title: Hetero-oligomerization between beta2- and beta3-adrenergic receptors generates a beta-adrenergic signaling unit with distinct functional properties.
abstract: The ability of the closely related beta(2)- and beta(3)-adrenergic receptors (AR) to form hetero-oligomers was assessed by bioluminescence resonance energy transfer. Quantitative bioluminescence resonance energy transfer titration curves revealed that the beta(2)AR has identical propensity to hetero-oligomerize with the beta(3)AR than to form homo-oligomers. To determine the influence of heterooligomerization, a HEK293 cell line stably expressing an excess of beta(3)AR over beta(2)AR was generated so that all beta(2)AR are engaged in hetero-oligomerization with beta(3)AR, providing a tool to study the effect of hetero-oligomerization on beta(2)AR function in the absence of any beta(2)AR homooligomer. The hetero-oligomerization had no effect on the ligand binding properties of various beta(2)AR ligands and did not affect the potency of isoproterenol to stimulate adenylyl cyclase. Despite the unaltered ligand binding properties of the beta(2/3)AR hetero-oligomer, the stable association of the beta(2)AR with the beta(3)AR completely blocked agonist-stimulated internalization of the beta(2)AR. Given that the beta(3)AR is resistant to agonist-promoted endocytosis, the results indicate that the beta(3)AR acted as a dominant negative of the beta(2)AR endocytosis process. Consistent with this notion, the beta(2/3)AR hetero-oligomer displayed a lower propensity to recruit beta-arrestin-2 than the beta(2)AR. The hetero-oligomerization also led to a change in G protein coupling selectivity. Indeed, in contrast to beta(2)AR and beta(3)AR, which regulate adenylyl cyclase and extracellular signal-regulated kinase activity through a coupling to G(s) and G(i/o), no G(i/o) coupling was observed for the beta(2/3)AR hetero-oligomer. Together, these results demonstrate that hetero-oligomerization between beta(2)AR and beta(3)AR forms a beta-adrenergic signaling unit that possesses unique functional properties.
authors.affiliation: Département de Biochimie et Groupe de Recherche sur le Système Nerveux Autonome, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Andreas
authors.initials: A
authors.lastname: Breit
authors.forename: Monique
authors.initials: M
authors.lastname: Lagacé
authors.forename: Michel
authors.initials: M
authors.lastname: Bouvier
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004705:Endocytosis; D031541:Fluorescence Resonance Energy Transfer; D005799:Genes, Dominant; D005822:Genetic Vectors; D006801:Humans; D007700:Kinetics; D008024:Ligands; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry* / Q000378:metabolism; D022702:Receptors, Adrenergic, beta-3 / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D008024:Ligands; D018343:Receptors, Adrenergic, beta-2; D022702:Receptors, Adrenergic, beta-3; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D000262:Adenylyl Cyclases