Subunit of TORC1 and TORC2, which regulate cell growth and survival in response to nutrient and hormonal signals (PubMed:22493059, PubMed:25999153). Essential for TORC2-mediated regulation of cell growth and phosphorylation of Akt1 (PubMed:22493059, PubMed:25999153). However it is not required for TORC1-mediated functions such as TORC1-dependent regulation of cell growth, autophagy and phosphorylation of S6K (PubMed:22493059). Part of a minimal complex, TORC1, consisting of tor, raptor and lst8. Interacts with tor but not raptor. Does not require raptor for binding to tor. Part of a minimal complex, TORC2, consisting of tor, rictor and lst8. Reduced tissue growth (PubMed:22493059, PubMed:25999153). Adults display an overall reduction in size with a 25% reduction in body weight, and have smaller wings and eyes (PubMed:22493059, PubMed:25999153). Reduced phosphorylation of Akt1 which is a direct target of the TORC2 complex but no effect on the phosphorylation of SK6 which is a major target of the TORC1 complex (PubMed:22493059). Belongs to the WD repeat LST8 family.