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剂， 间充质细胞 两种类型的PDGF受体（α和β） 已经被克隆并测序了。 的配体结合区， PDGF受体位于细胞外结构域，其由以下组成： 五个免疫球蛋白样区域。 的胞质区 PDGF受体含有与其他酪氨酸蛋白同源的序列， 激酶。 激酶序列被激酶插入片段中断 (KI)域 PDGF与其受体的相互作用引起一些快速的变化 包括受体激酶的激活 活性，刺激几个第二信使途径， 启动DNA合成。 主要的体内和体内 β-PDGF受体的体外磷酸化位点已经被 鉴定 我们正在研究这些磷酸化的作用 在信号转导中的α-PDGF受体的位点。 几 α-PDGF受体的点突变已经通过以下方法产生： 定点诱变。 酪氨酸731或742突变， KI结构域不损害PDGF诱导的酪氨酸磷酸化， 受体或体内底物PLC-γ。 但无论 损伤明显损害与PI-3激酶的受体结合。 抗-P-Tyr抗体可恢复的PI-3激酶也显著降低。 在表达任一突变受体的PDGF刺激的细胞中减少。 由于两种突变都不能消除PDGF诱导的有丝分裂， 趋化性，我们得出结论，α-PDGF受体相关的PI-3 这些主要的PDGF都不需要激酶活性 信号功能。

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.