TORC1 regulates metabolism and growth in response to a large array of upstream inputs. The evolutionary conserved trimeric GATOR1 complex inhibits TORC1 activity in response to amino acid limitation. In humans, the GATOR1 complex has been implicated in a wide array of pathologies including cancer and hereditary forms of epilepsy. However, the precise role of GATOR1 in animal physiology remains largely undefined. Over the last year we characterized null mutants of the GATOR1 components nprl2, nprl3 and iml1 in Drosophila melanogaster. We demonstrated that all three mutants have inappropriately high baseline levels of TORC1 activity and decreased adult viability. Consistent with increased TORC1 activity, GATOR1 mutants exhibited a cell autonomous increase in cell growth. Notably, escaper nprl2 and nprl3 mutant adults were profoundly ataxic. In line with a non-autonomous role in the regulation of systemic metabolism, expressing the Nprl3 protein in the fat body, a nutrient storage organ, and hemocytes but not muscles and neurons rescued the motility of nprl3 mutants. Finally, we determined that nprl2 and nprl3 mutants fail to activate autophagy in response to amino acid limitation and are extremely sensitive to both amino acid and complete starvation. Thus, in Drosophila, in addition to maintaining baseline levels of TORC1 activity, the GATOR1 complex has retained a critical role in the response to nutrient stress. In summary, the TORC1 inhibitor GATOR1 contributes to multiple aspects of the development and physiology of Drosophila. Over the last year we defined the in vivo role of the GATOR2 component Wdr24 in Drosophila. The GATOR complex contains two sub-complexes, GATOR1, which inhibits TORC1 activity, which opposes the activity of GATOR1. While the GATOR1 complex has been implicated in a wide array of human pathologies including cancer and hereditary forms of epilepsy, the in vivo relevance of the GATOR2 complex remains poorly understood in metazoans. Using a combination of genetic, biochemical, and cell biological techniques we demonstrated that Wdr24 has both TORC1 dependent and independent functions. Through the characterization of a null allele, we demonstrated that Wdr24 is a critical effector of the GATOR2 complex that promotes the robust activation of TORC1 and cellular growth in a broad array of Drosophila tissues. Additionally, epistasis analysis between wdr24 and genes that encode components of the GATOR1 complex revealed that Wdr24 has a second critical function, the TORC1 independent regulation of lysosome dynamics and autophagic flux. Notably, we determined that two additional members of the GATOR2 complex, Mio and Seh1, also have a TORC1 independent role in the regulation of lysosome function. These findings represent a surprising and previously unrecognized role for GATOR2 complex components in the regulation of lysosomes. Consistent with our results in Drosophila, we determined that Wdr24 promotes lysosome acidification and autophagic flux in mammalian cells. Taken together our data support the model that Wdr24 is a key effector of the GATOR2 complex, required for both TORC1 activation and the TORC1 independent regulation of lysosomes.
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