Manning D R, Brass L F
Department of Pharmacology, University of Pennsylvania, Philadelphia 19104.
Thromb Haemost. 1991 Oct 1;66(4):393-9.
Platelet activation begins with the binding of an agonist to the cell surface and culminates in the events of platelet aggregation, secretion and clot formation. Recent studies have identified two large families of GTP-binding proteins in platelets that are thought to participate in the events of platelet activation. The first of these are the G proteins, heterotrimeric proteins which are best known for their ability to mediate the interaction between agonist receptors and intracellular enzymes such as adenylyl cyclase, phospholipase C and phospholipase A2. To date, at least six G proteins have been identified in platelets: Gs, Gz, three variants of Gi and either Gq or G11 (or both). An additional, pertussis toxin-resistant G protein, Gq, may also be present. The second group of GTP-binding proteins present in platelets is substantially smaller than the heterotrimeric G proteins, ranging in size from 21 to 28 kDa. At least 15 such low molecular weight GTP-binding proteins have been identified in platelets, many of which are homologous to the products of the ras proto-oncogenes. In cells other than platelets, low molecular weight GTP-binding proteins have been implicated in protein transport, cell activation events and malignant transformation. Their role in platelets is unknown.
血小板激活始于激动剂与细胞表面的结合，并最终导致血小板聚集、分泌和凝块形成等事件。最近的研究已经在血小板中鉴定出两大类GTP结合蛋白，它们被认为参与血小板激活事件。其中第一类是G蛋白，即异源三聚体蛋白，它们最出名的是能够介导激动剂受体与细胞内酶如腺苷酸环化酶、磷脂酶C和磷脂酶A2之间的相互作用。迄今为止，在血小板中已鉴定出至少六种G蛋白：Gs、Gz、Gi的三种变体以及Gq或G11（或两者都有）。另外，可能还存在一种对百日咳毒素有抗性的G蛋白Gq。血小板中存在的第二类GTP结合蛋白比异源三聚体G蛋白小得多，大小在21至28 kDa之间。在血小板中已鉴定出至少15种这样的低分子量GTP结合蛋白，其中许多与ras原癌基因的产物同源。在血小板以外的细胞中，低分子量GTP结合蛋白与蛋白质转运、细胞激活事件和恶性转化有关。它们在血小板中的作用尚不清楚。
