G protein beta 5 is targeted to D2-dopamine receptor-containing biochemical compartments and blocks dopamine-dependent receptor internalization

• Published in: PloS one 2014-08, Vol.9 (8), p.e105791
• Main Authors: Octeau, J Christopher, Schrader, Joseph M, Masuho, Ikuo, Sharma, Meenakshi, Aiudi, Christopher, Chen, Ching-Kang, Kovoor, Abraham, Celver, Jeremy
• Format: Article
• Language: English
• Subjects: Arrestin; Arrestins - metabolism; beta-Arrestins; Biology and Life Sciences; Biotin; Brain; Carrier Proteins - metabolism; Cell lines; Cell membranes; Cell surface; Deactivation; Detergents; Detergents - pharmacology; Dopamine; Dopamine - metabolism; Dopamine D2 receptors; G proteins; GTP-Binding Protein beta Subunits - chemistry; GTP-Binding Protein beta Subunits - metabolism; HEK293 Cells; Humans; In Vitro Techniques; Internalization; Intracellular Signaling Peptides and Proteins; Kinases; Kinetics; Membranes; Octoxynol - pharmacology; Opioid receptors (type mu); Pharmaceutical sciences; Phenols (Class of compounds); Phosphorylation; Photoreceptors; Protein Stability; Proteins; Receptors, Dopamine D2 - metabolism; Receptors, Opioid, mu - metabolism; RGS Proteins; Rodents; Signal transduction; Signaling
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0105791

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.