynamic and heterogeneous membranous network that fulfills multiple homeostatic functions. Among them, it compartmentalizes, stores and releases calcium within the intracellular space. In the case of muscle cells, calcium released from the sarco/endoplasmic reticulum in the vicinity of the contractile machinery induces cell contraction. Furthermore, sarco/endoplasmic reticulum-derived calcium also regulates gene transcription in the nucleus, energy metabolism in mitochondria and cytosolic signaling pathways. These diverse and overlapping processes require a highly complex fine-tuning that the sarco/endoplasmic reticulum provides by means of its numerous tubules and cisternae, specialized domains and contacts with other organelles. The sarco/endoplasmic reticulum also possesses a rich calcium-handling machinery, functionally coupled to both contraction-inducing stimuli and the contractile apparatus. Such is the importance of the sarco/endoplasmic reticulum for muscle cell physiology, that alterations in its structure, function or its calcium-handling machinery are intimately associated with the development of cardiometabolic diseases. Cardiac hypertrophy, insulin resistance and arterial hypertension are age-related pathologies with a common mechanism at the muscle cell level: the accumulation of damaged proteins at the sarco/endoplasmic reticulum induces a stress response condition termed endoplasmic reticulum stress, which impairs proper organelle function, ultimately leading to pathogenesis.
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Eid AH, El-Yazbi AF, Zouein F, Arredouani A, Ouhtit A, Rahman MM, Zayed H, Pintus G, Abou-Saleh H. Inositol 1,4,5-Trisphosphate Receptors in Hypertension. Front Physiol 2018; 9:1018. [PMID: 30093868 PMCID: PMC6071574 DOI: 10.3389/fphys.2018.01018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 07/09/2018] [Indexed: 12/21/2022] Open
Abstract
Chronic hypertension remains a major cause of global mortality and morbidity. It is a complex disease that is the clinical manifestation of multiple genetic, environmental, nutritional, hormonal, and aging-related disorders. Evidence supports a role for vascular aging in the development of hypertension involving an impairment in endothelial function together with an alteration in vascular smooth muscle cells (VSMCs) calcium homeostasis leading to increased myogenic tone. Changes in free intracellular calcium levels ([Ca2+] i ) are mediated either by the influx of Ca2+ from the extracellular space or release of Ca2+ from intracellular stores, mainly the sarcoplasmic reticulum (SR). The influx of extracellular Ca2+ occurs primarily through voltage-gated Ca2+ channels (VGCCs), store-operated Ca2+ channels (SOC), and Ca2+ release-activated channels (CRAC), whereas SR-Ca2+ release occurs through inositol trisphosphate receptor (IP3R) and ryanodine receptors (RyRs). IP3R-mediated SR-Ca2+ release, in the form of Ca2+ waves, not only contributes to VSMC contraction and regulates VGCC function but is also intimately involved in structural remodeling of resistance arteries in hypertension. This involves a phenotypic switch of VSMCs as well as an alteration of cytoplasmic Ca2+ signaling machinery, a phenomena tightly related to the aging process. Several lines of evidence implicate changes in expression/function levels of IP3R isoforms in the development of hypertension, VSMC phenotypic switch, and vascular aging. The present review discusses the current knowledge of these mechanisms in an integrative approach and further suggests potential new targets for hypertension management and treatment.
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Affiliation(s)
- Ali H Eid
- Department of Pharmacology and Toxicology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.,Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
| | - Ahmed F El-Yazbi
- Department of Pharmacology and Toxicology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.,Department of Pharmacology and Toxicology, Faculty of Pharmacy, Alexandria University, Alexandria, Egypt
| | - Fouad Zouein
- Department of Pharmacology and Toxicology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Abdelilah Arredouani
- Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Qatar Foundation, Doha, Qatar
| | - Allal Ouhtit
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
| | - Md M Rahman
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
| | - Hatem Zayed
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha, Qatar
| | - Gianfranco Pintus
- Department of Biomedical Sciences, College of Health Sciences, Qatar University, Doha, Qatar
| | - Haissam Abou-Saleh
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
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Otsuki S, Yasuda T, Mukaida K, Noda Y, Kanzaki R, Miyoshi H, Kondo T, Hamada H, Kawamoto M. Myotoxicity of local anesthetics is equivalent in individuals with and without predisposition to malignant hyperthermia. J Anesth 2018; 32:616-623. [DOI: 10.1007/s00540-018-2526-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 06/19/2018] [Indexed: 01/25/2023]
