RhoA Signaling in Transformation by v-Src

描述(由申请人提供)：本提案的长期目标是了解RhoA在v-Src转化中的作用，RhoA是一种诱导肌动蛋白应激纤维的小GTP酶。在细胞中，v-Src是c-Src酪氨酸激酶的一种激活形式，被认为通过持续刺激正常的瞬时信号通路来促进转化。事实上，某些人类癌症具有c-Src活性升高，肿瘤进展与src活性水平相关。一些研究表明，v-Src降低了RhoA[GTP]的水平，这会导致转化细胞中肌动蛋白应激纤维的丢失。 然而，我们实验室的证据表明，v-Src活性提高了RhoA[GTP]水平。RhoA对未转化细胞的增殖也是必需的，可能是通过调节关键细胞周期调节因子的表达时间和维持细胞周期进程中MAPK的活性。这些观察结果导致了如下的普遍假设：v-Src诱导的有丝分裂转化需要RhoA信号，但v-Src诱导的肌动蛋白应激纤维解体和细胞运动，绕过了RhoA信号。三个特定的目的将验证这一假说：1)研究在v-Src介导的有丝分裂转化中对RhoA信号的要求。2)确定v-Src诱导Cofilin激活的机制。3)评价Cofilin激活在Src激酶活性升高的细胞迁移和侵袭中的意义。

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to understand the role of RhoA, a small GTPase that induces actin stress fibers, in v-Src transformation. In cells, v-Src, an activated form of the c-Src tyrosine kinase, is thought to promote transformation by continually stimulating normally transient signaling pathways. In fact, certain human cancers have elevated c-Src activity, and tumor progression correlates with the Src activity level. Several studies suggest that v-Src decreases RhoA[GTP] levels, and that this causes actin stress fiber loss in transformed cells. However, evidence from our laboratory indicates v-Src activity enhances RhoA[GTP] levels. RhoA is also required for the proliferation of non-transformed cells, likely by regulating the timing of expression of key cell cycle regulators and sustaining MAPK activity during cell cycle progression. These observations have led to the following general hypothesis: v-Src induced mitogenic transformation requires RhoA signaling, but v-Src induced actin stress fiber disassembly and cell motility, circumvent RhoA signaling. Three Specific Aims will test this hypothesis: 1) Investigate the requirement for RhoA signaling in v-Src-mediated mitogenic transformation. 2) Determine the mechanism by which v-Src induces cofilin activation. 3) Evaluate the significance of cofilin activation on cell migration and invasion in cells with elevated Src kinase activity.