8ef5

Structural highlights

Function

OPRM_HUMAN Receptor for endogenous opioids such as beta-endorphin and endomorphin (PubMed:12589820, PubMed:7891175, PubMed:7905839, PubMed:10529478, PubMed:7957926, PubMed:9689128). Receptor for natural and synthetic opioids including morphine, heroin, DAMGO, fentanyl, etorphine, buprenorphin and methadone (PubMed:12589820, PubMed:7891175, PubMed:7905839, PubMed:7957926, PubMed:10529478, PubMed:9689128, PubMed:10836142, PubMed:19300905). Also activated by enkephalin peptides, such as Met-enkephalin or Met-enkephalin-Arg-Phe, with higher affinity for Met-enkephalin-Arg-Phe (By similarity). Agonist binding to the receptor induces coupling to an inactive GDP-bound heterotrimeric G-protein complex and subsequent exchange of GDP for GTP in the G-protein alpha subunit leading to dissociation of the G-protein complex with the free GTP-bound G-protein alpha and the G-protein beta-gamma dimer activating downstream cellular effectors (PubMed:7905839). The agonist- and cell type-specific activity is predominantly coupled to pertussis toxin-sensitive G(i) and G(o) G alpha proteins, GNAI1, GNAI2, GNAI3 and GNAO1 isoforms Alpha-1 and Alpha-2, and to a lesser extent to pertussis toxin-insensitive G alpha proteins GNAZ and GNA15 (PubMed:12068084). They mediate an array of downstream cellular responses, including inhibition of adenylate cyclase activity and both N-type and L-type calcium channels, activation of inward rectifying potassium channels, mitogen-activated protein kinase (MAPK), phospholipase C (PLC), phosphoinositide/protein kinase (PKC), phosphoinositide 3-kinase (PI3K) and regulation of NF-kappa-B (By similarity). Also couples to adenylate cyclase stimulatory G alpha proteins (By similarity). The selective temporal coupling to G-proteins and subsequent signaling can be regulated by RGSZ proteins, such as RGS9, RGS17 and RGS4 (By similarity). Phosphorylation by members of the GPRK subfamily of Ser/Thr protein kinases and association with beta-arrestins is involved in short-term receptor desensitization (By similarity). Beta-arrestins associate with the GPRK-phosphorylated receptor and uncouple it from the G-protein thus terminating signal transduction (By similarity). The phosphorylated receptor is internalized through endocytosis via clathrin-coated pits which involves beta-arrestins (By similarity). The activation of the ERK pathway occurs either in a G-protein-dependent or a beta-arrestin-dependent manner and is regulated by agonist-specific receptor phosphorylation (By similarity). Acts as a class A G-protein coupled receptor (GPCR) which dissociates from beta-arrestin at or near the plasma membrane and undergoes rapid recycling (By similarity). Receptor down-regulation pathways are varying with the agonist and occur dependent or independent of G-protein coupling (By similarity). Endogenous ligands induce rapid desensitization, endocytosis and recycling (By similarity). Heterooligomerization with other GPCRs can modulate agonist binding, signaling and trafficking properties (By similarity).[UniProtKB:P33535]^{[1] [2] [3] [4] [5] [6] [7] [8] [9]} Couples to GNAS and is proposed to be involved in excitatory effects.^[10] Does not bind agonists but may act through oligomerization with binding-competent OPRM1 isoforms and reduce their ligand binding activity.^[11] Does not bind agonists but may act through oligomerization with binding-competent OPRM1 isoforms and reduce their ligand binding activity.^[12]

