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. Involved in BACE1 transport and sorting as well as regulation of BACE1 protein levels. Regulates retrograde transport of BACE1 from endosomes to the trans-Golgi network via interaction through the VHS motif and dependent of BACE1 phosphorylation. Modulates BACE1 protein levels independently of the interaction between VHS domain and DXXLL motif through recognition of ubiquitination (By similarity). Key player in a novel DXXLL-mediated endosomal sorting machinery to the recycling pathway that targets NTRK1 to the plasma membrane (PubMed:26446845). Monomer. Interacts with GGA1 and GGA2. Binds to clathrin and activated ARFs, such as ARF1, ARF5 and ARF6. Binds RABEP1 and RABGEF1. Interacts with the membrane proteins M6PR/CD-MPR and IGF2R/CI-MPR and the accessory proteins SYNRG, EPN4, NECAP1, NECAP2 and AFTPH/aftiphilin. Interacts with TSG101 and UBC. Interacts with ADRA2B (By similarity). Interacts with NTRK1; the interaction is independent of NTRK1 activation and ubiquitination (PubMed:26446845). Interacts (via VHS domain) with BACE1 (via DXXLL motif) (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 and an autoinhibitory (DXXLL) motifs. The GAE domain binds accessory proteins regulating GGAs function. Phosphorylated by CK2 and dephosphorylated by PP2A (By similarity). Phosphorylation of GGA3 allows the internal DXXLL motif to bind the VHS domain and to inhibit the recognition of cargo signals. Ubiquitinated. Proteolytically cleaved during apoptosis by CASP3. Belongs to the GGA protein family.