title: Agonist-induced receptor internalization in Chinese hamster ovary cells stably co-expressing β(1)- and β(2)-adrenergic receptors.
abstract: β(1)- and β(2)-Adrenergic receptors (β(1)-AR and β(2)-AR) are co-expressed in numerous tissues, for example, heart and bladder. They play a very important role in the responses of a variety of organs to sympathetic nerve stimulation. Recent studies suggest that many G protein-coupled receptors, such as β(1)-AR, β(2)-AR, μ opioid receptor and δ opioid receptor, can form homo- and heterooligomers. Previous studies demonstrated that the β(1)-AR and β(2)-AR formed dimers in living HEK 293 cells. The aim of the present study is to investigate whether such heterooligomerization affect the agonist-induced receptor internalization in the CHO-K1 cells stably co-expressing β(1)-AR and β(2)-AR. Using co-immunoprecipitation, we confirmed that β(1)-AR and β(2)-AR formed heterooligomers in the CHO-K1 cells. In cells co-expressing β(1)-AR and β(2)-AR, 30% of β(1)-AR was internalized by isoproterenol, whereas only 20% of β(1)-AR was internalized in cells expressing the β(1)-AR alone. Heterooligomerization did not affect the ratio of internalized β(2)-AR. Salmeterol, a specific β(2)-AR agonist, broke β(1)-AR/β(2)-AR heterooligomers, and induced β(2)-AR-specific internalization in cells co-expressing β(1)-AR and β(2)-AR. The present study demonstrated that heterooligomerization between β(1)-AR and β(2)-AR accelerates the isoproterenol-promoted internalization of the β(1)-AR, and that salmeterol induces β(2)-AR-specific internalization in Chinese hamster ovary (CHO) cells stably co-expressing β(1)-AR and β(2)-AR.
authors.affiliation: Department of Molecular Pharmacology, School of Pharmaceurical Sciences, Kitasato University, 5–9–1 Shirokane, Minato-ku, Tokyo 108–8641, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Yoshihara
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Yonoki
authors.forename: Maki
authors.initials: M
authors.lastname: Saito
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakahara
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Kunio
authors.initials: K
authors.lastname: Ishii
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000420:Albuterol / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism*; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D000068299:Salmeterol Xinafoate
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D000068299:Salmeterol Xinafoate; D007545:Isoproterenol; D000420:Albuterol