Functions as an intracellular leucine sensor that negatively regulates the mTORC1 signaling pathway through the GATOR complex (PubMed:18692468, PubMed:25263562, PubMed:25457612, PubMed:26449471, PubMed:26586190, PubMed:26612684, PubMed:31586034, PubMed:35114100, PubMed:35831510, PubMed:36528027). In absence of leucine, binds the GATOR subcomplex GATOR2 and prevents mTORC1 signaling (PubMed:18692468, PubMed:25263562, PubMed:25457612, PubMed:26449471, PubMed:26586190, PubMed:26612684, PubMed:31586034, PubMed:35114100, PubMed:35831510, PubMed:36528027). Binding of leucine to SESN2 disrupts its interaction with GATOR2 thereby activating the TORC1 signaling pathway (PubMed:26449471, PubMed:26586190, PubMed:35114100, PubMed:35831510, PubMed:36528027).

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 mTORC1 (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 (PubMed:26612684). Was originally reported to contribute to oxidative stress resistance by reducing PRDX1 (PubMed:15105503).

However, this could not be confirmed (PubMed:19113821)

Interacts with the GATOR2 complex which is composed of MIOS, SEC13, SEH1L, WDR24 and WDR59; the interaction is negatively regulated by leucine (PubMed:25263562, PubMed:25457612, PubMed:26449471, PubMed:35114100, PubMed:35831510, PubMed:36528027). Conveys leucine availability via direct interaction with SEH1L and WDR24 components of the GATOR2 complex (PubMed:35831510, PubMed:36528027). 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 (By similarity). Interacts with KEAP1, RBX1, SQSTM and ULK1; to regulate the degradation of KEAP1 (PubMed:23274085, 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 (PubMed:15105503)

Widely expressed

The N-terminal domain has an alkylhydroperoxide reductase activity

The C-terminal domain mediates interaction with GATOR2 through which it regulates TORC1 signaling