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主要作用。我们提出了一个三受体模型来解释ADP对血小板的影响：一个受体耦合到磷脂酶C，指定P2 Y1，第二个受体耦合到抑制腺苷酸环化酶，P2 T/AC，和第三个受体的内在离子通道家族，P2 X1受体，耦合到快速钙内流。我们已经表明，P2 Y1受体在ADP诱导的血小板形状变化中起着至关重要的作用。此外，已经证明纤维蛋白原受体活化需要P2 Y1和P2 T/AC受体两者的共活化，并且来自Gq和Gi的伴随信号传导对于血小板聚集是充分和必要的。我们假设任何激动剂引起的血小板聚集都需要来自Gq和Gi通路的伴随信号。我们建议，所有的血小板聚集剂，除了凝血酶和ADP，激活Gq或Gi，但不是两个，信号级联。我们进一步假设，这些血小板激动剂引起纤维蛋白原受体激活的补充信号事件从P2 YQ或P2 T/AC，通过Gq和Gi，分别。我们将阐明ADP、P2 Y1和P2 T/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，P2 Y1和P2 T/AC受体，在其他血小板激动剂诱导的聚集的选择性P2受体拮抗剂的作用。我们推测，激活新的和非典型的蛋白激酶C亚型是必不可少的纤维蛋白原受体激活。我们建议通过开发纤维蛋白原受体活化的细胞模型和转染组成性活性或显性阴性PKC亚型构建体来测试我们的假设。我们建议在低严格杂交条件下通过同源筛选克隆P2 T/AC受体。替代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的筛选。最后，我们将阐明ADP诱导的血小板活化异常患者中P2 Y1或P2 T/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活化的机制和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.