101
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Affiliation(s)
- Amy L Firth
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0725, USA.
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102
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Boittin FX, Gribi F, Serir K, Bény JL. Ca2+-independent PLA2 controls endothelial store-operated Ca2+ entry and vascular tone in intact aorta. Am J Physiol Heart Circ Physiol 2008; 295:H2466-74. [PMID: 18952717 DOI: 10.1152/ajpheart.00639.2008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During an agonist stimulation of endothelial cells, the sustained Ca2+ entry occurring through store-operated channels has been shown to significantly contribute to smooth muscle relaxation through the release of relaxing factors such as nitric oxide (NO). However, the mechanisms linking Ca2+ stores depletion to the opening of such channels are still elusive. We have used Ca2+ and tension measurements in intact aortic strips to investigate the role of the Ca2+-independent isoform of phospholipase A2 (iPLA2) in endothelial store-operated Ca2+ entry and endothelium-dependent relaxation of smooth muscle. We provide evidence that iPLA2 is involved in the activation of endothelial store-operated Ca2+ entry when Ca2+ stores are artificially depleted. We also show that the sustained store-operated Ca2+ entry occurring during physiological stimulation of endothelial cells with the circulating hormone ATP is due to iPLA2 activation and significantly contributes to the amplitude and duration of ATP-induced endothelium-dependent relaxation. Consistently, both iPLA2 metabolites arachidonic acid and lysophosphatidylcholine were found to stimulate Ca2+ entry in native endothelial cells. However, only the latter triggered endothelium-dependent relaxation through NO release, suggesting that lysophosphatidylcholine produced by iPLA2 upon Ca2+ stores depletion may act as an intracellular messenger that stimulates store-operated Ca2+ entry and subsequent NO production in endothelial cells. Finally, we found that ACh-induced endothelium relaxation also depends on iPLA2 activation, suggesting that the iPLA2-dependent control of endothelial store-operated Ca2+ entry is a key physiological mechanism regulating arterial tone.
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Affiliation(s)
- François-Xavier Boittin
- Department of Zoology and Animal Biology, Laboratory of Vascular Cell Physiology, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
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103
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Moon SH, Jenkins CM, Mancuso DJ, Turk J, Gross RW. Smooth muscle cell arachidonic acid release, migration, and proliferation are markedly attenuated in mice null for calcium-independent phospholipase A2beta. J Biol Chem 2008; 283:33975-87. [PMID: 18927078 DOI: 10.1074/jbc.m805817200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pharmacologic evidence suggests that the lipid products generated by one or more calcium-independent phospholipases A(2) (iPLA(2)s) participate in the regulation of vascular tone through smooth muscle cell (SMC) Ca(2+) signaling and the release of arachidonic acid. However, the recent identification of new members of the iPLA(2) family, each inhibitable by (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one, has rendered definitive identification of the specific enzyme(s) mediating these processes difficult. Accordingly, we used iPLA(2)beta(-/-) mice to demonstrate that iPLA(2)beta is responsible for the majority of thapsigargin and ionophore (A23187)-induced arachidonic acid release from SMCs. Both thapsigargin and A23187 stimulated robust [(3)H]arachidonate (AA) release from wild-type aortic SMCs that was dramatically attenuated in iPLA(2)beta(-/-) mice (>80% reduction at 5 min; p < 0.01). Moreover, iPLA(2)beta(-/-) mice displayed defects in SMC Ca(2+) homeostasis and decreased SMC migration and proliferation in a model of vascular injury. Ca(2+)-store depletion resulted in the rapid entry of external Ca(2+) into wild-type aortic SMCs that was significantly slower in iPLA(2)beta-null cells (p < 0.01). Furthermore, SMCs from iPLA(2)beta-null mesenteric arterial explants demonstrated decreased proliferation and migration. The defects in migration and proliferation in iPLA(2)beta-null SMCs were restored by 2 mum AA. Remarkably, the cyclooxygenase-2-specific inhibitor, NS-398, prevented AA-induced rescue of SMC migration and proliferation in iPLA(2)beta(-/-) mice. Moreover, PGE(2) alone rescued proliferation and migration in iPLA(2)beta(-/-) mice. We conclude that iPLA(2)beta is an important mediator of AA release and prostaglandin E(2) production in SMCs, modulating vascular tone, cellular signaling, proliferation, and migration.
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Affiliation(s)
- Sung Ho Moon
- Division of Bioorganic Chemistry and Molecular Pharmacology, Endocrinology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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104
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Harper MT, Sage SO. Is calcium-independent phospholipase A2 required for store-operated calcium entry in human platelets? J Thromb Haemost 2008; 6:1819-21. [PMID: 18680539 DOI: 10.1111/j.1538-7836.2008.03113.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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105
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Li J, Sukumar P, Milligan CJ, Kumar B, Ma ZY, Munsch CM, Jiang LH, Porter KE, Beech DJ. Interactions, functions, and independence of plasma membrane STIM1 and TRPC1 in vascular smooth muscle cells. Circ Res 2008; 103:e97-104. [PMID: 18802022 DOI: 10.1161/circresaha.108.182931] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Stromal interaction molecule 1 (STIM1) is a predicted single membrane-spanning protein involved in store-operated calcium entry and interacting with ion channels including TRPC1. Here, we focus on endogenous STIM1 of modulated vascular smooth muscle cells, which exhibited a nonselective cationic current in response to store depletion despite strong buffering of intracellular calcium at the physiological concentration. STIM1 mRNA and protein were detected and suppressed by specific short interfering RNA. Calcium entry evoked by store depletion was partially inhibited by STIM1 short interfering RNA, whereas calcium release was unaffected. STIM1 short interfering RNA suppressed cell migration but not proliferation. Antibody that specifically bound STIM1 revealed constitutive extracellular N terminus of STIM1 and extracellular application of the antibody caused fast inhibition of the current evoked by store depletion. The antibody also inhibited calcium entry and cell migration but not proliferation. STIM1 interacted with TRPC1, and TRPC1 contributed partially to calcium entry and cationic current. However, the underlying processes could not be explained only by a STIM1-TRPC1 partnership because extracellular TRPC1 antibody suppressed cationic current only in a fraction of cells, TRPC1-containing channels were important for cell proliferation as well as migration, and cell surface localization studies revealed TRPC1 alone, as well as with STIM1. The data suggest a complex situation in which there is not only plasma membrane-spanning STIM1 that is important for cell migration and TRPC1-independent store-operated cationic current but also TRPC1-STIM1 interaction, a TRPC1-dependent component of store-operated current, and STIM1-independent TRPC1 linked to cell proliferation.
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Affiliation(s)
- Jing Li
- Multidisciplinary Cardiovascular Research Centre, Faculty of Biological Sciences, University of Leeds, United Kingdom
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106
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Gwozdz T, Dutko-Gwozdz J, Zarayskiy V, Peter K, Bolotina VM. How strict is the correlation between STIM1 and Orai1 expression, puncta formation, and ICRAC activation? Am J Physiol Cell Physiol 2008; 295:C1133-40. [PMID: 18768920 DOI: 10.1152/ajpcell.00306.2008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Stromal interaction molecule 1 (STIM1) and Orai1 have been identified as crucial elements of the store-operated Ca(2+) entry (SOCE) pathway, but the mechanism of their functional interaction remains controversial. It is now well established that, upon depletion of the stores, both molecules can accumulate and colocalize in specific areas (puncta) where the endoplasmic reticulum comes in close proximity to the plasma membrane. Some models propose a direct interaction between STIM1 and Orai1 as the most straightforward mechanism for signal transduction from the stores to the plasma membrane. To test some of the predictions of a conformational coupling model, we assessed how tight the relationships are between STIM1 and Orai1 expression, puncta formation, and SOCE activation. Here we present evidence that STIM1 accumulates in puncta equally well in the presence or absence of Orai1 expression, that STIM1 accumulation is not sufficient for Orai1 accumulation in the same areas, and that normal Ca(2+) release-activated Ca(2+) current (I(CRAC)) can be activated in STIM1-deficient cells. These data challenge the idea of direct conformational coupling between STIM1 and Orai1 as a viable mechanism of puncta formation and SOCE activation and uncover greater complexity in their relationship, which may require additional intermediate elements.
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Affiliation(s)
- Tomasz Gwozdz
- Ion Channel and Calcium Signaling Unit, Dept. of Medicine, Boston Univ. School of Medicine, 650 Albany St., X-704, Boston, MA, 02118, USA
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107
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Guibert C, Ducret T, Savineau JP. Voltage-independent calcium influx in smooth muscle. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 98:10-23. [DOI: 10.1016/j.pbiomolbio.2008.05.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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108
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Siddiqui RA, Harvey KA, Zaloga GP. Modulation of enzymatic activities by n-3 polyunsaturated fatty acids to support cardiovascular health. J Nutr Biochem 2008; 19:417-37. [PMID: 17904342 DOI: 10.1016/j.jnutbio.2007.07.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Revised: 06/14/2007] [Accepted: 07/03/2007] [Indexed: 12/13/2022]
Abstract
Epidemiological evidence from Greenland Eskimos and Japanese fishing villages suggests that eating fish oil and marine animals can prevent coronary heart disease. Dietary studies from various laboratories have similarly indicated that regular fish oil intake affects several humoral and cellular factors involved in atherogenesis and may prevent atherosclerosis, arrhythmia, thrombosis, cardiac hypertrophy and sudden cardiac death. The beneficial effects of fish oil are attributed to their n-3 polyunsaturated fatty acid (PUFA; also known as omega-3 fatty acids) content, particularly eicosapentaenoic acid (EPA; 20:5, n-3) and docosahexaenoic acid (DHA; 22:6, n-3). Dietary supplementation of DHA and EPA influences the fatty acid composition of plasma phospholipids that, in turn, may affect cardiac cell functions in vivo. Recent studies have demonstrated that long-chain omega-3 fatty acids may exert beneficial effects by affecting a wide variety of cellular signaling mechanisms. Pathways involved in calcium homeostasis in the heart may be of particular importance. L-type calcium channels, the Na+-Ca2+ exchanger and mobilization of calcium from intracellular stores are the most obvious key signaling pathways affecting the cardiovascular system; however, recent studies now suggest that other signaling pathways involving activation of phospholipases, synthesis of eicosanoids, regulation of receptor-associated enzymes and protein kinases also play very important roles in mediating n-3 PUFA effects on cardiovascular health. This review is therefore focused on the molecular targets and signaling pathways that are regulated by n-3 PUFAs in relation to their cardioprotective effects.
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Affiliation(s)
- Rafat A Siddiqui
- Cellular Biochemistry Laboratory, Methodist Research Institute, Clarian Health, Indianapolis, IN 46202, USA.
