title: Opsin oligomerization in a heterologous cell system.
abstract: Using bioluminescence resonance energy transfer (BRET) we studied opsin oligomerization in heterologous expression systems and quantitatively assessed its oligomerization state. BRET2 saturation and competition experiments were performed with live COS-7 cells expressing Rluc-and GFP2-tagged receptor constructs. BRET2 saturation curves obtained were hyperbolic, and the calculated oligomerization state (N = 1 for dimers) suggested that opsin (N = 1.34 +/- 0.25) forms higher oligomers. Very high BRET2 values obtained for the opsin homo-dimer pair indicated a large energy transfer efficiency (E) and for cases where E >> 0.1 a modified saturation curve was proposed. The existence of homo-dimer complexes was additionally supported by competition assay results and was also observed in HEK-293 cells. Furthermore, evidence was provided for homo-and hetero-dimerization of family A (beta2-adrenergic) and B (gastric inhibitory polypeptide, GIP) receptors. In summary, these experiments demonstrate homo-and hetero-dimerization for opsin, beta 2-adrenergic, and GIP receptors.
authors.affiliation: Institute of Anatomy, Histology and Embryology, University of Ljubljana, Veterinary Faculty, Ljubljana, Slovenia. milka.vrecl@vf.uni-lj.si
authors.forename: Milka
authors.initials: M
authors.lastname: Vrecl
authors.forename: Luka
authors.initials: L
authors.lastname: Drinovec
authors.forename: Christian
authors.initials: C
authors.lastname: Elling
authors.forename: Anders
authors.initials: A
authors.lastname: Heding
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D049449:Luminescence; D008432:Mathematical Computing; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism; D017299:Rod Opsins / Q000378:metabolism*
chemical_list: D018343:Receptors, Adrenergic, beta-2; D011964:Receptors, Gastrointestinal Hormone; D017299:Rod Opsins; C041086:gastric inhibitory polypeptide receptor