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Suleiman MM, Oyelowo BB, Abubakar A, Mamman M, Bello KDT. A controlled study to investigate anti-diarrhoeal effect of the stem-bark fractions of Terminalia avicennioides in laboratory animal models. Int J Vet Sci Med 2017; 5:14-22. [PMID: 30255043 PMCID: PMC6137853 DOI: 10.1016/j.ijvsm.2017.04.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 02/24/2017] [Accepted: 04/21/2017] [Indexed: 11/18/2022] Open
Abstract
Due to the shortcomings associated with modern synthetic antidiarrhoeal drugs, it is important to find newer, safer and cheaper antidiarrhoeal agents from natural sources. The study was conducted to evaluate the anti-diarrhoeal activity of the fractions of the stem-bark of Terminalia avicennioides in laboratory animal models. The effect of different concentrations (1.0 × 10−3, 2.0 × 10−3, 4.0 × 10−3 and 8.0 × 10−3 mg/mL) of the aqueous methanol (AMF), ethyl acetate (EAF) and hexane (HXF) fractions of T. avicennioides were tested against spontaneous and acetylcholine-induced contractions of rabbit jejunum as well as on histamine-induced contraction of guinea pig ileum. Similarly, the effects of the AMF on gastro-intestinal transit time, castor oil-induced diarrhoea and castor oil-induced enteropooling were evaluated. The AMF, EAF and HXF at concentrations of 1.0 × 10−3, 2.0 × 10−3, 4.0 × 10−3 and 8.0 × 10−3 mg/mL attenuated the contractile effects of both the spontaneous and acetylcholine-induced contractions of rabbit jejunum and that of histamine-induced contraction of guinea pig ileum in a concentration-dependent manner. The AMF at doses of 200, 300 and 500 mg/kg produced significant (p < 0.05) reductions in gastrointestinal transit time of charcoal and incidence of castor oil-induced diarrhoea in mice relative to the untreated control. Similarly, at doses of 300 and 500 mg/kg, AMF significantly (p < 0.05) reduced the weight and volume of intestinal fluid in the treated mice when compared to the untreated animals. The results of this study showed that the stem-bark of T. avicennioides possesses spasmolytic effect and could be a potential antidiarrhoeal agent. However, detailed pharmacological trials are required to justify the clinical use of the plant for treating diarrhoea.
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Affiliation(s)
- Mohammed M Suleiman
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
| | - Balkisu B Oyelowo
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
| | - Ahmed Abubakar
- Department of Pharmacognosy and Drug Development, Faculty of Pharmaceutical Science, Ahmadu Bello University, Zaria, Nigeria
| | - Mohammed Mamman
- Department of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
| | - Kamar-Deen T Bello
- National Animal Production Research Institute, Ahmadu Bello University, Zaria, Shika, Nigeria
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Balemba OB, Stark TD, Lösch S, Patterson S, McMillan JS, Mawe GM, Hofmann T. (2R,3S,2'' R,3''R)-manniflavanone, a new gastrointestinal smooth muscle L-type calcium channel inhibitor, which underlies the spasmolytic properties of Garcinia buchananii stem bark extract. J Smooth Muscle Res 2016; 50:48-65. [PMID: 26081368 PMCID: PMC4826780 DOI: 10.1540/jsmr.50.48] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Garcinia buchananii Baker stem bark extract (GBB) is a traditional
medication of diarrhea and dysentery in sub-Saharan Africa. It is believed that GBB causes
gastrointestinal smooth muscle relaxation. The aim of this study was to determine whether
GBB has spasmolytic actions and identify compounds underlying these actions. Calcium
(Ca2+) imaging was used to analyze the effect of GBB on Ca2+
flashes and Ca2+ waves in guinea pig gallbladder and distal colon smooth
muscle. Intracellular microelectrode recording was used to determine the effect of GBB,
six fractions of GBB, M1–5 and M7, and
(2R,3S,2”R,3”R)-manniflavanone,
a compound isolated from M3 on action potentials in gallbladder smooth muscle. The
technique was also used to analyze the effect of GBB, M3, and
(2R,3S,2”R,3”R)-manniflavanone
on action potentials in the circular muscle of mouse and guinea pig distal colons, and the
effect of GBB and
(2R,3S,2”R,3”R)-manniflavanone
on slow waves in porcine ileum. GBB inhibited Ca2+ flashes and Ca2+
waves. GBB, M3 and
(2R,3S,2”R,3”R)-manniflavanone
inhibited action potentials. L-type Ca2+ channel activator Bay K 8644 increased
the discharge of action potentials in mouse colon but did not trigger or increase action
potentials in the presence of GBB and
(2R,3S,2”R,3”R)-manniflavanone.
GBB and
(2R,3S,2”R,3”R)-manniflavanone
inhibited action potentials in the presence of Bay K 8644. GBB and
(2R,3S,2”R,3”R)-manniflavanone
reduced the amplitude but did not alter the frequency of slow waves in the porcine ileum.
In conclusion, GBB and
(2R,3S,2”R,3”R)-manniflavanone
relax smooth muscle by inhibiting L-type Ca2+ channels, thus have potential for
use as therapies of gastrointestinal smooth muscle spasms, and arrhythmias.
