Molecular mechanisms for lipid sensing by mTORC1

项目摘要 细胞感知营养的分子机制在很大程度上仍然未知，但它们的 阐明是我们理解正常和疾病状态下代谢调节的关键。中心 营养传感和生长调节的关键是一种古老的蛋白激酶，被称为营养传感和生长调节的机制靶点。 雷帕霉素复合物1（mTORC 1）。为了响应营养素等代谢输入的联合作用， 生长因子、能量和氧，mTORC 1从细胞质易位到溶酶体表面， 其激酶功能被激活。越来越多的证据表明，异常mTORC 1激活 在溶酶体中的作用可能是从癌症到2型糖尿病， 神经变性因此，对mTORC 1如何响应于 营养素可以为这些疾病的新治疗策略指明方向。 目前的提议调查了迄今为止仍然存在的mTORC 1功能的一个中心方面 研究不足，了解甚少，即其感知脂质的能力。我们将根据最近的发现， mTORC 1在溶酶体处感知重要的脂质胆固醇。在细胞中使用创新方法， 在体外，我们将解决和阐明新发现的信号通路的关键方面。特别是要 确定i）调节mTORC 1的胆固醇池的细胞位置ii）使mTORC 1的转运回路 胆固醇可用于mTORC 1和iii）胆固醇诱导mTORC 1的分子机制 募集到溶酶体表面。此外，我们还将研究mTORC 1如何通过胆固醇传感 依赖于尼曼-匹克C1蛋白，其丢失会导致致命的代谢和神经退行性疾病。 疾病 我们最近将通过创新和高度互补的方法来实现这些研究目标 在我们的实验室优化，包括测量和选定的细胞器的脂质含量有针对性的操作 群体，结合mTORC 1调节的基于重建的测定。 我们的发现将影响目前对细胞脂质分子机制的理解， 稳态，并将指出新的方法来操纵mTORC 1信号在疾病设置的方式。

PROJECT SUMMARY The molecular mechanisms through which cells sense nutrients remain largely unknown, but their elucidation is key to our understanding of metabolic regulation both in normal and disease states. At the center of nutrient sensing and growth regulation is an ancient protein kinase known as the mechanistic Target of Rapamycin Complex 1 (mTORC1). In response to the combined action of metabolic inputs such as nutrients, growth factors, energy and oxygen, mTORC1 translocates from the cytoplasm to the surface of lysosomes, where its kinase function becomes activated. Accumulating evidence indicates that aberrant mTORC1 activation at the lysosome could be a driving force in diseases ranging from cancer to type-2 diabetes to neurodegeneration. Thus, a deep mechanistic understanding of how mTORC1 is activated in response to nutrients could point the way to novel therapeutic strategies in these diseases. The current proposal investigates a central aspect of mTORC1 function that has so far remained understudied and poorly understood, namely, its ability to sense lipids. We will build on our recent discovery that mTORC1 senses an important lipid, cholesterol, at the lysosome. Using innovative approaches both in cells and in vitro, we will address and elucidate key aspects of newly identified signaling pathway. In particular, we will determine i) the cellular location of the cholesterol pools that regulate mTORC1 ii) the transport circuits that make cholesterol available to mTORC1 and iii) the molecular mechanisms through which cholesterol induces mTORC1 recruitment to the lysosomal surface. Moreover, we will investigate how cholesterol sensing by mTORC1 depends on the Niemann-Pick C1 protein, loss of which causes a fatal metabolic and neurodegenerative disease. We will address these research aims via innovative and highly complementary approaches recently optimized in our lab, including measurement and targeted manipulations of the lipid content of selected organelle populations, combined with reconstitution-based assays of mTORC1 regulation. Our findings will impact the current understanding of the molecular mechanisms of cellular lipid homeostasis, and will point the way to novel approaches to manipulate mTORC1 signaling in disease settings.