Molecular Basis of Cell Growth Control by the TOR Kinase

描述（由申请人提供）：TOR被发现是最大的 雷帕霉素;后者是一种有效的和临床上重要的免疫抑制剂 和潜在的抗增殖药物。所有雷帕霉素的药理作用 这是因为它具有抑制TOR功能的能力。TOR是一种巨大的蛋白质 PIK家族中的一种激酶，其催化结构域与PIK家族中的 共济失调毛细血管扩张基因产物（ATM）。TOR首先在S. 其中它控制细胞的生长和增殖，以响应 营养信号当高质量的氮源和可发酵的碳源可用时， TOR促进增长。当营养物质有限时（或在存在 雷帕霉素），TOR活性的下降抑制整体mRNA翻译（从而 抑制生长），激活自噬以及蛋白体降解， 特异性蛋白质，并通过激活N-和C- 分解代谢物阻遏反应和抑制核糖体生物合成。这些 反应由TOR激酶活性控制，其通过两个 初级效应肢;通过TOR催化的磷酸化， 目标功能或标记目标的退化，并通过调制 蛋白磷酸酶活性，通过TOR催化的磷酸化 磷酸酶调节蛋白Tap 42。 在多细胞生物体中，TOR对细胞生长的控制与细胞生长的控制共享。 IR/IGF 1 R酪氨酸激酶。我们和其他人已经证明，mTOR控制着 1A型PI-3激酶的下游靶的子集的功能， 特别是p70 S6激酶和eIF-4 E抑制蛋白PHASI/4 E-BP。 因此，雷帕霉素或氨基酸的去除产生p70的去磷酸化 S6 K和4 E-BP对胰岛素和P1-3激酶无反应。 与此同时，几个mRNA子集的翻译对生长至关重要 被抑制了。虽然我们发现mTOR可以磷酸化并激活 p70 S6激酶，我们的数据表明mTOR对p70 S6激酶的调节在体外是可能的。 体内通过磷酸酶活性的调节间接发生。 此外，营养素调节mTOR活性的分子基础 和酪氨酸激酶是未知的。 我们建议研究mTOR的调节和信号转导机制， 遗传学和生物化学的结合。我们已经确定了功能丧失 突变体C. elegans TOR;这些逮捕作为小型幼虫。我们是带 筛选抑制突变体，寻找CeTOR下游的元件 对它在发展中的作用至关重要。第二项努力涉及直接 解决mTOR调节机制的生化实验 蛋白磷酸酶活性最后，我们将在体外表征的基础上， 对于对p70 S6 K和4 E BP的完全不同的TOR激酶活性，以及 寻求确定体内mTOR调节的分子基础。

DESCRIPTION (provided by applicant): TOR was discovered as the largest of Rapamycin; the latter is a potent and clinically important immunosuppressive and potential antiproliferative drug. All of rapamycins pharmacologic actions appear to he due to its ability to inhibit TOR function. TOR is a giant protein kinase in the PIK family, whose catalytic domain is closely related to the Ataxia Teleangiectasia gene product (ATM). TOR was first identified in S. Cerevisiae where it controls cell growth and proliferation in response to nutrient signals. When high quality N-and fermentable C-sources are available, TOR promotes growth. When nutrients are limiting (or in the presence of rapamycin) the fall in TOR activity inhibits overall mRNA translation (thereby arresting growth), activates autophagy as well as proteosomal degradation of specific proteins, and alters gene transcription by activation of the N- and C- catabolite repression responses and by inhibition of ribosome biogenesis. These responses are controlled by TOR kinase activity, which signals through two primary effector limbs; through TOR-catalyzed phosphorylation, which alters target function or marks targets for degradation, and through the modulation of protein phosphatase activity, achieved by TOR-catalyzed phosphorylation of the phosphatase regulatory protein Tap42. In multicellular organisms, TOR control of cell growth is shared with the IR/IGF1R tyrosine kinases. We and others have shown that mTOR controls the function of a subset of the downstream targets of the Type 1A PI-3 kinases, especially the p70 S6 kinase and the eIF-4E inhibitor proteins, PHASI/4E-BP. Thus, rapamycin or withdrawal of amino acids produces dephosphorylation of p70 S6K and 4E-BP, which become unresponsive to insulin and P1-3 kinase. Concomitantly, the translation of several subsets of rnRNA critical to growth are inhibited. Although we showed that mTOR can phosphorylate and activate the p70 S6 kinase in vitro, our data indicate that mTOR regulation of p70 S6K in vivo occurs indirectly, through the regulation of phosphatase activity. Moreover, the molecular basis for the regulation of mTOR activity by nutrients and tyrosine kinases is unknown. We propose to study the mechanism of mTOR regulation and signaling by a combination of genetics and biochemistry. We have identified loss-of-function mutants in C. elegans TOR; these arrest as undersized larvae. We are carrying out a screen for suppressor mutants, seeking the elements downstream of CeTOR most critical to its function in development. A second effort involves direct biochemical experiments addressing the mechanism by which mTOR regulates protein phosphatase activity. Finally, we will characterize in vitro the basis for the radically different TOR kinase activity toward p70 S6K and 4E BP, and seek to identify the molecular basis for mTOR regulation in vivo.