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Affiliation(s)
- Onesmo B Balemba
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States
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Gordienko D, Povstyan O, Sukhanova K, Raphaël M, Harhun M, Dyskina Y, Lehen'kyi V, Jama A, Lu ZL, Skryma R, Prevarskaya N. Impaired P2X signalling pathways in renal microvascular myocytes in genetic hypertension. Cardiovasc Res 2014; 105:131-42. [PMID: 25514930 DOI: 10.1093/cvr/cvu249] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
AIMS P2X receptors (P2XRs) mediate sympathetic control and autoregulation of renal circulation triggering preglomerular vasoconstriction, which protects glomeruli from elevated pressures. Although previous studies established a casual link between glomerular susceptibility to hypertensive injury and decreased preglomerular vascular reactivity to P2XR activation, the mechanisms of attenuation of the P2XR signalling in hypertension remained unknown. We aimed to analyse molecular mechanisms of the impairment of P2XR signalling in renal vascular smooth muscle cells (RVSMCs) in genetic hypertension. METHODS AND RESULTS We compared the expression of pertinent genes and P2XR-linked Ca(2+) entry and Ca(2+) release mechanisms in RVSMCs of spontaneously hypertensive rats (SHRs) and their normotensive controls, Wistar Kyoto (WKY) rats. We found that, in SHR RVSMCs, P2XR-linked Ca(2+) entry and Ca(2+) release from the sarcoplasmic reticulum (SR) are both significantly reduced. The former is due to down-regulation of the P2X1 subunit. The latter is caused by a decrease of the SR Ca(2+) load. The SR Ca(2+) load reduction is caused by attenuated Ca(2+) uptake via down-regulated sarco-/endoplasmic reticulum Ca(2+)-ATPase 2b and elevated Ca(2+) leak from the SR via ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors. Spontaneous activity of these Ca(2+)-release channels is augmented due to up-regulation of RyR type 2 and elevated IP3 production by up-regulated phospholipase C-β1. CONCLUSIONS Our study unravels the cellular and molecular mechanisms of attenuation of P2XR-mediated preglomerular vasoconstriction that elevates glomerular susceptibility to harmful hypertensive pressures. This provides an important impetus towards understanding of the pathology of hypertensive renal injury.
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Affiliation(s)
- Dmitri Gordienko
- INSERM U1003, Laboratory of Excellence, Ion Channels Science and Therapeutics, Université des Sciences et Technologies de Lille, Batiment SN3, Villeneuve d'Ascq 59655, France Laboratory of Molecular Pharmacology and Biophysics of Cell Signaling, Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - Oleksandr Povstyan
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signaling, Bogomoletz Institute of Physiology, Kiev, Ukraine Division of Basic Medical Sciences, St. George's, University of London, London, UK
| | - Khrystyna Sukhanova
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signaling, Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - Maylis Raphaël
- INSERM U1003, Laboratory of Excellence, Ion Channels Science and Therapeutics, Université des Sciences et Technologies de Lille, Batiment SN3, Villeneuve d'Ascq 59655, France
| | - Maksym Harhun
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signaling, Bogomoletz Institute of Physiology, Kiev, Ukraine Division of Basic Medical Sciences, St. George's, University of London, London, UK
| | - Yulia Dyskina
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signaling, Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - V'yacheslav Lehen'kyi
- INSERM U1003, Laboratory of Excellence, Ion Channels Science and Therapeutics, Université des Sciences et Technologies de Lille, Batiment SN3, Villeneuve d'Ascq 59655, France
| | - Abdirahman Jama
- MRC, Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Zhi-Liang Lu
- MRC, Centre for Reproductive Health, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK Department of Biological Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, China
| | - Roman Skryma
- INSERM U1003, Laboratory of Excellence, Ion Channels Science and Therapeutics, Université des Sciences et Technologies de Lille, Batiment SN3, Villeneuve d'Ascq 59655, France
| | - Natalia Prevarskaya
- INSERM U1003, Laboratory of Excellence, Ion Channels Science and Therapeutics, Université des Sciences et Technologies de Lille, Batiment SN3, Villeneuve d'Ascq 59655, France
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Sukhanova KY, Thugorka OM, Bouryi VA, Harhun MI, Gordienko DV. Mechanisms of the sarcoplasmic reticulum Ca2+ release induced by P2X receptor activation in mesenteric artery myocytes. Pharmacol Rep 2014; 66:363-72. [PMID: 24905510 DOI: 10.1016/j.pharep.2013.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 10/09/2013] [Accepted: 11/26/2013] [Indexed: 10/25/2022]
Abstract
BACKGROUND ATP is one of the principal sympathetic neurotransmitters which contracts vascular smooth muscle cells (SMCs) via activation of ionotropic P2X receptors (P2XRs). We have recently demonstrated that contraction of the guinea pig small mesenteric arteries evoked by stimulation of P2XRs is sensitive to inhibitors of IP3 receptors (IP3Rs). Here we analyzed contribution of IP3Rs and ryanodine receptors (RyRs) to [Ca(2+)]i transients induced by P2XR agonist αβ-meATP (10 μM) in single SMCs from these vessels. METHODS The effects of inhibition of L-type Ca(2+) channels (VGCCs), RyRs and IP3Rs (5 μM nicardipine, 100 μM tetracaine and 30 μM 2-APB, respectively) on αβ-meATP-induced [Ca(2+)]i transients were analyzed using fast x-y confocal Ca(2+) imaging. RESULTS The effect of IP3R inhibition on the [Ca(2+)]i transient was significantly stronger (67 ± 7%) than that of RyR inhibition (40 ± 5%) and was attenuated by block of VGCCs. The latter indicates that activation of VGCCs is linked to IP3R-mediated Ca(2+) release. Immunostaining of RyRs and IP3Rs revealed that RyRs are located mainly in deeper sarcoplasmic reticulum (SR) while sub-plasma membrane (PM) SR elements are enriched with type 1 IP3Rs. This structural peculiarity makes IP3Rs more accessible to Ca(2+) entering the cell via VGCCs. Thus, IP3Rs may serve as an "intermediate amplifier" between voltage-gated Ca(2+) entry and RyR-mediated Ca(2+) release. CONCLUSIONS P2X receptor activation in mesenteric artery SMCs recruits IP3Rs-mediated Ca(2+) release from sub-PM SR, which is facilitated by activation of VGCCs. Sensitivity of IP3R-mediated release to VGCC antagonists in vascular SMCs makes this mechanism of special therapeutic significance.
