9o5a
The KICSTOR-GATOR1 complex
Structural highlights
DiseaseNPRL2_HUMAN Inactivating mutations and truncating deletions in the genes encoding GATOR1 proteins, including NPRL2, are detected in glioblastoma and ovarian tumors and are associated with loss of heterozygosity events. Inactivation of GATOR1 proteins promotes constitutive localization of mTORC1 to the lysosomal membrane and blocks mTORC1 inactivation following amino acid withdrawal (PubMed:23723238).[1] The disease is caused by mutations affecting the gene represented in this entry. FunctionNPRL2_HUMAN As a component of the GATOR1 complex functions as an inhibitor of the amino acid-sensing branch of the TORC1 pathway. The GATOR1 complex strongly increases GTP hydrolysis by RRAGA and RRAGB within RRAGC-containing heterodimers, thereby deactivating RRAGs, releasing mTORC1 from lysosomal surface and inhibiting mTORC1 signaling. The GATOR1 complex is negatively regulated by GATOR2 the other GATOR subcomplex in this amino acid-sensing branch of the TORC1 pathway.[2] Suppresses Src-dependent tyrosine phosphorylation and activation of PDPK1 and its downstream signaling. Down-regulates PDPK1 kinase activity by interfering with tyrosine phosphorylation at 'Tyr-9', 'Tyr-373' and 'Tyr-376' residues. May act as a tumor suppressor. Suppresses cell growth and enhances sensitivity to various anticancer drugs.[3] Publication Abstract from PubMedThe guanosine triphosphate (GTP)-bound state of the heterodimeric Rag GTPases functions as a molecular switch regulating mechanistic target of rapamycin complex 1 (mTORC1) activation at the lysosome downstream of amino acid fluctuations. Under low amino acid conditions, GTPase-activating protein (GAP) activity toward Rags 1 (GATOR1) promotes RagA GTP hydrolysis, preventing mTORC1 activation. KICSTOR recruits and regulates GATOR1 at the lysosome by undefined mechanisms. Here, we resolve the KICSTOR-GATOR1 structure, revealing a striking approximately 60-nm crescent-shaped assembly. GATOR1 anchors to KICSTOR via an extensive interface, and mutations that disrupt this interaction impair mTORC1 regulation. The S-adenosylmethionine sensor SAMTOR binds KICSTOR in a manner incompatible with metabolite binding, providing structural insight into methionine sensing via SAMTOR-KICSTOR association. We discover that KICSTOR and GATOR1 form a dimeric supercomplex. This assembly restricts GATOR1 to an orientation that favors the low-affinity active GAP mode of Rag GTPase engagement while sterically restricting access to the high-affinity inhibitory mode, consistent with a model of an active lysosomal GATOR1 docking complex. Structure of the lysosomal KICSTOR-GATOR1-SAMTOR nutrient-sensing supercomplex.,Lupton CJ, Bayly-Jones C, Dong S, Lam T, Luo W, Jones GD, Mastos C, Frescher NJ, Lim SS, Keen AC, Formosa LE, Venugopal H, Chang YG, Halls ML, Ellisdon AM Cell. 2026 Jan 8:S0092-8674(25)01418-7. doi: 10.1016/j.cell.2025.12.005. PMID:41512879[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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