Deciphering the Molecular Mechanisms by which PKA inhibits mTORC1

摘要 雷帕霉素的哺乳动物靶点(MTOR)是一种进化保守的丝氨酸/苏氨酸激酶，可以感知多个 上游刺激调节细胞生长、新陈代谢和自噬。MTOR是多个 蛋白质复合体称为mTOR复合体1(MTORC1)。MTORC1激活增加在人类中很常见 疾病包括癌症、2型糖尿病、代谢紊乱和神经退行性变。小分子如 雷帕霉素是一种靶向和抑制mTORC1的药物，目前在临床上应用效果有限。因此，破译 参与mTORC1调控的分子机制对于治疗mTORC1介导的 疾病。大多数研究都集中在激活mTORC1的刺激物，如生长因子和氨基 酸。相反，人们对直接抑制mTORC1活性的信号通路知之甚少。G蛋白 与G-α偶联的受体S蛋白通过增加细胞内活性来激活蛋白激酶A 环腺苷3‘5’一磷酸(CAMP)水平。PKA使mTORC1组分Raptor和 有效地抑制mTORC1的活性。重要的是，GPCR是最大的药物靶标家族，许多 化合物已被FDA批准用于调节GPCR信号。我们的初步数据进一步揭示了 从机制上详细说明并确定参与PKA抑制mTORC1的新成分(特定目标1-2)。 此外，我们将确定PKA信号在mTORC1介导的生物学和疾病中的作用(特定目标 3)。因此，这项提议的总体目标是破译分子机制， PKA抑制mTORC1，调节mTORC1介导的生物学行为。我们预期拟议的研究 将为PKA对mTORC1的调控提供新的见解，并将发现扰乱mTORC1的治疗靶点- 媒介疾病。

ABSTRACT The mammalian target of rapamycin (mTOR) is an evolutionary conserved Ser/Thr kinase that can sense multiple upstream stimuli to regulate cell growth, metabolism, and autophagy. mTOR is the key component of a multi- protein complex termed mTOR complex 1 (mTORC1). Increased mTORC1 activation is common in human disease including cancer, type 2 diabetes, metabolic disorders, and neurodegeneration. Small molecules like rapamycin that target and inhibit mTORC1, are currently used in the clinic with limited success. Thus, deciphering the molecular mechanisms involved in mTORC1 regulation is crucial in order to treat mTORC1-mediated disease. The majority of research has focused on stimuli that activate mTORC1, like growth factors and amino acids. In contrast, less is known about signaling pathways that can directly inhibit mTORC1 activity. G-protein coupled receptors (GPCRs) paired to Gαs proteins activate Protein Kinase A (PKA) by increasing intracellular cyclic adenosine 3’5’ monophosphate (cAMP) levels. PKA phosphorylates the mTORC1 component Raptor and potently inhibits mTORC1 activity. Importantly, GPCRs are the largest family of drug targets and many compounds have been approved by the FDA to regulate GPCR signaling. Our preliminary data reveals further mechanistic detail and identifies new components involved in mTORC1 inhibition by PKA (Specific Aims 1-2). Moreover, we will determine the role of PKA signaling in mTORC1-mediated biology and disease (Specific Aim 3). Therefore, the overall objective of this proposal is to decipher the molecular mechanisms by which PKA inhibits mTORC1 and regulates mTORC1-mediated biology. We anticipate that the proposed studies will yield new insights into mTORC1 regulation by PKA and will uncover therapeutic targets to perturb mTORC1- mediated disease.