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Affiliation(s)
- Khrystyna Yu Sukhanova
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, State Key Laboratory of Molecular and Cellular Biology, A.A. Bogomoletz Institute of Physiology, Kiev, Ukraine.
| | - Oleksandr M Thugorka
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, State Key Laboratory of Molecular and Cellular Biology, A.A. Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - Vitali A Bouryi
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, State Key Laboratory of Molecular and Cellular Biology, A.A. Bogomoletz Institute of Physiology, Kiev, Ukraine
| | - Maksym I Harhun
- Division of Biomedical Sciences, St. George's, University of London, London, UK
| | - Dmitri V Gordienko
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, State Key Laboratory of Molecular and Cellular Biology, A.A. Bogomoletz Institute of Physiology, Kiev, Ukraine; Inserm U1003, Equipe labellisée par la Ligue Nationale Contre le Cancer, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France.
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Quijano JC, Vianay B, Bény JL, Meister JJ. Ultrafast Ca2+ wave in cultured vascular smooth muscle cells aligned on a micropatterned surface. Cell Calcium 2013; 54:436-45. [PMID: 24183802 DOI: 10.1016/j.ceca.2013.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 10/08/2013] [Accepted: 10/09/2013] [Indexed: 11/29/2022]
Abstract
Communication between vascular smooth muscle cells (SMCs) allows control of their contraction and so regulation of blood flow. The contractile state of SMCs is regulated by cytosolic Ca2+ concentration ([Ca2+]i) which propagates as Ca2+ waves over a significant distance along the vessel. We have characterized an intercellular ultrafast Ca2+ wave observed in cultured A7r5 cell line and in primary cultured SMCs (pSMCs) from rat mesenteric arteries. This wave, induced by local mechanical or local KCl stimulation, had a velocity around 15 mm/s. Combining of precise alignment of cells with fast Ca2+ imaging and intracellular membrane potential recording, allowed us to analyze rapid [Ca2+]i dynamics and membrane potential events along the network of cells. The rate of [Ca2+]i increase along the network decreased with distance from the stimulation site. Gap junctions or voltage-operated Ca2+ channels (VOCCs) inhibition suppressed the ultrafast Ca2+ wave. Mechanical stimulation induced a membrane depolarization that propagated and that decayed exponentially with distance. Our results demonstrate that an electrotonic spread of membrane depolarization drives a rapid Ca2+ entry from the external medium through VOCCs, modeled as an ultrafast Ca2+ wave. This wave may trigger and drive slower Ca2+ waves observed ex vivo and in vivo.
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Affiliation(s)
- Jairo C Quijano
- Laboratory of Cell Biophysics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Facultad de Ciencias Básicas, Politécnico Colombiano JIC, Medellín, Colombia.
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9
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Sukhanova KY, Harhun MI, Bouryi VA, Gordienko DV. Mechanisms of [Ca2+]i elevation following P2X receptor activation in the guinea-pig small mesenteric artery myocytes. Pharmacol Rep 2013; 65:152-63. [PMID: 23563033 DOI: 10.1016/s1734-1140(13)70973-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 09/24/2012] [Indexed: 11/25/2022]
Abstract
BACKGROUND There is growing evidence suggesting involvement of L-type voltage-gated Ca2+ channels (VGCCs) in purinergic signaling mechanisms. However, detailed interplay between VGCCs and P2X receptors in intracellular Ca2+ mobilization is not well understood. This study examined relative contribution of the Ca2+ entry mechanisms and induced by this entry Ca2+ release from the intracellular stores engaged by activation of P2X receptors in smooth muscle cells (SMCs) from the guinea-pig small mesenteric arteries. METHODS P2X receptors were stimulated by the brief local application of αβ-meATP and changes in [Ca2+]i were monitored in fluo-3 loaded SMCs using fast x-y confocal Ca2+ imaging. The effects of the block of L-type VGCCs and/or depletion of the intracellular Ca2+ stores on αβ-meATP-induced [Ca2+]i transients were analyzed. RESULTS Our analysis revealed that Ca2+ entry via L-type VGCCs is augmented by the Ca2+-induced Ca2+ release significantly more than Ca2+ entry via P2X receptors, even though net Ca2+ influxes provided by the two mechanisms are not significantly different. CONCLUSIONS Thus, arterial SMCs upon P2X receptor activation employ an effective mechanism of the Ca2+ signal amplification, the major component of which is the Ca2+ release from the SR activated by Ca2+ influx via L-type VGCCs. This signaling pathway is engaged by depolarization of the myocyte membrane resulting from activation of P2X receptors, which, being Ca2+ permeable, per se form less effective Ca2+ signaling pathway. This study, therefore, rescales potential targets for therapeutic intervention in purinergic control of vascular tone.
