Accumulation of PtdIns(3,4)P2 and PtdIns(3,4,5)P3 in thrombin-stimulated platelets. Different sensitivities to Ca2+ or functional integrin.
Differences in regulation of the accumulation of PtdIns(3,4)P2 versus that of PtdIns(3,4,5)P3 were noted in thrombin-stimulated human platelets. The rapid (within 20 s) response of PtdIns(3,4,5)P3 contrasted with a distinct lag in the accumulation of PtdIns(3,4)P2 that was followed by a pronounced increase by 90 s. The presence of 2.5 mM-CaCl2 further elevated PtdIns(3,4)P2 by 50-120%, but only at a late stage (after 90 s). Tetrapeptide RGDS (Arg-Gly-Asp-Ser), which blocks the interaction of ligands such as fibrinogen with platelet integrin alpha IIb beta 3 (GPIIb-IIIa), inhibited only the late-phase PtdIns(3,4)P2 accumulation that was associated with added Ca2+. Although stimulated tyrosine phosphorylation of platelet protein (total cell lysate) was altered by Ca2+ or RGDS, we could not identify any such proteins that were affected comparably to PtdIns(3,4)P2. In contrast to the PtdIns(3,4)P2 response, the accumulation of PtdIns(3,4,5)P3 was unaffected by Ca2+ or RGDS at any time.
Sorisky
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A
Department of Biochemistry, University of Vermont College of Medicine, Burlington 05405.
King
W G
WG
Rittenhouse
S E
SE
D000215:Acylation; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D002118:Calcium / Q000502:physiology*; D002413:Cations, Divalent; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D016023:Integrins / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology
D002413:Cations, Divalent; D016023:Integrins; D009842:Oligopeptides; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; C060974:phosphatidylinositol 3,4,5-triphosphate; C060980:phosphatidylinositol 3,4-diphosphate; C046617:arginyl-glycyl-aspartyl-serine; D013917:Thrombin; D002118:Calcium