Role of G Protein-Coupled Receptor Kinases 2 and 3 in μ-Opioid Receptor Desensitization and Internalization

Janet D Lowe, Helen S Sanderson, Alexandra E Cooke, Mehrnoosh Ostovar, Elena Tsisanova, Sarah L Withey, Charles Chavkin, Stephen M Husbands, Eamonn Kelly, Graeme Henderson, Chris P Bailey

Research output: Contribution to journalArticlepeer-review


There is ongoing debate about the role of G protein-coupled receptor kinases (GRKs) in agonist-induced desensitization of the μ-opioid receptor (MOPr) in brain neurons. In the present paper, we have used a novel membrane-permeable, small-molecule inhibitor of GRK2 and GRK3, Takeda compound 101 (Cmpd101; 3-[[[4-methyl-5-(4-pyridyl)-4H-1,2,4-triazole-3-yl] methyl] amino]-N-[2-(trifuoromethyl) benzyl] benzamidehydrochloride), to study the involvement of GRK2/3 in acute agonist-induced MOPr desensitization. We observed that Cmpd101 inhibits the desensitization of the G protein-activated inwardly-rectifying potassium current evoked by receptor-saturating concentrations of methionine-enkephalin (Met-Enk), [d-Ala(2), N-MePhe(4), Gly-ol(5)]-enkephalin (DAMGO), endomorphin-2, and morphine in rat and mouse locus coeruleus (LC) neurons. In LC neurons from GRK3 knockout mice, Met-Enk-induced desensitization was unaffected, implying a role for GRK2 in MOPr desensitization. Quantitative analysis of the loss of functional MOPrs following acute agonist exposure revealed that Cmpd101 only partially reversed MOPr desensitization. Inhibition of extracellular signal-regulated kinase 1/2, protein kinase C, c-Jun N-terminal kinase, or GRK5 did not inhibit the Cmpd101-insensitive component of desensitization. In HEK 293 cells, Cmpd101 produced almost complete inhibition of DAMGO-induced MOPr phosphorylation at Ser(375), arrestin translocation, and MOPr internalization. Our data demonstrate a role for GRK2 (and potentially also GRK3) in agonist-induced MOPr desensitization in the LC, but leave open the possibility that another, as yet unidentified, mechanism of desensitization also exists.

Original languageEnglish
Pages (from-to)347-56
Number of pages10
JournalMolecular Pharmacology
Issue number2
Publication statusPublished - Aug 2015


  • Animals
  • Benzamides/pharmacology
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
  • G-Protein-Coupled Receptor Kinase 2/metabolism
  • G-Protein-Coupled Receptor Kinase 3/metabolism
  • HEK293 Cells
  • Humans
  • Locus Coeruleus/drug effects
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Rats
  • Rats, Wistar
  • Receptors, Opioid, mu/metabolism


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