SIGNAL TRANSDUCTION TO PP70 S6K

该提案的长期目标是确定 70 kD-S6蛋白激酶（pp 70 S6 k）的调节，以响应于 多种生长调节剂，包括血小板衍生生长因子 （PDGF），表皮生长因子（EGF），神经生长因子（NGF），胰岛素， 白细胞介素2（IL-2）和促进肿瘤的佛波醇酯。这些生长 先前已经显示调节剂调节pp 70 S6 k活性，但是 这是如何发生的，以及调节信号通路的作用是什么， pp 70 S6 k在细胞对这些因子的生理反应中起作用， 不知道。我们的直接目标是通过各种方式产生和表达 意味着，不同形式的pp 70 S6 k（野生型、组成型激活的和 显性干扰），以帮助确定这一辊 蛋白激酶在细胞生理过程中的作用;进一步确定 pp 7 OS 6 k受磷酸化调节;为了鉴定和表征 pp 70 S6 k-蛋白激酶;并鉴定和表征其他组分 这个重要的信号系统。定义监管的组成部分 pp 70 S6 k活性和酶本身的进一步表征可以 不仅导致对细胞生长控制更好的一般理解， 它与癌症问题的明显相关性，但也可能特别 与我们对免疫系统的理解有关， 胰岛素反应性最近对果蝇的遗传学研究表明， 40 S核糖体蛋白S6（pp 70 S6 k的唯一已知靶标）可以作为 免疫系统中的肿瘤抑制因子这一观察可能与 40 S亚基内未磷酸化的S6不能 翻译具有独特5'非翻译区的特定mRNA。的 假设是S6磷酸化或蛋白质的去除将 解除这种翻译的抑制。此外， T细胞免疫抑制剂雷帕霉素有效抑制IL-2依赖性T细胞 细胞增殖，特别是pp 70 S6 k活性，表明 pp 70 S6 k在T细胞增殖中的重要作用。一个明显的 在一些胰岛素抵抗的人的缺陷是无法正常的 胰岛素受体激活pp 70 S6 k，如在胰岛素应答的人中所见。 此外，生长调节脂质激酶的特异性抑制剂 磷脂酰肌醇3-激酶，不仅拮抗IL-2-，胰岛素-，PDGF-， 和NGF介导的pp 70 S6 k活化，但也干扰胰岛素- 调节葡萄糖转运蛋白GLUT 4的转运，PDGF刺激 肌动蛋白细胞骨架重组和IgE介导的组胺释放 不同的细胞系统。因此，很明显， 这将有助于我们了解pp 70 S6 k是如何调节的， 对翻译、转录和一般的潜在下游影响 增长控制，以及提高我们对流程的理解 调节蛋白质分选/分泌和细胞形状。

The long-term goals of this proposal are to define the mechanism of regulation of the 70kD-S6 protein kinases (pp70S6k) in response to a variety of growth modulators including platelet-derived growth factor (PDGF), epidermal growth factor (EGF), nerve growth factor (NGF), insulin, interleukin2 (IL-2) and tumor promoting phorbol esters. These growth modulators have been previously shown to regulate pp70S6k activity,, but how this occurs and what role the signalling pathway that regulates pp70S6k plays in the physiological response of cells to these factors in not known. Our immediate goals are to generate and express by various means, different forms of pp70S6k (wild type, constitutively-activated and dominant-interfering) in cultured cells to help define the roll of this protein kinase in cell physiological processes; to further define how pp7OS6k is regulated by phosphorylation; to identify and characterize the pp70S6k-protein kinases; and to identify and characterize other components of this important signalling system. Defining the components that regulate pp70S6k activity and the further characterization of the enzyme itself may lead not only to a better general understanding of cell growth control and its obvious relevance to the cancer problem, but also may be particularly relevant with regards to our understanding of the immune system and insulin responsiveness. Recent genetic studies in Drosophila indicate that the 40S ribosomal protein S6 (the only known target of pp70S6k) may act as a tumor suppressor in the immune system. This observation may be related to the inability of unphosphorylated S6, within the 40S subunit, to translate specific mRNA with unique 5' untranslated regions. The hypothesis is that S6 phosphorylation or removal of the protein would relieve this inhibition of translation. Additionally, the ability of the T cell immunosuppressant rapamycin to potently inhibit IL-2-dependent T cell proliferation and very specifically, pp70S6k activity, suggests an important role for pp70S6k in T cell proliferation. One of the apparent defects in some insulin-resistant humans is the inability of a normal insulin receptor to activate pp70S6k as seen in insulin-responsive humans. Additionally, specific inhibitors of the growth-regulated lipid kinase phosphatidylinositol 3-kinase, not only antagonize IL-2-, insulin-, PDGF- and NGF-mediated activation of pp70S6k, but also interfere with insulin- regulated translocation of the glucose transporter GLUT4, PDGF-stimulated actin cytoskeleton reorganization and IgE-mediated histamine release in different cell systems. Thus it is clear that defining this signalling pathway will improve our understanding of how pp70S6k is regulated and its potential downstream effects on translation, transcription and in general growth control, as well as improve our understanding of processes regulating protein sorting/secretion and cell shape.