May function in protein sorting in late endosomes or multivesucular bodies (MVBs). Involved in MVB-assisted maturation of hepatitis B virus (HBV). May interact with AP1S1/Sigma1A-adaptin and AP1S2/Sigma1B-adaptin (By similarity). Probably does not interact with APB1 (By similarity). Interacts (via GAE domain) with RABEP1, NECAP1, CLINT1 and AFTPH/aftiphilin (By similarity). Interacts with HBV major surface antigen L. Interacts with HBV core protein C in a ubiquitin-dependent manner. Binds ubiquitin. Mainly localized to perinuclear vesicular structures. Colocalizes with HBV major surface antigen L and HBV core protein C in CD63-containing compartments. Colocalizes with HBV major surface antigen L to cis-Golgi-like structures. Widely expressed. Belongs to the adaptor complexes large subunit family.