Inhibition of the Dopamine D1 Receptor Signaling by PSD-95

Abstract

Dopamine D1 receptors play an important role in movement, reward, and learning and are implicated in a number of neurological and psychiatric disorders. These receptors are concentrated in dendritic spines of neurons, including the spine head and the postsynaptic density. D1 within spines is thought to modulate the local channels and receptors to control the excitability and synaptic properties of spines. The molecular mechanisms mediating D1 trafficking, anchorage, and function in spines remain elusive. Here we show that the synaptic scaffolding protein PSD-95 thought to play a role in stabilizing glutamate receptors in the postsynaptic density, interacts with D1 and regulates its trafficking and function. Interestingly, the D1-PSD-95 interaction does not require the well characterized domains of PSD-95 but is mediated by the carboxyl-terminal tail of D1 and the NH 2 terminus of PSD-95, a region that is recognized only recently to participate in protein-protein interaction. Co-expression of PSD-95 with D1 in mammalian cells inhibits the D1-mediated cAMP accumulation without altering the total expression level or the agonist binding properties of the receptor. The diminished D1 signaling is mediated by reduced D1 expression at the cell surface as a consequence of an enhanced constitutive, dynamin-dependent endocytosis. In addition, genetically engineered mice lacking PSD-95 show a heightened behavioral response to either a D1 agonist or the psychostimulant amphetamine. These studies demonstrate a role for a glutamatergic scaffold in dopamine receptor signaling and trafficking and identify a new potential target for the modulation of abnormal dopaminergic function.The dopamine D1-class receptors (D1 and D5) regulate movement, reward, and learning and are implicated in multiple neurological and psychiatric conditions (1-3). This dopamine receptor class is positively coupled to G s ␣ to regulate the PKA/ DARPP-32/PP1 pathway (4 -7), leading to the regulation of neuronal excitability, synaptic transmission and plasticity, and gene expression (8). A key site of action for D1, the predominant subtype of the D1-class receptor, is the dendritic spine of glutamatergic synapses, where the receptor is especially concentrated. Ultrastructural studies reveal that the majority of D1 receptors are localized postsynaptically in the neck, head, as well as the postsynaptic density (PSD) 2 of medium spiny neurons (9, 10) and cortical pyramidal neurons (11-13). This subcellular specialization thus provides a location where D1 can modulate the channels and receptors located at spines to control the excitability and synaptic properties of the (glutamatergic) spines. The molecular and cellular mechanisms that regulate D1 targeting and signaling within spines are poorly understood.PSD-95 is a prototypical scaffolding protein highly enriched in the PSD and belongs to the membrane-associated guanylate kinase family (14). PSD-95 contains three PSD-95, Dlg, ZO-1 homology (PDZ) domains, a Src homology 3 (SH3) domain, and a guanylate kinase-...

Dopaminergic signaling in dendritic spines

“…First, western blot studies consistently detecte a substantial amount of D1 and D2 receptors in purified PSD fractions [41][42][43]. Second, DA receptors interact and co-localize with a number of PSD proteins in dendritic spines (see Section 6 below).…”

“…DA receptors, like most GPCRs, internalize via the dynamin-dependent, clathrin-mediated endocytic pathway [43] (Figure 1B). Endocytosis occurs frequently in dendritic shafts, and core endocytic proteins, including adaptor protein 2 (AP-2), clathrin, and dynamin-3, are present in the spine heads [49].…”

“…Besides short peptide sequences involved in G protein and arrestin binding, the remaining portions of these intracellular domains are presumably free to interact with other proteins. Using approaches such as co-immunoprecipitation and the yeast two-hybrid system, an increasing number of DRIPs are being identified [41][42][43]53,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83]. The confirmed DRIPs and their suggested functions are summarized in Table 1.…”

“…The level of PSD-95 is reduced in the striatum of several mouse models of DA supersensitivity, and mice lacking PSD-95 show enhanced behavioral responses to the psychostimulants cocaine and amphetamine [43,85]. The role of PSD-95 in DA sensitivity is mediated by, at least in part, its interaction with the D1 receptor [43]. The D1-PSD-95 interaction does not require the wellcharacterized protein-protein interaction domains of PSD-95, but is instead mediated by the carboxyl terminal tail of the D1 receptor and the N-terminus of PSD-95.…”

Calcyon Forms a Novel Ternary Complex with Dopamine D1 Receptor through PSD-95 Protein and Plays a Role in Dopamine Receptor Internalization

“…It forms the backbone of the postsynaptic protein complex that organizes receptors and signal transduction molecules, enabling the functional effects of the receptors at PSDs. PSD-95 is known to regulate D 1 DR signaling and the formation of the D 1 DR-associated protein⅐protein complex (13,14). The NH 2 terminus of PSD-95 interacts with the carboxyl-terminal tail of D 1 DR and facilitates constitutive D 1 DR internalization as well as internalization of the NMDA receptor, which complexes with D 1 DR, thus linking dopamine signaling and glutamatergic signaling (15).…”