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Affiliation(s)
- Khrystyna Yu Sukhanova
- Laboratory of Molecular Pharmacology and Biophysics of Cell Signalling, A.A. Bogomoletz, Institute of Physiology, Bogomoletz 4, Kiev, 01024, Ukraine.
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Opiates Modulate Thermosensation by Internalizing Cold Receptor TRPM8. Cell Rep 2013; 4:504-15. [DOI: 10.1016/j.celrep.2013.07.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/07/2013] [Accepted: 07/01/2013] [Indexed: 11/21/2022] Open
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Kyle BD, Bradley E, Large R, Sergeant GP, McHale NG, Thornbury KD, Hollywood MA. Mechanisms underlying activation of transient BK current in rabbit urethral smooth muscle cells and its modulation by IP3-generating agonists. Am J Physiol Cell Physiol 2013; 305:C609-22. [PMID: 23804200 DOI: 10.1152/ajpcell.00025.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used the perforated patch-clamp technique at 37°C to investigate the mechanisms underlying the activation of a transient large-conductance K(+) (tBK) current in rabbit urethral smooth muscle cells. The tBK current required an elevation of intracellular Ca(2+), resulting from ryanodine receptor (RyR) activation via Ca(2+)-induced Ca(2+) release, triggered by Ca(2+) influx through L-type Ca(2+) (CaV) channels. Carbachol inhibited tBK current by reducing Ca(2+) influx and Ca(2+) release and altered the shape of spike complexes recorded under current-clamp conditions. The tBK currents were blocked by iberiotoxin and penitrem A (300 and 100 nM, respectively) and were also inhibited when external Ca(2+) was removed or the CaV channel inhibitors nifedipine (10 μM) and Cd(2+) (100 μM) were applied. The tBK current was inhibited by caffeine (10 mM), ryanodine (30 μM), and tetracaine (100 μM), suggesting that RyR-mediated Ca(2+) release contributed to the activation of the tBK current. When IP3 receptors (IP3Rs) were blocked with 2-aminoethoxydiphenyl borate (2-APB, 100 μM), the amplitude of the tBK current was not reduced. However, when Ca(2+) release via IP3Rs was evoked with phenylephrine (1 μM) or carbachol (1 μM), the tBK current was inhibited. The effect of carbachol was abolished when IP3Rs were blocked with 2-APB or by inhibition of muscarinic receptors with the M3 receptor antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (1 μM). Under current-clamp conditions, bursts of action potentials could be evoked with depolarizing current injection. Carbachol reduced the number and amplitude of spikes in each burst, and these effects were reduced in the presence of 2-APB. In the presence of ryanodine, the number and amplitude of spikes were also reduced, and carbachol was without further effect. These data suggest that IP3-generating agonists can modulate the electrical activity of rabbit urethral smooth muscle cells and may contribute to the effects of neurotransmitters on urethral tone.
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Affiliation(s)
- Barry D Kyle
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
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van Breemen C, Fameli N, Evans AM. Pan-junctional sarcoplasmic reticulum in vascular smooth muscle: nanospace Ca2+ transport for site- and function-specific Ca2+ signalling. J Physiol 2013; 591:2043-54. [PMID: 23339179 DOI: 10.1113/jphysiol.2012.246348] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This review focuses on how smooth muscle sarcoplasmic reticulum (SR), the major releasable Ca(2+) store in these cells, performs its many functions by communicating with the plasma membrane (PM) and other organelles across cytoplasmic nanospaces, defined by membrane-membrane junctions less than 50 nm across. In spite of accumulating evidence in favour of the view that cytoplasmic nanospaces are a prerequisite for effective control of diverse cellular functions, our current understanding of how smooth muscle cells accomplish site- and function-specific Ca(2+) signalling remains in its infancy. We first present evidence in support of the view that effective Ca(2+) signalling depends on the restricted diffusion of Ca(2+) within cytoplasmic nanospaces. We then develop an evidence-based model of the smooth muscle SR - the 'pan-junctional SR' model - that incorporates a network of tubules and quilts that are capable of auto-regulating their Ca(2+) content and determining junctional [Ca(2+)]i through loading and unloading at membrane-membrane nanojunctions. Thereby, we provide a novel working hypothesis in order to inform future investigation into the control of a variety of cellular functions by local Ca(2+) signals at junctional nanospaces, from contraction and energy metabolism to nuclear transcription. Based on the current literature, we discuss the molecular mechanisms whereby the SR mediates these multiple functions through the interaction of ion channels and pumps embedded in apposing membranes within inter-organellar junctions. We finally highlight the fact that although most current hypotheses are qualitatively supported by experimental data, solid quantitative simulations are seriously lacking. Considering that at physiological concentrations the number of calcium ions in a typical junctional nanospace between the PM and SR is of the order of 1, ion concentration variability plays a major role as the currency of information transfer and stochastic quantitative modelling will be required to both test and develop working hypotheses.
