Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Trp-like protein (TrpL, where Trp is transient receptor-potential protein) of Drosophila, a non-selective cation channel activated in photoreceptor cells by a phospholipase C-dependent mechanism, is thought to be a prototypical receptor-activated channel. Our previous studies showed that TrpL channels are not activated by depletion of internal Ca2+ stores when expressed in Sf9 cells. Using fura-2 to measure cation influx via TrpL, and cell-attached patch recordings to monitor TrpL single-channel activity directly, we have found a thapsigargin-induced increase in TrpL activity in the presence of extracellular bivalent cations, with Ca2+>Sr2+>> Ba2+. The increase in TrpL channel activity was blocked by concentrations of La3+ that completely inhibited endogenous capacitative Ca2+ entry (CCE), but have no effect on TrpL, suggesting that TrpL exhibits trans-stimulation by cation entry via CCE. TrpL has two putative calmodulin (CaM)-binding domains, designated CBS-1 and CBS-2. To determine which site may be required for stimulation of TrpL by the cytosolic free Ca2+ concentration ([Ca2+]i), a chimaeric construct was created in which the C-terminal domain of TrpL containing CBS-2 was attached to human TrpC1, a short homologue of Trp that is not activated by depletion of internal Ca2+ stores or by a rise in [Ca2+]i. This gain-of-function mutant, designated TrpC1-TrpL, exhibited trans-stimulation by Ca2+ entry via CCE. Examination of CaM binding in gel-overlay experiments showed that TrpL and the TrpC1-TrpL chimaera bound CaM, but TrpC1 or a truncated version of TrpL lacking CBS-2 did not. These results suggest that only CBS-2 binds CaM in native TrpL and that the C-terminal domain containing this site is important for trans-stimulation of TrpL by CCE.
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PMID:Stimulation of Drosophila TrpL by capacitative Ca2+ entry. 1037 43

The orexins are peptide transmitters/hormones, which exert stimulatory actions in many types of cells via the G-protein-coupled OX(1) and OX(2) receptors. Our previous results have suggested that low (subnanomolar) concentrations of orexin-A activate Ca(2+) entry, whereas higher concentrations activate phospholipase C, Ca(2+) release, and capacitative Ca(2+) entry. As shown here, the Ca(2+) response to subnanomolar orexin-A concentrations was blocked by activation of protein kinase C by using different approaches (12-O-tetradecanoylphorbol acetate, dioctanoylglycerol, and diacylglycerol kinase inhibition) and protein phosphatase inhibition by calyculin A. The Ca(2+) response to subnanomolar orexin-A concentrations was also blocked by Mg(2+), dextromethorphan, and tetraethylammonium. These treatments neither affected the response to high concentrations of orexin-A nor the thapsigargin-stimulated capacitative entry. The capacitative entry was instead strongly suppressed by SKF96365. An inward membrane current activated by subnanomolar concentrations of orexin-A and the currents activated upon transient expression of trpc3 channels were also sensitive to Mg(2+), dextromethorphan, and tetraethylammonium. Responses to subnanomolar concentrations of orexin-A (Ca(2+) elevation, inward current, and membrane depolarization) were voltage-dependent with a loss of the response around -15 mV. By using reverse transcription-PCR, mRNA for the trpc1-4 channel isoforms were detected in the CHO-hOX1-C1 cells. The expression of truncated TRPC channel isoforms, in particular trpc1 and trpc3, reduced the response to subnanomolar concentrations of orexin-A but did not affect the response to higher concentrations of orexin-A. The results suggest that activation of the OX(1) receptor leads to opening of a Ca(2+)-permeable channel, involving trpc1 and -3, which is controlled by protein kinase C.
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PMID:Orexin-A-induced Ca2+ entry: evidence for involvement of trpc channels and protein kinase C regulation. 1553 48

