Plays a role in protein sorting and trafficking between the trans-Golgi network (TGN) and endosomes (PubMed:25405894). 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 (By similarity). Required for targeting PKD1:PKD2 complex from the trans-Golgi network to the cilium membrane (PubMed:25405894). Regulates retrograde transport of proteins such as phosphorylated form of BACE1 from endosomes to the trans-Golgi network (By similarity). Monomer. Interacts with GGA2 and GGA3 (By similarity). Binds to clathrin and activated ARFs, including ARF1, ARF5 and ARF6 (PubMed:22522702, PubMed:11950392). Interacts with RABEP1 and RABGEF1 (PubMed:25405894). Interacts with the type-I membrane proteins LRP3, M6PR/CD-MPR and IGF2R/CI-MPR. Interacts (via N-terminal VHS domain) with SORL1/sorLA and SORT1 (via C-terminal cytosolic domain) (By similarity). Interacts with EPN4. Interacts with CCDC91 (By similarity). Interacts with HEATR5B/p200a (By similarity). Interacts with SYNRG/gamma-synergin (By similarity). Interacts (via GAE doamin) with NECAP1 and NECAP2 (By similarity). Interacts (via GAE domain) with AFTPH/aftiphilin (By similarity). Interacts with TSG101 and UBC. Interacts with RNF11. Interacts (via VHS domain) with BACE1 (via DXXLL motif); the interaction highly increases when BACE1 is phosphorylated at 'Ser-498' (By similarity). Interacts with CNST (PubMed:19864490). Interacts with ADRA2B (By similarity). Interacts with ARL3; the interaction recruits, in collaboration with RABEP1, PKD1:PKD2 complex to trans-Golgi network and is required for ciliary targeting (PubMed:25405894). 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. Phosphorylated by CK2 and dephosphorylated by PP2A. Phosphorylation of GGA1 allows the internal DXXLL motif to bind the VHS domain and to inhibit the recognition of cargo signals. Ubiquitinated. Belongs to the GGA protein family.