Functions as an intracellular leucine sensor that negatively regulates the TORC1 signaling pathway through the GATOR complex. In absence of leucine, binds the GATOR subcomplex GATOR2 and prevents TORC1 signaling. Binding of leucine to SESN2 disrupts its interaction with GATOR2 thereby activating the TORC1 signaling pathway (PubMed:18692468, PubMed:25259925). This stress-inducible metabolic regulator also plays a role in protection against oxidative and genotoxic stresses. May negatively regulate protein translation in response to endoplasmic reticulum stress, via TORC1 (PubMed:24947615). May positively regulate the transcription by NFE2L2 of genes involved in the response to oxidative stress by facilitating the SQSTM1-mediated autophagic degradation of KEAP1 (PubMed:23274085). May also mediate TP53 inhibition of TORC1 signaling upon genotoxic stress (PubMed:18692468). Moreover, may prevent the accumulation of reactive oxygen species (ROS) through the alkylhydroperoxide reductase activity born by the N-terminal domain of the protein (By similarity). Was originally reported to contribute to oxidative stress resistance by reducing PRDX1 (By similarity). However, this could not be confirmed (By similarity). a hydroperoxide + L-cysteinyl-[protein] = an alcohol + S-hydroxy-L-cysteinyl-[protein] Interacts with the GATOR2 complex which is composed of MIOS, SEC13, SEH1L, WDR24 and WDR59; the interaction is negatively regulated by leucine (By similarity). Interacts with RRAGA, RRAGB, RRAGC and RRAGD; may function as a guanine nucleotide dissociation inhibitor for RRAGs and regulate them (PubMed:25259925). May interact with the TORC2 complex (PubMed:25377878). Interacts with KEAP1, RBX1, SQSTM and ULK1; to regulate the degradation of KEAP1 (PubMed:25040165). May also associate with the complex composed of TSC1, TSC2 and the AMP-responsive protein kinase/AMPK to regulate TORC1 signaling (PubMed:18692468). May interact with PRDX1 (By similarity). Detected in heart, liver and skeletal muscles (at protein level). Up-regulated by treatments inducing endoplasmic reticulum stress. The N-terminal domain has an alkylhydroperoxide reductase activity. The C-terminal domain mediates interaction with GATOR2 through which it regulates TORC1 signaling. Phosphorylated by ULK1 at multiple sites. Ubiquitinated at Lys-175 by RNF167 via 'Lys-63'-linked polyubiquitination in response to leucine deprivation: ubiquitination promotes SESN2-interaction with the GATOR2 complex, leading to inhibit the TORC1 signaling pathway. Deubiquitinated at Lys-175 by STAMBPL1, promoting the TORC1 signaling pathway. Ubiquitinated by RNF186; ubiquitination mediates proteasomal degradation. Sesn2 knockout mice are fully viable and do not display any overt developmental abnormalities. When kept on high fat diet, they display higher insulin resistance and glucose intolerance (PubMed:22958918). The oxidative stress induced by acute lipogenesis upon refeeding results in increased liver damages in the Sesn2 knockout mice. Any condition, like obesity, that triggers chronic or acute endoplasmic reticulum stresses have the same consequences in these mice and can lead to liver fibrosis (PubMed:23274085, PubMed:24947615). Sesn2 and Sesn3 double knockout mice display insulin resistance and glucose intolerance (PubMed:22958918). Triple knockout mice lacking Sesn1, Sesn2 and Sesn3 do not display an embryonic lethal phenotype since they are born at an expected Mendelian ratio. Moreover, they are not distinguishable from their wild-type littermates. However, their survival at 10 days is dramatically affected. This is associated with a constitutive activation of TORC1 signaling in the liver, heart and skeletal muscle during postnatal fasting, that occurs between birth and suckling (PubMed:25259925). Belongs to the sestrin family.