Several receptors, including those for AVP (Arg8-vasopressin) and 5-HT (5-hydroxytryptamine), share an ability to stimulate PLC (phospholipase C) and so production of IP3 (inositol 1,4,5-trisphosphate) and DAG (diacylglycerol) in A7r5 vascular smooth muscle cells. Our previous analysis of the effects of AVP on Ca2+ entry [Moneer, Dyer and Taylor (2003) Biochem. J. 370, 439-448] showed that arachidonic acid released from DAG stimulated NO synthase. NO then stimulated an NCCE (non-capacitative Ca2+ entry) pathway, and, via cGMP and protein kinase G, it inhibited CCE (capacitative Ca2+ entry). This reciprocal regulation ensured that, in the presence of AVP, all Ca2+ entry occurred via NCCE to be followed by a transient activation of CCE only when AVP was removed [Moneer and Taylor (2002) Biochem. J. 362, 13-21]. We confirm that, in the presence of AVP, all Ca2+ entry occurs via NCCE, but 5-HT, despite activating PLC and evoking release of Ca2+ from intracellular stores, stimulates Ca2+ entry only via CCE. We conclude that two PLC-coupled receptors differentially regulate CCE and NCCE. We also address evidence that, in some A7r5 cells lines, AVP fails either to stimulate NCCE or inhibit CCE [Brueggemann, Markun, Barakat, Chen and Byron (2005) Biochem. J. 388, 237-244]. Quantitative PCR analysis suggests that these cells predominantly express TRPC1 (transient receptor potential canonical 1), whereas cells in which AVP reciprocally regulates CCE and NCCE express a greater variety of TRPC subtypes (TRPC1=6>2>3).
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PMID:Different phospholipase-C-coupled receptors differentially regulate capacitative and non-capacitative Ca2+ entry in A7r5 cells. 1591 94

Movement toward the source of a chemoattractant gradient is a basic cellular property in health and disease. Enhanced migration during metastasis involves deregulated growth factor signaling. Growth factor stimulation and cell migration converge both on the important second messenger Ca(2+). To date, the molecular identification of Ca(2+) entry pathways activated by growth factors during chemotaxis is still an open issue. We investigated the involvement of the nonselective Ca(2+) channel TRPC1 (transient receptor potential canonical 1) in FGF-2 guided chemotaxis by means of time-lapse video microscopy and by functional Ca(2+) measurements. To specifically address TRPC1 function in transformed MDCK cells we altered the expression levels by siRNA or overexpression. We report that TRPC1 channels are required for the orientation of transformed MDCK cells in FGF-2 gradients because TRPC1 knockdown or pharmacological blockade prevented chemotaxis. Stimulation with FGF-2 triggered an immediate Ca(2+) influx via TRPC1 channels that depended on phospholipase C and phosphatidylinositol 3-kinase signaling. Impeding this Ca(2+) influx abolished chemotaxis toward FGF-2. This functional connection correlated with clustering of FGF receptors and TRPC1 channels as was observed by immunolabeling. These findings show the important interplay between growth factor signaling and Ca(2+) influx in chemotaxis.
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PMID:Chemotaxis of MDCK-F cells toward fibroblast growth factor-2 depends on transient receptor potential canonical channel 1. 2112 Jun 65

Endothelial progenitor cells could be implicated in the aberrant neoangiogenesis that occurs in bone marrow and spleen in patients with primary myelofibrosis (PMF). However, antivascular endothelial growth factor (VEGF) monotherapy had only a modest and transient effect in these individuals. Recently it was found that VEGF-induced proangiogenic intracellular Ca(2+) oscillations could be impaired in endothelial progenitor cells of subjects with malignancies. Therefore, we employed Ca(2+) imaging, wavelet analysis, and functional assays to assess whether and how VEGF-induced Ca(2+) oscillations are altered in PMF-derived endothelial progenitor cells. We focused on endothelial colony-forming cells (ECFCs), which are the only endothelial progenitor cell subtype capable of forming neovessels both in vivo and in vitro. VEGF triggers repetitive Ca(2+) spikes in both normal ECFCs (N-ECFCs) and ECFCs obtained from PMF patients (PMF-ECFCs). However, the spiking response to VEGF is significantly weaker in PMF-ECFCs. VEGF-elicited Ca(2+) oscillations are patterned by the interaction between inositol-1,4,5-trisphosphate-dependent Ca(2+) mobilization and store-operated Ca(2+) entry. However, in most PMF-ECFCs, Ca(2+) oscillations are triggered by a store-independent Ca(2+) entry pathway. We found that diacylglycerol gates transient receptor potential canonical 1 channel to trigger VEGF-dependent Ca(2+) spikes by recruiting the phospholipase C/inositol-1,4,5-trisphosphate signaling pathway, reflected as a decrease in endoplasmic reticulum Ca(2+) content. Finally, we found that, apart from being less robust and dysregulated as compared with N-ECFCs, VEGF-induced Ca(2+) oscillations modestly stimulate PMF-ECFC growth and in vitro angiogenesis. These results may explain the modest effect of anti-VEGF therapies in PMF.
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PMID:Dysregulation of VEGF-induced proangiogenic Ca2+ oscillations in primary myelofibrosis-derived endothelial colony-forming cells. 2643 19