Subunit of clathrin-associated adaptor protein complex 1 that plays a role in protein sorting in the late-Golgi/trans-Golgi network (TGN) and/or endosomes. The AP complexes mediate both the recruitment of clathrin to membranes and the recognition of sorting signals within the cytosolic tails of transmembrane cargo molecules. In association with AFTPH/aftiphilin in the aftiphilin/p200/gamma-synergin complex, involved in the trafficking of transferrin from early to recycling endosomes, and the membrane trafficking of furin and the lysosomal enzyme cathepsin D between the trans-Golgi network (TGN) and endosomes (PubMed:15758025). Adaptor protein complex 1 (AP-1) is a heterotetramer composed of two large adaptins (gamma-type subunit AP1G1 and beta-type subunit AP1B1), a medium adaptin (mu-type subunit AP1M1 or AP1M2) and a small adaptin (sigma-type subunit AP1S1 or AP1S2 or AP1S3) (PubMed:34102099). Interacts (via GAE domain) with RABEP1 (PubMed:12773381, PubMed:14665628, PubMed:12042876). Interacts with SYNRG/gamma-synergin (PubMed:12042876). Interacts with EPS15 (By similarity). Interacts (via GAE domain) with AP1AR (via coiled-coil domain) (PubMed:15775984). Interacts with CLN3 (via dileucine motif); this interaction facilitates lysosomal targeting (PubMed:15598649). Interacts (via GAE domain) with AFTPH/aftiphilin; the interaction is required to recruit AFTPH/aftiphilin to the perinuclear region of the cell (PubMed:14665628, PubMed:15758025). Component of the coat surrounding the cytoplasmic face of coated vesicles located at the Golgi complex (PubMed:12773381). Co-localizes with AFTPH/aftiphilin in the cytoplasm (PubMed:15758025). Widely expressed. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the adaptor complexes large subunit family.