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109
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Bréchard S, Tschirhart EJ. Regulation of superoxide production in neutrophils: role of calcium influx. J Leukoc Biol 2008; 84:1223-37. [PMID: 18519744 PMCID: PMC2567897 DOI: 10.1189/jlb.0807553] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Upon stimulation, activation of NADPH oxidase complexes in neutrophils produces a burst of superoxide anions contributing to oxidative stress and the development of inflammatory process. Store-operated calcium entry (SOCE), whereby the depletion of intracellular stores induces extracellular calcium influx, is known to be a crucial element of NADPH oxidase regulation. However, the mechanistic basis mediating SOCE is still only partially understood, as is the signal-coupling pathway leading to modulation of store-operated channels. This review emphasizes the role of calcium influx in the control of the NADPH oxidase and summarizes the current knowledge of pathways mediating this extracellular calcium entry in neutrophils. Such investigations into the cross-talk between NADPH oxidase and calcium might allow the identification of novel pharmacological targets with clinical use, particularly in inflammatory diseases.
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Affiliation(s)
- Sabrina Bréchard
- Life Sciences Research Unit, University of Luxembourg, Luxembourg.
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110
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New developments in the signaling mechanisms of the store-operated calcium entry pathway. Pflugers Arch 2008; 457:405-15. [PMID: 18536932 DOI: 10.1007/s00424-008-0533-2] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Accepted: 05/15/2008] [Indexed: 01/09/2023]
Abstract
The most ubiquitous pathway for regulated calcium (Ca(2+)) entry into the cells is the store-operated Ca(2+) (SOC) entry pathway (also called capacitative Ca(2+) entry) that is conserved from lower organisms such as yeast, worms, and flies to man. The SOC concept was proposed over two decades ago, and SOC channels are defined by their activation in response to depletion of the internal Ca(2+) stores. Influx through SOC channels is necessary for the replenishment of the Ca(2+) stores and is also involved in cell signaling to the nucleus. Despite intensive investigations, most of which are focusing on transient receptor potential (TRP) channels as molecular candidates for SOC channels, the mechanisms of activation and the identity of the key molecular players participating in this signaling pathway have long remained elusive. In the last 2-3 years, however, the improvements of RNA silencing protocols combined with high throughput platforms have yielded significant breakthroughs, with the identification of Stim1 as the Ca(2+) store sensor and Orai1 (CRACM1) as the pore-forming subunit of the archetypical SOC channel, CRAC. This review summarizes the recent advances in the mechanisms of activation of SOC channels and their molecular composition, with emphasis on the roles of Stim, Orai, and TRP proteins.
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111
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Rericha EC, Parent CA. Steering in quadruplet: the complex signaling pathways directing chemotaxis. Sci Signal 2008; 1:pe26. [PMID: 18523238 DOI: 10.1126/scisignal.122pe26] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Studies in the social amoeba Dictyostelium discoideum reveal that signaling cascades coordinating chemotactic directional sensing and migration are complex, with redundant pathways emerging as cells differentiate. Lack of accumulation of the leading-edge marker phosphatidylinositol-3,4,5-trisphosphate can be compensated by a pathway containing phospholipase A2 (PLA2) in early developed cells and guanylyl cyclase (GC) in later developed, polarized cells. Because numerous signaling networks operational during Dictyostelium chemotaxis are conserved in mammalian cells, PLA2 and GC pathways may also be effective in higher eukaryotes, providing avenues for future research.
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Affiliation(s)
- Erin C Rericha
- Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA
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112
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Smani T, Patel T, Bolotina VM. Complex regulation of store-operated Ca2+entry pathway by PKC-ε in vascular SMCs. Am J Physiol Cell Physiol 2008; 294:C1499-508. [DOI: 10.1152/ajpcell.00365.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The role of PKC in the regulation of store-operated Ca2+entry (SOCE) is rather controversial. Here, we used Ca2+-imaging, biochemical, pharmacological, and molecular techniques to test if Ca2+-independent PLA2β (iPLA2β), one of the transducers of the signal from depleted stores to plasma membrane channels, may be a target for the complex regulation of SOCE by PKC and diacylglycerol (DAG) in rabbit aortic smooth muscle cells (SMCs). We found that the inhibition of PKC with chelerythrine resulted in significant inhibition of thapsigargin (TG)-induced SOCE in proliferating SMCs. Activation of PKC by the diacylglycerol analog 1-oleoyl-2-acetyl- sn-glycerol (OAG) caused a significant depletion of intracellular Ca2+stores and triggered Ca2+influx that was similar to TG-induced SOCE. OAG and TG both produced a PKC-dependent activation of iPLA2β and Ca2+entry that were absent in SMCs in which iPLA2β was inhibited by a specific chiral enantiomer of bromoenol lactone ( S-BEL). Moreover, we found that PKC regulates TG- and OAG-induced Ca2+entry only in proliferating SMCs, which correlates with the expression of the specific PKC-ε isoform. Molecular downregulation of PKC-ε impaired TG- and OAG-induced Ca2+influx in proliferating SMCs but had no effect in confluent SMCs. Our results demonstrate that DAG (or OAG) can affect SOCE via multiple mechanisms, which may involve the depletion of Ca2+stores as well as direct PKC-ε-dependent activation of iPLA2β, resulting in a complex regulation of SOCE in proliferating and confluent SMCs.
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113
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Abstract
The mechanism of store-operated Ca(2+) entry (SOCE) remains one of the intriguing mysteries in the field of Ca(2+) signalling. Recent discoveries have resulted in the molecular identification of STIM1 as a Ca(2+) sensor in endoplasmic reticulum, Orai1 (CRACM1) as a plasma membrane channel that is activated by the store-operated pathway, and iPLA(2)beta as an essential component of signal transduction from the stores to the plasma membrane channels. Numerous studies have confirmed that molecular knock-down of any one of these three molecules impair SOCE in a wide variety of cell types, but their mutual relations are far from being understood. This report will focus on the functional roles of Orai1, STIM1 and iPLA(2)beta, and will address some specific questions about Orai1 and TRPC1, and their relation to SOC channels in excitable and non-excitable cells. Also, it will analyse the novel role of STIM1 as a trigger for CIF production, and the complex relationship between STIM1 and Orai1 expression, puncta formation and SOCE activation. It will highlight some of the most recent findings that may challenge simple conformational coupling models of SOCE, and will offer some new perspectives on the complex relationships between Orai1, STIM1 and iPLA(2)beta in the SOCE pathway.
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Affiliation(s)
- Victoria M Bolotina
- Ion Channel and Calcium Signaling Unit, Department of Medicine, Boston University School of Medicine, 650 Albany Street, X-704, Boston, MA 02118, USA.
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114
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Lu W, Wang J, Shimoda LA, Sylvester JT. Differences in STIM1 and TRPC expression in proximal and distal pulmonary arterial smooth muscle are associated with differences in Ca2+ responses to hypoxia. Am J Physiol Lung Cell Mol Physiol 2008; 295:L104-13. [PMID: 18424621 DOI: 10.1152/ajplung.00058.2008] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxic pulmonary vasoconstriction (HPV) requires Ca(2+) influx through store-operated Ca(2+) channels (SOCC) in pulmonary arterial smooth muscle cells (PASMC) and is greater in distal than proximal pulmonary arteries (PA). SOCC may be composed of canonical transient receptor potential (TRPC) proteins and activated by stromal interacting molecule 1 (STIM1). To assess the possibility that HPV is greater in distal PA because store-operated Ca(2+) entry (SOCE) is greater in distal PASMC, we measured intracellular Ca(2+) concentration ([Ca(2+)](i)) and SOCE in primary cultures of PASMC using fluorescent microscopy and the Ca(2+)-sensitive dye fura 2. Both hypoxia (4% O(2)) and KCl (60 mM) increased [Ca(2+)](i). Responses to hypoxia, but not KCl, were greater in distal cells. We measured SOCE in PASMC perfused with Ca(2+)-free solutions containing cyclopiazonic acid to deplete Ca(2+) stores in sarcoplasmic reticulum and nifedipine to prevent Ca(2+) entry through L-type voltage-operated Ca(2+) channels. Under these conditions, the increase in [Ca(2+)](i) caused by restoration of extracellular Ca(2+) and the decrease in fura 2 fluorescence caused by Mn(2+) were greater in distal PASMC, indicating greater SOCE. Moreover, the increase in SOCE caused by hypoxia was also greater in distal cells. Real-time quantitative polymerase chain reaction analysis of PASMC and freshly isolated deendothelialized PA tissue demonstrated expression of STIM1 and five of seven known TRPC isoforms (TRPC1 > TRPC6 > TRPC4 >> TRPC3 approximately TRPC5). For both protein, as measured by Western blotting, and mRNA, expression of STIM1, TRPC1, TRPC6, and TRPC4 was greater in distal than proximal PASMC and PA. These results provide further support for the importance of SOCE in HPV and suggest that HPV is greater in distal than proximal PA because greater numbers and activation of SOCC in distal PASMC generate bigger increases in [Ca(2+)](i).
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Affiliation(s)
- Wenju Lu
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins School of Medicine, Baltimore, Maryland 21224, USA
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115
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Ueda H. Peripheral mechanisms of neuropathic pain - involvement of lysophosphatidic acid receptor-mediated demyelination. Mol Pain 2008; 4:11. [PMID: 18377664 PMCID: PMC2365930 DOI: 10.1186/1744-8069-4-11] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Accepted: 04/01/2008] [Indexed: 01/23/2023] Open
Abstract
Recent advances in pain research provide a clear picture for the molecular mechanisms of acute pain; substantial information concerning plasticity that occurs during neuropathic pain has also become available. The peripheral mechanisms responsible for neuropathic pain are found in the altered gene/protein expression of primary sensory neurons. With damage to peripheral sensory fibers, a variety of changes in pain-related gene expression take place in dorsal root ganglion neurons. These changes, or plasticity, might underlie unique neuropathic pain-specific phenotype modifications - decreased unmyelinated-fiber functions, but increased myelinated A-fiber functions. Another characteristic change is observed in allodynia, the functional change of tactile to nociceptive perception. Throughout a series of studies, using novel nociceptive tests to characterize sensory-fiber or pain modality-specific nociceptive behaviors, it was demonstrated that communication between innocuous and noxious sensory fibers might play a role in allodynia mechanisms. Because neuropathic pain in peripheral and central demyelinating diseases develops as a result of aberrant myelination in experimental animals, demyelination seems to be a key mechanism of plasticity in neuropathic pain. More recently, we discovered that lysophosphatidic acid receptor activation initiates neuropathic pain, as well as possible peripheral mechanism of demyelination after nerve injury. These results lead to further hypotheses of physical communication between innocuous Abeta- and noxious C- or Adelta-fibers to influence the molecular mechanisms of allodynia.
