Suppressor of apoptosis (By similarity). Modulates unfolded protein response signaling (PubMed:19328063). Negatively regulates autophagy and autophagosome formation, especially during periods of nutrient deprivation, and reduces cell survival during starvation (PubMed:21926971). RNAi-mediated knockdown induces autophagy in larvae under basal and fasting conditions with larvae showing an increased number of autophagosomes. Decreased larval survival following treatment with tunicamycin. Impaired pupal salivary gland degradation with pupae undergoing autophagy prematurely by six hours after puparium formation. Increased adult survival during nutrient starvation. Belongs to the BI1 family.