The PDZ Domain of PICK1 Differentially Accepts Protein Kinase C-α and GluR2 as Interacting Ligands

Abstract

The C terminus (ct) of protein kinase C-α (PKCα) has a type I PDZ binding motif, whereas GluR2 has a type II PDZ binding motif. Both motifs are recognized by the PDZ domain of protein interacting with protein kinase C (PICK1), and PICK1-PKCα-controlled phosphorylation regulates the synaptic expression and function of GluR2. Here, we show that a specific mutation within the carboxylate-binding loop of the PDZ domain of PICK1 (K27E; PICK1-KE) results in a loss of interaction with GluR2 but not with PKCα. In GST pull-down studies, PICK1-WT (wild type) but not PICK1-KE was retained by GST-ct-GluR2. Furthermore, PICK1-WT co-immunoprecipitated both PKCα and GluR2, whereas PICK1-KE only co-immunoprecipitated PKCα. In heterologous cells, PICK1-WT, but not PICK1-KE, clustered GluR2 and also clustered GluR1 in a GluR2-dependent manner. However, neither PICK1-WT nor PICK1-KE altered the distribution of PKCα, even after phorbol ester-induced redistribution of PKCα to the membrane. Finally, PICK1-KE showed no mislocalization when compared with PICK1-WT in neurons. Taken together, it appears that the PDZ domain of PICK1 is less sensitive to mutations for PKCα when compared with GluR2 binding. These results suggest that the PDZ domain of PICK1 has distinct PKCα and GluR2 binding subsite(s).