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

PLoS One. 2014 Aug 27;9(8):e105791. doi: 10.1371/journal.pone.0105791. eCollection 2014.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Arrestins / metabolism
  • Carrier Proteins / metabolism
  • Detergents / pharmacology
  • Dopamine / metabolism*
  • GTP-Binding Protein beta Subunits / chemistry*
  • GTP-Binding Protein beta Subunits / metabolism*
  • HEK293 Cells
  • Humans
  • In Vitro Techniques
  • Intracellular Signaling Peptides and Proteins
  • Octoxynol / pharmacology
  • Protein Stability
  • RGS Proteins
  • Receptors, Dopamine D2 / metabolism*
  • Receptors, Opioid, mu / metabolism
  • beta-Arrestins

Substances

  • Arrestins
  • Carrier Proteins
  • Detergents
  • GNB1 protein, human
  • GNB5 protein, human
  • GTP-Binding Protein beta Subunits
  • Intracellular Signaling Peptides and Proteins
  • RGS Proteins
  • RGS7BP protein, human
  • Receptors, Dopamine D2
  • Receptors, Opioid, mu
  • beta-Arrestins
  • Octoxynol
  • Dopamine