title: FKBP52 is involved in the regulation of SOCE channels in the human platelets and MEG 01 cells.
abstract: Immunophilins are FK506-binding proteins that have been involved in the regulation of calcium homeostasis, either by modulating Ca(2+) channels located in the plasma membrane or in the rough endoplasmic reticulum (RE). We have investigated whether immunophilins would participate in the regulation of stored-operated Ca(2+) entry (SOCE) in human platelets and MEG 01. Both cell types were loaded with fura-2 for determining cytosolic calcium concentration changes ([Ca(2+)](c)), or stimulated and fixed to evaluate the protein interaction profile by performing immunoprecipitation and western blotting. We have found that incubation of platelets with FK506 increases Ca(2+) mobilization. Thapsigargin (TG)-evoked, Thr-evoked SOCE and TG-evoked Mn(2+) entry resulted in significant reduction by treatment of platelets with immunophilin antagonists. We confirmed by immunoprecipitation that immunophilins interact with transient receptor potential channel 1 (TRPC1) and Orai1 in human platelets. FK506 and rapamycin reduced the association between TRPC1 and Orai1 with FK506 binding protein (52) (FKBP52) in human platelets, and between TRPC1 and the type II IP(3)R, which association is known to be crucial for the maintenance of SOCE in human platelets. FKBP52 role in SOCE activation was confirmed by silencing FKBP52 using SiRNA FKBP52 in MEG 01 as demonstrated by single cell configuration imaging technique. TRPC1 silencing and depletion of cell of TRPC1 and FKBP52 simultaneously, impair activation of SOCE evoked by TG in MEG 01. Finally, in MEG 01 incubated with FK506 we observed a reduction in TRPC1/FKBP52 coupling, and similarly, FKBP52 silencing reduced the association between IP3R type II and TRPC1 during SOCE. All together, these results demonstrate that immunophilins participate in the regulation of SOCE in human platelets.
authors.affiliation: Department of Physiology Cellular Physiology Research Group, University of Extremadura, 10003 Cáceres, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: López
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
authors.forename: Pedro C
authors.initials: PC
authors.lastname: Redondo
mesh_terms: D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D020104:Immunophilins / Q000494:pharmacology; D047468:Immunoprecipitation; D007166:Immunosuppressive Agents / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D055016:Megakaryocyte Progenitor Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000071740:ORAI1 Protein; D034741:RNA, Small Interfering / Q000235:genetics; D050052:TRPC Cation Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016559:Tacrolimus / Q000494:pharmacology; D022021:Tacrolimus Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D053496:Inositol 1,4,5-Trisphosphate Receptors; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D034741:RNA, Small Interfering; D050052:TRPC Cation Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; D019284:Thapsigargin; D022021:Tacrolimus Binding Proteins; C403485:tacrolimus binding protein 4; D020104:Immunophilins; D002118:Calcium; D016257:Fura-2; D016559:Tacrolimus