C-CBL IN MODULATION OF CELL ADHESION AND MORPHOLOGY

描述：(改编自调查人员的摘要)有 大量证据表明原癌蛋白c-Cbl参与了 正常细胞和转化细胞的信号转导。C-Cbl变成酪氨酸 通过各种受体对刺激作出反应而被磷酸化，如 通过致癌形式的蛋白质酪氨酸转化的细胞也是如此 激酶Abl.C-Cbl酪氨酸磷酸化显著上调其 与各种重要的信号分子结合。然而，生物学上的 C-Cbl介导的信号转导的后果还知之甚少。 最近，我们成功地定位了酪氨酸磷酸化位点。 C-Cbl.为了分析c-Cbl的生物学功能，我们 过表达野生型c-Cbl或其缺乏酪氨酸的突变体 Abl转化成纤维细胞中的磷酸化位点并证明 野生型c-Cbl抑制癌基因Abl转化，而野生型c-Cbl 磷酸化缺陷的c-Cbl促进了这种转化。的影响 野生型c-Cbl与细胞黏附和扩散的诱导有关 在细胞外基质上。这些观察结果与 之前的发现，使我们假设c-Cbl招募，在一个 酪氨酸磷酸化依赖方式与PI-3激酶和Crk家族 蛋白质到膜和/或焦点黏附复合体。这又反过来， 触发促进焦点组装的信号转导通路 黏附复合体和肌动蛋白应激纤维。酪氨酸 依赖于磷酸化的细胞形态和黏附调节可能 构成了c-Cbl的主要生物学功能。 当前提案的总体目标是检验这一假设。 因此，我们项目的具体目标是：1)确定 ITS必需的c-Cbl酪氨酸磷酸化位点 变换抑制函数；2)确定关系 C-Cbl酪氨酸磷酸化的生物学效应与 C-Cbl与膜的相互作用、焦点黏附复合体和 Abl转化成纤维细胞中的细胞骨架；3)测定 PI-3激酶与Crk依赖信号转导的关系 C-Cbl在Abl转化成纤维细胞中的途径和生物学效应 以及4)评估c-Cbl在不同生物反应中的作用。 蛋白酪氨酸激酶介导的细胞外刺激类型 未转化的成纤维细胞。 调查人员相信，这项工作将定义生物 C-Cbl的功能并确定其分子基础。这应该是 大大提高了我们对正常细胞激活和 肿瘤转化，并可能提出新的治疗方法 靶向信号转导机制。

DESCRIPTION: (adapted from the investigator's abstract) There is substantial evidence that the protooncogenic protein c-Cbl is involved in signal transduction in normal and transformed cells. c-Cbl becomes tyrosine phosphorylated in response to stimulation through a variety of receptors, as well as in the cells transformed by oncogenic forms of the protein tyrosine kinase Abl. Tyrosine phosphorylation of c-Cbl dramatically upregulates its binding to various crucial signaling molecules. However, the biological consequences of c-Cbl-mediated signal transduction are poorly understood. Recently, we have succeeded in mapping the tyrosine phosphorylation sites of c-Cbl. In order to analyze the biological functions of c-Cbl, we overexpressed wild-type c-Cbl or its mutant form lacking tyrosine phosphorylation sites in Abl-transformed fibroblasts and demonstrated that the wild-type c-Cbl suppresses transformation by oncogenic Abl, whereas the phosphorylation-defective c-Cbl enhances this transformation. The effect of wild-type c-Cbl is connected to the induction of cell adhesion and spreading on the extracellular matrix. These observations, taken together with the previous findings, led us to the hypothesis that c-Cbl recruits, in a tyrosine-phosphorylation dependent manner, PI-3 kinase and Crk-family proteins to the membrane and/or focal adhesion complexes. This, in turn, triggers signal transduction pathways facilitating the assembly of focal adhesion complexes and actin stress fibers. The tyrosine phosphorylation-dependent regulation of cell morphology and adhesion may constitute the major biological functions of c-Cbl. The overall objective of the current proposal is to test this hypothesis. Accordingly, the specific aims of our project are: 1) to determine the tyrosine phosphorylation sites of c-Cbl essential for its transformation-suppressing function; 2) to determine the relationship between the biological effects of c-Cbl tyrosine phosphorylation and the interactions of c-Cbl with the membrane, focal adhesion complexes and cytoskeleton in Abl-transformed fibroblasts; 3) to determine the relationship between PI-3 kinase- and Crk-dependent signal transduction pathways and the biological effects of c-Cbl in Abl-transformed fibroblasts; and 4) to assess the involvement of c-Cbl in biological responses to various types of extracellular stimulation mediated by protein tyrosine kinases in untransformed fibroblasts. The investigators are confident that this work will define the biological functions of c-Cbl and determine their molecular basis. This should substantially advance our understanding of normal cell activation and neoplastic transformation and may suggest novel therapeutic approaches that target signal transduction mechanisms.