Regulation of mTOR complexes (mTORCs) by directly acting kinases

描述（由申请人提供）：雷帕霉素的机制靶点（mTOR）对不同的环境信号作出反应，以控制基本的细胞功能，发挥关键作用。 在代谢、肿瘤发生和免疫功能相关过程中的作用。mTOR构成了两种功能不同的信号复合物mTORC 1和mTORC 2的催化核心：mTORC 1促进合成代谢细胞过程;而mTORC 2促进细胞存活并调节肌动蛋白细胞骨架。尽管mTOR具有明确的生理和治疗重要性，但我们对细胞mTOR调节的认识存在根本性差距，特别是关于调节mTOR活性的分子途径。我们实验室最近令人兴奋的工作表明，mTOR磷酸化在mTORC 1功能中发挥着重要且以前未被认识到的作用。使用磷酸特异性抗体和体外激酶组筛选作为工具，我们发现TBK 1/IKKe（促进先天免疫信号传导和宿主防御反应的激酶）和AMPK（一种对能量应激反应的激酶）在不同位点磷酸化mTOR。重要的是，这些磷酸化事件响应于培养细胞和体内（即小鼠）的生理信号而发生。我们的初步数据显示， TBK 1/IKKe介导的mTOR S2159磷酸化促进mTORC 1信号传导，而AMPK促进mTORC 2信号传导响应急性能量应激。在本申请中，我们提出阐明这些生理学和病理学上重要的信号分子在mTOR的细胞调节和功能中的作用。在目的1中，我们研究TBK 1和IKKe直接作用于mTORC 1以促进生长因子反应和先天免疫的假设;在目的2中，我们研究AMPK直接作用于mTORC 2以抑制细胞凋亡并增强线粒体功能以维持急性能量应激期间的能量稳态的假设。新的数据表明，TBK 1/IKKe有助于慢性炎症性疾病和肥胖相关的胰岛素抵抗;此外，癌细胞劫持TBK 1/IKKe以促进肿瘤发生。由于细胞TBK 1/IKKe信号网络仍然知之甚少，这项专注于TBK 1/IKKe-mTORC 1轴的研究有可能影响慢性炎症性疾病和癌症的未来临床管理。为了应对ATP水平不足，AMPK刺激能量产生分解代谢并抑制能量消耗合成代谢途径。这项研究集中在AMPK-mTORC 2轴可以部分解释新出现的悖论，即AMPK可以作为肿瘤抑制剂（通过抑制细胞凋亡）和肿瘤促进剂（通过抑制细胞凋亡），这取决于细胞环境。这项工作将揭示直接影响mTOR的新的调控模式，并揭示mTOR与这些激酶控制的过程之间先前未知的联系，包括细胞存活，细胞代谢，肿瘤发生和先天免疫。由于调节mTORC 2的信号几乎仍然未知，因此AMPK作为mTORC 2激活剂的鉴定代表了一个特别重要的里程碑。

DESCRIPTION (provided by applicant): The mechanistic target of rapamycin (mTOR) responds to diverse environmental signals to control essential cellular functions, playing critical roles in processes related to metabolism, tumorigenesis, and immune function. mTOR constitutes the catalytic core of two functionally distinct signaling complexes, mTORC1 and mTORC2: mTORC1 promotes anabolic cellular processes; while significantly less well understood; mTORC2 promotes cell survival and modulates the actin cytoskeleton. Despite the clear physiologic and therapeutic importance of mTOR, fundamental gaps exist in our knowledge regarding cellular mTOR regulation, especially with regard to the molecular pathways that regulate mTOR activity. Exciting recent work from our laboratory revealed that mTOR phosphorylation plays an important and previously unrecognized role in mTORC1 function. Using phospho specific antibodies and an in vitro kinome screen as tools, we discovered that TBK1/IKKe (kinases that promote innate immune signaling and the host defense response) and AMPK (a kinase that responds to energetic stress) phosphorylate mTOR on distinct sites. Importantly, these phosphorylation events occur in response to physiological signals in cultured cells and in vivo (i.e. mice). Our preliminary data indicate that TBK1/IKKe-mediated phosphorylation of mTOR S2159 promotes mTORC1 signaling while AMPK promotes mTORC2 signaling in response to acute energetic stress. In this application we propose to elucidate roles for these physiologically and pathologically significant signaling molecules in the cellular regulation and function of mTOR. In Aim 1, we investigate the hypothesis that TBK1 and IKKe act directly on mTORC1 to promote growth factor responses and innate immunity; in Aim 2, we investigate the hypothesis that AMPK acts directly on mTORC2 to suppress apoptosis and enhance mitochondrial function to maintain energy homeostasis during acute energetic stress. Emerging data suggest that TBK1/IKKe contribute to chronic inflammatory diseases and obesity-linked insulin resistance; moreover, cancer cells hijack TBK1/IKKe to promote tumorigenesis. As cellular TBK1/IKKe signaling networks remain poorly understood, this research focused on the TBK1/IKKe-mTORC1 axis has potential to impact the future clinical management of chronic inflammatory diseases and cancer. In response to insufficient ATP levels, AMPK stimulates energy producing catabolic and suppresses energy consuming anabolic pathways. This research focused on the AMPK-mTORC2 axis may explain in part the emerging paradox that AMPK can act as a tumor suppressor (by inhibiting cellular anabolism) and a tumor promoter (by inhibiting apoptosis), depending on cellular context. This work will unveil novel regulatory paradigms that directly impact mTOR and will reveal previously unknown links between mTOR and the processes controlled by these kinases, including cell survival, cell metabolism, tumorigenesis, and innate immunity. As the signals that regulate mTORC2 remain virtually unknown, the identification of AMPK as an mTORC2 activator represents a particularly important milestone.