Structural mechanism of a Rag GTPase activation checkpoint by the lysosomal folliculin complex

• Published in: Science (American Association for the Advancement of Science) Vol. 366; no. 6468; pp. 971 - 977
• Main Authors: Lawrence, Rosalie E, Fromm, Simon A, Fu, Yangxue, Yokom, Adam L, Kim, Do Jin, Thelen, Ashley M, Young, Lindsey N, Lim, Chun-Yan, Samelson, Avi J, Hurley, James H, Zoncu, Roberto
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 22-11-2019
• Subjects: Activation; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors - metabolism; Carrier Proteins - metabolism; Cell Nucleus - metabolism; Cryoelectron Microscopy; Cytoplasm - metabolism; Deactivation; Dismantling; Electron microscopy; GTPase-Activating Proteins - metabolism; Guanosine Diphosphate - metabolism; Guanosine triphosphatases; Humans; Inactivation; Kinases; Lysosomes; Lysosomes - chemistry; Lysosomes - metabolism; Mechanistic Target of Rapamycin Complex 1 - metabolism; Microscopy; Models, Molecular; Monomeric GTP-Binding Proteins - chemistry; Monomeric GTP-Binding Proteins - metabolism; Multiprotein Complexes - chemistry; Multiprotein Complexes - metabolism; Nucleotides; Nutrient status; Nutrients; Physiological responses; Protein Conformation; Protein Domains; Protein Multimerization; Proteins; Proto-Oncogene Proteins - chemistry; Proto-Oncogene Proteins - metabolism; Rapamycin; Regulatory mechanisms (biology); Signal Transduction; Signaling; Tumor Suppressor Proteins - chemistry; Tumor Suppressor Proteins - metabolism; Tumors
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aax0364

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.