Requirement of PSD-95 for dopamine D₁ receptor modulating glutamate NR1a/NR2B receptor function

Aim: To elucidate the role of scaffold protein postsynaptic density (PSD)-95 in the dopamine D₁ receptor (D₁R)-modulated NR1a/NR2B receptor response. Methods: The human embryonic kidney 293 cells expressing D₁R (tagged with the enhanced yellow fluorescent protein) and NR1a/NR2B with or without co-expression of PSD-95 were used in the experiments. The Ca²⁺ influx measured by imaging technique was employed to monitor N -methyl-D-aspartic acid receptors (NMDAR) function. Results: The application of dopamine (DA, 100 μmol/L) did not alter glutamate/glycine (Glu/Gly)-induced NMDAR-mediated CaM²⁺ influx in cells only expressing the D₁R/NR1a/NR2B receptor. However, DA increased Glu/Gly-induced Ca²⁺ influx in a concentration-dependent manner while the cells were co-expressed with PSD-95. D₁R-stimulated Ca²⁺ influx was inhibited by a selective D₁R antagonist SCH23390. Moreover, pre-incubation with either the protein kinase A (PKA) inhibitor H89, or the protein kinase C (PKC) inhibitor chelerythrine attenuated D₁R-enhanced Ca²⁺ influx induced by the N-methyl-D-aspartic acid (NMDA) agonist. The results clearly indicate that D₁R-modulated NR1a/NR2B receptor function depends on PSD-95 and is subjected to the regulation of PKA and PKC. Conclusion: The present study provides the first evidence that PSD-95 is essential in D₁R-regulated NR1a/NR2B receptor function.