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McCarron JG, Chalmers S, Olson ML, Girkin JM. Subplasma membrane Ca2+ signals. IUBMB Life 2012; 64:573-85. [PMID: 22653514 PMCID: PMC3638344 DOI: 10.1002/iub.1032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 02/24/2012] [Indexed: 12/03/2022]
Abstract
Ca2+ may selectively activate various processes in part by the cell's ability to localize changes in the concentration of the ion to specific subcellular sites. Interestingly, these Ca2+ signals begin most often at the plasma membrane space so that understanding subplasma membrane signals is central to an appreciation of local signaling. Several experimental procedures have been developed to study Ca2+ signals near the plasma membrane, but probably the most prevalent involve the use of fluorescent Ca2+ indicators and fall into two general approaches. In the first, the Ca2+ indicators themselves are specifically targeted to the subplasma membrane space to measure Ca2+ only there. Alternatively, the indicators are allowed to be dispersed throughout the cytoplasm, but the fluorescence emanating from the Ca2+ signals at the subplasma membrane space is selectively measured using high resolution imaging procedures. Although the targeted indicators offer an immediate appeal because of selectivity and ease of use, their limited dynamic range and slow response to changes in Ca2+ are a shortcoming. Use of targeted indicators is also largely restricted to cultured cells. High resolution imaging applied with rapidly responding small molecule Ca2+ indicators can be used in all cells and offers significant improvements in dynamic range and speed of response of the indicator. The approach is technically difficult, however, and realistic calibration of signals is not possible. In this review, a brief overview of local subplasma membrane Ca2+ signals and methods for their measurement is provided. © 2012 IUBMB IUBMB Life, 64(7): 573–585, 2012
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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McCarron JG, Olson ML, Chalmers S. Mitochondrial regulation of cytosolic Ca²⁺ signals in smooth muscle. Pflugers Arch 2012; 464:51-62. [PMID: 22555917 DOI: 10.1007/s00424-012-1108-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 04/11/2012] [Indexed: 11/25/2022]
Abstract
The cytosolic Ca²⁺ concentration ([Ca²⁺]c) controls virtually every activity of smooth muscle, including contraction, migration, transcription, division and apoptosis. These processes may be activated by large (>10 μM) amplitude [Ca²⁺]c increases, which occur in small restricted regions of the cell or by smaller (<1 μM) amplitude changes throughout the bulk cytoplasm. Mitochondria contribute to the regulation of these signals by taking up Ca²⁺. However, mitochondria's reported low affinity for Ca²⁺ is thought to require the organelle to be positioned close to ion channels and within a microdomain of high [Ca²⁺]. In cultured smooth muscle, mitochondria are highly dynamic structures but in native smooth muscle mitochondria are immobile, apparently strategically positioned organelles that regulate the upstroke and amplitude of IP₃-evoked Ca²⁺ signals and IP₃ receptor (IP₃R) cluster activity. These observations suggest mitochondria are positioned within the high [Ca²⁺] microdomain arising from an IP₃R cluster to exert significant local control of channel activity. On the other hand, neither the upstroke nor amplitude of voltage-dependent Ca²⁺ entry is modulated by mitochondria; rather, it is the declining phase of the transient that is regulated by the organelle. Control of the declining phase of the transient requires a high mitochondrial affinity for Ca²⁺ to enable uptake to occur over the normal physiological Ca²⁺ range (<1 μM). Thus, in smooth muscle, mitochondria regulate Ca²⁺ signals exerting effects over a large range of [Ca²⁺] (∼200 nM to at least tens of micromolar) to provide a wide dynamic range in the control of Ca²⁺ signals.
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Affiliation(s)
- John G McCarron
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 161 Cathedral Street, Glasgow, G4 0NR, UK.
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Narayanan D, Adebiyi A, Jaggar JH. Inositol trisphosphate receptors in smooth muscle cells. Am J Physiol Heart Circ Physiol 2012; 302:H2190-210. [PMID: 22447942 DOI: 10.1152/ajpheart.01146.2011] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are a family of tetrameric intracellular calcium (Ca(2+)) release channels that are located on the sarcoplasmic reticulum (SR) membrane of virtually all mammalian cell types, including smooth muscle cells (SMC). Here, we have reviewed literature investigating IP(3)R expression, cellular localization, tissue distribution, activity regulation, communication with ion channels and organelles, generation of Ca(2+) signals, modulation of physiological functions, and alterations in pathologies in SMCs. Three IP(3)R isoforms have been identified, with relative expression and cellular localization of each contributing to signaling differences in diverse SMC types. Several endogenous ligands, kinases, proteins, and other modulators control SMC IP(3)R channel activity. SMC IP(3)Rs communicate with nearby ryanodine-sensitive Ca(2+) channels and mitochondria to influence SR Ca(2+) release and reactive oxygen species generation. IP(3)R-mediated Ca(2+) release can stimulate plasma membrane-localized channels, including transient receptor potential (TRP) channels and store-operated Ca(2+) channels. SMC IP(3)Rs also signal to other proteins via SR Ca(2+) release-independent mechanisms through physical coupling to TRP channels and local communication with large-conductance Ca(2+)-activated potassium channels. IP(3)R-mediated Ca(2+) release generates a wide variety of intracellular Ca(2+) signals, which vary with respect to frequency, amplitude, spatial, and temporal properties. IP(3)R signaling controls multiple SMC functions, including contraction, gene expression, migration, and proliferation. IP(3)R expression and cellular signaling are altered in several SMC diseases, notably asthma, atherosclerosis, diabetes, and hypertension. In summary, IP(3)R-mediated pathways control diverse SMC physiological functions, with pathological alterations in IP(3)R signaling contributing to disease.
