Heterodimerization with beta2-adrenergic receptors promotes surface expression and functional activity of alpha1D-adrenergic receptors

J Pharmacol Exp Ther. 2005 Apr;313(1):16-23. doi: 10.1124/jpet.104.079541. Epub 2004 Dec 22.

Abstract

The alpha1D-adrenergic receptor (alpha1D-AR) is a G protein-coupled receptor (GPCR) that is poorly trafficked to the cell surface and largely nonfunctional when heterologously expressed by itself in a variety of cell types. We screened a library of approximately 30 other group I GPCRs in a quantitative luminometer assay for the ability to promote alpha1D-AR cell surface expression. Strikingly, these screens revealed only two receptors capable of inducing robust increases in the amount of alpha1D-AR at the cell surface: alpha1B-AR and beta2-AR. Confocal imaging confirmed that coexpression with beta2-AR resulted in translocation of alpha1D-AR from intracellular sites to the plasma membrane. Additionally, coimmunoprecipitation studies demonstrated that alpha1D-AR and beta2-AR specifically interact to form heterodimers when coexpressed in HEK-293 cells. Ligand binding studies revealed an increase in total alpha1D-AR binding sites upon coexpression with beta2-AR, but no apparent effect on the pharmacological properties of the receptors. In functional studies, coexpression with beta2-AR significantly enhanced the coupling of alpha1D-AR to norepinephrine-stimulated Ca2+ mobilization. Heterodimerization of beta2-AR with alpha1D-AR also conferred the ability of alpha1D-AR to cointernalize upon beta2-AR agonist stimulation, revealing a novel mechanism by which these different adrenergic receptor subtypes may regulate each other's activity. These findings demonstrate that the selective association of alpha1D-AR with other receptors is crucial for receptor surface expression and function and also shed light on a novel mechanism of cross talk between alpha1- and beta2-ARs that is mediated through heterodimerization and cross-internalization.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adrenergic beta-Agonists / pharmacology
  • Albuterol / pharmacology
  • Blotting, Western
  • Calcium / metabolism
  • Cell Line
  • Humans
  • Immunoprecipitation
  • Microscopy, Confocal
  • Plasmids / genetics
  • Radioligand Assay
  • Receptors, Adrenergic, alpha-1 / biosynthesis
  • Receptors, Adrenergic, alpha-1 / genetics
  • Receptors, Adrenergic, alpha-1 / physiology*
  • Receptors, Adrenergic, beta-2 / genetics
  • Receptors, Adrenergic, beta-2 / physiology*
  • Receptors, Cell Surface / metabolism*
  • Receptors, G-Protein-Coupled / metabolism

Substances

  • ADRA1D protein, human
  • Adrenergic beta-Agonists
  • Receptors, Adrenergic, alpha-1
  • Receptors, Adrenergic, beta-2
  • Receptors, Cell Surface
  • Receptors, G-Protein-Coupled
  • Albuterol
  • Calcium