Platelet ADP receptors

ADP是血小板活化的重要激动剂，在止血和血栓形成中起重要作用。我们提出了一个三受体模型来解释ADP对血小板的影响：一个受体与磷脂酶C偶联，命名为P2Y1，第二个受体与腺苷环化酶抑制，P2T/AC，以及内在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，而Gq和Gi的伴随信号对于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Gq和Gi信号通路的伴随。我们认为，除了凝血酶和ADP外，所有的血小板聚集剂只激活Gq或Gi中的一个，而不是同时激活两个信号级联。我们进一步假设这些血小板激动剂通过P2YQ或P2T/AC分别通过Gq和Gi补充信号事件引起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受体在选择性P2受体拮抗剂诱导的其他血小板激动剂聚集中的作用。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。我们建议通过建立纤维蛋白原受体激活的细胞模型和转染组成活性或显性阴性PKC异构体来验证我们的假设。我们建议在低严格杂交条件下通过同源性筛选克隆P2T/AC受体。替代策略包括RT-PCR方法与退化引物，表达克隆，筛选与寡核苷酸探针。最后，我们将阐明P2Y1或P2T/AC受体在adp诱导的异常血小板活化患者中的分子缺陷。这些研究将揭示纤维蛋白原受体活化的机制以及ADP受体亚型在血小板活化中的作用。

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.