SIGNALING & FUNCTION OF THE SGK STEROID INDUCIBLE KINASE

描述：类固醇受体信号和细胞之间的动态平衡 磷酸化级联在以下关键步骤协调控制细胞生长 这些信号转导通路汇聚在一起。可以想象，严格的 对这种汇聚点的监管赋予了对 正常细胞中的抗增殖信号，并可能调节 如果适当诱导，转化细胞的不受控制的增殖或 激活了。糖皮质激素是类固醇激素的一种，它可以强烈地 抑制Con8大鼠乳腺癌细胞的体内和体外生长， 它们来自荷尔蒙反应性大鼠乳腺腺癌。至 确定这种生长停滞的类固醇调节介质，减法 乳腺肿瘤细胞中糖皮质激素反应基因的克隆 文库发现了一种新的丝氨酸/苏氨酸蛋白激酶SGK，即 受糖皮质激素和血清的转录调控。的存在 SGK提示类固醇激素和类固醇激素之间存在相互作用的新途径 细胞磷酸化的级联反应。SGK的结构/功能分析 将通过体外诱变进行关系以确定 特定蛋白编码区在底物转磷酸化中的作用 特异性和作为细胞磷酸化的靶点。角色 SGK在培养细胞糖皮质激素生长抑制反应中的作用 在乳腺细胞来源的肿瘤将通过分析载体进行检查 编码这种蛋白激酶的野生型、突变型或反义形式 吉恩。最后，交互式克隆策略，如酵母双杂交 系统，将用于鉴定发现的SGK结合蛋白 免疫共沉淀法及其功能表征 阐明SGK细胞内信号转导途径。因此， 总体目标是定义 SGK介导的类固醇调节信号与糖皮质激素的生长 抑制乳腺肿瘤细胞生长。

DESCRIPTION: A dynamic balance of steroid receptor signaling and cellular phosphorylation cascades coordinately control cell growth at key steps where these signal transduction pathways converge. Conceivably, the stringent regulation of such points of convergence confer responsiveness to anti-proliferative signals in normal cells, and may regulate the uncontrolled proliferation of transformed cells if appropriately induced or activated. Glucocorticoids, one class of steroid hormones, can strongly inhibit the in vivo and in vitro growth of Con8 rat mammary tumor cells, which are derived from a hormone responsive rat mammary adenocarcinoma. To identify the steroid regulated mediators of this growth arrest, subtractive cloning of glucocorticoid responsive genes from a mammary tumor cell cDNA library uncovered a novel serine/threonine protein kinase, sgk, that is transcriptionally regulated by glucocorticoids and serum. The existence of sgk suggests a new pathway of cross-talk between steroid hormones and cellular phosphorylation cascades. Analysis of sgk structure/function relationships by in vitro mutagenesis will be carried out to determine the role of specific protein coding domains in transphosphorylation, substrate specificity and as targets of cellular phosphorylation cascades. The role of sgk in the glucocorticoid growth suppression response in cultured cells and in mammary cell derived tumors will be examined by analyzing vectors encoding the wild type, mutant or anti-sense forms of this protein kinase gene. Finally, interactive cloning strategies, such as the yeast two hybrid system, will be employed to identify the sgk binding proteins uncovered by co-immunoprecipitation and their functional characterization carried out to elucidate the sgk intracellular signal transduction pathway. Thus, the overall goal is to define the precise functional relationships between the steroid regulated signaling mediated by sgk and the glucocorticoid growth arrest of mammary tumor cells.