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. Within the GATOR complex, component of the GATOR1 subcomplex, made of DEPDC5, NPRL2 and NPRL3. GATOR1 mediates the strong interaction of the GATOR complex with RRAGA/RRAGC and RRAGB/RRAGC heterodimers. Interacts (via DEP domain) with KLHL22; the interaction depends on amino acid availability (PubMed:29769719). Localization to lysosomes is amino acid-independent. Expressed in developing and adult brain. The DEP domain mediates the interaction with KLHL22. Ubiquitinated. Amino acid-induced 'Lys-48'-linked polyubiquitination of DEPDC5 by the BCR(KLHL22) ubiquitin ligase complex leads to DEPDC5 proteasomal degradation and inhibition of the GATOR1 complex (PubMed:29769719). Ubiquitination may occur at multiple lysines (PubMed:29769719). The disease is caused by variants affecting the gene represented in this entry. Inactivating mutations and truncating deletions in the genes encoding GATOR1 proteins, including DEPDC5, 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). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the IML1 family. Extended N-terminus. Aberrant splicing. Truncated N-terminus.