Molecular Basis of Cell Growth Control by the TOR Kinase

TOR 激酶控制细胞生长的分子基础

• 批准号: 6721528
• 负责人: JOSEPH AVRUCH
• 金额: $ 34.64万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-04-01 至 2006-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6721528
• 关键词: Caenorhabditis elegans; alternatives to animals in research; biological signal transduction; cell adhesion; cell growth regulation; enzyme activity; enzyme induction /repression; genetically modified animals; mutant; pharmacology; phosphoprotein phosphatase; phosphoproteins; phosphorylation; protein kinase; sirolimus; suppressor mutations

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.

描述(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。雷帕霉素的所有药理作用 似乎是由于其抑制TOR功能的能力所致。Tor是一种巨大的蛋白质 PIK家族中的一种蛋白激酶，其催化结构域与 共济失调血管扩张症基因产物(ATM)。Tor最早是在S. 它控制细胞的生长和增殖以响应 营养信号。当有高质量的氮源和可发酵的碳源时， Tor促进增长。当营养物质有限时(或在存在 雷帕霉素)TOR活性的下降抑制了整个mRNA的翻译(从而 抑制生长)，激活自噬以及蛋白酶体的降解 通过激活N-和C-来改变基因转录。 分解代谢抑制反应和核糖体生物发生的抑制。这些 反应是由TOR激酶活性控制的，它通过两个 主要效应器肢体；通过TOR催化的磷酸化，改变 目标函数或将目标标记为降级，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Tap42。 在多细胞生物体中，TOR对细胞生长的控制与 IR/IGF1R酪氨酸激酶。我们和其他人已经证明，mTOR控制着 类型1API-3的下游靶标的子集的功能， 尤其是p70S6蛋白和eIF-4E抑制蛋白PHASI/4E-BP。 因此，雷帕霉素或停用氨基酸会导致p70去磷酸化。 S6K和4E-BP，对胰岛素和P1-3K无反应。 与此同时，对生长至关重要的rnRNA的几个子集的翻译 是被抑制的。尽管我们证明了mTOR可以磷酸化并激活 P70S6K，我们的研究结果表明，p70S6K在体外对mTOR的调节作用 活体是通过调节磷酸酶活性间接发生的。 此外，营养物质调节mTOR活性的分子基础 而酪氨酸激酶是未知的。 我们建议研究mTOR的调节和信号转导的机制 遗传学和生物化学的结合。我们已经确定了功能丧失 线虫中的突变体；这些突变体作为体型较小的幼虫而停滞。我们带着 寻找抑制突变体，寻找CeTOR下游的元素 对其在发展中的作用最为关键。第二个努力涉及直接 解决mTOR调节机制的生化实验 蛋白磷酸酶活性。最后，我们将在体外表征该基础 对于p70 S6K和4E碱基的TOR激酶活性的根本不同，以及 寻求确定体内mTOR调控的分子基础。