Characterisation of mu-opioid receptors on SH-SY5Y cells using naloxonazine and beta-funaltrexamine.
The irreversible opioid receptor antagonists naloxonazine and beta-funaltrexamine have been used to determine whether multiple mu-opioid receptors exist on undifferentiated SH-SY5Y human neuroblastoma cells. Naloxonazine binds irreversibly to the mu 1-opioid receptor subtype and reversibly to the mu 2-opioid receptor subtype. On SH-SY5Y cells naloxonazine afforded a Ki of 3.4 +/- 0.7 nM, and was fully reversible, indicating the mu-opioid receptor population on SH-SY5Y cells was solely of the mu 2-opioid receptor subtype. The alkylating agent beta-funaltrexamine was maximally able to alkylate only 60% of the mu-opioid receptor sites on SH-SY5Y cells, labelled with [3H]diprenorphine or [3H][D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAMGO). The reversible binding of naloxonazine and the insensitivity of a percentage of the mu-opioid receptor sites to alkylation by beta-funaltrexamine suggests that differences do exist in the mu 2-opioid receptor population on undifferentiated SH-SY5Y cells. This may indicate further heterogeneity or the inability of beta-funaltrexamine to alkylate all relevant nucleophilic groups in a single population of receptors.
Elliott
J
J
Department of Chemistry, Loughborough University of Technology, Leics, UK.
Smart
D
D
Lambert
D G
DG
Traynor
J R
JR
D000595:Amino Acid Sequence; D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D004174:Diprenorphine; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism; D051381:Rats; D017450:Receptors, Opioid, mu / Q000187:drug effects*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004745:Enkephalins; D008024:Ligands; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; D004174:Diprenorphine; D009270:Naloxone; D013004:Somatostatin; D009271:Naltrexone; C024524:beta-funaltrexamine; C034643:naloxonazine