Phosphatidylinositol 4,5-bisphosphate enhances store-operated calcium entry through hTRPC6 channel in human platelets.
Phosphatidylinositol 4,5-bisphosphate (PIP2) is a versatile regulator of TRP channels. We report that inclusion of a PIP2 analogue, PIP2 1,2-dioctanoyl, does not induce non-capacitative Ca2+ entry per se but enhanced Ca2+ entry stimulated either by thrombin or by selective depletion of the Ca2+ stores in platelets, the dense tubular system, using 10 nM TG, and the acidic stores, using 20 microM 2,5-di-(tert-butyl)-1,4-hydroquinone (TBHQ). Reduction of PIP2 levels by blocking PIP2 resynthesis with Li+ or introducing a monoclonal anti-PIP2 antibody, or sequestering PIP2 using poly-lysine, attenuated Ca2+ entry induced by thrombin, TG and TBHQ, and reduced thrombin-evoked, but not TG- or TBHQ-induced, Ca2+ release from the stores. Incubation with the anti-hTRPC1 antibody did not alter the stimulation of Ca2+ entry by PIP2, whilst introduction of anti-hTRPC6 antibody directed towards the C-terminus of hTRPC6 reduced Ca2+ and Mn2+ entry induced by thrombin, TG or TBHQ, and abolished the stimulation of Ca2+ entry by PIP2. The anti-hTRPC6 antibody, but not the anti-hTRPC1 antibody or PIP2, reduced non-capacitative Ca2+ entry by the DAG analogue 1-oleoyl-2-acetyl-sn-glycerol. In summary, hTRPC6 plays a role both in store-operated and in non-capacitative Ca2+ entry. PIP2 enhances store-operated Ca2+ entry in human platelets, most probably by stimulation of hTRPC6 channels.
Jardín
Isaac
I
Department of Physiology (Cell Physiology Research Group), University of Extremadura, 10071 Cáceres, Spain.
Redondo
Pedro C
PC
Salido
Ginés M
GM
Rosado
Juan A
JA
D000143:Acids / Q000737:chemistry; D000906:Antibodies / Q000276:immunology; D001792:Blood Platelets / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004579:Electron Transport; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006873:Hydroquinones / Q000494:pharmacology; D008094:Lithium / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology*; D050052:TRPC Cation Channels / Q000276:immunology / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D013917:Thrombin / Q000494:pharmacology
D000143:Acids; D000906:Antibodies; D006873:Hydroquinones; D019269:Phosphatidylinositol 4,5-Diphosphate; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C096351:transient receptor potential cation channel, subfamily C, member 1; D008094:Lithium; C018855:2-tert-butylhydroquinone; D013917:Thrombin; D002118:Calcium