Beta-arrestin-mediated activation of MAPK by inverse agonists reveals distinct active conformations for G protein-coupled receptors

Proc Natl Acad Sci U S A. 2003 Sep 30;100(20):11406-11. doi: 10.1073/pnas.1936664100. Epub 2003 Sep 17.

Abstract

It is becoming increasingly clear that signaling via G protein-coupled receptors is a diverse phenomenon involving receptor interaction with a variety of signaling partners. Despite this diversity, receptor ligands are commonly classified only according to their ability to modify G protein-dependent signaling. Here we show that beta2AR ligands like ICI118551 and propranolol, which are inverse agonists for Gs-stimulated adenylyl cyclase, induce partial agonist responses for the mitogen-activated protein kinases extracellular signal-regulated kinase (ERK) 1/2 thus behaving as dual efficacy ligands. ERK1/2 activation by dual efficacy ligands was not affected by ADP-ribosylation of Galphai and could be observed in S49-cyc- cells lacking Galphas indicating that, unlike the conventional agonist isoproterenol, these drugs induce ERK1/2 activation in a Gs/i-independent manner. In contrast, this activation was inhibited by a dominant negative mutant of beta-arrestin and was abolished in mouse embryonic fibroblasts lacking beta-arrestin 1 and 2. The role of beta-arrestin was further confirmed by showing that transfection of beta-arrestin 2 in these knockout cells restored ICI118551 promoted ERK1/2 activation. ICI118551 and propranolol also promoted beta-arrestin recruitment to the receptor. Taken together, these observations suggest that beta-arrestin recruitment is not an exclusive property of agonists, and that ligands classically classified as inverse agonists rely exclusively on beta-arrestin for their positive signaling activity. This phenomenon is not unique to beta2-adrenergic ligands because SR121463B, an inverse agonist on the V2 vasopressin receptor-stimulated adenylyl cyclase, recruited beta-arrestin and stimulated ERK1/2. These results point to a multistate model of receptor activation in which ligand-specific conformations are capable of differentially activating distinct signaling partners.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Agonists / pharmacology*
  • Animals
  • Arrestins / metabolism*
  • Cell Line
  • GTP-Binding Proteins / metabolism*
  • Humans
  • Mice
  • Microscopy, Fluorescence
  • Mitogen-Activated Protein Kinases / metabolism*
  • Propanolamines / pharmacology
  • Protein Conformation
  • Receptors, Cell Surface / chemistry
  • Receptors, Cell Surface / metabolism*
  • beta-Arrestin 1
  • beta-Arrestin 2
  • beta-Arrestins

Substances

  • ARRB1 protein, human
  • ARRB2 protein, human
  • Adrenergic beta-Agonists
  • Arrb1 protein, mouse
  • Arrb2 protein, mouse
  • Arrestins
  • Propanolamines
  • Receptors, Cell Surface
  • beta-Arrestin 1
  • beta-Arrestin 2
  • beta-Arrestins
  • ICI 118551
  • Mitogen-Activated Protein Kinases
  • GTP-Binding Proteins