A Direct Interaction of PSD-95 with 5-HT2A Serotonin Receptors Regulates Receptor Trafficking and Signal Transduction

Abstract

(1) but not all hallucinogens (2, 3) and is the target of a number of commonly prescribed therapeutic agents including atypical antipsychotics, antidepressants, and anxiolytics (4, 5). As with other G protein-coupled receptors (GPCRs) (6 -8), elucidating the regulatory mechanisms for 5-HT 2A receptor signaling and trafficking provides important insights into the therapeutic mechanisms of drugs that target the 5-HT 2A receptor and has implications for the rational design of novel medications (5, 6).The 5-HT 2A receptor, the most abundant serotonin receptor in the cerebral cortex, is enriched in dendritic shafts and, to a lesser extent, asymmetric synapses and dendritic spines of pyramidal neurons primarily from Layers IV and V (9 -13). The last four amino acids (VSCV) of the carboxyl terminus of the 5-HT 2A receptor constitute a canonical Type I PDZ-binding domain (X-Ser/Thr-X-⌽) (14). The PDZ-binding domain is located at the carboxyl terminus of a variety of proteins including many GPCRs and is known to associate with PSD-95/Discslarge/ZO-1 (PDZ) domain-containing proteins of which postsynaptic density 95 (PSD-95, also known as synapse-associated protein 90 or SAP-90, is a prototypic member (15, 16). These multi-domain molecules not only target and provide scaffolds for protein-protein interactions but can also modulate the functions of ion channels and receptors with which they associate (16 -20). The disruption of the association between PDZ proteins and their targets contributes to the pathogenesis of a number of human diseases (16,21,22), most probably because of the failure of PDZ proteins to appropriately target and modulate the actions of the associated proteins. Na ϩ /H ϩ exchanger regulatory factor (NHE-RF) was the first PDZ domain-containing protein that was reported to modulate the function of a GPCR (e.g. the ␤ 2 -adrenergic receptor (␤ 2 -AR)) (23). Subsequently, PSD-95 was found to associate with and inhibit the internalization of ␤ 1 -ARs and to facilitate the interaction between the ␤ 1 -AR and the N-methyl-D-aspartate ionotropic glutamate receptor (24,25). Among the 5-HT 2 class of serotonin receptors, a multi-PDZ domain-containing protein, MUPP1, associates with 5-HT 2C receptors in vitro and in vivo (26). MUPP1 has also been predicted to interact with both the 5-HT 2A and the 5-HT 2B receptor based on its ability to bind to purified COOH-terminal fusion proteins of both receptors in vitro (26). Furthermore, a proteomic approach has recently identified PSD-95 as a component of a multi-protein complex that associates with the 5-HT 2C receptor in vivo (27). PSD-95, similar to the 5-HT 2A receptor, is enriched in asymmetric synapses and dendritic spines of cortical pyramidal neurons (28,29) and is thus predicted to interact with 5-HT 2A receptors. The functional significance of any association between PDZ proteins and 5-HT receptors is unknown because none has been previously reported.Therefore, we set out to investigate whether PSD-95 interacts with and regulates 5-HT 2A receptors. A combination...

The PDZ-binding domain is essential for the dendritic targeting of 5-HT2A serotonin receptors in cortical pyramidal neurons in vitro

“…1G-I), confirming that this major synaptic protein of the excitatory post-synaptic density was appropriately sorted to the plasma membrane of cortical pyramidal neurons in culture. Furthermore, PSD-95 is known to associate directly with NMDA ionotropic glutamate receptors (NMDA-R) and indirectly with AMPA ionotropic glutamate receptors (AMPA-R) via stargazin (Kornau et al, 1995;Chen et al, 2000;El-Husseini et al, 2000;Chetkovich et al, 2002;Choi et al, 2002;Schnell et al, 2002), and has been shown to directly interact with the 5-HT 2A receptor (Xia et al, 2003). As expected, PSD-95 in cultured neurons co-localized with NMDA receptors (data not shown) and 5-HT 2A receptors (Fig.…”

“…We have recently obtained convincing evidence that PSD-95, a prototypic PDZ domain-containing protein and a key component of the excitatory post-synaptic density, directly associates with the PDZ-binding domain of the 5-HT 2A receptor and regulates the signaling and subcellular distribution of 5-HT 2A receptors (Xia et al, 2003). Interestingly, whereas the PDZ-binding domain of the mGluR7 receptor (⌽ -X-⌽, where ⌽ is a hydrophobic residue) is recognized by class II PDZ domains, that of the 5-HT 2A receptor (S/T-X-V/I) is recognized by class I PDZ domains.…”

Decreased Serotonin 5-HT2A Receptor-Stimulated Phosphoinositide Signaling in Fibroblasts from Melancholic Depressed Patients

“…Given that the reduction in 5-HT 2A receptor signal was retained after many cell passages, a genetic alteration is likely, either in the receptor itself or key regulatory factors, such as multidomain scaffolding proteins. For example, recent evidence suggests that the 5-HT 2A receptor (Xia et al, 2003) and its close relative, the 5-HT 2C receptor (Parker et al, 2003), are regulated by interaction with a multifunctional PDZ domain protein. In addition, genetic studies have suggested that polymorphisms of the 5-HT 2A receptor are associated with mood disorders, but the results have been mixed (Zhang et al, 1997;Spurlock et al, 1998;Turecki et al, 1999;Du et al, 1999;Hrdina and Du, 2001;Crawford et al, 2000;Arias et al, 2001).…”

p90 ribosomal S6 kinase 2 exerts a tonic brake on G protein-coupled receptor signaling

“…We have previously shown an interaction of 5-HT 2A receptors with postsynaptic density protein 95 (PSD-95), a PSD-95͞discs large͞ZO-1 (PDZ) domain-containing scaffolding protein that interacts with the extreme C-terminal tail of the 5-HT 2A receptor via a canonical type 1 PDZ ligand (18). In addition, a number of other GPCRs have previously been shown to interact with PDZ domain-containing scaffolding proteins (see ref.…”