Ligand-directed c-Jun N-terminal kinase activation disrupts opioid receptor signaling.
Ligand-directed signaling has been suggested as a basis for the differences in responses evoked by otherwise receptor-selective agonists. The underlying mechanisms are not understood, yet clearer definition of this concept may be helpful in the development of novel, pathway-selective therapeutic agents. We previously showed that kappa-opioid receptor activation of JNK by one class of ligand, but not another, caused persistent receptor inactivation. In the current study, we found that the mu-opioid receptor (MOR) could be similarly inactivated by a specific ligand class including the prototypical opioid, morphine. Acute analgesic tolerance to morphine and related opioids (morphine-6-glucuronide and buprenorphine) was blocked by JNK inhibition, but not by G protein receptor kinase 3 knockout. In contrast, a second class of mu-opioids including fentanyl, methadone, and oxycodone produced acute analgesic tolerance that was blocked by G protein receptor kinase 3 knockout, but not by JNK inhibition. Acute MOR desensitization, demonstrated by reduced D-Ala(2)-Met(5)-Glyol-enkephalin-stimulated [(35)S]GTPgammaS binding to spinal cord membranes from morphine-pretreated mice, was also blocked by JNK inhibition; however, desensitization of D-Ala(2)-Met(5)-Glyol-enkephalin-stimulated [(35)S]GTPgammaS binding following fentanyl pretreatment was not blocked by JNK inhibition. JNK-mediated receptor inactivation of the kappa-opioid receptor was evident in both agonist-stimulated [(35)S]GTPgammaS binding and opioid analgesic assays; however, gene knockout of JNK 1 selectively blocked kappa-receptor inactivation, whereas deletion of JNK 2 selectively blocked MOR inactivation. These findings suggest that ligand-directed activation of JNK kinases may generally provides an alternate mode of G protein-coupled receptor regulation.
Melief
Erica J
EJ
Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
Miyatake
Mayumi
M
Bruchas
Michael R
MR
Chavkin
Charles
C
D000700:Analgesics / Q000378:metabolism; D000701:Analgesics, Opioid / Q000737:chemistry; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation; D005283:Fentanyl / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008024:Ligands; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D009020:Morphine / Q000378:metabolism; D010098:Oxycodone / Q000378:metabolism; D011957:Receptors, Opioid / Q000378:metabolism*; D015398:Signal Transduction; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism
D000700:Analgesics; D000701:Analgesics, Opioid; D008024:Ligands; D011957:Receptors, Opioid; D009020:Morphine; D010098:Oxycodone; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D005283:Fentanyl