title: Serotonin 5-HT(2C) receptor homodimerization is not regulated by agonist or inverse agonist treatment.
abstract: Serotonin 5-HT(2C) receptors represent targets for therapeutics aimed at treating anxiety, depression, schizophrenia, and obesity. Previously, we demonstrated that 5-HT(2C) receptors function as homodimers. Herein, we investigated the effect of agonist and inverse agonist treatment on the homodimer status of two naturally occurring 5-HT(2C) receptor isoforms, one without basal activity (VGV) and one with constitutive activity (INI) with respect to Galpha(q) signaling. Cyan- and yellow-fluorescent proteins were used to monitor VGV and INI homodimer formation by western blot, and in living cells using bioluminescence and fluorescence resonance energy transfer (BRET and FRET). Western blots of solubilized membrane proteins revealed equal proportions of homodimeric receptor species from HEK293 cells transfected with either the VGV or INI isoform in the absence and presence of 5-HT. BRET ratios measured in HEK293 cells transfected with the VGV or INI isoform were the same and were not modulated by 5-HT. Similarly, FRET efficiencies were the same regardless of whether measured in cells expressing the VGV or INI isoform in the absence or presence of 5-HT or clozapine. The results indicate that serotonin 5-HT(2C) receptors form homodimers regardless of whether they are in an inactive or active conformation and are not regulated by drug treatment.
authors.affiliation: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, United States. daviskh@mail.amc.edu
authors.forename: Katharine
authors.initials: K
authors.lastname: Herrick-Davis
authors.forename: Ellinor
authors.initials: E
authors.lastname: Grinde
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Weaver
mesh_terms: D019390:Arrestins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003024:Clozapine / Q000494:pharmacology; D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D049410:Luciferases, Renilla / Q000378:metabolism; D008163:Luminescent Measurements; D008164:Luminescent Proteins / Q000378:metabolism; D044405:Receptor, Serotonin, 5-HT2C / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D008164:Luminescent Proteins; D044405:Receptor, Serotonin, 5-HT2C; D011993:Recombinant Fusion Proteins; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D000071557:beta-Arrestins; D012701:Serotonin; D015544:Inositol 1,4,5-Trisphosphate; D049410:Luciferases, Renilla; D003024:Clozapine