title: G protein beta 5 is targeted to D2-dopamine receptor-containing biochemical compartments and blocks dopamine-dependent receptor internalization.
abstract: G beta 5 (Gbeta5, Gβ5) is a unique G protein β subunit that is thought to be expressed as an obligate heterodimer with R7 regulator of G protein signaling (RGS) proteins instead of with G gamma (Gγ) subunits. We found that D2-dopamine receptor (D2R) coexpression enhances the expression of Gβ5, but not that of the G beta 1 (Gβ1) subunit, in HEK293 cells, and that the enhancement of expression occurs through a stabilization of Gβ5 protein. We had previously demonstrated that the vast majority of D2R either expressed endogenously in the brain or exogenously in cell lines segregates into detergent-resistant biochemical fractions. We report that when expressed alone in HEK293 cells, Gβ5 is highly soluble, but is retargeted to the detergent-resistant fraction after D2R coexpression. Furthermore, an in-cell biotin transfer proximity assay indicated that D2R and Gβ5 segregating into the detergent-resistant fraction specifically interacted in intact living cell membranes. Dopamine-induced D2R internalization was blocked by coexpression of Gβ5, but not Gβ1. However, the same Gβ5 coexpression levels had no effect on agonist-induced internalization of the mu opioid receptor (MOR), cell surface D2R levels, dopamine-mediated recruitment of β-arrestin to D2R, the amplitude of D2R-G protein coupling, or the deactivation kinetics of D2R-activated G protein signals. The latter data suggest that the interactions between D2R and Gβ5 are not mediated by endogenously expressed R7 RGS proteins.
authors.affiliation: Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Octeau
authors.affiliation: Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Schrader
authors.affiliation: Department of Neuroscience, The Scripps Research Institute, Jupiter, Florida, United States of America.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Masuho
authors.affiliation: Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Meenakshi
authors.initials: M
authors.lastname: Sharma
authors.affiliation: Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Christopher
authors.initials: C
authors.lastname: Aiudi
authors.affiliation: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Ching-Kang
authors.initials: CK
authors.lastname: Chen
authors.affiliation: Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Abraham
authors.initials: A
authors.lastname: Kovoor
authors.affiliation: Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island, United States of America.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Celver
mesh_terms: D019390:Arrestins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000737:chemistry* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D017830:Octoxynol / Q000494:pharmacology; D055550:Protein Stability; D020710:RGS Proteins; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000378:metabolism; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D002352:Carrier Proteins; D003902:Detergents; C516790:GNB1 protein, human; C490611:GNB5 protein, human; D044387:GTP-Binding Protein beta Subunits; D047908:Intracellular Signaling Peptides and Proteins; D020710:RGS Proteins; C542323:RGS7BP protein, human; D017448:Receptors, Dopamine D2; D017450:Receptors, Opioid, mu; D000071557:beta-Arrestins; D017830:Octoxynol; D004298:Dopamine