Adaptor gamma ear homology domain conserved in gamma-adaptin and GGA proteins that interact with gamma-synergin.

We identified a novel family of proteins that have a VHS domain and an AGEH (adaptor gamma ear homology) domain that is homologous to the ear domain of the gamma-adaptin subunit of the AP-1 clathrin adaptor. When overexpressed, the proteins, called GGA1, GGA2, and GGA3, localized to the trans-Golgi network (TGN) and often caused fragmentation and vacuolation of the compartment. Yeast two-hybrid analysis showed that the AGEH domains of the GGA proteins as well as those of gamma-adaptins are able to interact with gamma-synergin, which was previously shown to localized in the TGN region and interact with gamma-adaptin. Furthermore, gamma-synergin and either of the GGA proteins coexpressed were colocalized in the TGN region. These results suggest that the GGA proteins regulate the function of the TGN or membrane trafficking from this compartment and that the AGEH domains of GGAs and gamma-adaptins, like the ear domain of alpha-adaptin, are involved in interaction with molecules that modulate their functions.