The carboxyl terminus of the prolactin-releasing peptide receptor interacts with PDZ domain proteins involved in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor clustering

PDZ domain proteins use the PDZ domain binding motif to bind to the C-termi nal sequence of membrane proteins to help scaffold them and spatially organ ize the components of the intracellular signaling machinery. We have identi fied a sequence at the C terminus of a G protein-coupled receptor, the PrRP receptor, that shares similarities with the C-terminal sequence of alpha - amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPA-R) subuni ts that interact with PDZ domain proteins. When coexpressed in human embryo nic kidney 293 cells, PrRP receptor was able to coimmunoprecipitate the thr ee PDZ domain proteins known to interact with AMPA receptors: glutamate rec eptor interacting protein (GRIP), AMPA binding protein (ABP), and protein t hat interacts with C-kinase (PICK1), but not the PDZ domain protein PSD-95, which does not interact with AMPA receptors. These interactions are sequen ce-selective as determined by mutagenesis. Furthermore, we show that PrRP r eceptor forms intracellular clusters when coexpressed with PICK1, and that this clustering effect is dependent on the interaction between the PICK1 PD Z domain and the last four amino acids of PrRP receptor. We found that PrRP receptor interaction with GRIP is not protein kinase C-regulated but may b e regulated by other unidentified kinase because okadaic acid dramatically reduced GRIP interaction. By in situ hybridization, we show that the PrRP r eceptor is expressed in neurons that also express these PDZ domain proteins . We thus demonstrate that PrRP receptor interacts with the same PDZ domain proteins as the AMPA-Rs, raising the possibility that these two proteins c ould be scaffolded together at the synapse. These results may help to gain important insights into PrRP functions within the central nervous system.