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Affiliation(s)
- Damodaran Narayanan
- Department of Physiology, University of Tennessee Health Science Center, Memphis, 38163, USA
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Halidi N, Boittin FX, Bény JL, Meister JJ. Propagation of fast and slow intercellular Ca2+ waves in primary cultured arterial smooth muscle cells. Cell Calcium 2011; 50:459-67. [DOI: 10.1016/j.ceca.2011.08.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2011] [Revised: 08/02/2011] [Accepted: 08/02/2011] [Indexed: 11/30/2022]
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Lam M, Kerr K, Ventura S, Exintaris B. Extracellular Ca2+ entry and mobilization of inositol trisphosphate-dependent Ca2+ stores modulate histamine and electrical field stimulation induced contractions of the guinea-pig prostate. Pharmacol Res 2011; 64:235-41. [DOI: 10.1016/j.phrs.2011.04.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 04/18/2011] [Accepted: 04/18/2011] [Indexed: 11/25/2022]
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Povstyan OV, Harhun MI, Gordienko DV. Ca2+ entry following P2X receptor activation induces IP3 receptor-mediated Ca2+ release in myocytes from small renal arteries. Br J Pharmacol 2011; 162:1618-38. [PMID: 21175582 PMCID: PMC3057298 DOI: 10.1111/j.1476-5381.2010.01169.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 11/04/2010] [Accepted: 11/25/2010] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE P2X receptors mediate sympathetic control and autoregulation of the renal circulation triggering contraction of renal vascular smooth muscle cells (RVSMCs) via an elevation of intracellular Ca(2+) concentration ([Ca(2+) ](i) ). Although it is well-appreciated that the myocyte Ca(2+) signalling system is composed of microdomains, little is known about the structure of the [Ca(2+) ](i) responses induced by P2X receptor stimulation in vascular myocytes. EXPERIMENTAL APPROACHES Using confocal microscopy, perforated-patch electrical recordings, immuno-/organelle-specific staining, flash photolysis and RT-PCR analysis we explored, at the subcellular level, the Ca(2+) signalling system engaged in RVSMCs on stimulation of P2X receptors with the selective agonist αβ-methylene ATP (αβ-meATP). KEY RESULTS RT-PCR analysis of single RVSMCs showed the presence of genes encoding inositol 1,4,5-trisphosphate receptor type 1(IP(3) R1) and ryanodine receptor type 2 (RyR2). The amplitude of the [Ca(2+) ](i) transients depended on αβ-meATP concentration. Depolarization induced by 10 µmol·L(-1) αβ-meATP triggered an abrupt Ca(2+) release from sub-plasmalemmal ('junctional') sarcoplasmic reticulum enriched with IP(3) Rs but poor in RyRs. Depletion of calcium stores, block of voltage-gated Ca(2+) channels (VGCCs) or IP(3) Rs suppressed the sub-plasmalemmal [Ca(2+) ](i) upstroke significantly more than block of RyRs. The effect of calcium store depletion or IP(3) R inhibition on the sub-plasmalemmal [Ca(2+) ](i) upstroke was attenuated following block of VGCCs. CONCLUSIONS AND IMPLICATIONS Depolarization of RVSMCs following P2X receptor activation induces IP(3) R-mediated Ca(2+) release from sub-plasmalemmal ('junctional') sarcoplasmic reticulum, which is activated mainly by Ca(2+) influx through VGCCs. This mechanism provides convergence of signalling pathways engaged in electromechanical and pharmacomechanical coupling in renal vascular myocytes.
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MESH Headings
- Adenosine Triphosphate/analogs & derivatives
- Adenosine Triphosphate/metabolism
- Adenosine Triphosphate/pharmacology
- Animals
- Calcium/metabolism
- Calcium Channels/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Kidney/blood supply
- Male
- Muscle Cells/metabolism
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/metabolism
- Purinergic P2X Receptor Agonists/pharmacology
- Rats
- Rats, Inbred WKY
- Receptors, Purinergic P2X/metabolism
- Renal Artery/metabolism
- Ryanodine Receptor Calcium Release Channel/genetics
- Sarcoplasmic Reticulum/metabolism
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Affiliation(s)
- Oleksandr V Povstyan
- Division of Basic Medical Sciences, St. George's, University of London, London, UK
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Chokri A, Doukali R, Abida KE, Cheikh RB. Myorelaxant and Spasmolytic Effects of Globularia alypum L. Extract on Rabbit Jejunum. INT J PHARMACOL 2010. [DOI: 10.3923/ijp.2010.608.615] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Abstract
The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a "one model fits all" approach to this subject, we have tried to synthesize conclusions wherever possible.