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Affiliation(s)
- Hiroshi Ueda
- Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
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116
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Saleh SN, Albert AP, Peppiatt-Wildman CM, Large WA. Diverse properties of store-operated TRPC channels activated by protein kinase C in vascular myocytes. J Physiol 2008; 586:2463-76. [PMID: 18356201 DOI: 10.1113/jphysiol.2008.152157] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In vascular smooth muscle, store-operated channels (SOCs) contribute to many physiological functions including vasoconstriction and cell growth and proliferation. In the present work we compared the properties of SOCs in freshly dispersed myocytes from rabbit coronary and mesenteric arteries and portal vein. Cyclopiazonic acid (CPA)-induced whole-cell SOC currents were sixfold greater at negative membrane potentials and displayed markedly different rectification properties and reversal potentials in coronary compared to mesenteric artery myocytes. Single channel studies showed that endothelin-1, CPA and the cell-permeant Ca(2+) chelator BAPTA-AM activated the same 2.6 pS SOC in coronary artery. In 1.5 mM [Ca(2+)](o) the unitary conductance of SOCs was significantly greater in coronary than in mesenteric artery. Moreover in 0 mM [Ca(2+)](o) the conductance of SOCs in coronary artery was unaltered whereas the conductance of SOCs in mesenteric artery was increased fourfold. In coronary artery SOCs were inhibited by the protein kinase C (PKC) inhibitor chelerythrine and activated by the phorbol ester phorbol 12,13-dibutyrate (PDBu), the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) and a catalytic subunit of PKC. These data infer an important role for PKC in activation of SOCs in coronary artery similar to mesenteric artery and portal vein. Anti-TRPC1 and -TRPC5 antibodies inhibited SOCs in coronary and mesenteric arteries and portal vein but anti-TRPC6 blocked SOCs only in coronary artery and anti-TRPC7 blocked SOCs only in portal vein. Immunoprecipitation showed associations between TRPC1 and TRPC5 in all preparations but between TRPC5 and TRPC6 only in coronary artery and between TRPC5 and TRPC7 only in portal vein. Finally, flufenamic acid increased SOC activity in coronary artery but inhibited SOCs in mesenteric artery and portal vein myocytes. These data provide strong evidence that vascular myocytes express diverse SOC isoforms, which are likely to be composed of different TRPC proteins and have different physiological functions.
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Affiliation(s)
- Sohag N Saleh
- Ion Channels and Cell Signalling Research Centre, Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London SW17 0RE, UK
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117
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Csutora P, Peter K, Kilic H, Park KM, Zarayskiy V, Gwozdz T, Bolotina VM. Novel role for STIM1 as a trigger for calcium influx factor production. J Biol Chem 2008; 283:14524-31. [PMID: 18337241 DOI: 10.1074/jbc.m709575200] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
STIM1 has been recently identified as a Ca(2+) sensor in endoplasmic reticulum (ER) and an initiator of the store-operated Ca(2+) entry (SOCE) pathway, but the mechanism of SOCE activation remains controversial. Here we focus on the early ER-delimited steps of the SOCE pathway and demonstrate that STIM1 is critically involved in initiating of production of calcium influx factor (CIF), a diffusible messenger that can deliver the signal from the stores to plasma membrane and activate SOCE. We discovered that CIF production is tightly coupled with STIM1 expression and requires functional integrity of its intraluminal sterile alpha-motif (SAM) domain. We demonstrate that 1) molecular knockdown or overexpression of STIM1 results in corresponding impairment or amplification of CIF production and 2) inherent deficiency in the ER-delimited CIF production and SOCE activation in some cell types can be a result of their deficiency in STIM1 protein; expression of a wild-type STIM1 in such cells was sufficient to fully rescue their ability to produce CIF and SOCE. We found that glycosylation sites in the ER-resident SAM domain of STIM1 are essential for initiation of CIF production. We propose that after STIM1 loses Ca(2+) from EF hand, its intraluminal SAM domain may change conformation, and via glycosylation sites it can interact with and activate CIF-producing machinery. Thus, CIF production appears to be one of the earliest STIM1-dependent events in the ER lumen, and impairment of this process results in impaired SOCE response.
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Affiliation(s)
- Peter Csutora
- Boston University School of Medicine, Boston, MA 02118, USA
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118
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Park KM, Trucillo M, Serban N, Cohen RA, Bolotina VM. Role of iPLA2 and store-operated channels in agonist-induced Ca2+ influx and constriction in cerebral, mesenteric, and carotid arteries. Am J Physiol Heart Circ Physiol 2008; 294:H1183-7. [DOI: 10.1152/ajpheart.01148.2007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Store-operated channels (SOC) and store-operated Ca2+ entry are known to play a major role in agonist-induced constriction of smooth muscle cells (SMC) in conduit vessels. In microvessels the role of SOC remains uncertain, in as much as voltage-gated L-type Ca2+ (CaL2+) channels are thought to be fully responsible for agonist-induced Ca2+ influx and vasoconstriction. We present evidence that SOC and their activation via a Ca2+-independent phospholipase A2 (iPLA2)-mediated pathway play a crucial role in agonist-induced constriction of cerebral, mesenteric, and carotid arteries. Intracellular Ca2+ in SMC and intraluminal diameter were measured simultaneously in intact pressurized vessels in vitro. We demonstrated that 1) Ca2+ and contractile responses to phenylephrine (PE) in cerebral and carotid arteries were equally abolished by nimodipine (a CaL2+ inhibitor) and 2-aminoethyl diphenylborinate (an inhibitor of SOC), suggesting that SOC and CaL2+ channels may be involved in agonist-induced constriction of cerebral arteries, and 2) functional inhibition of iPLA2β totally inhibited PE-induced Ca2+ influx and constriction in cerebral, mesenteric, and carotid arteries, whereas K+-induced Ca2+ influx and vasoconstriction mediated by CaL2+ channels were not affected. Thus iPLA2-dependent activation of SOC is crucial for agonist-induced Ca2+ influx and vasoconstriction in cerebral, mesenteric, and carotid arteries. We propose that, on PE-induced depletion of Ca2+ stores, nonselective SOC are activated via an iPLA2-dependent pathway and may produce a depolarization of SMC, which could trigger a secondary activation of CaL2+ channels and lead to Ca2+ entry and vasoconstriction.
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119
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Bao S, Jacobson DA, Wohltmann M, Bohrer A, Jin W, Philipson LH, Turk J. Glucose homeostasis, insulin secretion, and islet phospholipids in mice that overexpress iPLA2beta in pancreatic beta-cells and in iPLA2beta-null mice. Am J Physiol Endocrinol Metab 2008; 294:E217-29. [PMID: 17895289 PMCID: PMC2268609 DOI: 10.1152/ajpendo.00474.2007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Studies with genetically modified insulinoma cells suggest that group VIA phospholipase A(2) (iPLA(2)beta) participates in amplifying glucose-induced insulin secretion. INS-1 insulinoma cells that overexpress iPLA(2)beta, for example, exhibit amplified insulin-secretory responses to glucose and cAMP-elevating agents. To determine whether similar effects occur in whole animals, we prepared transgenic (TG) mice in which the rat insulin 1 promoter (RIP) drives iPLA(2)beta overexpression, and two characterized TG mouse lines exhibit similar phenotypes. Their pancreatic islet iPLA(2)beta expression is increased severalfold, as reflected by quantitative PCR of iPLA(2)beta mRNA, immunoblotting of iPLA(2)beta protein, and iPLA(2)beta enzymatic activity. Immunofluorescence microscopic studies of pancreatic sections confirm iPLA(2)beta overexpression in RIP-iPLA(2)beta-TG islet beta-cells without obviously perturbed islet morphology. Male RIP-iPLA(2)beta-TG mice exhibit lower blood glucose and higher plasma insulin concentrations than wild-type (WT) mice when fasting and develop lower blood glucose levels in glucose tolerance tests, but WT and TG blood glucose levels do not differ in insulin tolerance tests. Islets from male RIP-iPLA(2)beta-TG mice exhibit greater amplification of glucose-induced insulin secretion by a cAMP-elevating agent than WT islets. In contrast, islets from male iPLA(2)beta-null mice exhibit blunted insulin secretion, and those mice have impaired glucose tolerance. Arachidonate incorporation into and the phospholipid composition of RIP-iPLA(2)beta-TG islets are normal, but they exhibit reduced Kv2.1 delayed rectifier current and prolonged glucose-induced action potentials and elevations of cytosolic Ca(2+) concentration that suggest a molecular mechanism for the physiological role of iPLA(2)beta to amplify insulin secretion.
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MESH Headings
- Animals
- Arachidonic Acid/metabolism
- Blood Glucose/metabolism
- Blood Glucose/physiology
- Blotting, Western
- Calcium/physiology
- Cell Line, Tumor
- DNA, Complementary/biosynthesis
- DNA, Complementary/genetics
- Fasting/metabolism
- Gene Expression Regulation, Enzymologic/physiology
- Genotype
- Glucose Tolerance Test
- Group IV Phospholipases A2/biosynthesis
- Group IV Phospholipases A2/genetics
- Homeodomain Proteins/genetics
- Homeostasis/physiology
- Insulin/blood
- Insulin/metabolism
- Insulin Secretion
- Insulin-Secreting Cells/metabolism
- Insulinoma/metabolism
- Islets of Langerhans/metabolism
- Kv1.2 Potassium Channel/metabolism
- Mice
- Mice, Knockout
- Mice, Transgenic
- Microscopy, Fluorescence
- Pancreatic Neoplasms/metabolism
- Patch-Clamp Techniques
- Phospholipids/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Spectrometry, Mass, Electrospray Ionization
- Trans-Activators/genetics
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Affiliation(s)
- Shunzhong Bao
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
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120
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Tai K, Hamaide MC, Debaix H, Gailly P, Wibo M, Morel N. Agonist-evoked calcium entry in vascular smooth muscle cells requires IP3 receptor-mediated activation of TRPC1. Eur J Pharmacol 2008; 583:135-47. [PMID: 18289524 DOI: 10.1016/j.ejphar.2008.01.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Revised: 12/17/2007] [Accepted: 01/14/2008] [Indexed: 11/27/2022]
Abstract
Transient receptor potential canonical (TRPC) proteins have been proposed to function as plasma membrane Ca2+ channels activated by store depletion and/or by receptor stimulation. However, their role in the increase in cytosolic Ca2+ activated by contractile agonists in vascular smooth muscle is not yet elucidated. The present study was designed to investigate the functional and molecular properties of the Ca2+ entry pathway activated by endothelin-1 in primary cultured aortic smooth muscle cells. Measurement of the Ca2+ signal in fura-2-loaded cells allowed to characterize endothelin-1-evoked Ca2+ entry, which was resistant to dihydropyridine, and was blocked by 2-aminoethoxydiphenylborate (2-APB) and micromolar concentration of Gd3+. It was not activated by store depletion, but was inhibited by the endothelin ETA receptor antagonist BQ-123, and by heparin. On the opposite, thapsigargin-induced store depletion activated a Ca2+ entry pathway that was not affected by 2-APB, BQ-123 or heparin, and was less sensitive to Gd3+ than was endothelin-1-evoked Ca2+ entry. Investigation of the gene expression of TRPC isoforms by real-time RT-PCR revealed that TRPC1 was the most abundant. In cells transfected with TRPC1 small interfering RNA sequence, TRPC1 mRNA and protein expression were decreased by 72+/-3% and 86+/-2%, respectively, while TRPC6 expression was unaffected. In TRPC1 knockdown cells, both endothelin-1-evoked Ca2+ entry and store-operated Ca2+ entry evoked by thapsigargin were blunted. These results indicate that in aortic smooth muscle cells, TRPC1 is not only involved in Ca2+ entry activated by store depletion but also in receptor-operated Ca2+ entry, which requires inositol (1,4,5) triphosphate receptor activation.
