Lysosomal cholesterol-dependent anabolic regulation

项目摘要 MTORC1主要通过刺激细胞合成代谢过程来刺激细胞和器官的生长，包括蛋白质， 脂质和核苷酸合成，并抑制分解代谢过程，如自噬。异常激活 MTORC1信号与许多人类健康问题有关，包括癌症、神经退行性变 疾病，以及肥胖症和糖尿病等代谢紊乱。MTORC1的活性受到严格的调控 生长因子和多种细胞代谢信号，如氨基酸，其中氨基酸招募mTORC1到 溶酶体通过RAG小分子GTP酶激活，这是mTORC1激活的关键过程。虽然是最近的 研究揭示了氨基酸诱导溶酶体mTORC1的分子机制 通过RAG GTP酶的定位和激活，它才刚刚开始揭示细胞脂质是如何 胆固醇也调节mTORC1的活性。最近的一项研究表明，除了氨基酸之外， 溶酶体胆固醇也在通过SLC38A9增强RAG GTP酶活性方面发挥关键作用，SLC38A9是 我们发现BASP1(脑丰富的信号膜附着) 信号蛋白1)是一种已知的脂筏胆固醇/PIP2结合蛋白，是mTORC1的关键刺激因子 活动。从机制上讲，BASP1在溶酶体上的表达依赖于细胞胆固醇和 与GATOR1相互作用并抑制GATOR1，GATOR1是RAGA/B的GTPase激活蛋白复合物，从而刺激 细胞mTORC1活性。此外，BASP1的消融大大减少了细胞内mTORC1的异常激活 缺乏功能性Niemann-Pick病，C1型(NPC1)，一种溶酶体胆固醇输出子。Basp1 发育不良的小鼠表现为发育减慢，这使人想起mTOR发育不良的小鼠或小鼠 用mTORC1抑制剂雷帕霉素治疗。有趣的是，而成年的Basp1亚型表现出更高的胰岛素 他们对饮食引起的肥胖表现出抵抗力。我们认为BASP1在这一过程中起着至关重要的作用 通过感知溶酶体膜胆固醇刺激细胞mTORC1活性诱导合成代谢过程 或其他脂类，并有助于发育发育和饮食诱导的肥胖。这项建议将澄清 溶酶体脂促进BASP1活性及抑制GATOR1的分子机制 BASP1的活性及其在小鼠代谢紊乱中的病理生理学意义 模特们。该项目的完成确立了NPC1-BASP1-GATOR1-mTORC1通路在 对细胞合成代谢活动的调节，应该会产生有价值的信息，以便进行更多的实验 探索在代谢紊乱和其他疾病中面向溶酶体的mTORC1调节信号的这一新分支 与mTORC1相关的人类健康问题，包括神经退行性疾病、溶酶体储存障碍、 和癌症。

Project Summary mTORC1 stimulates cell and organ growth mainly by stimulating cellular anabolic processes, including protein, lipid, and nucleotide synthesis, and inhibiting catabolic processes such as autophagy. Aberrant activation of mTORC1 signaling has been linked to many human health problems, including cancer, neurodegenerative diseases, and metabolic disorders such as obesity and diabetes. The activity of mTORC1 is tightly regulated by growth factors and multiple cellular metabolic cues such as amino acids, where amino acids recruit mTORC1 to the lysosome through Rag small GTPases activation, a key process for mTORC1 activation. Although recent studies have revealed the molecular mechanisms by which amino acids induce the lysosomal mTORC1 localization and its activation via Rag GTPases, it has just begun to uncover how cellular lipids such as cholesterol also regulate the activity of mTORC1. A recent study demonstrated that, in addition to amino acids, lysosomal cholesterol also plays a key role in enhancing the activity of Rag GTPases through SLC38A9, the guanine exchange factor for RagA/B. We discovered that BASP1 (Brain abundant signal membrane attached signal protein 1), a known lipid raft cholesterol/PIP2-binding protein, functions as a key stimulator of mTORC1 activity. Mechanistically, BASP1 expresses on the lysosome in a manner dependent on cellular cholesterol and interacts with and inhibits GATOR1, the GTPase activating protein complex for RagA/B, thereby stimulating cellular mTORC1 activity. In addition, ablation of BASP1 largely diminished aberrant mTORC1 activation in cells lacking functional Niemann-Pick Disease, Type C1 (NPC1), a lysosomal cholesterol exporter. Basp1 hypomorphic mice display a reduced developmental growth, reminiscent of mTOR hypomorphic mice or mice treated with the mTORC1 inhibitor, rapamycin. Interestingly, while adult Basp1 hypomorphs show higher insulin sensitivity, they display resistance to diet-induced obesity. We propose that BASP1 plays a crucial role in stimulating cellular mTORC1 activity to induce anabolic processes by sensing lysosomal membrane cholesterol or other lipids and contribute to developmental growth and diet-induced obesity. This proposal will elucidate the molecular mechanisms by which lysosomal lipids enhance BASP1 activity and how BASP1 inhibits GATOR1 activity and investigates the pathophysiological importance of BASP1 in developing metabolic disorders in mice models. Completing this project establishes the role of the NPC1-BASP1-GATOR1-mTORC1 pathway in the regulation of cellular anabolic actions and should yield valuable information to set additional experiments to explore this new branch of lysosomal-oriented mTORC1 regulatory signaling in metabolic disorders and other mTORC1-related human health problems, including neurodegenerative disease, lysosomal storage disorders, and cancer.