title: STIM1 and STIM2 are located in the acidic Ca2+ stores and associates with Orai1 upon depletion of the acidic stores in human platelets.
abstract: Mammalian cells accumulate Ca2+ into agonist-sensitive acidic organelles, vesicles that possess a vacuolar proton-ATPase. Acidic Ca2+ stores include secretory granules and lysosome-related organelles. Current evidence clearly indicates that acidic Ca2+ stores participate in cell signaling and function, including the activation of store-operated Ca2+ entry in human platelets upon depletion of the acidic stores, although the mechanism underlying the activation of store-operated Ca2+ entry controlled by the acidic stores remains unclear. STIM1 has been presented as the endoplasmic reticulum Ca2+ sensor, but its role sensing intraluminal Ca2+ concentration in the acidic stores has not been investigated. Here we report that STIM1 and STIM2 are expressed in the lysosome-related organelles and dense granules in human platelets isolated by immunomagnetic sorting. Depletion of the acidic Ca2+ stores using the specific vacuolar proton-ATPase inhibitor, bafilomycin A1, enhanced the association between STIM1 and STIM2 as well as between these proteins and the plasma membrane channel Orai1. Depletion of the acidic Ca2+ stores also induces time-dependent co-immunoprecipitation of STIM1 with the TRPC proteins hTRPC1 and hTRPC6, as well as between Orai1 and both TRPC proteins. In addition, bafilomycin A1 enhanced the association between STIM2 and SERCA3. These findings demonstrate the location of STIM1 and STIM2 in the acidic Ca2+ stores and their association with Ca2+ channels and ATPases upon acidic stores discharge.
authors.affiliation: Department of Physiology (Cell Physiology Research Group) University of Extremadura, 10003 Cáceres, Spain.
authors.forename: Hanene
authors.initials: H
authors.lastname: Zbidi
authors.forename: Isaac
authors.initials: I
authors.lastname: Jardin
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Woodard
authors.forename: Jose J
authors.initials: JJ
authors.lastname: Lopez
authors.forename: Alejandro
authors.initials: A
authors.lastname: Berna-Erro
authors.forename: Ginés M
authors.initials: GM
authors.lastname: Salido
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D018274:Electroporation; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D018942:Macrolides / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D000071740:ORAI1 Protein; D011485:Protein Binding / Q000187:drug effects; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2
chemical_list: D015220:Calcium Channels; D015815:Cell Adhesion Molecules; D018942:Macrolides; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; C513279:STIM2 protein, human; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; C040929:bafilomycin A1; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium