Capacitative and non-capacitative signaling complexes in human platelets.
Discharge of the intracellular Ca(2+) stores activates Ca(2+) entry through store-operated channels (SOCs). Since the recent identification of STIM1 and STIM2, as well as the Orai1 homologs, Orai2 and Orai3, the protein complexes involved in Ca(2+) signaling needs re-evaluation in native cells. Using real time PCR combined with Western blotting we have found the expression of the three Orai isoforms, STIM1, STIM2 and different TRPCs in human platelets. Depletion of the intracellular Ca(2+) stores with thapsigargin, independently of changes in cytosolic Ca(2+) concentration, enhanced the formation of a signaling complex involving STIM1, STIM2, Orai1, Orai2 and TRPC1. Furthermore, platelet treatment with the dyacylglicerol analog 1-oleoyl-2-acetyl-sn-glycerol (OAG) resulted in specific association of Orai3 with TRPC3. Treatment of platelets with arachidonic acid enhanced the association between Orai1 and Orai3 in human platelets and overexpression of Orai1 and Orai3 in HEK293 cells increased arachidonic acid-induced Ca(2+) entry. These results indicate that Ca(2+) store depletion results in the formation of exclusive signaling complexes involving STIM proteins, as well as Orai1, Orai2 and TRPC1, but not Orai3, which seems to be involved in non-capacitative Ca(2+) influx in human platelets.
Department of Physiology, University of Extremadura, Caceres, Spain.
Alejandro
A
Berna-Erro
Carmen
C
Galan
Natalia
N
Dionisio
Luis J
LJ
Gomez
Gines M
GM
Salido
Juan A
JA
Rosado
D016718:Arachidonic Acid / Q000494:pharmacology / Q000502:physiology; D001792:Blood Platelets / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology / Q000502:physiology; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D000071740:ORAI1 Protein; D000071741:ORAI2 Protein; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism; D000074287:TRPC6 Cation Channel
C520323:1-oleoyl-2-acetoyl-sn-glycerol; D015220:Calcium Channels; D015815:Cell Adhesion Molecules; D004075:Diglycerides; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D000071741:ORAI2 Protein; C514506:ORAI2 protein, human; C522867:Orai3 protein, human; D020033:Protein Isoforms; C103530:STIM1 protein, human; C513279:STIM2 protein, human; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C096351:transient receptor potential cation channel, subfamily C, member 1; D016718:Arachidonic Acid