References

1. ↑ Zhang P, Johnson PS, Zollner C, Wang W, Wang Z, Montes AE, Seidleck BK, Blaschak CJ, Surratt CK. Mutation of human mu opioid receptor extracellular "disulfide cysteine" residues alters ligand binding but does not prevent receptor targeting to the cell plasma membrane. Brain Res Mol Brain Res. 1999 Oct 1;72(2):195-204. doi:, 10.1016/s0169-328x(99)00241-7. PMID:10529478 doi:http://dx.doi.org/10.1016/s0169-328x(99)00241-7
2. ↑ Massotte D, Brillet K, Kieffer B, Milligan G. Agonists activate Gi1 alpha or Gi2 alpha fused to the human mu opioid receptor differently. J Neurochem. 2002 Jun;81(6):1372-82. doi: 10.1046/j.1471-4159.2002.00946.x. PMID:12068084 doi:http://dx.doi.org/10.1046/j.1471-4159.2002.00946.x
3. ↑ Pan YX, Xu J, Mahurter L, Xu M, Gilbert AK, Pasternak GW. Identification and characterization of two new human mu opioid receptor splice variants, hMOR-1O and hMOR-1X. Biochem Biophys Res Commun. 2003 Feb 21;301(4):1057-61. PMID:12589820
4. ↑ Mestek A, Hurley JH, Bye LS, Campbell AD, Chen Y, Tian M, Liu J, Schulman H, Yu L. The human mu opioid receptor: modulation of functional desensitization by calcium/calmodulin-dependent protein kinase and protein kinase C. J Neurosci. 1995 Mar;15(3 Pt 2):2396-406. PMID:7891175
5. ↑ Wang JB, Johnson PS, Persico AM, Hawkins AL, Griffin CA, Uhl GR. Human mu opiate receptor. cDNA and genomic clones, pharmacologic characterization and chromosomal assignment. FEBS Lett. 1994 Jan 31;338(2):217-22. PMID:7905839
6. ↑ Bare LA, Mansson E, Yang D. Expression of two variants of the human mu opioid receptor mRNA in SK-N-SH cells and human brain. FEBS Lett. 1994 Nov 7;354(2):213-6. PMID:7957926
7. ↑ Bond C, LaForge KS, Tian M, Melia D, Zhang S, Borg L, Gong J, Schluger J, Strong JA, Leal SM, Tischfield JA, Kreek MJ, Yu L. Single-nucleotide polymorphism in the human mu opioid receptor gene alters beta-endorphin binding and activity: possible implications for opiate addiction. Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9608-13. PMID:9689128
8. ↑ Law PY, Wong YH, Loh HH. Molecular mechanisms and regulation of opioid receptor signaling. Annu Rev Pharmacol Toxicol. 2000;40:389-430. doi:, 10.1146/annurev.pharmtox.40.1.389. PMID:10836142 doi:http://dx.doi.org/10.1146/annurev.pharmtox.40.1.389
9. ↑ Lopez A, Salome L. Membrane functional organisation and dynamic of mu-opioid receptors. Cell Mol Life Sci. 2009 Jul;66(13):2093-108. doi: 10.1007/s00018-009-0008-4. Epub, 2009 Mar 20. PMID:19300905 doi:http://dx.doi.org/10.1007/s00018-009-0008-4
10. ↑ Gris P, Gauthier J, Cheng P, Gibson DG, Gris D, Laur O, Pierson J, Wentworth S, Nackley AG, Maixner W, Diatchenko L. A novel alternatively spliced isoform of the mu-opioid receptor: functional antagonism. Mol Pain. 2010 Jun 2;6:33. doi: 10.1186/1744-8069-6-33. PMID:20525224 doi:http://dx.doi.org/10.1186/1744-8069-6-33
11. ↑ Choi HS, Kim CS, Hwang CK, Song KY, Wang W, Qiu Y, Law PY, Wei LN, Loh HH. The opioid ligand binding of human mu-opioid receptor is modulated by novel splice variants of the receptor. Biochem Biophys Res Commun. 2006 May 19;343(4):1132-40. doi:, 10.1016/j.bbrc.2006.03.084. Epub 2006 Mar 23. PMID:16580639 doi:http://dx.doi.org/10.1016/j.bbrc.2006.03.084
12. ↑ Choi HS, Kim CS, Hwang CK, Song KY, Wang W, Qiu Y, Law PY, Wei LN, Loh HH. The opioid ligand binding of human mu-opioid receptor is modulated by novel splice variants of the receptor. Biochem Biophys Res Commun. 2006 May 19;343(4):1132-40. doi:, 10.1016/j.bbrc.2006.03.084. Epub 2006 Mar 23. PMID:16580639 doi:http://dx.doi.org/10.1016/j.bbrc.2006.03.084