title: Fluorescence resonance energy transfer analysis reveals the existence of endothelin-A and endothelin-B receptor homodimers.
abstract: Endothelin-1 is a potent vasoactive peptide that exerts its action via endothelin-A (ETA) and endothelin-B (ETB) receptors. Both types of receptor belong to the rhodopsin-like (class A) G protein-coupled receptors. Since there is an increasing body of evidence that G protein-coupled receptors function as homo- and heterodimers, we sought to prove whether endothelin receptor subtypes also exist as homodimers. To this end we generated plasmids encoding fusion proteins of the endothelin-A and endothelin-B receptor with cyan (ETA.CFP, ETB.CFP) or yellow fluorescent protein (ETA.YFP, ETB.YFP), suitable for fluorescence resonance energy transfer experiments. HEK293 cells transiently co-expressing either ETA.CFP and ETA.YFP or ETB.CFP and ETB.YFP showed significant fluorescence resonance energy transfer. The calculated efficiencies of fluorescence resonance energy transfer were between 12 and 18% for both endothelin-A and endothelin-B receptor homodimers. When cells co-expressing ETA.CFP and ETA.YFP or ETB.CFP and ETB.YFP were treated with endothelin-1 for 30 minutes at 37degreesC, no change in fluorescence resonance energy transfer efficiencies was found. Similarly, the endothelin-A receptor-selective antagonist, BQ123, and the endothelin-B receptor-selective antagonist, BQ788, did not change the fluorescence resonance energy transfer efficiencies of ETA.CFP/ ETA.YFP and ETB.CFP/ETB.YFP homodimers, respectively. The data demonstrate that endothelin-A and endothelin-B receptors exist as constitutive homodimers, which are not altered in the presence of agonists or antagonists.
authors.affiliation: Institut für Pharmakologie, Charité - Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Gregan
authors.forename: Michael
authors.initials: M
authors.lastname: Schaefer
authors.forename: Walter
authors.initials: W
authors.lastname: Rosenthal
authors.forename: Alexander
authors.initials: A
authors.lastname: Oksche
mesh_terms: D002460:Cell Line; D019281:Dimerization; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D044022:Receptor, Endothelin A / Q000235:genetics / Q000378:metabolism*; D044023:Receptor, Endothelin B / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: C485182:Cyan Fluorescent Protein; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C086539:BQ 788; C072247:cyclo(Trp-Asp-Pro-Val-Leu)