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Affiliation(s)
- Khalid Tai
- Unit of Cellular Physiology, Université Catholique de Louvain, Bruxelles, Belgium
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121
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Kuehn HS, Beaven MA, Ma HT, Kim MS, Metcalfe DD, Gilfillan AM. Synergistic activation of phospholipases Cgamma and Cbeta: a novel mechanism for PI3K-independent enhancement of FcepsilonRI-induced mast cell mediator release. Cell Signal 2008; 20:625-36. [PMID: 18207701 DOI: 10.1016/j.cellsig.2007.11.016] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 11/19/2007] [Accepted: 11/20/2007] [Indexed: 10/24/2022]
Abstract
Antigen/IgE-mediated mast cell activation via FcvarepsilonRI can be markedly enhanced by the activation of other receptors expressed on mast cells and these receptors may thus contribute to the allergic response in vivo. One such receptor family is the G protein-coupled receptors (GPCRs). Although the signaling cascade linking FcvarepsilonRI aggregation to mast cell activation has been extensively investigated, the mechanisms by which GPCRs amplify this response are relatively unknown. To investigate this, we utilized prostaglandin (PG)E2 based on initial studies demonstrating its greater ability to augment antigen-mediated degranulation in mouse mast cells than other GPCR agonists examined. This enhancement, and the ability of PGE2 to amplify antigen-induced calcium mobilization, was independent of phosphoinositide 3-kinase but was linked to a pertussis toxin-sensitive synergistic translocation to the membrane of phospholipase (PL)Cgamma and PLCbeta and to an enhancement of PLCgamma phosphorylation. This "trans-synergistic" activation of PLCbeta and gamma, in turn, enhanced production of inositol 1,4,5-trisphosphate, store-operated calcium entry, and activation of protein kinase C (PKC) (alpha and beta). These responses were critical for the promotion of degranulation. This is the first report of synergistic activation between PLCgamma and PLCbeta that permits reinforcement of signals for degranulation in mast cells.
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Affiliation(s)
- Hye Sun Kuehn
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 10 Center Drive MSC 1881, Bethesda, MD 20892-1881, USA
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122
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Muik M, Frischauf I, Derler I, Fahrner M, Bergsmann J, Eder P, Schindl R, Hesch C, Polzinger B, Fritsch R, Kahr H, Madl J, Gruber H, Groschner K, Romanin C. Dynamic coupling of the putative coiled-coil domain of ORAI1 with STIM1 mediates ORAI1 channel activation. J Biol Chem 2008; 283:8014-22. [PMID: 18187424 DOI: 10.1074/jbc.m708898200] [Citation(s) in RCA: 332] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
STIM1 and ORAI1 (also termed CRACM1) are essential components of the classical calcium release-activated calcium current; however, the mechanism of the transmission of information of STIM1 to the calcium release-activated calcium/ORAI1 channel is as yet unknown. Here we demonstrate by Förster resonance energy transfer microscopy a dynamic coupling of STIM1 and ORAI1 that culminates in the activation of Ca(2+) entry. Förster resonance energy transfer imaging of living cells provided insight into the time dependence of crucial events of this signaling pathway comprising Ca(2+) store depletion, STIM1 multimerization, and STIM1-ORAI1 interaction. Accelerated store depletion allowed resolving a significant time lag between STIM1-STIM1 and STIM1-ORAI1 interactions. Store refilling reversed both STIM1 multimerization and STIM1-ORAI1 interaction. The cytosolic STIM1 C terminus itself was able, in vitro as well as in vivo, to associate with ORAI1 and to stimulate channel function, yet without ORAI1-STIM1 cluster formation. The dynamic interaction occurred via the C terminus of ORAI1 that includes a putative coiled-coil domain structure. An ORAI1 C terminus deletion mutant as well as a mutant (L273S) with impeded coiled-coil domain formation lacked both interaction as well as functional communication with STIM1 and failed to generate Ca(2+) inward currents. An N-terminal deletion mutant of ORAI1 as well as the ORAI1 R91W mutant linked to severe combined immune deficiency syndrome was similarly impaired in terms of current activation despite being able to interact with STIM1. Hence, the C-terminal coiled-coil motif of ORAI1 represents a key domain for dynamic coupling to STIM1.
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Affiliation(s)
- Martin Muik
- Institute of Biophysics, University of Linz, A-4040 Linz, Austria
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123
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Harper AGS, Sage SO. A key role for reverse Na+/Ca2+ exchange influenced by the actin cytoskeleton in store-operated Ca2+ entry in human platelets: Evidence against the de novo conformational coupling hypothesis. Cell Calcium 2007; 42:606-17. [PMID: 17383000 DOI: 10.1016/j.ceca.2007.02.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Revised: 02/13/2007] [Accepted: 02/13/2007] [Indexed: 11/24/2022]
Abstract
We have previously demonstrated a role for the reorganization of the actin cytoskeleton in store-operated calcium entry (SOCE) in human platelets and interpreted this as evidence for a de novo conformational coupling step in SOCE activation involving the type II IP(3) receptor and the platelet hTRPC1-containing store-operated channel (SOC). Here, we present evidence challenging this model. The actin polymerization inhibitors cytochalasin D or latrunculin A significantly reduced Ca2+ but not Mn2+ or Na+ entry into thapsigargin (TG)-treated platelets. Jasplakinolide, which induces actin polymerization, also inhibited Ca2+ but not Mn2+ or Na+ entry. However, an anti-hTRPC1 antibody inhibited TG-evoked entry of all three cations, indicating that they all permeate an hTRPC1-containing store-operated channel (SOC). These results indicate that the reorganization of the actin cytoskeleton is not involved in SOC activation. The inhibitors of the Na+/Ca2+ exchanger (NCX), KB-R7943 or SN-6, caused a dose-dependent inhibition of Ca2+ but not Mn2+ or Na+ entry into TG-treated platelets. The effects of the NCX inhibitors were not additive with those of actin polymerization inhibitors, suggesting a common point of action. These results indicate a role for two Ca2+ permeable pathways activated following Ca2+ store depletion in human platelets: A Ca2+-permeable, hTRPC1-containing SOC and reverse Na+/Ca2+ exchange, which is activated following Na+ entry through the SOC and requires a functional actin cytoskeleton.
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Affiliation(s)
- Alan G S Harper
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
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124
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Ross K, Parker G, Whitaker M, Reynolds NJ. Inhibition of calcium-independent phospholipase A impairs agonist-induced calcium entry in keratinocytes. Br J Dermatol 2007; 158:31-7. [PMID: 18028502 PMCID: PMC2658711 DOI: 10.1111/j.1365-2133.2007.08298.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Background In many cells, depletion of intracellular calcium (Ca2+) reservoirs triggers Ca2+ entry through store-operated Ca2+ channels in the plasma membrane. However, the mechanisms of agonist-induced calcium entry (ACE) in keratinocytes are not fully understood. Objectives This study was designed to determine if pharmacological inhibition of calcium-independent phospholipase A (iPLA2) impairs ACE in normal human epidermal keratinocytes. Methods Confocal laser scanning microscopy was used to monitor the dynamics of Ca2+ signalling in keratinocytes loaded with the calcium-sensitive dye Fluo-4. Cells were stimulated with extracellular nucleotides [adenosine triphosphate (ATP) or uridine triphosphate (UTP)] or with lysophosphatidic acid (LPA), a bioactive lipid that regulates keratinocyte proliferation and differentiation. Results Both ATP and UTP induced Ca2+ release in primary human keratinocytes. This was not followed by robust Ca2+ influx when the experiments were performed in low Ca2+ (70 μmol L−1) medium. Upon elevation of extracellular Ca2+ to 1·2 mmol L−1, however, a biphasic response consisting of an initial Ca2+ peak followed by an elevated plateau was observed. The plateau phase was inhibited when cells were treated with bromoenol lactone, a specific pharmacological inhibitor of iPLA2. These findings indicate that iPLA2 activity is required for ACE in keratinocytes. LPA also evoked Ca2+ release in keratinocytes but failed to induce sustained Ca2+ entry even when extracellular Ca2+ was elevated to 1·2 mmol L−1. Conclusion Our results demonstrate for the first time an important role for iPLA2 in regulating ACE in primary human keratinocytes.
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Affiliation(s)
- K Ross
- Dermatological Sciences, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, U.K.
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125
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Poulsen KA, Pedersen SF, Kolko M, Lambert IH. Induction of group VIA phospholipase A2activity during in vitro ischemia in C2C12 myotubes is associated with changes in the level of its splice variants. Am J Physiol Cell Physiol 2007; 293:C1605-15. [PMID: 17804611 DOI: 10.1152/ajpcell.00012.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The involvement of group VI Ca2+-independent PLA2s (iPLA2-VI) in in vitro ischemia [oxygen and glucose deprivation (OGD)] in mouse C2C12 myotubes was investigated. OGD induced a time-dependent (0–6 h) increase in bromoenol lactone (BEL)-sensitive iPLA2activity, which was suppressed by specific short interfering (si)RNA knockdown of iPLA2-VIA. OGD was associated with an increase in iPLA2-VIA protein levels, whereas mRNA levels were unchanged. The levels of iPLA2-VIB mRNA and protein were not increased by OGD. RT-PCR and Western blot analysis identified a mouse iPLA2-VIA homolog to catalytically inactive 50-kDa iPLA2-VIA-ankyrin variants previously identified in humans. Both the mRNA and protein levels of this ∼50-kDa variant were reduced significantly within 1 h following OGD. In C2C12 myoblasts, iPLA2-VIA seemed to predominantly reside at the endoplasmatic reticulum, where it accumulated further during OGD. A time-dependent reduction in cell viability during the early OGD period (3 h) was partially prevented by iPLA2-VIA knockdown or pharmacological inhibition (10 μM BEL), whereas iPLA2-VIA overexpression had no effect on cell viability. Taken together, these data demonstrate that OGD in C2C12 myotubes is associated with an increase in iPLA2-VIA activity that decreases cell viability. iPLA2-VIA activation may be modulated by changes in the levels of active and inactive iPLA2-VIA isoforms.
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Affiliation(s)
- K A Poulsen
- Dept. of Molecular Biology, Univ. of Copenhagen, Universitetsparken 13, Copenhagen Ø DK-2100, Denmark.
