Plays a role in protein sorting and trafficking between the trans-Golgi network (TGN) and endosomes. Mediates the ARF-dependent recruitment of clathrin to the TGN and binds ubiquitinated proteins and membrane cargo molecules with a cytosolic acidic cluster-dileucine (DXXLL) motif (PubMed:10747088). Mediates export of the GPCR receptor ADRA2B to the cell surface (PubMed:27901063). Regulates retrograde transport of phosphorylated form of BACE1 from endosomes to the trans-Golgi network (PubMed:15615712). Monomer (Probable). Interacts with NECAP1, TSG101, UBC and AFTPH/aftiphilin. Interacts with CNST (By similarity). Interacts with GGA1 and GGA3 (PubMed:14638859). Binds to clathrin and activated ARFs, such as ARF1, ARF5 and ARF6 (PubMed:11301005, PubMed:11950392). Binds RABEP1 and RABGEF1 (PubMed:12505986). Interacts with the type-I membrane proteins LRP3, M6PR/CD-MPR, IGF2R/CI-MPR and BACE1 (PubMed:11390366, PubMed:11387475, PubMed:11886874, PubMed:14567678). Interacts (via N-terminal VHS domain) with SORL1/sorLA and SORT1 (via C-terminal cytosolic domain) (PubMed:11331584, PubMed:11390366, PubMed:11821067). Binds the accessory proteins CCDC91, P200, SYNRG, EPN4 and NECAP2 (PubMed:10814529, PubMed:12429846, PubMed:12808037, PubMed:14665628). Interacts with ADRA2B (PubMed:27901063). Interacts (via VHS domain) with PIK4B; the interaction is important for PIK4B location at the Golgi apparatus membrane (PubMed:28289207). Ubiquitously expressed. The VHS domain functions as a recognition module for sorting signals composed of an acidic cluster followed by two leucines (DXXLL motif). The GAT domain is responsible for interaction with ARF-GTP, UBC and RABEP1. Required for recruitment to the TGN it prevents ARF-GTP hydrolysis. The unstructured hinge region contains clathrin-binding but no autoinhibitory (DXXLL) motifs. The GAE domain binds accessory proteins regulating GGAs function. Ubiquitinated. Belongs to the GGA protein family.