title: Intracellular Ca2+ store depletion induces the formation of macromolecular complexes involving hTRPC1, hTRPC6, the type II IP3 receptor and SERCA3 in human platelets.
abstract: Endogenously expressed human canonical transient receptor potential 1 (hTRPC1) and human canonical transient receptor potential 6 (hTRPC6) have been shown to play a role in store-operated Ca2+ entry (SOCE) in human platelets, where two mechanisms for SOCE, regulated by the dense tubular system (DTS) or the acidic granules, have been identified. In cells preincubated for 1 min with 100 microM flufenamic acid we show that hTRPC6 is involved in SOCE activated by both mechanisms, as demonstrated by selective depletion of the DTS or the acidic stores, using thapsigargin (TG) (10 nM) or 2,5-di-(tert-butyl)-1,4-hydroquinone (TBHQ) (20 microM), respectively, although it is more relevant after acidic store depletion. Co-immunoprecipitation experiments indicated that depletion of both stores separately results in time-dependent interaction between hTRPC1 and hTRPC6, and also between both hTRPCs and the type II IP3 receptor (IP3RII). The latter was greater after treatment with TG. TBHQ-induced coupling between hTRPC1 and 6 was transient and decreased after 30s of treatment, while that induced by TG increased for at least 3 min. TBHQ induced association between SERCA3, located in the acidic stores, hTRPC1, hTRPC6 and Orai1. TBHQ also evoked coupling between SERCA3 and IP3RII, presumably located in the DTS, thus suggesting interplay between both Ca2+ stores. Similarly, TG induces the interaction of SERCA2b with hTRPC1 and 6 and the IP3RII. The interactions between hTRPC1, hTRPC6, IP3RII and SERCA3 were impaired by disruption of the microtubules, supporting a role for microtubules in Ca2+ homeostasis. In conclusion, the present data demonstrate for the first time that hTRPC1, hTRPC6, IP3RII and SERCA3 are parts of a macromolecular protein complex activated by depletion of the intracellular Ca2+ stores in human platelets.
authors.affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, CB2 3EG Cambridge, UK. pcr@unex.es
authors.forename: Pedro C
authors.initials: PC
authors.lastname: Redondo
authors.forename: Isaac
authors.initials: I
authors.lastname: Jardin
authors.forename: Jose J
authors.initials: JJ
authors.lastname: Lopez
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 / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D018274:Electroporation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005439:Flufenamic Acid / Q000494:pharmacology; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D047468:Immunoprecipitation; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D006873:Hydroquinones; D053496:Inositol 1,4,5-Trisphosphate Receptors; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C096351:transient receptor potential cation channel, subfamily C, member 1; C019359:2,5-di-tert-butylhydroquinone; D005439:Flufenamic Acid; D019284:Thapsigargin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506949:ATP2A3 protein, human; D000252:Calcium-Transporting ATPases; D002118:Calcium