Negative regulator of the mTORC1 and mTORC2 signaling pathways. Inhibits the kinase activity of both complexes. Part of the mammalian target of rapamycin complex 1 (mTORC1) which contains MTOR, MLST8, RPTOR, AKT1S1/PRAS40 and DEPTOR. Part of the mammalian target of rapamycin complex 2 (mTORC2) which contains MTOR, MLST8, PROTOR1, RICTOR, MAPKAP1 and DEPTOR. Interacts (via PDZ domain) with MTOR; interacts with MTOR within both mammalian target of rapamycin complexes mTORC1 and mTORC2 (PubMed:19446321). Interacts (via PDZ domain) with MINAR1 (via N-terminus) (PubMed:30080879). Interacts with SIK3 (PubMed:30232230). Expression is negatively regulated by both mTORC1 and mTORC2 (at protein level). Phosphorylated. Phosphorylation weakens interaction with MTOR within mTORC1 and mTORC2. Ubiquitinated; ubiquitination leads to proteasomal degradation. Truncated N-terminus.