AP3S1 belongs to the adaptor complexes 3 (AP3) small subunit family which is not clathrin-associated. The complex is associated with the Golgi region as well as more peripheral structures. It facilitates the budding of vesicles from the Golgi membrane and may be directly involved in trafficking to lysosomes. AP3 is an heterotetramer composed of two large adaptins (AP3D1, AP3B1 or AP3B2), a medium adaptin (AP3M1 or AP3M2) and a small adaptin (APS1 or AP3S2). AP3S1 Interacts with AGAP1 and may play an important role in carcinoma.