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126
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Han MS, Park SY, Shinzawa K, Kim S, Chung KW, Lee JH, Kwon CH, Lee KW, Lee JH, Park CK, Chung WJ, Hwang JS, Yan JJ, Song DK, Tsujimoto Y, Lee MS. Lysophosphatidylcholine as a death effector in the lipoapoptosis of hepatocytes. J Lipid Res 2007; 49:84-97. [PMID: 17951222 DOI: 10.1194/jlr.m700184-jlr200] [Citation(s) in RCA: 178] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The pathogenesis of nonalcoholic steatohepatitis (NASH) is unclear, despite epidemiological data implicating FFAs. We studied the pathogenesis of NASH using lipoapoptosis models. Palmitic acid (PA) induced classical apoptosis of hepatocytes. PA-induced lipoapoptosis was inhibited by acyl-CoA synthetase inhibitor but not by ceramide synthesis inhibitors, suggesting that conversion products other than ceramide are involved. Phospholipase A(2) (PLA(2)) inhibitors blocked PA-induced hepatocyte death, suggesting an important role for PLA(2) and its product lysophosphatidylcholine (LPC). Small interfering RNA for Ca(2+)-independent phospholipase A(2) (iPLA(2)) inhibited the lipoapoptosis of hepatocytes. PA increased LPC content, which was reversed by iPLA(2) inhibitors. Pertussis toxin or dominant-negative Galpha(i) mutant inhibited hepatocyte death by PA or LPC acting through G-protein-coupled receptor (GPCR)/Galpha(i). PA decreased cardiolipin content and induced mitochondrial potential loss and cytochrome c translocation. Oleic acid inhibited PA-induced hepatocyte death by diverting PA to triglyceride and decreasing LPC content, suggesting that FFAs lead to steatosis or lipoapoptosis according to the abundance of saturated/unsaturated FFAs. LPC administration induced hepatitis in vivo. LPC content was increased in the liver specimens from NASH patients. These results demonstrate that LPC is a death effector in the lipoapoptosis of hepatocytes and suggest potential therapeutic values of PLA(2) inhibitors or GPCR/Galpha(i) inhibitors in NASH.
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Affiliation(s)
- Myoung Sook Han
- Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea
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127
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Smani T, Domínguez-Rodríguez A, Hmadcha A, Calderón-Sánchez E, Horrillo-Ledesma A, Ordóñez A. Role of Ca2+-independent phospholipase A2 and store-operated pathway in urocortin-induced vasodilatation of rat coronary artery. Circ Res 2007; 101:1194-203. [PMID: 17885217 DOI: 10.1161/circresaha.107.159053] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Urocortin has been shown to produce vasodilatation in several arteries, but the precise mechanism of its action is still poorly understood. Here we demonstrate the role of store operated Ca2+ entry (SOCE) regulated by Ca2+-independent phospholipase A2 (iPLA2) in phenylephrine hydrochloride (PE)-induced vasoconstriction, and we present the first evidence that urocortin induces relaxation by the modulation of SOCE and iPLA2 in rat coronary artery. Urocortin produces an endothelium independent relaxation, and its effect is concentration-dependent (IC50 approximately = 4.5 nmol/L). We show in coronary smooth muscle cells (SMCs) that urocortin inhibits iPLA2 activation, a crucial step for SOC channel activation, and prevents Ca2+ influx evoked by the emptying of the stores via a cAMP and protein kinase A (PKA)-dependent mechanism. Lysophophatidylcholine and lysophosphatidylinositol, products of iPLA2, exactly mimic the effect of the depletion of the stores in presence of urocortin. Furthermore, we report that long treatment with urocortin downregulates iPLA2 mRNA and proteins expression in rat coronary smooth muscle cells. In summary, we propose a new mechanism of vasodilatation by urocortin which involves the regulation of iPLA2 and SOCE via the stimulation of a cAMP/PKA-dependent signal transduction cascade in rat coronary artery.
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Affiliation(s)
- Tarik Smani
- Laboratorio de Investigación Cardiovascular, Quirófanos Experimentales, Hospital General Universitario Virgen del Rocío, Avenida Manuel Siurot s/n, E-41013 Sevilla, Spain.
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128
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Leung FP, Yung LM, Yao X, Laher I, Huang Y. Store-operated calcium entry in vascular smooth muscle. Br J Pharmacol 2007; 153:846-57. [PMID: 17876304 PMCID: PMC2267267 DOI: 10.1038/sj.bjp.0707455] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In non-excitable cells, activation of G-protein-coupled phospholipase C (PLC)-linked receptors causes the release of Ca(2+) from intracellular stores, which is followed by transmembrane Ca(2+) entry. This Ca(2+) entry underlies a small and sustained phase of the cellular [Ca(2+)](i) increases and is important for several cellular functions including gene expression, secretion and cell proliferation. This form of transmembrane Ca(2+) entry is supported by agonist-activated Ca(2+)-permeable ion channels that are activated by store depletion and is referred to as store-operated Ca(2+) entry (SOCE) and represents a major pathway for agonist-induced Ca(2+) entry. In excitable cells such as smooth muscle cells, Ca(2+) entry mechanisms responsible for sustained cellular activation are normally considered to be mediated via either voltage-operated or receptor-operated Ca(2+) channels. Although SOCE occurs following agonist activation of smooth muscle, this was thought to be more important in replenishing Ca(2+) stores rather than acting as a source of activator Ca(2+) for the contractile process. This review summarizes our current knowledge of SOCE as a regulator of vascular smooth muscle tone and discusses its possible role in the cardiovascular function and disease. We propose a possible hypothesis for its activation and suggest that SOCE may represent a novel target for pharmacological therapeutic intervention.
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Affiliation(s)
- F P Leung
- Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong Hong Kong, China
- Department of Physiology, Chinese University of Hong Kong Hong Kong, China
| | - L M Yung
- Department of Physiology, Chinese University of Hong Kong Hong Kong, China
| | - X Yao
- Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong Hong Kong, China
- Department of Physiology, Chinese University of Hong Kong Hong Kong, China
- Institute of Vascular Medicine, Chinese University of Hong Kong Hong Kong, China
| | - I Laher
- Department of Pharmacology and Therapeutics, University of British Columbia Vancouver, Canada
| | - Y Huang
- Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong Hong Kong, China
- Department of Physiology, Chinese University of Hong Kong Hong Kong, China
- Institute of Vascular Medicine, Chinese University of Hong Kong Hong Kong, China
- Author for correspondence:
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129
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Xie Z, Gong MC, Su W, Turk J, Guo Z. Group VIA phospholipase A2 (iPLA2beta) participates in angiotensin II-induced transcriptional up-regulation of regulator of g-protein signaling-2 in vascular smooth muscle cells. J Biol Chem 2007; 282:25278-89. [PMID: 17613534 PMCID: PMC2096773 DOI: 10.1074/jbc.m611206200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rgs2 (regulator of G-protein signaling-2)-deficient mice exhibit severe hypertension, and genetic variations of RGS2 occur in hypertensive patients. RGS2 mRNA up-regulation by angiotensin II (Ang II) in vascular smooth muscle cells (VSMC) is a potentially important negative feedback mechanism in blood pressure homeostasis, but how it occurs is unknown. Here we demonstrate that group VIA phospholipase A2 (iPLA2beta) plays a pivotal role in Ang II-induced RGS2 mRNA up-regulation in VSMC by three independent approaches, including pharmacologic inhibition with a bromoenol lactone suicide substrate, suppression of iPLA2beta expression with antisense oligonucleotides, and genetic deletion in iPLA2beta-null mice. Selective inhibition of iPLA2beta by each of these approaches abolishes Ang II-induced RGS2 mRNA up-regulation. Furthermore, using adenovirus-mediated gene transfer, we demonstrate that restoration of iPLA2beta-expression in iPLA2beta-null VSMC reconstitutes the ability of Ang II to up-regulate RGS2 mRNA expression. In contrast, Ang II-induced vasodilator-stimulated phosphoprotein phosphorylation and Ang II receptor expression are unaffected. Moreover, in wild-type but not iPLA2beta-null VSMC, Ang II stimulates iPLA2 enzymatic activity significantly. Both arachidonic acid and lysophosphatidylcholine, products of iPLA2beta action, induce RGS2 mRNA up-regulation. Inhibition of lipoxygenases, particularly 15-lipoxygenase, and cyclooxygenases, but not cytochrome P450-dependent epoxygenases inhibits Ang II- or AA-induced RGS2 mRNA expression. Moreover, RGS2 protein expression is also up-regulated by Ang II, and this is attenuated by bromoenol lactone. Disruption of the Ang II/iPLA2beta/RGS2 feedback pathway in iPLA2beta-null cells potentiates Ang II-induced vasodilator-stimulated phosphoprotein and Akt phosphorylation in a time-dependent manner. Collectively, our results demonstrate that iPLA2beta participates in Ang II-induced transcriptional up-regulation of RGS2 in VSMC.
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MESH Headings
- Adenoviridae
- Angiotensin II/pharmacology
- Animals
- Arachidonic Acid/pharmacology
- Blood Pressure/drug effects
- Blood Pressure/physiology
- Cell Adhesion Molecules/metabolism
- Enzyme Activation/drug effects
- Enzyme Activation/physiology
- Gene Deletion
- Gene Expression Regulation, Enzymologic/drug effects
- Gene Expression Regulation, Enzymologic/physiology
- Group VI Phospholipases A2
- Homeostasis/drug effects
- Homeostasis/physiology
- Lysophosphatidylcholines/pharmacology
- Mice
- Mice, Knockout
- Microfilament Proteins/metabolism
- Muscle, Smooth, Vascular/enzymology
- Myocytes, Smooth Muscle/enzymology
- Naphthalenes/pharmacology
- Oligodeoxyribonucleotides, Antisense/pharmacology
- Oxidoreductases/antagonists & inhibitors
- Oxidoreductases/metabolism
- Phospholipases A/antagonists & inhibitors
- Phospholipases A/deficiency
- Phospholipases A/metabolism
- Phospholipases A2
- Phosphoproteins/metabolism
- Phosphorylation/drug effects
- Proto-Oncogene Proteins c-akt/metabolism
- Pyrones/pharmacology
- RGS Proteins/antagonists & inhibitors
- RGS Proteins/deficiency
- RGS Proteins/metabolism
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Rats
- Rats, Sprague-Dawley
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Time Factors
- Transcription, Genetic/drug effects
- Transcription, Genetic/physiology
- Transduction, Genetic
- Up-Regulation/drug effects
- Up-Regulation/physiology
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Zhongwen Xie
- Department of Physiology and the Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, Kentucky 40536, USA
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130
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Firth AL, Remillard CV, Yuan JXJ. TRP channels in hypertension. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1772:895-906. [PMID: 17399958 PMCID: PMC2025589 DOI: 10.1016/j.bbadis.2007.02.009] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 02/08/2007] [Accepted: 02/08/2007] [Indexed: 01/05/2023]
Abstract
Pulmonary and systemic arterial hypertension are associated with profound alterations in Ca(2+) homeostasis and smooth muscle cell proliferation. A novel class of non-selective cation channels, the transient receptor potential (TRP) channels, have emerged at the forefront of research into hypertensive disease states. TRP channels are identified as molecular correlates for receptor-operated and store-operated cation channels in the vasculature. Over 10 TRP isoforms are identified at the mRNA and protein expression levels in the vasculature. Current research implicates upregulation of specific TRP isoforms to be associated with increased Ca(2+) influx, characteristic of vasoconstriction and vascular smooth muscle cell proliferation. TRP channels are implicated as Ca(2+) entry pathways in pulmonary hypertension and essential hypertension. Caveolae have recently emerged as membrane microdomains in which TRP channels may be co-localized with the endoplasmic reticulum in both smooth muscle and endothelial cells. Such enhanced expression and function of TRP channels and their localization in caveolae in pathophysiological hypertensive disease states highlights their importance as potential targets for pharmacological intervention.
