Association of GABA(B) receptors and members of the 14-3-3 family of signaling proteins

Two GABA, receptors, GABA(B)R1 and GABA,RP, have been cloned recently. Unli ke other G protein-coupled receptors, the formation of a heterodimer betwee n GABA(B)R1 and GABA(B)RP is required for functional expression. We have us ed the yeast two hybrid system to identify proteins that interact with the C-terminus of GABA(B)R1. We report a direct association between GABA(B) rec eptors and two members of the 14-3-3 protein family, 14-3-3 eta and 14-3-3 zeta, We demonstrate that the C-terminus of GABA(B)R1 associates with 14-3- 3 zeta in rat brain preparations and tissue cultured cells, that they codis tribute after rat brain fractionation, colocalize in neurons, and that the binding site overlaps partially with the coiled-coil domain of GABA(B)R1. F urthermore we show a reduced interaction between the C-terminal domains of GABA(B)R1 and GABA(B)R2 in the presence of 14-3-3. The results strongly sug gest that GABA(B)R1 and 14-3-3 associate in the nervous system and begin to reveal the signaling complexities of the GABA(B)R1/GABA(B)R2 receptor hete rodimer.