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OPRM1  -  opioid receptor, mu 1

Sus scrofa

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Disease relevance of MOR


High impact information on MOR

  • Purification of the mu-opioid receptor from bovine striatum reveals a glycoprotein of Mr 65,000 which demonstrates opioid binding activity [4].
  • Low concentrations of trimebutine inhibit norepinephrine release via the mu-opioid receptor and enhance intestinal motility by preventing the adrenergic inhibition of acetylcholine release [5].
  • Therefore, peptide E loses mu-opioid receptor affinity (1.8-497 nmol/L) after proteolytic processing and the loss of the amino terminal tyrosine but maintains a high delta-opioid affinity (38.8-50.6 nmol/L) [6].
  • Interestingly, morphine, a high-affinity MOR agonist, did not cause detectable internalization, but it partially inhibited the etorphine-induced MOR endocytosis [7].
  • Abundant MOR immunoreactivity (MOR-IR) was localized to the cell body, dendrites, and axonal processes of myenteric neurons [7].

Biological context of MOR

  • Porcine MOR is 96% identical with human MOR in amino acid sequence [8].
  • These results demonstrate the occurrence of agonist-selective MOR endocytosis in neurons naturally expressing this receptor in vivo and suggest the existence of different mechanisms regulating cellular responsiveness to ligands [7].
  • Antibody specificity was confirmed by the positive staining of human embryonic kidney 293 cells transfected with epitope-tagged MOR cDNA, by the lack of staining of cells transfected with the delta or kappa receptor cDNA, and by the abolition of staining when the MOR antibody was preadsorbed with the MOR peptide fragment [7].
  • A synthetic peptide combinatorial library made up of 52,128,400 hexapeptides, each having an acetyl group at the N terminus and an amide group on the C terminus, was screened to find compounds able to displace tritiated [D-Ala2,MePhe4,Gly-ol5]enkephalin from mu opioid receptor binding sites in crude rat brain homogenates [9].
  • Cyclization between D-Asp(2) and Lys(6) in c[D-Asp(2),Lys(6)]Dyn A(1-11)-NH2 led to an analogue with pronounced potency and selectivity enhancement for the mu opioid receptor, whereas cyclization between D-Asp(3) and Lys(7) in c[D-Asp(3),Lys(7)]Dyn A(1-11)-NH2 led to a potent ligand (IC(50) 4.9 nM) with kappa receptor selectivity [10].

