title: The PDZ scaffold NHERF-2 interacts with mGluR5 and regulates receptor activity.
abstract: The two members of the group I metabotropic glutamate receptor family, mGluR1 and mGluR5, both couple to G(q) to mediate rises in intracellular calcium. The alternatively spliced C termini (CT) of mGluRs1 and 5are known to be critical for regulating receptor activity and to terminate in motifs suggestive of potential interactions with PDZ domains. We therefore screened the CTs of both mGluR1a and mGluR5 against a PDZ domain proteomic array. Out of 96 PDZ domains examined, the domain that bound most strongly to mGluR5-CT was the second PDZ domain of the Na(+)/H(+) exchanger regulatory factor 2 (NHERF-2). This interaction was confirmed by reverse overlay, and a single point mutation to the mGluR5-CT was found to completely disrupt the interaction. Full-length mGluR5 robustly associated with full-length NHERF-2 in cells, as assessed by co-immunoprecipitation and confocal microscopy experiments. In contrast, mGluR1a was found to bind NHERF-2 in vitro with a weaker affinity than mGluR5, and furthermore mGluR1a did not detectably associate with NHERF-2 in a cellular context. Immunohistochemical experiments revealed that NHERF-2 and mGluR5 exhibit overlapping patterns of expression in mouse brain, being found most abundantly in astrocytic processes and postsynaptic neuronal elements. In functional experiments, the interaction of NHERF-2 with mGluR5 in cells was found to prolong mGluR5-mediated calcium mobilization and to also potentiate mGluR5-mediated cell death, whereas coexpression of mGluR1a with NHERF-2 had no evident effects on mGluR1a functional activity. These observations reveal that NHERF-2 can selectively modulate mGluR5 signaling, which may contribute to cell-specific regulation of mGluR5 activity.
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Maryse
authors.initials: M
authors.lastname: Paquet
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Asay
authors.forename: Sami R
authors.initials: SR
authors.lastname: Fam
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Inuzuka
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Castleberry
authors.forename: Heide
authors.initials: H
authors.lastname: Oller
authors.forename: Yoland
authors.initials: Y
authors.lastname: Smith
authors.forename: C Chris
authors.initials: CC
authors.lastname: Yun
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Traynelis
authors.forename: Randy A
authors.initials: RA
authors.lastname: Hall
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D000076122:Disks Large Homolog 4 Protein; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism* / Q000502:physiology; D020543:Proteome; D051381:Rats; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism* / Q000502:physiology
chemical_list: C501444:DLG4 protein, human; D000076122:Disks Large Homolog 4 Protein; C578935:GRM5 protein, human; C578936:Grm5 protein, mouse; C578937:Grm5 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D020543:Proteome; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D017923:Sodium-Hydrogen Exchangers; C033652:postsynaptic density proteins; C093376:sodium-hydrogen exchanger regulatory factor