Heterodimerization of opioid receptor-like 1 and mu-opioid receptors impairs the potency of micro receptor agonist.

Nociceptin activation of ORL1 (opioid receptor-like 1 receptor) has been shown to antagonize mu receptor-mediated analgesia at the supraspinal level. ORL1 and mu-opioid receptor (muR) are co-expressed in several subpopulations of CNS neurons involved in regulating pain transmission. The amino acid sequence of ORL1 also shares a high degree of ...
homology with that of mu receptor. Thus, it is hypothesized that ORL1 and muR interact to form the heterodimer and that ORL1/muR heterodimerization may be one molecular basis for ORL1-mediated antiopioid effects in the brain. To test this hypothesis, myc-tagged ORL1 and HA-tagged muR are co-expressed in human embryonic kidney (HEK) 293 cells. Co-immunoprecipitation experiments demonstrate that ORL1 dimerizes with muR and that intracellular C-terminal tails of ORL1 and muR are required for the formation of ORL1/muR heterodimer. Second messenger assays further indicate that formation of ORL1/muR heterodimer selectively induces cross-desensitization of muR and impairs the potency by which [D-Ala(2),N-methyl-Phe(4),Gly-ol(5)]enkephalin (DAMGO) inhibits adenylate cyclase and stimulates p42/p44 mitogen-activated protein kinase (MAPK) phosphorylation. These results provide the evidence that ORL1/muR heterodimerization and the resulting impairment of mu receptor-activated signaling pathways may contribute to ORL1-mediated antiopioid effects in the brain.
Mesh Terms:
Adenylyl Cyclases, Analgesics, Opioid, Animals, Cell Line, Central Nervous System, Dimerization, Enkephalin, Ala(2)-MePhe(4)-Gly(5)-, Humans, Mitogen-Activated Protein Kinase 1, Neurons, Pain, Protein Structure, Tertiary, Rats, Receptors, Opioid, Receptors, Opioid, mu, Signal Transduction
J. Neurochem.
Date: Mar. 01, 2005
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