Synapse-Associated Protein 102 and Postsynaptic Density 95 Regulate Dopamine D1-Class Receptors in Subtype-Specific Manner

Abstract

Neuromodulation by dopamine D1-class receptor subtypes (D1R and D5R) act via G-protein coupled receptors (GPCRs) and controls essential cognitive and motor functions. The dysfunction of D1R and D5R have been implicated in multiple neurological and psychiatric disorders. D1R and D5R are localized in the postsynaptic density (PSD) of dendritic spines within neurons, where they modulate intracellular signaling pathways and interact with scaffolding partners. Included among the many proteins highly enriched in the PSD are the scaffolding proteins; synapseassociated protein 102 (SAP102) and postsynaptic density 95 protein (PSD95). SAP102 and PSD95 belong to the membrane-associated guanylate kinase (MAGUK) family and regulate glutamate receptors, channel protein localization, and organize numerous signaling protein complexes required for synaptic development and plasticity. Despite the important role of dopaminergic and glutamatergic crosstalk, little is known about how PSD proteins regulate signaling and trafficking properties of dopaminergic receptors. Here, we specifically investigate the binary interaction of SAP102 and PSD95 with D1R and D5R, and the role these MAGUKs have in the regulation of signaling and trafficking of these D1-class receptor subtypes. Our results showed D1R•SAP102 and D1R•PSD95 complexes in vivo and in vitro, and these interactions differentially regulate agonist-mediated signaling, phosphorylation, and trafficking of D1R. In addition, we showed PSD95, but not SAP102, interacts with D5R in vivo and in vitro, and the D5R•PSD95 complex modulates agonist-mediated signaling and trafficking of D5R. Together, these results demonstrate an important role for SAP102 and PSD95 in regulating D1-class receptor in subtype-specific manner. Interestingly, we found that β-arrestin1 (βArr1) and β-arrestin2 (βArr2), versatile adaptor proteins that regulate desensitization and trafficking of GPCRs, including D1R, interact with SAP102 and PSD95 in vivo and in vitro. Additionally, we found that SAP102 and PSD95 positively mediate βArr2 recruitment to D1R, but not with βArr1, suggesting a potential ternary complex of D1R•MAGUK•βArr2. Future studies might exploit the pharmacological potential of D1R•SAP102, D1R•PSD95, and D5R•PSD95 complexes in the design of novel therapeutic approaches to mitigate abnormal dopaminergic D1-class function as seen in Parkinson’s Disease.