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Affiliation(s)
- Susan Wray
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Liverpool, Merseyside L69 3BX, United Kingdom.
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Xing J, Strange K. Phosphatidylinositol 4,5-bisphosphate and loss of PLCgamma activity inhibit TRPM channels required for oscillatory Ca2+ signaling. Am J Physiol Cell Physiol 2009; 298:C274-82. [PMID: 19923421 DOI: 10.1152/ajpcell.00394.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Caenorhabditis elegans intestinal epithelium generates rhythmic inositol 1,4,5-trisphosphate (IP(3))-dependent Ca(2+) oscillations that control muscle contractions required for defecation. Two highly Ca(2+)-selective transient receptor potential (TRP) melastatin (TRPM) channels, GON-2 and GTL-1, function with PLCgamma in a common signaling pathway that regulates IP(3)-dependent intracellular Ca(2+) release. A second PLC, PLCbeta, is also required for IP(3)-dependent Ca(2+) oscillations, but functions in an independent signaling mechanism. PLCgamma generates IP(3) that regulates IP(3) receptor activity. We demonstrate here that PLCgamma via hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)) also regulates GON-2/GTL-1 function. Knockdown of PLCgamma but not PLCbeta activity by RNA interference (RNAi) inhibits channel activity approximately 80%. Inhibition is fully reversed by agents that deplete PIP(2) levels. PIP(2) added to the patch pipette has no effect on channel activity in PLCgamma RNAi cells. However, in control cells, 10 microM PIP(2) inhibits whole cell current approximately 80%. Channel inhibition by phospholipids is selective for PIP(2) with an IC(50) value of 2.6 microM. Elevated PIP(2) levels have no effect on channel voltage and Ca(2+) sensitivity and likely inhibit by reducing channel open probability, single-channel conductance, and/or trafficking. We conclude that hydrolysis of PIP(2) by PLCgamma functions in the activation of both the IP(3) receptor and GON-2/GTL-1 channels. GON-2/GTL-1 functions as the major intestinal cell Ca(2+) influx pathway. Calcium influx through the channel feedback regulates its activity and likely functions to modulate IP(3) receptor function. PIP(2)-dependent regulation of GON-2/GTL-1 may provide a mechanism to coordinate plasma membrane Ca(2+) influx with PLCgamma and IP(3) receptor activity as well as intracellular Ca(2+) store depletion.
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Affiliation(s)
- Juan Xing
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Xing J, Yan X, Estevez A, Strange K. Highly Ca2+-selective TRPM channels regulate IP3-dependent oscillatory Ca2+ signaling in the C. elegans intestine. ACTA ACUST UNITED AC 2008; 131:245-55. [PMID: 18299395 PMCID: PMC2248719 DOI: 10.1085/jgp.200709914] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Posterior body wall muscle contraction (pBoc) in the nematode Caenorhabditis elegans occurs rhythmically every 45–50 s and mediates defecation. pBoc is controlled by inositol-1,4,5-trisphosphate (IP3)–dependent Ca2+ oscillations in the intestine. The intestinal epithelium can be studied by patch clamp electrophysiology, Ca2+ imaging, genome-wide reverse genetic analysis, forward genetics, and molecular biology and thus provides a powerful model to develop an integrated systems level understanding of a nonexcitable cell oscillatory Ca2+ signaling pathway. Intestinal cells express an outwardly rectifying Ca2+ (ORCa) current with biophysical properties resembling those of TRPM channels. Two TRPM homologues, GON-2 and GTL-1, are expressed in the intestine. Using deletion and severe loss-of-function alleles of the gtl-1 and gon-2 genes, we demonstrate here that GON-2 and GTL-1 are both required for maintaining rhythmic pBoc and intestinal Ca2+ oscillations. Loss of GTL-l and GON-2 function inhibits IORCa ∼70% and ∼90%, respectively. IORCa is undetectable in gon-2;gtl-1 double mutant cells. These results demonstrate that (a) both gon-2 and gtl-1 are required for ORCa channel function, and (b) GON-2 and GTL-1 can function independently as ion channels, but that their functions in mediating IORCa are interdependent. IORCa, IGON-2, and IGTL-1 have nearly identical biophysical properties. Importantly, all three channels are at least 60-fold more permeable to Ca2+ than Na+. Epistasis analysis suggests that GON-2 and GTL-1 function in the IP3 signaling pathway to regulate intestinal Ca2+ oscillations. We postulate that GON-2 and GTL-1 form heteromeric ORCa channels that mediate selective Ca2+ influx and function to regulate IP3 receptor activity and possibly to refill ER Ca2+ stores.
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Affiliation(s)
- Juan Xing
- Department of Anesthesiology, Vanderbilt University Medical Center,Nashville, TN 37232, USA
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