title: mGluR7 undergoes rapid internalization in response to activation by the allosteric agonist AMN082.
abstract: The G-protein coupled receptor (GPCR) metabotropic glutamate receptor 7 (mGluR7) is widely expressed throughout the nervous system and is implicated in diverse physiological processes ranging from synaptic plasticity to neuroprotection. To date, unequivocally assigning specific functions to mGluR7 has been hampered by a lack of specific pharmacological tools, however, an mGluR7 specific allosteric agonist, AMN082, was recently discovered. Accumulating evidence indicates that in addition to G-protein activation, GPCRs trigger critical intracellular signalling cascades during agonist-induced internalization. Thus, to determine if AMN082 will be useful for evaluating signalling events related to mGluR7 internalization as well as receptor activation we have examined whether AMN082 induces mGluR7 endocytosis. Using an immunofluorescence assay we demonstrate that AMN082 induces robust internalization of mGluR7 overexpressed in dissociated hippocampal neurons. AMN082-induced mGluR7 internalization was resistant to inhibition by a competitive antagonist consistent with the distinct binding site of the allosteric agonist from the glutamate-binding pocket utilized by conventional orthosteric ligands. Finally, as an independent assay of receptor internalization we overexpressed N-terminal pHluorin-tagged mGluR7 in neurons, allowing live imaging of surface receptors in real time. AMN082 treatment produced a rapid loss of surface mGluR7 as indicated by decreased fluorescence confirming the ability of allosteric receptor activation to trigger mGluR7 endocytosis. Thus, AMN082 will be effective for investigating physiological processes related to both mGluR7 activation and internalization such as control of bidirectional plasticity at mossy fiber-st. lucidum interneuron synapses.
authors.affiliation: Laboratory of Cellular and Synaptic Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Building 35, 35 Lincoln Drive, Bethesda, MD 20892, USA. pelkeyk2@mail.nih.gov
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Pelkey
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Yuan
authors.forename: Gabriela
authors.initials: G
authors.lastname: Lavezzari
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Roche
authors.forename: Chris J
authors.initials: CJ
authors.lastname: McBain
mesh_terms: D000613:Aminobutyrates / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001559:Benzhydryl Compounds / Q000494:pharmacology*; D002478:Cells, Cultured; D003952:Diagnostic Imaging / Q000379:methods; D004622:Embryo, Mammalian; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D007150:Immunohistochemistry / Q000379:methods; D009474:Neurons / Q000187:drug effects*; D021381:Protein Transport / Q000187:drug effects*; D051381:Rats; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection / Q000379:methods
chemical_list: D000613:Aminobutyrates; D001559:Benzhydryl Compounds; D018690:Excitatory Amino Acid Agonists; C507346:N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride; D018094:Receptors, Metabotropic Glutamate; C102719:metabotropic glutamate receptor 7; D000643:Ammonium Chloride; D049452:Green Fluorescent Proteins; C479550:2-amino-4-phenylbutanoic acid