Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, 455 Main Street, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Broad Institute of Harvard and Massachusetts Institute of Technology, 7 Cambridge Center, Cambridge, MA 02142, USA; Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, 01605, USA.
Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, 455 Main Street, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; Broad Institute of Harvard and Massachusetts Institute of Technology, 7 Cambridge Center, Cambridge, MA 02142, USA.
Cell. 2019 Nov 27;179(6):1319-1329.e8. doi: 10.1016/j.cell.2019.10.036. Epub 2019 Nov 6.
mTORC1 controls anabolic and catabolic processes in response to nutrients through the Rag GTPase heterodimer, which is regulated by multiple upstream protein complexes. One such regulator, FLCN-FNIP2, is a GTPase activating protein (GAP) for RagC/D, but despite its important role, how it activates the Rag GTPase heterodimer remains unknown. We used cryo-EM to determine the structure of FLCN-FNIP2 in a complex with the Rag GTPases and Ragulator. FLCN-FNIP2 adopts an extended conformation with two pairs of heterodimerized domains. The Longin domains heterodimerize and contact both nucleotide binding domains of the Rag heterodimer, while the DENN domains interact at the distal end of the structure. Biochemical analyses reveal a conserved arginine on FLCN as the catalytic arginine finger and lead us to interpret our structure as an on-pathway intermediate. These data reveal features of a GAP-GTPase interaction and the structure of a critical component of the nutrient-sensing mTORC1 pathway.
mTORC1 通过 Rag GTPase 异二聚体响应营养物质来控制合成代谢和分解代谢过程，该异二聚体受多个上游蛋白复合物调节。FLCN-FNIP2 是 RagC/D 的 GTPase 激活蛋白 (GAP)，是一个重要的调节因子，但它如何激活 Rag GTPase 异二聚体仍然未知。我们使用冷冻电镜技术确定了 FLCN-FNIP2 与 Rag GTPases 和 Ragulator 复合物的结构。FLCN-FNIP2 采用伸展构象，由两对异二聚化结构域组成。Longin 结构域异二聚化并与 Rag 异二聚体的两个核苷酸结合结构域相互作用，而 DENN 结构域在结构的远端相互作用。生化分析揭示了 FLCN 上的一个保守精氨酸是催化精氨酸指，这使我们将我们的结构解释为一个途径中间产物。这些数据揭示了 GAP-GTPase 相互作用的特征以及营养感应 mTORC1 途径的关键组成部分的结构。