Anatomical context of MOR


Associations of MOR with chemical compounds


Other interactions of MOR


Analytical, diagnostic and therapeutic context of MOR


  1. Dermorphin-related peptides from the skin of Phyllomedusa bicolor and their amidated analogs activate two mu opioid receptor subtypes that modulate antinociception and catalepsy in the rat. Negri, L., Erspamer, G.F., Severini, C., Potenza, R.L., Melchiorri, P., Erspamer, V. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  2. Comparison of mu opioid receptor binding on intact neuroblastoma cells with guinea pig brain and neuroblastoma cell membranes. Toll, L. J. Pharmacol. Exp. Ther. (1992) [Pubmed]
  3. Chronic in utero morphine exposure alters mu-agonist-stimulated [35S]-GTPgammaS binding in neonatal and juvenile guinea pig brainstem regions associated with breathing control. Matsuda, A.Y., Olsen, G.D. Neurotoxicology and teratology. (2001) [Pubmed]
  4. The molecular basis of opioid receptor function. Simonds, W.F. Endocr. Rev. (1988) [Pubmed]
  5. Dual effect of trimebutine on contractility of the guinea pig ileum via the opioid receptors. Taniyama, K., Sano, I., Nakayama, S., Matsuyama, S., Takeda, K., Yoshihara, C., Tanaka, C. Gastroenterology (1991) [Pubmed]
  6. Changes in opioid receptor selectivity following processing of peptide E: effect on gut motility. Davis, T.P., Gillespie, T.J., Shook, J., Kramer, T.H., Hoyer, G., Hawkins, K., Davis, P., Yamamura, H.I., Burks, T.F. Gastroenterology (1991) [Pubmed]
  7. Agonist-selective endocytosis of mu opioid receptor by neurons in vivo. Sternini, C., Spann, M., Anton, B., Keith, D.E., Bunnett, N.W., von Zastrow, M., Evans, C., Brecha, N.C. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  8. The porcine mu opioid receptor: molecular cloning and mRNA distribution in lymphoid tissues. Pampusch, M.S., Osinski, M.A., Brown, D.R., Murtaugh, M.P. J. Neuroimmunol. (1998) [Pubmed]
  9. Acetalins: opioid receptor antagonists determined through the use of synthetic peptide combinatorial libraries. Dooley, C.T., Chung, N.N., Schiller, P.W., Houghten, R.A. Proc. Natl. Acad. Sci. U.S.A. (1993) [Pubmed]
  10. Design, synthesis, and biological activities of cyclic lactam peptide analogues of dynorphine A(1-11)-NH2. Lung, F.D., Collins, N., Stropova, D., Davis, P., Yamamura, H.I., Porreca, F., Hruby, V.J. J. Med. Chem. (1996) [Pubmed]
  11. Synthesis and biological evaluation of 14-alkoxymorphinans. 2. (-)-N-(cyclopropylmethyl)-4,14-dimethoxymorphinan-6-one, a selective mu opioid receptor antagonist. Schmidhammer, H., Burkard, W.P., Eggstein-Aeppli, L., Smith, C.F. J. Med. Chem. (1989) [Pubmed]
  12. Protein kinase A maintains cellular tolerance to mu opioid receptor agonists in hypothalamic neurosecretory cells with chronic morphine treatment: convergence on a common pathway with estrogen in modulating mu opioid receptor/effector coupling. Wagner, E.J., Rønnekleiv, O.K., Kelly, M.J. J. Pharmacol. Exp. Ther. (1998) [Pubmed]
  13. Mu opioid receptor activation reduces inhibitory postsynaptic potentials in hippocampal CA3 pyramidal cells of rat and guinea pig. Caudle, R.M., Chavkin, C. J. Pharmacol. Exp. Ther. (1990) [Pubmed]
  14. A comparison of the role of dynorphin in the hippocampal mossy fiber pathway in guinea pig and rat. Salin, P.A., Weisskopf, M.G., Nicoll, R.A. J. Neurosci. (1995) [Pubmed]
  15. Modulation of G protein-coupled receptors by an estrogen receptor that activates protein kinase A. Lagrange, A.H., Ronnekleiv, O.K., Kelly, M.J. Mol. Pharmacol. (1997) [Pubmed]
  16. Topographically designed analogues of [D-Pen,D-Pen5]enkephalin. Hruby, V.J., Toth, G., Gehrig, C.A., Kao, L.F., Knapp, R., Lui, G.K., Yamamura, H.I., Kramer, T.H., Davis, P., Burks, T.F. J. Med. Chem. (1991) [Pubmed]
  17. Cyclic beta-casomorphin analogues with mixed mu agonist/delta antagonist properties: synthesis, pharmacological characterization, and conformational aspects. Schmidt, R., Vogel, D., Mrestani-Klaus, C., Brandt, W., Neubert, K., Chung, N.N., Lemieux, C., Schiller, P.W. J. Med. Chem. (1994) [Pubmed]
  18. Subsensitivity to opioids is receptor-specific in isolated guinea pig ileum and mouse vas deferens after obstructive cholestasis. Dehpour, A.R., Rastegar, H., Jorjani, M., Roushanzamir, F., Joharchi, K., Ahmadiani, A. J. Pharmacol. Exp. Ther. (2000) [Pubmed]
  19. Kappa opioid receptor tolerance in the guinea pig hippocampus. Jin, W., Terman, G.W., Chavkin, C. J. Pharmacol. Exp. Ther. (1997) [Pubmed]
  20. N-methyl-D-aspartate receptors mediate endogenous opioid release in enteric neurons after abdominal surgery. Patierno, S., Zellalem, W., Ho, A., Parsons, C.G., Lloyd, K.C., Tonini, M., Sternini, C. Gastroenterology (2005) [Pubmed]
  21. Sympathetic denervation-induced changes in G protein expression in enteric neurons of the guinea pig colon. Giaroni, C., Zanetti, E., Vanti, A., Canciani, L., Lecchini, S., Frigo, G. Life Sci. (2002) [Pubmed]
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