Signal transduction defects in human platelets

血小板功能的先天性缺陷与出血表现有关，血小板在止血中起主要作用。本项目的目标是确定先天性血小板功能缺陷患者血小板功能障碍的生化机制，从而提高我们对正常血小板活化机制的理解，这对出血和血栓性疾病的新治疗策略的发展至关重要。绝大多数先天性血小板缺陷患者的特征通常是聚集反应受损和活化时的致密颗粒分泌;他们中的大多数具有正常的致密颗粒储存。这些患者被归类为定义不严格的“血小板分泌缺陷”或“活化缺陷”。在这些疾病中，根本的生化和分子机制是完全未知的。我们的假设是这些患者在信号转导机制中有缺陷。该项目集中于特定的患者，在这些患者中，我们证明了涉及信号转导机制的两种主要蛋白质中迄今未描述的缺陷，即a）磷脂酶C-β 2（Aim 1）和B）GTP结合蛋白Galphaq（Aim 2）。我们迄今为止的研究表明，PLC-β 2和Galphaq基因的编码序列在这些患者中是正常的，但各自的mRNA水平降低。我们将研究PLC-β 2（Aim 1）和Galphaq（Aim 2）的转录调控，以确定其机制。在其他几个血小板功能缺陷的患者中，我们已经获得了信号传导事件异常的证据（例如Ca 2+动员，pleckstrin磷酸化）。在目标3中，我们将对3-4名患者及其家属进行详细研究，以描述导致反应受损的机制。该项目代表了应用最先进的技术来定义一组患者血小板功能障碍的分子机制，这些患者目前的特征非常差，并构成了一个未开发的新信息来源。这些研究将为两种主要蛋白质PLC-β 2和Galphaq在血小板信号转导机制中的作用提供新的信息。

Platelets play a major role in hemostasis in congenital defects in platelet function are associated with bleeding manifestations. The goal of this project is to define the biochemical mechanisms underlying the platelet dysfunction in patients with congenital platelet function defects and thereby enhance our understanding of the normal platelet activation mechanisms, which are vital to the development of newer therapeutic strategies for both bleeding and thrombotic disorders. The vast majority of patients with congenital platelet defects are generally characterized by impaired aggregation responses and dense granule secretion on activation; most of them have normal dense granule stores. These patients are lumped in the loosely defined group called "platelet secretion defects" or "activation defects". In them, the underlying biochemical and molecular mechanisms are totally unknown. Our hypothesis is that these patients have defects in the signal transduction mechanisms This project focuses on specific patients in whom we demonstrate hitherto undescribed deficiencies in two major proteins involved in signal transduction mechanisms, namely, a) phospholipase C-beta2 (Aim 1), and b) GTP- binding protein Galphaq (Aim 2), respectively. Our studies to date demonstrate that the coding sequence of PLC-beta2 and Galphaq gene is normal in these patients but the respective mRNA levels are decreased. We will study the transcriptional regulation of PLC-beta2 (Aim 1) and Galphaq (Aim 2) to define the mechanisms. In several other patient with platelet function defects, we have obtained evidence for abnormalities in the signaling events (e.g. Ca2+ mobilization, pleckstrin phosphorylation). In Aim 3, we will perform detailed studies in 3-4 patients and their family members to characterize the mechanisms leading to the impaired responses. This project represents application of state-of-the-art techniques to define the molecular mechanisms of platelet dysfunction in a group of patients who are very poorly characterized at present and constituted an untapped source of new information. These studies will provide new information on the role of two major protein, PLC-beta2 and Galphaq, in platelet signal transduction mechanisms.