Beta-arrestin2 and c-Src regulate the constitutive activity and recycling of mu opioid receptors in dorsal root ganglion neurons

Wendy Walwyn, Christopher J Evans, Tim G Hales

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85 Citations (Scopus)


Beta-arrestins bind to agonist-activated G-protein-coupled receptors regulating signaling events and initiating endocytosis. In beta-arrestin2-/- (beta arr2-/-) mice, a complex phenotype is observed that includes altered sensitivity to morphine. However, little is known of how beta-arrestin2 affects mu receptor signaling. We investigated the coupling of mu receptors to voltage-gated Ca2+ channels (VGCCs) in beta arr2+/+ and beta arr2-/- dorsal root ganglion neurons. A lack of beta-arrestin2 reduced the maximum inhibition of VGCCs by morphine and DAMGO (D-Ala2-N-Me-Phe4-glycol5-enkephalin) without affecting agonist potency, the onset of receptor desensitization, or the functional contribution of N-type VGCCs. The reduction in inhibition was accompanied by increased naltrexone-sensitive constitutive inhibitory coupling of mu receptors to VGCCs. Agonist-independent mu receptor inhibitory coupling was insensitive to CTAP (Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2), a neutral antagonist that inhibited the inverse agonist action of naltrexone. These functional changes were accompanied by diminished constitutive recycling and increased cell-surface mu receptor expression in beta arr2-/- compared with beta arr2+/+ neurons. Such changes could not be explained by the classical role of beta-arrestins in agonist-induced endocytosis. The localization of the nonreceptor tyrosine kinase c-Src appeared disrupted in beta arr2-/- neurons, and there was reduced activation of c-Src by DAMGO. Using the Src inhibitor PP2 [4-amino-5-(4-chlorophenyl)-(t-butyl)pyrazolo[3,4-d]pyrimidine], we demonstrated that defective Src signaling mimics the beta arr2-/- cellular phenotype of reduced mu agonist efficacy, increased constitutive mu receptor activity, and reduced constitutive recycling. We propose that beta-arrestin2 is required to target c-Src to constitutively active mu receptors, resulting in their internalization, providing another dimension to the complex role of beta-arrestin2 and c-Src in G-protein-coupled receptor function.

Original languageEnglish
Pages (from-to)5092-5104
Number of pages13
JournalJournal of Neuroscience
Issue number19
Publication statusPublished - 9 May 2007


  • Analgesics, Opioid/pharmacology
  • Animals
  • Arrestins/genetics
  • Calcium Channels/drug effects
  • Calcium Signaling/drug effects
  • Cells, Cultured
  • Endocytosis/drug effects
  • Female
  • Ganglia, Spinal/metabolism
  • Male
  • Membrane Potentials/drug effects
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neurons, Afferent/drug effects
  • Nociceptors/drug effects
  • Pain/metabolism
  • Patch-Clamp Techniques
  • Protein Transport/drug effects
  • Protein-Tyrosine Kinases/metabolism
  • Receptors, G-Protein-Coupled/drug effects
  • Receptors, Opioid, mu/drug effects
  • Signal Transduction/drug effects
  • beta-Arrestin 2
  • beta-Arrestins
  • src-Family Kinases


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