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MESH Headings
- Animals
- Caveolae/metabolism
- Cell Proliferation/drug effects
- Cytoskeleton/metabolism
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Gene Expression Regulation
- Humans
- Hypertension/etiology
- Hypertension/genetics
- Hypertension/physiopathology
- Hypertension/therapy
- Hypertension, Pulmonary/etiology
- Hypertension, Pulmonary/genetics
- Hypertension, Pulmonary/therapy
- Models, Biological
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiology
- Pulmonary Artery/physiology
- Transient Receptor Potential Channels/agonists
- Transient Receptor Potential Channels/genetics
- Transient Receptor Potential Channels/metabolism
- Transient Receptor Potential Channels/physiology
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Affiliation(s)
- Amy L Firth
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0725, La Jolla, CA 92093-0725, USA
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131
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Bao S, Li Y, Lei X, Wohltmann M, Jin W, Bohrer A, Semenkovich CF, Ramanadham S, Tabas I, Turk J. Attenuated free cholesterol loading-induced apoptosis but preserved phospholipid composition of peritoneal macrophages from mice that do not express group VIA phospholipase A2. J Biol Chem 2007; 282:27100-27114. [PMID: 17627946 PMCID: PMC2044506 DOI: 10.1074/jbc.m701316200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mouse macrophages undergo ER stress and apoptosis upon free cholesterol loading (FCL). We recently generated iPLA(2)beta-null mice, and here we demonstrate that iPLA(2)beta-null macrophages have reduced sensitivity to FCL-induced apoptosis, although they and wild-type (WT) cells exhibit similar increases in the transcriptional regulator CHOP. iPLA(2)beta-null macrophages are also less sensitive to apoptosis induced by the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin and the scavenger receptor A ligand fucoidan, and restoring iPLA(2)betaexpression with recombinant adenovirus increases apoptosis toward WT levels. WT and iPLA(2)beta-null macrophages incorporate [(3)H]arachidonic acid ([(3)H]AA]) into glycerophosphocholine lipids equally rapidly and exhibit identical zymosan-induced, cPLA(2)alpha-catalyzed [(3)H]AA release. In contrast, although WT macrophages exhibit robust [(3)H]AA release upon FCL, this is attenuated in iPLA(2)beta-null macrophages and increases toward WT levels upon restoring iPLA(2)beta expression. Recent reports indicate that iPLA(2)beta modulates mitochondrial cytochrome c release, and we find that thapsigargin and fucoidan induce mitochondrial phospholipid loss and cytochrome c release into WT macrophage cytosol and that these events are blunted in iPLA(2)beta-null cells. Immunoblotting studies indicate that iPLA(2)beta associates with mitochondria in macrophages subjected to ER stress. AA incorporation into glycerophosphocholine lipids is unimpaired in iPLA(2)beta-null macrophages upon electrospray ionization-tandem mass spectrometry analyses, and their complex lipid composition is similar to WT cells. These findings suggest that iPLA(2)beta participates in ER stress-induced macrophage apoptosis caused by FCL or thapsigargin but that deletion of iPLA(2)beta does not impair macrophage arachidonate incorporation or phospholipid composition.
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Affiliation(s)
- Shunzhong Bao
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Yankun Li
- Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032
| | - Xiaoyong Lei
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Mary Wohltmann
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Wu Jin
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Alan Bohrer
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Sasanka Ramanadham
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the
| | - Ira Tabas
- Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032
| | - John Turk
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
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132
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Albert AP, Saleh SN, Peppiatt-Wildman CM, Large WA. Multiple activation mechanisms of store-operated TRPC channels in smooth muscle cells. J Physiol 2007; 583:25-36. [PMID: 17615095 PMCID: PMC2277241 DOI: 10.1113/jphysiol.2007.137802] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Store-operated channels (SOCs) are plasma membrane Ca2+-permeable cation channels which are activated by agents that deplete intracellular Ca2+ stores. In smooth muscle SOCs are involved in contraction, gene expression, cell growth and proliferation. Single channel recording has demonstrated that SOCs with different biophysical properties are expressed in smooth muscle indicating diverse molecular identities. Moreover it is apparent that several gating mechanisms including calmodulin, protein kinase C and lysophospholipids are involved in SOC activation. Evidence is accumulating that TRPC proteins are important components of SOCs in smooth muscle. More recently Orai and STIM proteins have been proposed to underlie the well-described calcium-release-activated current (ICRAC) in non-excitable cells but at present there is little information on the role of Orai and STIM proteins in smooth muscle. In addition it is likely that different TRPC subunits coassemble as heterotetrameric structures to form smooth muscle SOCs. In this brief review we summarize the diverse properties and gating mechanisms of SOCs in smooth muscle. We propose that the heterogeneity of the properties of these conductances in smooth muscle results from the formation of heterotetrameric TRPC structures in different smooth muscle preparations.
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Affiliation(s)
- A P Albert
- Ion Channel and Cell Signalling, Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London SW17 ORE, UK.
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133
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Mueller P, Quintana A, Griesemer D, Hoth M, Pieters J. Disruption of the cortical actin cytoskeleton does not affect store operated Ca2+ channels in human T-cells. FEBS Lett 2007; 581:3557-62. [PMID: 17624329 DOI: 10.1016/j.febslet.2007.06.068] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 06/24/2007] [Accepted: 06/25/2007] [Indexed: 11/17/2022]
Abstract
Lymphocyte signaling and activation leads to the influx of extracellular Ca(2+) via the activation of Ca(2+) release activated Ca(2+) (CRAC) channels in the plasma membrane. Activation of CRAC channels occurs following emptying of the endoplasmic reticulum intracellular Ca(2+) stores. One model to explain the coupling of store-emptying to CRAC activation is the secretion-like conformational coupling model. This model proposes that store depletion increases junctions between the endoplasmic reticulum and the plasma membrane in a manner that could be regulated by the cortical actin cytoskeleton. Here, we show that stabilization or depolymerization of the actin cytoskeleton failed to affect CRAC activation. We therefore conclude that rearrangement of the actin cytoskeleton is dispensable for store-operated Ca(2+) entry in T-cells.
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Affiliation(s)
- Philipp Mueller
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH 4056 Basel, Switzerland
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134
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Abstract
TRPC5 [TRP (transient receptor potential) canonical (or classical) 5] is a widely expressed mammalian homologue of Drosophila TRP, forming a calcium- and sodium-permeable channel in the plasma membrane either as a homomultimer or heteromultimer with other proteins (e.g. TRPC1). Although several factors are known to stimulate the channel, understanding of its endogenous activators and functions is limited. This paper provides a brief and focused review of our latest findings that show that TRPC5 is a sensor of important signalling phospholipids, including lysophosphatidylcholine and sphingosine 1-phosphate, acting extracellularly or intracellularly. Underlying mechanisms of action and biological relevance are discussed.
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Affiliation(s)
- D J Beech
- Institute of Membrane and Systems Biology, Garstang Building, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
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135
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Abstract
The mechanisms of agonist-induced calcium entry (ACE) following depletion of intracellular calcium stores have not been fully established. We report here that calcium-independent phospholipase A (iPLA2) is required for robust Ca2+ entry in HaCaT keratinocytes following ATP or UTP stimulation. Lysophosphatidic acid (LPA), an unrelated agonist, evoked Ca2+ release without inducing robust Ca2+ entry. Both LPA and UTP induced the redistribution of STIM1 into puncta which localized to regions near or at the plasma membrane, as well as within the cytoplasm. Plasma membrane-associated STIM1 remained high for up to 10 min after UTP stimulation, whereas it had returned almost to baseline by that time point in LPA-stimulated cells. This correlated with faster reloading of the endoplasmic reticulum Ca2+ stores in LPA treated cells. Thus by differentially regulating store-refilling after agonist-mediated depletion, LPA and UTP may exert distinct effects on the duration of STIM1 localization at the plasma membrane, and thus, on the magnitude and duration of ACE.
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Affiliation(s)
- Kehinde Ross
- Dermatological Sciences, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.
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136
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Strokin M, Sergeeva M, Reiser G. Prostaglandin synthesis in rat brain astrocytes is under the control of the n-3 docosahexaenoic acid, released by group VIB calcium-independent phospholipase A2. J Neurochem 2007; 102:1771-1782. [PMID: 17555549 DOI: 10.1111/j.1471-4159.2007.04663.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the current study, we reveal that in astrocytes the VIB Ca(2+)-independent phospholipase A(2) is the enzyme responsible for the release of docosahexaenoic acid (22:6n-3). After pharmacological inhibition and siRNA silencing of VIB Ca(2+)-independent phospholipase A(2), docosahexaenoic acid release was strongly suppressed in astrocytes, which were acutely stimulated (30 min) with ATP and glutamate or after prolonged (6 h) stimulation with the endotoxin lipopolysaccharide. Docosahexaenoic acid release proceeds simultaneously with arachidonic acid (20:4n-6) release and prostaglandin liberation from astrocytes. We found that prostaglandin production is negatively controlled by endogenous docosahexaenoic acid, since pharmacological inhibition and siRNA silencing of VIB Ca(2+)-independent phospholipase A(2) significantly amplified the prostaglandin release by astrocytes stimulated with ATP, glutamate, and lipopolysaccharide. Addition of exogenous docosahexaenoic acid inhibited prostaglandin synthesis, which suggests that the negative control of prostaglandin synthesis observed here is likely due to competitive inhibition of cyclooxygenase-1/2 by free docosahexaenoic acid. Additionally, treatment of astrocytes with docosahexaenoic acid leads to the reduction in cyclooxygenase-1 expression, which also contributes to reduced prostaglandin production observed in lipopolysaccharide-stimulated cells. Thus, we identify a regulatory mechanism important for the brain, in which docosahexaenoic acid released from astrocytes by VIB Ca(2+)-independent phospholipase A(2) negatively controls prostaglandin production.
