SIGNAL TRANSDUCTION BY LYSOPHOSPHATIDIC ACID

溶血磷脂酸（LPA）是血清中的主要有丝分裂原， 一系列与癌症发病机制相关的细胞过程， 其他人类疾病。 尽管LPA在控制 细胞生长和其他细胞活动， LPA的信号机制而蛋白酪氨酸 磷酸化被认为是一种重要的信号传导机制 LPA和G蛋白偶联受体的其他激动剂，它仍然是 很大程度上未知G蛋白的激活如何导致酪氨酸 磷酸化 为了解决这一重要问题，LPA诱导的 表皮生长因子受体（EGFR）的酪氨酸磷酸化 将被研究。 根据我们的初步观察， 细胞信号传导中氧化还原调节的证据，据推测， LPA通过降低EGF受体磷酸酶来反式激活EGFR 活性通过钙和活性氧介导的机制 物种（ROS）。 提出了三个具体目标，以严格评估 这一假设的关键方面。 在具体目标一中， 内在EGFR酪氨酸激酶活性将使用激酶- 缺陷型EGFR和新的EGFR特异性抑制剂。 的影响 降低蛋白酪氨酸磷酸酶对EGFR的活性也将 接受检查。 或者，提出了一种新的敏感方法， 确定LPA是否激活EGFR激酶。为了进一步评估 LPA诱导的酪氨酸磷酸化是否由内源性 EGF受体激酶或另一种细胞激酶，特异性Aim II 提出了磷酸肽作图和诱变实验来分析 EGFR上LPA诱导的酪氨酸磷酸化位点。 具体目标 III，LPA对EGFR去磷酸化活性的调节将是 在体外和完整细胞中研究， 可以检测到氧化还原介导的变化， 将对ROS进行评估。 这些研究不仅将促进我们的 了解LPA和G蛋白的信号转导， 许多对癌症发展至关重要的细胞过程， 其他人类疾病，但也将刺激进一步的研究， 氧化信号的新兴领域。

Lysophosphatidic acid (LPA) is a major mitogen in serum that regulates an array of cellular processes related to pathogenesis of cancer and other human diseases. Despite the central role of LPA in controlling cell growth and other cellular activities, very little is understood about the signaling mechanisms of LPA. While protein tyrosine phosphorylation has been recognized as an important signaling mechanism of LPA and other agonists of G protein-coupled receptors, it remains largely unknown how activation of G-proteins leads to tyrosine phosphorylation. To address this important question, LPA-induced tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) will be studied. Based on our preliminary observations and increasing evidence of redox-regulation in cell signaling, it is postulated that LPA transactivates the EGFR by decreasing EGF receptor phosphatase activity through a mechanism mediated by calcium and reactive oxygen species (ROS). Three specific aims are proposed to critically evaluate key aspects of this hypothesis. In Specific Aim I, the requirement for intrinsic EGFR tyrosine kinase activity will be assessed using kinase- defective EGFR and new specific inhibitors for the EGFR. Effects of decreasing protein tyrosine phosphatase activity toward EGFR will also be examined. Alternatively, a novel sensitive approach is proposed to determine whether LPA activates the EGFR kinase. TO further evaluate whether LPA-induced tyrosine phosphorylation is catalyzed by intrinsic EGF receptor kinase or by another cellular kinase, Specific Aim II proposes phosphopeptide mapping and mutagenesis experiments to analyze LPA-induced tyrosine phosphorylation sites on the EGFR. In Specific Aim III, regulation of EGFR-dephosphorylating activity by LPA will be investigated both in vitro and in intact cells under conditions that redox-mediated changes can be detected, and the involvement of calcium and ROS will be evaluated. These studies not only will advance our understanding of signal transduction by LPA and G-proteins that control many cellular processes fundamental to the development of cancer and other human diseases, but also will stimulate further research in the emerging area of oxidative signaling.