The PDZ scaffold NHERF-2 interacts with mGluR5 and regulates receptor activity

• Authors: Maryse Paquet, Emory University; Matthew J. Asay, Emory University; Sami R. Fam, Emory University; Hiroyuki Inuzuka, Emory University; Amanda M. Castleberry, Emory University; Heide Oller, Emory University; Yoland Smith, Emory University; Chris Yun, Emory University; Stephen Traynelis, Emory University; Randy Hall, Emory University
• Journal Title: Journal of Biological Chemistry
• Volume: Volume 281, Number 40
• Publisher: American Society for Biochemistry and Molecular Biology | 2006-10-06, Pages 29949-29961
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1074/jbc.M602262200
• Subjects: Chemistry, Biochemistry; Biology, Molecular
• Keywords: Science & Technology; Life Sciences & Biomedicine; Biochemistry & Molecular Biology; METABOTROPIC GLUTAMATE RECEPTORS; GROUP-I; UP-REGULATION; HIPPOCAMPAL ASTROCYTES; REACTIVE ASTROCYTES; SHANK FAMILY; SPINAL-CORD; PROTEIN; EXPRESSION; HOMER

Abstract

The two members of the group I metabotropic glutamate receptor family, mGluR1 and mGluR5, both couple to Gq to mediate rises in intracellular calcium. The alternatively spliced C termini (CT) of mGluRs 1 & 5 are 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 co-expression 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.