title: Mechanisms of STIM1 activation of store-independent leukotriene C4-regulated Ca2+ channels.
abstract: We recently showed, in primary vascular smooth muscle cells (VSMCs), that the platelet-derived growth factor activates canonical store-operated Ca(2+) entry and Ca(2+) release-activated Ca(2+) currents encoded by Orai1 and STIM1 genes. However, thrombin activates store-independent Ca(2+) selective channels contributed by both Orai3 and Orai1. These store-independent Orai3/Orai1 channels are gated by cytosolic leukotriene C4 (LTC4) and require STIM1 downstream LTC4 action. However, the source of LTC4 and the signaling mechanisms of STIM1 in the activation of this LTC4-regulated Ca(2+) (LRC) channel are unknown. Here, we show that upon thrombin stimulation, LTC4 is produced through the sequential activities of phospholipase C, diacylglycerol lipase, 5-lipo-oxygenease, and leukotriene C4 synthase. We show that the endoplasmic reticulum-resident STIM1 is necessary and sufficient for LRC channel activation by thrombin. STIM1 does not form sustained puncta and does not colocalize with Orai1 either under basal conditions or in response to thrombin. However, STIM1 is precoupled to Orai3 and Orai3/Orai1 channels under basal conditions as shown using Forster resonance energy transfer (FRET) imaging. The second coiled-coil domain of STIM1 is required for coupling to either Orai3 or Orai3/Orai1 channels and for LRC channel activation. We conclude that STIM1 employs distinct mechanisms in the activation of store-dependent and store-independent Ca(2+) entry pathways.
authors.affiliation: Nanobioscience Constellation, College of Nanoscale Science and Engineering, University at Albany, State University of New York, Albany, New York, USA.
authors.forename: Xuexin
authors.initials: X
authors.lastname: Zhang
authors.forename: José C
authors.initials: JC
authors.lastname: González-Cobos
authors.forename: Rainer
authors.initials: R
authors.lastname: Schindl
authors.forename: Martin
authors.initials: M
authors.lastname: Muik
authors.forename: Brian
authors.initials: B
authors.lastname: Ruhle
authors.forename: Rajender K
authors.initials: RK
authors.lastname: Motiani
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Bisaillon
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Marc
authors.initials: M
authors.lastname: Fahrner
authors.forename: Margarida
authors.initials: M
authors.lastname: Barroso
authors.forename: Khalid
authors.initials: K
authors.lastname: Matrougui
authors.forename: Christoph
authors.initials: C
authors.lastname: Romanin
authors.forename: Mohamed
authors.initials: M
authors.lastname: Trebak
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D017997:Leukotriene C4 / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D000071740:ORAI1 Protein; D018408:Patch-Clamp Techniques; D054730:Protein Interaction Domains and Motifs; D051381:Rats; D015398:Signal Transduction; D000071737:Stromal Interaction Molecule 1; D013917:Thrombin / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D008562:Membrane Glycoproteins; D000071740:ORAI1 Protein; C532493:Orai1 protein, rat; C573659:Orai3 protein, rat; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D017997:Leukotriene C4; D013917:Thrombin