Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA.
The Paul F. Glenn Center for Aging Research at the University of California, Berkeley, Berkeley, CA 94720, USA.
Science. 2019 Nov 22;366(6468):971-977. doi: 10.1126/science.aax0364. Epub 2019 Oct 31.
The tumor suppressor folliculin (FLCN) enables nutrient-dependent activation of the mechanistic target of rapamycin complex 1 (mTORC1) protein kinase via its guanosine triphosphatase (GTPase) activating protein (GAP) activity toward the GTPase RagC. Concomitant with mTORC1 inactivation by starvation, FLCN relocalizes from the cytosol to lysosomes. To determine the lysosomal function of FLCN, we reconstituted the human lysosomal FLCN complex (LFC) containing FLCN, its partner FLCN-interacting protein 2 (FNIP2), and the RagA:RagC GTPases as they exist in the starved state with their lysosomal anchor Ragulator complex and determined its cryo-electron microscopy structure to 3.6 angstroms. The RagC-GAP activity of FLCN was inhibited within the LFC, owing to displacement of a catalytically required arginine in FLCN from the RagC nucleotide. Disassembly of the LFC and release of the RagC-GAP activity of FLCN enabled mTORC1-dependent regulation of the master regulator of lysosomal biogenesis, transcription factor E3, implicating the LFC as a checkpoint in mTORC1 signaling.
抑癌基因成纤维细胞生长因子受体结合蛋白 2 (FLCN) 通过其对 GTP 酶 RagC 的鸟嘌呤三磷酸酶 (GTPase) 激活蛋白 (GAP) 活性，使机械靶标雷帕霉素复合物 1 (mTORC1) 蛋白激酶能够依赖营养物质激活。在饥饿导致 mTORC1 失活的同时，FLCN 从细胞质重新定位到溶酶体。为了确定 FLCN 的溶酶体功能，我们重建了包含 FLCN、其伴侣 FLCN 相互作用蛋白 2 (FNIP2) 和 RagA:RagC GTPases 的人溶酶体 FLCN 复合物 (LFC)，这些物质在饥饿状态下与它们的溶酶体锚定 Ragulator 复合物一起存在，并以 3.6 埃的分辨率确定了其冷冻电子显微镜结构。由于 FLCN 中的一个催化必需的精氨酸从 RagC 核苷酸中位移，FLCN 的 RagC-GAP 活性在 LFC 内受到抑制。LFC 的解体和 FLCN 的 RagC-GAP 活性的释放，使 mTORC1 能够调节溶酶体生物发生的主要调节因子，转录因子 E3，这表明 LFC 是 mTORC1 信号通路的一个检查点。
