FUNCTIONAL CHARACTERIZATION OF CYTOPLASMIC DOMAIN OF ALPHAPDGF RECEPTOR

血小板衍生生长因子(PDGF)是一种有效的促有丝分裂原 间充质细胞。两种类型的PDGF受体(α和β) 已经被克隆和测序。的配基结合区 PDGF受体位于细胞外域，它包括 五个免疫球蛋白样区。细胞的细胞质区域 PDGF受体含有与其他酪氨酸同源的序列 激活剂。该激酶序列被该激酶插入片段打断 (KI)域。 血小板衍生生长因子与其受体的相互作用引起一些快速的变化 在细胞中，这包括受体激酶的激活 活动，刺激几个第二信使通路和 DNA合成的启动。体内和体内的主要生物 β-PDGF受体的体外磷酸化位点已被 已确认身份。我们正在研究这些磷酸化的作用。 α-PDGF受体在信号转导中的位置。几个 α-PDGF受体的点突变是由 定点突变。酪氨酸731或742基因突变的研究 KI结构域不影响PDGF诱导的心肌细胞酪氨酸磷酸化 活体底物的受体，PLC-伽马。然而，两者 损伤显著损害了与PI-3激酶的受体联系。 抗P-Tyr抗体可回收的PI-3激酶也显著 在PDGF刺激的细胞中，表达任何一个突变受体的数量都减少了。 因为这两个突变都没有破坏PDGF诱导的有丝分裂或 趋化性，我们认为α-PDGF受体相关的PI-3 这两种主要的PDGF都不需要激酶活性 信令功能。

Platelet-derived growth factor (PDGF) is a potent mitogen for mesenchymal cells. Two types (alpha and beta) of PDGF receptor have been cloned and sequenced. The ligand-binding region of the PDGF receptor is in the extracellular domain, which consists of five immunoglobulin-like regions. The cytoplasmic region of the PDGF receptor contains sequences homologous to other tyrosine kinases. The kinase sequences are interrupted by the kinase insert (KI) domain. The interaction of PDGF with its receptor causes some rapid changes in the cell, which include the activation of the receptor kinase activity, stimulation of several second messenger pathways and initiation of DNA synthesis. Both of the major in vivo and in vitro phosphorylation sites of the beta-PDGF receptor have been identified. We are studying the role of these phosphorylation sites of the alpha-PDGF receptor in signal transduction. Several point mutations of the alpha-PDGF receptor have been generated by site-directed mutagenesis. Mutation of tyrosine 731 or 742 in the KI domain does not impair PDGF-induced tyrosine phosphorylation of the receptor or of an in vivo substrate, PLC-gamma. However, both lesions markedly impair receptor association with PI-3 kinase. Anti-P-Tyr antibody recoverable PI-3 kinase was also dramatically reduced in PDGF-stimulated cells expressing either mutant receptor. Since neither mutation abolished PDGF-induced mitogenesis or chemotaxis, we conclude that alpha-PDGF receptor-associated PI-3 kinase activity is not required for either of these major PDGF signalling functions.