Threonine 82 at the PDZ domain of PICK1 is critical for AMPA receptor interaction and localization

Trafficking of AMPA receptors to and from synapses and their final localizations are critical for the expression of synaptic plasticity, which is regarded as the cellular basis of learning and memory. Protein that interacts with C Kinase 1 (PICK1), is one of the scaffolding proteins that interacts with AMPA receptors and regulates their trafficking in synaptic plasticity. In this study, we found that PICK1 could be a threonine-phosphorylated protein and identified threonine 82 (T82) in the PDZ domain of PICK1 as a potential phosphorylation site based on sequence and structural modeling analysis. We further performed co-immunoprecipitation experiments to confirm that T82 was indeed critical for the interaction between PICK1 and GluR2. In addition, T82E mutation mimicking the phosphorylation of PICK1 dispersed the colocalization of PICK1 and GluR2 in heterologous cells. Finally, the phosphorylated analog, T82E, inhibited PICK1's effect in regulating surface distribution of GluR2 and current mediated by GluR2. In summary, our data suggest that T82 is a potential phosphorylation site of PICK1 and is critical for the interaction of PICK1 with AMPA receptors and PICK1-regulated AMPA receptor localization.