title: Group II metabotropic glutamate receptor interactions with NHERF scaffold proteins: Implications for receptor localization in brain.
abstract: The group II metabotropic glutamate receptors mGluR2 and mGluR3 are key modulators of glutamatergic neurotransmission. In order to identify novel Group II metabotropic glutamate receptor (mGluR)-interacting partners, we screened the C-termini of mGluR2 and mGluR3 for interactions with an array of PDZ domains. These screens identified the Na+/H+ exchanger regulatory factors 1 and 2 (NHERF-1 & -2) as candidate interacting partners. Follow-up co-immunoprecipitation studies demonstrated that both mGluR2 and mGluR3 can associate with NHERF-1 and NHERF-2 in a cellular context. Functional studies revealed that disruption of PDZ interactions with mGluR2 enhanced receptor signaling to Akt. However, further studies of mGluR2 and mGluR3 signaling in astrocytes in which NHERF expression was reduced by gene knockout (KO) and/or siRNA knockdown techniques revealed that the observed differences in signaling between WT and mutant mGluR2 were likely not due to disruption of interactions with the NHERF proteins. Electron microscopic analyses revealed that Group II mGluRs were primarily expressed in glia and unmyelinated axons in WT, NHERF-1 and NHERF-2 KO mice, but the relative proportion of labeled axons over glial processes was higher in NHERF-2 KO mice than in controls and NHERF-1 KO mice. Interestingly, our anatomical studies also revealed that loss of either NHERF protein results in ventriculomegaly, which may be related to the high incidence of hydrocephaly that has previously been observed in NHERF-1 KO mice. Together, these studies support a role for NHERF-1 and NHERF-2 in regulating the distribution of Group II mGluRs in the murine brain, while conversely the effects of the mGluR2/3 PDZ-binding motifs on receptor signaling are likely mediated by interactions with other PDZ scaffold proteins beyond the NHERF proteins.
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Stefanie L
authors.initials: SL
authors.lastname: Ritter-Makinson
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Maryse
authors.initials: M
authors.lastname: Paquet
authors.affiliation: Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Bogenpohl
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Rodin
authors.affiliation: Department of Medicine, Division of Digestive Diseases, Emory University School of Medicine, Atlanta, GA 30329, USA.
authors.forename: C
authors.initials: C
authors.lastname: Chris Yun
authors.affiliation: Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Weinman
authors.affiliation: Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Yoland
authors.initials: Y
authors.lastname: Smith
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA. Electronic address: rhall3@emory.edu.
authors.forename: Randy A
authors.initials: RA
authors.lastname: Hall
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001921:Brain / Q000378:metabolism* / Q000648:ultrastructure; D057809:HEK293 Cells; D006801:Humans; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D036421:Nerve Fibers, Unmyelinated / Q000378:metabolism; D054731:PDZ Domains; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D018094:Receptors, Metabotropic Glutamate; D017923:Sodium-Hydrogen Exchangers; C108822:metabotropic glutamate receptor 2; C102718:metabotropic glutamate receptor 3; C093376:sodium-hydrogen exchanger regulatory factor; D051057:Proto-Oncogene Proteins c-akt
keywords: astrocyte; axon; electron microscopy; knockout mice; pre-synaptic; protein–protein interaction