INTESTINAL CELL GROWTH CONTROL: ROLE OF TYROSINE KINASES

描述(摘自申请者摘要)：结肠癌排在第三位 是美国癌症死亡的主要原因。这项研究的重点是 Src酪氨酸激酶在结肠癌发生中的作用其他人和 PI已经表明，下调Src活性对 分化和上调Src活性对 肠道细胞的恶性转化。因此，目标是定义 正常结肠组织中Src表达下调的分子机制 上调src在结肠癌中的表达。假设是Src的特定结构域， 与它们结合的蛋白质是Src活性的重要调节因子。 因此，努力的方向是识别调节细胞的蛋白质 SRC在肠道细胞成熟和恶变过程中的作用。 利用酵母双杂交试验，PI最近确定了RACK1，一种受体 对于活化的C激酶和G蛋白的β亚基的同系物，作为 新的Src SH2结合蛋白。PI发现RACK1抑制特异性 Src活性与NIH3T3细胞生长的关系。RACK1对 细胞生长，部分是通过延长细胞周期的G0/G1期。《少年派》 将进一步描述Src的合作伙伴RACK1以及RACK1 调节Src活性和肠道细胞生长的功能。一个目标是 评估两种蛋白质结合和磷酸化的需要 RACK1，由Src用于RACK1对Src活性和细胞生长的抑制。第二 目的是分析串扰产生的机制 RACK1连接的Src和PKC信号通路。第三个目标是评估 Rackl对v-Src转化细胞的影响。第四个目标是进一步 分析RACK1在细胞周期和细胞周期中对Src活性的影响 细胞周期。这些研究应该产生关于以下方面的重要新信息 一种新型的src和细胞生长抑制因子。了解抑制剂是如何 有丝分裂信号在调节肠道细胞生长中的作用以及这种作用的丧失 抑制导致不受控制的生长和恶变，应该 影响我们对结肠癌生物学的基本认识，并导致 结肠癌治疗的新策略。内源性致癌抑制物 激酶是潜在的肿瘤抑制因子；它们代表着令人兴奋的新靶点 进行治疗干预。

DESCRIPTION (Adapted from the Applicant's Abstract): Colon cancer is the third leading cause of cancer deaths in the United States. This research focuses on the role of the Src tyrosine kinase in colonic carcinogenesis. Others and the PI have shown that downregulation of Src activity is important for differentiation and that upregulation of Src activity is important for malignant transformation of intestinal cells. Thus, the goal is to define molecular mechanisms that downregulate Src in normal colon and those that upregulate Src in colon cancer. The hypothesis is that specific domains of Src, and the proteins that bind to them, are important regulators of Src activity. Thus, effort is directed towards identifying cellular proteins that modulate Src function during intestinal cell maturation and malignant transformation. Using a yeast two-hybrid assay, the PI recently identified RACK1, a receptor for activated C kinase and a homolog of the beta subunit of G proteins, as a novel Src SH2-binding protein. The PI found that RACK1 inhibits the specific activity of Src and the growth of NIH 3T3 cells. RACK1 exerts its effect on cell growth, in part, by prolonging the G0/G1 phase of the cell cycle. The PI will further characterize Src's partner RACK1 and the mechanism by which RACK1 functions to regulate Src activity and intestinal cell growth. One aim is to assess the requirement of binding of the two proteins and of phosphorylation of RACK1, by Src for RACK1 inhibition of Src activity and cell growth. The second aim is to analyze the mechanism by which cross talk occurs between the RACK1-linked signaling pathways of Src and PKC. The third aim is to assess RACKl's influence on cell transformation by v-Src. The fourth aim is to further analyze the effect of RACK1 on the cell cycle and on Src activity during the cell cycle. These studies should generate significant new information regarding a novel inhibitor of Src and cell growth. Understanding how inhibitors of mitogenic signals work to regulate intestinal cell growth and how loss of that inhibition results in uncontrolled growth and malignant transformation, should impact our basic understanding colon cancer biology and lead to development of novel strategies for colon cancer therapy. Endogenous inhibitors of oncogenic kinases are potentially tumor suppressors; they represent exciting new targets for therapeutic intervention.