KSR, a Modifier of Ras Mediated Cell Transformation

描述(申请人提供)：体内和体外肿瘤形成 从原代组织培养的细胞需要多次转化 致癌事件。这些事件是由于创建或引入 显性作用癌基因与肿瘤抑制基因的失活。 细胞对这些基因转化特性的敏感性可能是 被其他细胞基因修饰，虽然不是驱动致癌过程， 是转换事件转导所必需的。中环 这一建议的假设是，蛋白产物的基因激酶 RAS抑制因子(KSR)是一种有效的细胞转化调节剂，通过 致癌RAS。这项提议的目的是解释分子机制。 这种推定的修饰物的生物学作用。已鉴定出KSR 作为一种功能丧失的等位基因抑制激活的RAS的表型 果蝇和线虫。这些数据表明，正常的KSR可能是一种 低等真核生物中RAS调节通路的正调节因子。分析 大骨节菌Ras基因在原代成纤维细胞中的转化 老鼠表明，KSR在哺乳动物中的功能类似。其他分析 证明KSR是RAS/Raf/MEK/ERK激酶的特异性效应器 卡斯卡德。KSR是磷酸化的，这些基因的子集突变 磷酸化位点导致KSR从细胞质重新分布到 原子核。这些观察结果导致了一种假设，即 KSR的磷酸化决定了它的亚细胞位置，并且 KSR的定位影响其调节Ras/Raf/MEK/ERK激酶的能力 级联和RAS介导的细胞转化。这些假说将得到检验。 通过：1)确定KSR中调节其亚细胞的序列 分布；2)确定KSR磷酸化在调节 KSR在细胞质和胞核之间的分布；3)特征性 KSR与Raf、MEK和ERK的物理相互作用及其生物学意义 结果；以及4)确定KSR对细胞的贡献 转化受其亚细胞分布和磷酸化的影响。

DESCRIPTION (provided by applicant): Tumor formation in vivo and the in vitro transformation of cells cultured from primary tissues require multiples oncogenic events. These events result from the creation or introduction of dominant acting oncogenes and the inactivation of tumor suppressors. Susceptibility of a cell to the transforming properties of these genes may be modified by other cellular genes that, while not driving the oncogenic process, are necessary for the transduction of the transforming event. The central hypothesis of this proposal is that the protein product of the gene Kinase Suppressor of Ras (KSR) is a potent modifier of cell transformation by oncogenic Ras. The goal of this proposal is to explain the molecular mechanisms underlying the biological actions of this putative modifier. KSR was identified as a loss-of-function allele that suppresses the phenotype of activated Ras in Drosophila and C. elegans. These data indicated that normal KSR may be a positive regulator of Ras-regulated pathways in lower eukaryotes. Analysis of oncogenic Ras-mediated transformation in primary fibroblasts from KSR about mice indicate that KSR functions similarly in mammals. Additional analyses demonstrate that KSR is a specific effector of the Ras/Raf/MEK/ERK kinase cascade. KSR is phosphorylated, and mutation of a subset of these phosphorylation sites causes the redistribution of KSR from the cytoplasm to the nucleus. These observations have lead to the hypotheses that the phosphorylation of KSR determines its subcellular location and that the localization of KSR affects its ability to regulate the Ras/Raf/MEK/ERK kinase cascade and Ras-mediated cell transformation. These hypotheses will be tested by: 1) identifying the sequences in KSR that regulate its subcellular distribution; 2) determining the role of KSR phosphorylation in regulating the distribution of KSR between the cytoplasm and the nucleus; 3) characterizing the physical interaction of KSR with Raf, MEK and ERK and its biological consequences; and 4) determining how the contribution of KSR to cell transformation is affected by its subcellular distribution and phosphorylation.