TRPC3 Regulates Agonist-stimulated Ca2+ Mobilization by Mediating the Interaction between Type I Inositol 1,4,5-Trisphosphate Receptor, RACK1, and Orai1 |
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Authors: | Geoffrey E Woodard Jos?? J L??pez Isaac Jard??n Gin??s M Salido and Juan A Rosado |
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Institution: | From the ‡NIDDK, National Institutes of Health, Bethesda, Maryland 20892-2560 and ;the §Department of Physiology, Cell Physiology Research Group, University of Extremadura, 10071 Caceres, Spain |
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Abstract: | There is a body of evidence suggesting that Ca2+ handling proteins assemble into signaling complexes required for a fine regulation of Ca2+ signals, events that regulate a variety of critical cellular processes. Canonical transient receptor potential (TRPC) and Orai proteins have both been proposed to form Ca2+-permeable channels mediating Ca2+ entry upon agonist stimulation. A number of studies have demonstrated that inositol 1,4,5-trisphosphate receptors (IP3Rs) interact with plasma membrane TRPC channels; however, at present there is no evidence supporting the interaction between Orai proteins and IP3Rs. Here we report that treatment with thapsigargin or cellular agonists results in association of Orai1 with types I and II IP3Rs. In addition, we have found that TRPC3, RACK1 (receptor for activated protein kinase C-1), and STIM1 (stromal interaction molecule 1) interact with Orai1 upon stimulation with agonists. TRPC3 expression silencing prevented both the interaction of Orai1 with TRPC3 and, more interestingly, the association of Orai1 with the type I IP3R, but not with the type II IP3R, thus suggesting that TRPC3 selectively mediates interaction between Orai1 and type I IP3R. In addition, TRPC3 expression silencing attenuated ATP- and CCh-stimulated interaction between RACK1 and the type I IP3R, as well as Ca2+ release and entry. In conclusion, our results indicate that agonist stimulation results in the formation of an Orai1-STIM1-TRPC3-RACK1-type I IP3R complex, where TRPC3 plays a central role. This Ca2+ signaling complex might be important for both agonist-induced Ca2+ release and entry. |
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Keywords: | Calcium Calcium/Cellular Regulation Calcium/Channels Calcium Intracellular Release Ion Channels IP3 Receptors Orai1 TRPC3 |
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