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Affiliation(s)
- Mikhail Strokin
- Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Institut für Neurobiochemie, Leipziger Straße, Magdeburg, GermanyBelozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
| | - Marina Sergeeva
- Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Institut für Neurobiochemie, Leipziger Straße, Magdeburg, GermanyBelozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
| | - Georg Reiser
- Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Institut für Neurobiochemie, Leipziger Straße, Magdeburg, GermanyBelozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
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137
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Chen L, Iijima M, Tang M, Landree MA, Huang YE, Xiong Y, Iglesias PA, Devreotes PN. PLA2 and PI3K/PTEN pathways act in parallel to mediate chemotaxis. Dev Cell 2007; 12:603-14. [PMID: 17419997 PMCID: PMC1986835 DOI: 10.1016/j.devcel.2007.03.005] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 10/31/2006] [Accepted: 03/08/2007] [Indexed: 01/12/2023]
Abstract
Directed cell migration involves signaling events that lead to local accumulation of PI(3,4,5)P(3), but additional pathways act in parallel. A genetic screen in Dictyostelium discoideum to identify redundant pathways revealed a gene with homology to patatin-like phospholipase A(2). Loss of this gene did not alter PI(3,4,5)P(3) regulation, but chemotaxis became sensitive to reductions in PI3K activity. Likewise, cells deficient in PI3K activity were more sensitive to inhibition of PLA(2) activity. Deletion of the PLA(2) homolog and two PI3Ks caused a strong defect in chemotaxis and a reduction in receptor-mediated actin polymerization. In wild-type cells, chemoattractants stimulated a rapid burst in an arachidonic acid derivative. This response was absent in cells lacking the PLA(2) homolog, and exogenous arachidonic acid reduced their dependence on PI3K signaling. We propose that PLA(2) and PI3K signaling act in concert to mediate chemotaxis, and metabolites of PLA(2) may be important mediators of the response.
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Affiliation(s)
- Lingfeng Chen
- Department of Cell Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
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138
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Hu JS, Li YB, Wang JW, Sun L, Zhang GJ. Mechanism of Lysophosphatidylcholine-Induced Lysosome Destabilization. J Membr Biol 2007; 215:27-35. [PMID: 17510762 DOI: 10.1007/s00232-007-9002-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 01/02/2007] [Indexed: 10/23/2022]
Abstract
Lysosomal destabilization is critical for the organelle and living cells. Phospholipase A(2 )(PLA(2)) was shown to be able to destabilize lysosomes under some conditions. By what mechanism the enzyme affects lysosomal stability is not fully studied. In this study, we investigated the effects of lysophosphatidylcholine (lysoPC), a PLA(2)-produced lipid metabolite, on lysosomal ion permeability, osmotic sensitivity and stability. By measuring lysosomal beta-hexosaminidase free activity, membrane potential, proton leakage and their enzyme latency loss in hypotonic sucrose medium, we established that lysoPC could increase the lysosomal permeability to both potassium ions and protons and enhance lysosomal osmotic sensitivity. These changes in lysosomal membrane properties promoted entry of potassium ions into lysosomes via K(+)/H(+) exchange. The resultant osmotic imbalance across the membranes led to losses of lysosomal integrity. The enhancement of lysosomal osmotic sensitivity caused the lysosomes to become more liable to destabilization in osmotic shock. These results suggest that lysoPC may play a key role in PLA(2)-induced lysosomal destabilization.
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Affiliation(s)
- Jin-Shan Hu
- School of Science, Hebei University of Technology, Tianjin, 300130, People's Republic of China
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139
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Wu MM, Luik RM, Lewis RS. Some assembly required: constructing the elementary units of store-operated Ca2+ entry. Cell Calcium 2007; 42:163-72. [PMID: 17499354 PMCID: PMC2323433 DOI: 10.1016/j.ceca.2007.03.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 03/15/2007] [Accepted: 03/16/2007] [Indexed: 11/23/2022]
Abstract
The means by which Ca(2+) store depletion evokes the opening of store-operated Ca(2+) channels (SOCs) in the plasma membrane of excitable and non-excitable cells has been a longstanding mystery. Indirect evidence has supported local interactions between the ER and SOCs as well as long-range interactions mediated through a diffusible activator. The recent molecular identification of the ER Ca(2+) sensor (STIM1) and a subunit of the CRAC channel (Orai1), a prototypic SOC, has now made it possible to visualize directly the sequence of events that links store depletion to CRAC channel opening. Following store depletion, STIM1 moves from locations throughout the ER to accumulate in ER subregions positioned within 10-25nm of the plasma membrane. Simultaneously, Orai1 gathers at discrete sites in the plasma membrane directly opposite STIM1, resulting in local CRAC channel activation. These new studies define the elementary units of store-operated Ca(2+) entry, and reveal an unprecedented mechanism for channel activation in which the stimulus brings a channel and its activator/sensor together for interaction across apposed membrane compartments. We discuss the implications of this choreographic mechanism with regard to Ca(2+) dynamics, specificity of Ca(2+) signaling, and the existence of a specialized ER subset dedicated to the control of the CRAC channel.
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Affiliation(s)
- Minnie M Wu
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, United States
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140
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Kuwata H, Fujimoto C, Yoda E, Shimbara S, Nakatani Y, Hara S, Murakami M, Kudo I. A novel role of group VIB calcium-independent phospholipase A2 (iPLA2gamma) in the inducible expression of group IIA secretory PLA2 in rat fibroblastic cells. J Biol Chem 2007; 282:20124-32. [PMID: 17475622 DOI: 10.1074/jbc.m611883200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Group IIA secretory phospholipase A(2) (sPLA(2)-IIA) is a prototypic sPLA(2) enzyme that may play roles in modification of eicosanoid biosynthesis as well as antibacterial defense. In several cell types, inducible expression of sPLA(2) by pro-inflammatory stimuli is attenuated by group IVA cytosolic PLA(2) (cPLA(2)alpha) inhibitors such as arachidonyl trifluoromethyl ketone, leading to the proposal that prior activation of cPLA(2)alpha is required for de novo induction of sPLA(2). However, because of the broad specificity of several cPLA(2)alpha inhibitors used so far, a more comprehensive approach is needed to evaluate the relevance of this ambiguous pathway. Here, we provide evidence that the induction of sPLA(2)-IIA by pro-inflammatory stimuli requires group VIB calcium-independent PLA(2) (iPLA(2)gamma), rather than cPLA(2)alpha, in rat fibroblastic 3Y1 cells. Results with small interfering RNA unexpectedly showed that the cytokine induction of sPLA(2)-IIA in cPLA(2)alpha knockdown cells, in which cPLA(2)alpha protein was undetectable, was similar to that in replicate control cells. By contrast, knockdown of iPLA(2)gamma, another arachidonyl trifluoromethyl ketone-sensitive intracellular PLA(2), markedly reduced the cytokine-induced expression of sPLA(2)-IIA. Supporting this finding, the R-enantiomer of bromoenol lactone, an iPLA(2)gamma inhibitor, suppressed the cytokine-induced sPLA(2)-IIA expression, whereas (S)-bromoenol lactone, an iPLA(2)beta inhibitor, failed to do so. Moreover, lipopolysaccharide-stimulated sPLA(2)-IIA expression was also abolished by knockdown of iPLA(2)gamma. These findings open new insight into a novel regulatory role of iPLA(2)gamma in stimulus-coupled sPLA(2)-IIA expression.
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Affiliation(s)
- Hiroshi Kuwata
- Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555
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141
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Dissecting ICRAC, a store-operated calcium current. Trends Biochem Sci 2007; 32:235-45. [PMID: 17434311 DOI: 10.1016/j.tibs.2007.03.009] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Revised: 03/05/2007] [Accepted: 03/28/2007] [Indexed: 02/02/2023]
Abstract
The use of Ca(2+) for intracellular signalling necessitates tight local and global control of cytoplasmic Ca(2+) concentration, and mechanisms for maintaining the net Ca(2+) balance. It has long been recognized that intracellular Ca(2+) stores exert control over Ca(2+) influx at the plasma membrane through a process of store-operated Ca(2+) entry (SOCE). The Ca(2+) current I(CRAC) is the best characterized instance of SOCE, but the elements of the pathway leading to I(CRAC) have eluded biochemical definition for more than a decade. However, the recent identification of key proteins underlying I(CRAC)--STIM1 and Orai1--has led to several insights into this ER-to-plasma membrane signalling system and to the recognition that it is an ancient and conserved mechanism in multicellular organisms.
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142
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Andersson DA, Nash M, Bevan S. Modulation of the cold-activated channel TRPM8 by lysophospholipids and polyunsaturated fatty acids. J Neurosci 2007; 27:3347-55. [PMID: 17376995 PMCID: PMC2726637 DOI: 10.1523/jneurosci.4846-06.2007] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We investigated the role of phospholipase A2 (PLA2) and the effects of PLA2 products (polyunsaturated fatty acids and lysophospholipids) on the cold-sensitive channel transient receptor potential (melastatin)-8 (TRPM8), heterologously expressed in Chinese hamster ovary cells. TRPM8 responses to cold and the agonist icilin were abolished by inhibitors of the calcium-independent (iPLA2) form of the enzyme, whereas responses to menthol were less sensitive to iPLA2 inhibition. Inhibition of PLA2 similarly abolished the cold responses of the majority of cold-sensitive dorsal root ganglion neurons. The products of PLA2 had opposing effects on TRPM8. Lysophospholipids (LPLs) (lysophosphatidylcholine, lysophosphatidylinositol, and lysophosphatidylserine) altered the thermal sensitivity of TRPM8, raising the temperature threshold toward normal body temperature. Polyunsaturated fatty acids (PUFAs), such as arachidonic acid, inhibited the activation of TRPM8 by cold, icilin, and menthol. The relative potencies of lysophospholipids and PUFAs are such that lysophosphatidylcholine is able to modulate TRPM8 in the presence of an equimolar concentration of arachidonic acid. Positive modulation by LPLs provides a potential physiological mechanism for sensitizing and activating TRPM8 in the absence of temperature variations.
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Affiliation(s)
- David A Andersson
- Wolfson Centre for Age-Related Diseases, King's College London, London SE1 1UL, United Kingdom.
