SIGNALING & FUNCTION OF THE SGK STEROID INDUCIBLE KINASE

描述：类固醇受体信号传导和细胞内 磷酸化级联在关键步骤协调控制细胞生长， 这些信号转导途径会聚。 可以想象， 对这些汇合点的管制赋予了对以下问题的反应能力： 正常细胞中的抗增殖信号，并可能调节 如果适当诱导，转化细胞的增殖不受控制， 激活 糖皮质激素是一类类固醇激素， 抑制Con 8大鼠乳腺肿瘤细胞的体内外生长， 其来源于激素反应性大鼠乳腺癌。 到 确定这种生长停滞的类固醇调节介质， 乳腺肿瘤细胞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， 由糖皮质激素和血清进行转录调节。 的存在 SGK提出了类固醇激素之间相互作用的新途径， 细胞磷酸化级联反应。 SGK结构/功能分析 将通过体外诱变进行关系，以确定 特异性蛋白质编码结构域在转磷酸化底物中的作用 特异性和作为细胞磷酸化级联反应的靶标。 的作用 SGK在培养细胞中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中，将通过分析载体 编码该蛋白激酶的野生型、突变体或反义形式 基因 最后是交互克隆策略，如酵母双杂交 系统，将被用来鉴定未被发现的sgk结合蛋白， 免疫共沉淀及其功能表征， 阐明sgk细胞内信号转导通路。 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生长 抑制乳腺肿瘤细胞。

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.