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. Mediates export of the GPCR receptor ADRA2B to the cell surface. Regulates retrograde transport of phosphorylated form of BACE1 from endosomes to the trans-Golgi network. Monomer (By similarity). Interacts with NECAP1, TSG101, UBC and AFTPH/aftiphilin. Interacts with CNST (PubMed:19864490). Interacts with GGA1 and GGA3 (By similarity). Binds to clathrin and activated ARFs, such as ARF1, ARF5 and ARF6 (PubMed:11950392). Binds RABEP1 and RABGEF1. Interacts with the type-I membrane proteins LRP3, M6PR/CD-MPR, IGF2R/CI-MPR and BACE1. Interacts (via N-terminal VHS domain) with SORL1/sorLA and SORT1 (via C-terminal cytosolic domain) (By similarity). Binds the accessory proteins CCDC91, P200, SYNRG, EPN4 and NECAP2. Interacts with ADRA2B. Interacts (via VHS domain) with PIK4B; the interaction is important for PIK4B location at the Golgi apparatus membrane (By similarity). 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. Truncated N-terminus. Extended N-terminus.