| The γ-aminobutyric acid (GABA) transporter type two (GAT-2) is a member of the sodium and chloride dependent neurotransmitter family. The members of this family share a twelve membrane spanning domain topology with cytosolic N- and C-termini. There are four members of the GABA transporter family, GAT-1, 2, 3, and the betaine transporter. When expressed in an in vitro model of kidney epithelia, GAT-2 localizes to the basolateral membrane and GAT-3 to the apical membrane, though the proteins are 64% identical. By creating chimeras of the two proteins in which dissimilar sections were exchanged, our laboratory demonstrated that the cytosolic C-terminus of GAT-2 contained necessary and sufficient distribution information for these transporters. This work locates necessary basolateral sorting information in the C-terminal ten amino acids, specifically in the seven preceding the three amino acid C-terminal PDZ domain interacting motif. We demonstrate that these seven encode targeting as well as steady state distribution information. We also show that the C-terminal tail interacts with a PDZ domain containing protein, GIPC, through the final three amino acids of the GAT-2 tail. We present evidence that this interaction is regulated in a novel fashion through reversible post translational modification of the GAT-2 tail with an acyl moiety. This interaction does not seem to be important for the polarity of steady state distribution or targeting. However, we present some preliminary evidence that GIPC may play a role in the transport of GAT-2 through the secretory pathway. |
