The biochemical basis for the functional heterogeneity of @entity1 blood platelets was investigated in terms of protein phosphorylation, cytoplasmic @entity460 ([ @entity141 ]i), the ratio of 46 and 50 kDa @entity19319 ( @entity19319 ), and @entity3007 -binding proteins (G-proteins). Platelets were fractionated by density. Comparing resting low-density platelets (LDP) to @entity2101 ( @entity2101 ) revealed higher phosphorylation of proteins in the 47, 31, and 24 kDa ranges. A higher phosphorylation of the 20 kDa protein in LDP compared to @entity2101 was related to an enhanced [ @entity141 ]i, an increased @entity857 -ribosylation of the inhibitory G-protein (G(i alpha1-3)) and @entity3547 , and a decreased @entity857 -ribosylation of the stimulatory G-protein (G(s alpha)). The differences in the ribosylation patterns of the subpopulations were not influenced by thrombin stimulation or exposure to @entity5015 ( @entity5015 ). An 18 kDa phosphoprotein was more highly phosphorylated in resting @entity2101 than in LDP. Thrombin exposure caused dephosphorylation of the 18 kDa phosphoprotein in the @entity2101 , but generally increased phosphorylation of both @entity2101 and LDP in the 47, 31, 24, and 20 kDa bands. Preincubation with @entity5015 or @entity1854 diminished the subsequent thrombin-induced increase in phosphorylation, particularly in @entity2101 . In unstimulated @entity2101 , the 50 kDa @entity19319 phospho form was enhanced, whereas in unstimulated LDP the 46 kDa @entity19319 dephospho form was increased. Our findings suggest that the functional heterogeneity of platelets is partly derived from differences in signal transduction mechanisms reflected in varying phosphoprotein patterns and G-protein properties of platelet stimulatory and inhibitory pathways.

Analysis of GTP-binding proteins, phosphoproteins, and cytosolic XXXX in functional heterogeneous @entity1 blood platelet subpopulations.

@entity1 :: ('9606', 'Species') :: ['human'] @entity3007 :: ('MESH:D006160', 'Chemical') :: ['GTP'] @entity3547 :: ('387', 'Gene') :: ['rhoA'] @entity1854 :: ('MESH:D009599', 'Chemical') :: ['sodium nitroprusside'] @entity5015 :: ('MESH:D000527', 'Chemical') :: ['prostaglandin E1', 'PGE1'] @entity2101 :: ('MESH:C538394', 'Disease') :: ['high-density platelets', 'HDP'] @entity460 :: ('MESH:D002118', 'Chemical') :: ['calcium'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+'] @entity857 :: ('MESH:D000244', 'Chemical') :: ['ADP'] @entity19319 :: ('7408', 'Gene') :: ['vasodilator-stimulated protein', 'VASP']
@entity460 :: (MESH:D002118,Chemical) :: ['calcium']