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143
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Jacobson DA, Weber CR, Bao S, Turk J, Philipson LH. Modulation of the pancreatic islet beta-cell-delayed rectifier potassium channel Kv2.1 by the polyunsaturated fatty acid arachidonate. J Biol Chem 2007; 282:7442-9. [PMID: 17197450 PMCID: PMC2044499 DOI: 10.1074/jbc.m607858200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose stimulates both insulin secretion and hydrolysis of arachidonic acid (AA) esterified in membrane phospholipids of pancreatic islet beta-cells, and these processes are amplified by muscarinic agonists. Here we demonstrate that nonesterified AA regulates the biophysical activity of the pancreatic islet beta-cell-delayed rectifier channel, Kv2.1. Recordings of Kv2.1 currents from INS-1 insulinoma cells incubated with AA (5 mum) and subjected to graded degrees of depolarization exhibit a significantly shorter time-to-peak current interval than do control cells. AA causes a rapid decay and reduced peak conductance of delayed rectifier currents from INS-1 cells and from primary beta-cells isolated from mouse, rat, and human pancreatic islets. Stimulating mouse islets with AA results in a significant increase in the frequency of glucose-induced [Ca(2+)] oscillations, which is an expected effect of Kv2.1 channel blockade. Stimulation with concentrations of glucose and carbachol that accelerate hydrolysis of endogenous AA from islet phosphoplipids also results in accelerated Kv2.1 inactivation and a shorter time-to-peak current interval. Group VIA phospholipase A(2) (iPLA(2)beta) hydrolyzes beta-cell membrane phospholipids to release nonesterified fatty acids, including AA, and inhibiting iPLA(2)beta prevents the muscarinic agonist-induced accelerated Kv2.1 inactivation. Furthermore, glucose and carbachol do not significantly affect Kv2.1 inactivation in beta-cells from iPLA(2)beta(-/-) mice. Stably transfected INS-1 cells that overexpress iPLA(2)beta hydrolyze phospholipids more rapidly than control INS-1 cells and also exhibit an increase in the inactivation rate of the delayed rectifier currents. These results suggest that Kv2.1 currents could be dynamically modulated in the pancreatic islet beta-cell by phospholipase-catalyzed hydrolysis of membrane phospholipids to yield non-esterified fatty acids, such as AA, that facilitate Ca(2+) entry and insulin secretion.
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Affiliation(s)
- David A. Jacobson
- Department of Medicine, University of Chicago, Chicago, Illinois 60637
| | | | - Shunzhong Bao
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
| | - John Turk
- Medicine Department Mass Spectrometry Facility and Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110
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144
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Luik RM, Lewis RS. New insights into the molecular mechanisms of store-operated Ca2+ signaling in T cells. Trends Mol Med 2007; 13:103-7. [PMID: 17267286 DOI: 10.1016/j.molmed.2007.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 12/14/2006] [Accepted: 01/19/2007] [Indexed: 12/28/2022]
Abstract
The activation of Ca(2+) entry through store-operated channels by agonists that deplete Ca(2+) from the endoplasmic reticulum (ER) is an ubiquitous signaling mechanism, the molecular basis of which has remained elusive for the past 20 years. In T lymphocytes, store-operated Ca(2+)-release-activated Ca(2+) (CRAC) channels constitute the sole pathway for Ca(2+) entry following antigen-receptor engagement, and their function is essential for driving the program of gene expression that underlies T-cell activation by antigen. The first molecular components of this pathway have recently been identified: stromal interaction molecule 1 (STIM1), the ER Ca(2+) sensor, and Orai1, a pore-forming subunit of the CRAC channel. Recent work shows that CRAC channels are activated in a complex fashion that involves the co-clustering of STIM1 in junctional ER directly opposite Orai1 in the plasma membrane. These studies reveal an abundance of sites where Ca(2+) signaling might be controlled to modulate the activity of T cells during the immune response.
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Affiliation(s)
- Riina M Luik
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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145
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Abstract
Ca2+ entry forms an essential component of platelet activation; however, the mechanisms associated with this process are not understood. Ca2+ entry upon receptor activation occurs as a consequence of intracellular store depletion (referred to as store-operated Ca2+ entry or SOCE), a direct action of second messengers on cation entry channels or the direct occupancy of a ligand-gated P2(Xi) receptor. The molecular identity of the SOCE channel has yet to be established. Transient receptor potential (TRP) proteins are candidate cation entry channels and are classified into a number of closely related subfamilies including TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin) and TRPML (mucolipins). From the TRPC family, platelets have been shown to express TRPC6 and TRPC1, and are likely to express other TRPC and other TRP members. TRPC6 is suggested to be involved with receptor-activated, diacyl-glycerol-mediated cation entry. TRPC1 has been suggested to be involved with SOCE, though many of the suggested mechanisms remain controversial. As no single TRP channel has the properties described for SOCE in platelets, it is likely that it is composed of a heteromeric association of TRP and related subunits, some of which may be present in intracellular compartments in the resting cell.
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Affiliation(s)
- K S Authi
- Cardiovascular Division, King's College London, New Hunts House, Guy's Campus, London SE1 1UL, UK.
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146
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Woodard GE, Sage SO, Rosado JA. Transient Receptor Potential Channels and Intracellular Signaling. ACTA ACUST UNITED AC 2007; 256:35-67. [PMID: 17241904 DOI: 10.1016/s0074-7696(07)56002-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
The transient receptor potential (TRP) family of ion channels is composed of more than 50 functionally versatile cation-permeant ion channels expressed in most mammalian cell types. Considerable research has been brought to bear on the members of this family, especially with regard to their possible role as store-operated calcium channels, although studies have provided evidence that TRP channels exhibit a number of regulatory and functional aspects. Endogenous and transiently expressed TRP channels can be activated by different mechanisms grouped into four main categories: receptor-operated activation, store depletion-mediated activation, ligand-induced activation, and direct activation. This article reviews the biochemical characteristics of the different members of the TRP family and summarizes their involvement in a number of physiological events ranging from sensory transduction to development, which might help in understanding the relationship between TRP channel dysfunction and the development of several diseases.
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Affiliation(s)
- Geoffrey E Woodard
- Metabolic Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland, USA
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147
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Vanden Abeele F, Zholos A, Bidaux G, Shuba Y, Thebault S, Beck B, Flourakis M, Panchin Y, Skryma R, Prevarskaya N. Ca2+-independent Phospholipase A2-dependent Gating of TRPM8 by Lysophospholipids. J Biol Chem 2006; 281:40174-82. [PMID: 17082190 DOI: 10.1074/jbc.m605779200] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPM8 represents an ion channel activated by cold temperatures and cooling agents, such as menthol, that underlies the cold-induced excitation of sensory neurons. Interestingly, the only human tissue outside the peripheral nervous system, in which the expression of TRPM8 transcripts has been detected at high levels, is the prostate, a tissue not exposed to any essential temperature variations. Here we show that the TRPM8 cloned from human prostate and heterologously expressed in HEK-293 cells is regulated by the Ca(2+)-independent phospholipase A(2) (iPLA(2)) signaling pathway with its end products, lysophospholipids (LPLs), acting as its endogenous ligands. LPLs induce prominent prolongation of TRPM8 channel openings that are hardly detectable with other stimuli (e.g. cold, menthol, and depolarization) and that account for more than 90% of the total channel open time. Down-regulation of iPLA(2) resulted in a strong inhibition of TRPM8-mediated functional responses and abolished channel activation. The action of LPLs on TRPM8 channels involved either changes in the local lipid bilayer tension or interaction with the critical determinant(s) in the transmembrane channel core. Based on this, we propose a novel concept of TRPM8 regulation with the involvement of iPLA(2) stimulation. This mechanism employs chemical rather than physical (temperature change) signaling and thus may be the main regulator of TRPM8 activation in organs not exposed to any essential temperature variations, as in the prostate gland.
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Affiliation(s)
- Fabien Vanden Abeele
- INSERM U800, Equipe Labellisée par la Ligue contre le Cancer, Villeneuve d'Ascq F-59650, France and Universite Lille 1, Villeneuve d'Ascq F-59650, France
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148
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Smyth JT, Dehaven WI, Jones BF, Mercer JC, Trebak M, Vazquez G, Putney JW. Emerging perspectives in store-operated Ca2+ entry: Roles of Orai, Stim and TRP. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1147-60. [PMID: 17034882 DOI: 10.1016/j.bbamcr.2006.08.050] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 08/30/2006] [Indexed: 11/28/2022]
Abstract
Depletion of intracellular Ca2+ stores induces Ca2+ influx across the plasma membrane through store-operated channels (SOCs). This store-operated Ca2+ influx is important for the replenishment of the Ca2+ stores, and is also involved in many signaling processes by virtue of the ability of intracellular Ca2+ to act as a second messenger. For many years, the molecular identities of particular SOCs, as well as the signaling mechanisms by which these channels are activated, have been elusive. Recently, however, the mammalian proteins STIM1 and Orai1 were shown to be necessary for the activation of store-operated Ca2+ entry in a variety of mammalian cells. Here we present molecular, pharmacological, and electrophysiological properties of SOCs, with particular focus on the roles that STIM1 and Orai1 may play in the signaling processes that regulate various pathways of store-operated entry.
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Affiliation(s)
- Jeremy T Smyth
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health/DHHS, Research Triangle Park, NC 27709, USA
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149
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Herbert SP, Walker JH. Group VIA Calcium-independent Phospholipase A2 Mediates Endothelial Cell S Phase Progression. J Biol Chem 2006; 281:35709-16. [PMID: 16966332 DOI: 10.1074/jbc.m600699200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Arachidonic acid and its metabolites have been previously implicated in the regulation of endothelial cell proliferation. Arachidonic acid may be liberated from cellular phospholipids by the action of group VIA calcium-independent phospholipase A2 (iPLA2-VIA). Consequently, we tested the hypothesis that iPLA2-VIA activity is linked to the regulation of endothelial cell proliferation. Inhibition of iPLA2 activity by bromoenol lactone (BEL) was sufficient to entirely block endothelial cell growth. BEL dose-dependently inhibited endothelial cell DNA synthesis in a manner that was reversed upon the exogenous addition of arachidonic acid. DNA synthesis was inhibited by the S-isomer and not by the R-isomer of BEL, demonstrating that endothelial cell proliferation is mediated specifically by iPLA2-VIA. iPLA2-VIA activity was critical to the progression of endothelial cells through S phase and is required for the expression of the cyclin A/cdk2 complex. Thus, inhibition of iPLA2-VIA blocks S phase progression and results in exit from the cell cycle. Inhibition of iPLA2-VIA-mediated endothelial cell proliferation is sufficient to block angiogenic tubule formation in co-culture assays. Consequently, iPLA2-VIA is a novel regulator of endothelial cell S phase progression, cell cycle residence, and angiogenesis.
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Affiliation(s)
- Shane P Herbert
- Faculty of Biological Sciences, Institute of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
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150
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Taylor CW. Store-operated Ca2+ entry: A STIMulating stOrai. Trends Biochem Sci 2006; 31:597-601. [PMID: 17029812 DOI: 10.1016/j.tibs.2006.09.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 09/06/2006] [Accepted: 09/22/2006] [Indexed: 01/21/2023]
Abstract
Store-operated Ca2+ entry (SOCE) mediates much of the Ca2+ entry evoked by receptors that stimulate phospholipase C. However, for 20 years, the plasma membrane Ca2+ channel and the signal linking its activation to loss of Ca2+ from the endoplasmic reticulum (ER) have eluded detection. But the search might now be over. Two proteins, STIM1 (the ER Ca2+ sensor) and Orai1 (the Ca2+ channel), have recently been identified as the missing links in SOCE.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD, UK.
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