Lysosomal cholesterol-dependent anabolic regulation

项目摘要 mTORC 1主要通过刺激细胞合成代谢过程，包括蛋白质， 脂质和核苷酸合成，以及抑制分解代谢过程如自噬。的异常活化 mTORC1信号传导与许多人类健康问题有关，包括癌症、神经退行性疾病、 疾病和代谢紊乱如肥胖症和糖尿病。mTORC1的活性受到以下因素的严格调节： 生长因子和多种细胞代谢因子，如氨基酸，其中氨基酸招募mTORC 1， 溶酶体通过Rag小GTPases活化，这是mTORC1活化的关键过程。虽然最近 研究揭示了氨基酸诱导溶酶体mTORC 1的分子机制， 定位及其通过Rag GTP酶的激活，它刚刚开始揭示细胞脂质， 胆固醇还调节mTORC1的活性。最近的一项研究表明，除了氨基酸， 溶酶体胆固醇也通过SLC38A9在增强Rag GTP酶的活性中起关键作用， RagA/B的鸟嘌呤交换因子。我们发现BASP 1（Brain abundant signal membrane attached 信号蛋白1），一种已知的脂筏胆固醇/PIP 2结合蛋白，作为mTORC 1的关键刺激物起作用 活动在机制上，BASP 1以依赖于细胞胆固醇的方式在溶酶体上表达， 与RagA/B的GTOR活化蛋白复合物GATOR 1相互作用并抑制GATOR 1，从而刺激 细胞mTORC1活性。此外，BASP 1的消融在很大程度上减少了细胞中异常的mTORC 1激活。 缺乏功能性尼曼-匹克病，C1型（NPC1），一种溶酶体胆固醇输出蛋白。basp1 亚型小鼠显示发育生长减少，使人联想到mTOR亚型小鼠或小鼠 用mTORC1抑制剂雷帕霉素治疗。有趣的是，虽然成年Basp1亚型显示较高的胰岛素水平， 敏感性，他们表现出抵抗饮食引起的肥胖。我们认为BASP 1在以下方面起着至关重要的作用 通过感受溶酶体膜胆固醇刺激细胞mTORC 1活性以诱导合成代谢过程 或其他脂质，并有助于发育生长和饮食诱导的肥胖。本提案将阐明 溶酶体脂质增强BASP 1活性的分子机制以及BASP 1如何抑制GATOR 1 活性，并研究BASP 1在小鼠代谢紊乱中的病理生理学重要性 模型完成该项目确立了NPC1-BASP1-GATOR1-mTORC1通路在肿瘤发生中的作用。 调节细胞合成代谢的行动，并应产生有价值的信息，设置额外的实验， 探索代谢紊乱和其他疾病中溶酶体导向mTORC 1调节信号的这一新分支 mTORC 1相关的人类健康问题，包括神经退行性疾病、溶酶体贮积症， 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.