The mechanistic target of rapamycin complex 1 (mTORC1) couples cell growth to nutrient, energy and growth factor availability1-3. mTORC1 is activated at the lysosomal membrane when amino acids are replete via the Rag guanosine triphosphatases (GTPases)4-6. Rags exist in two stable states, an inactive (RagA/BGDP:RagC/DGTP) and active (RagA/BGTP:RagC/DGDP) state, during low and high cellular amino acid levels4,5. The lysosomal folliculin (FLCN) complex (LFC) consists of the inactive Rag dimer, the pentameric scaffold Ragulator7,8, and the FLCN:FNIP (FLCN-interacting protein) GTPase activating protein (GAP) complex9, and prevents activation of the Rag dimer during amino acid starvation10,11. How the LFC is released upon amino acid refeeding is a major outstanding question in amino-acid dependent Rag activation. Here we show that the cytoplasmic tail of the lysosomal solute carrier family 38 member 9 (SLC38A9), a known Rag activator12-14, destabilizes the LFC. By breaking up the LFC, SLC38A9 triggers the GAP activity of FLCN:FNIP toward RagC. We present the cryo electron microscopy (cryo-EM) structures of Rags in complex with their lysosomal anchor complex Ragulator and the cytoplasmic tail of SLC38A9 in the pre and post GTP hydrolysis state of RagC, which explain how SLC38A9 destabilizes the LFC and so promotes Rag dimer activation.

中文翻译：

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SLC38A9进行氨基酸依赖性Rag GTP酶转换的结构机理

雷帕霉素复合物1（mTORC1）的机械目标将细胞生长与营养，能量和生长因子的可用性1-3耦合。当通过Rag鸟苷三磷酸酶（GTPases）4-6补充氨基酸时，mTORC1在溶酶体膜上被激活。在低和高细胞氨基酸水平期间，碎布以两种稳定状态存在，即处于非活动状态（RagA / BGDP：RagC / DGTP）和处于活动状态（RagA / BGTP：RagC / DGDP）4,5。溶酶体滤泡蛋白（FLCN）复合物（LFC）由无活性的Rag二聚体，五聚支架Ragulator7,8和FLCN：FNIP（FLCN相互作用蛋白）GTPase活化蛋白（GAP）复合物9组成，可防止Rag二聚体的活化在氨基酸饥饿期间10,11。氨基酸补给后，LFC如何释放是氨基酸依赖性Rag激活中一个主要的悬而未决的问题。在这里，我们显示溶酶体溶质载体家族38成员9（SLC38A9）（已知的Rag激活剂12-14）的细胞质尾使LFC不稳定。通过分解LFC，SLC38A9触发了FLCN：FNIP朝向RagC的GAP活性。我们介绍了Rags的冷冻电子显微镜（cryo-EM）结构与它们的溶酶体锚复合物Ragulator和SLC38A9的胞质尾在RagC的GTP水解之前和之后的复合状态，这解释了SLC38A9如何破坏LFC的稳定性并促进Rags的生长二聚体激活。