Platelet ADP receptors

ADP是一种重要的血小板激动剂，在止血和血栓形成中发挥重要作用。我们提出了一个三受体模型来解释ADP对血小板的影响：一个与磷脂酶C偶联的受体，命名为P2Y1，第二个与腺苷环化酶抑制偶联的受体，P2T/AC，以及本征离子通道家族的第三个受体，P2X1受体，与快速钙内流偶联。我们已经证明，P2Y1受体在ADP诱导的血小板形状改变中起着重要作用。此外，我们已经证明，纤维蛋白原受体的激活需要P2Y1和P2T/AC受体的共同激活，GQ和GI伴随的信号对血小板聚集是充分和必要的。我们假设，任何激动剂的血小板聚集都需要来自GQ和GI通路的伴随信号。我们认为，除凝血酶和ADP外，所有的血小板聚集剂只激活GQ或GI，而不是两者，信号级联。我们进一步假设，这些血小板激动剂分别通过GQ和GI，通过来自P2YQ或P2T/AC的补充信号事件而导致纤维蛋白原受体激活。我们将阐明ADP、P2Y1和P2T/AC受体在其他血小板激动剂诱导的聚集中的作用。我们将阐明ADP、P2Y1和P2T/AC受体在其他血小板激动剂通过选择性P2受体拮抗剂诱导聚集中的作用。我们假设，新的和非典型的蛋白激酶C亚型的激活对于纤维蛋白原受体的激活是必不可少的。我们建议通过建立一个纤维蛋白原受体激活的细胞模型，并通过转染组成为活性的或显性的负的PKC亚型构建来检验我们的假设。我们建议在低严格杂交条件下通过同源筛选来克隆P2T/AC受体。可供选择的策略包括使用简并引物的RT-PCR方法、表达克隆和使用寡核苷酸探针进行筛选。最后，我们将阐明ADP诱导的血小板异常激活患者的P2Y1或P2T/AC受体的分子缺陷。这些研究将有助于阐明纤维蛋白原受体激活的机制以及ADP受体亚型在血小板激活中的作用。

ADP is an important agonist for platelet activation and plays a major role in hemostasis and thrombosis. We have proposed a three receptor model to explain the effects ADP on platelets: a receptor coupled to phospholipase C, designated P2Y1, a second receptor coupled to inhibition of adenyl cyclase, P2T/AC, and the third receptor of the intrinsic ion channel family, P2X1 receptor, coupled to rapid calcium influx. We have shown that the P2Y1 receptor plays an essential role in ADP-induced platelet shape change. Furthermore, e have demonstrated that fibrinogen receptor activation requires co-activation of both the P2Y1 and P2T/AC receptors and concomitant signaling from Gq and Gi is sufficient and necessary for platelet aggregation. We hypothesize that platelet aggregation by any agonist requires concomitant signaling from Gq and Gi pathways. We propose that all platelet aggregating agents, with the exception of thrombin and ADP, activate only either Gq or Gi, but not both, signaling cascades. We further hypothesize that these platelet agonists cause fibrinogen receptor activation by supplementary signaling events from either P2YQ or P2T/AC, through Gq and Gi, respectively. We will elucidate the role of ADP, the P2Y1, and P2T/AC receptors, in other platelet agonist-induced aggregation. We will elucidate the role of ADP, the P2Y1, and P2T/AC receptors, in other platelet agonist-induced aggregation by selective P2 receptor antagonists. We hypothesize that activation of novel and atypical protein kinase C isoforms is essential for fibrinogen receptor activation. We propose to test our hypothesis by developing a cell model for fibrinogen receptor activation and by transfection of constitutively active or dominant negative PKC isoform constructs. We propose to clone the P2T/AC receptor by homology screening under low stringency hybridization conditions. Alternative strategies include RT-PCR approach with degenerate primers, expression cloning, and screening with oligonucleotide probes. Finally, we will elucidate the molecular defect in the P2Y1 or P2T/AC receptors in the patients with abnormal ADP-induced platelet activation. These studies will shed light on the mechanisms of fibrinogen receptor activation and role of ADP receptor subtypes in platelet activation.