Effects of beta-endorphin on mu and delta opioid receptor-coupled G-protein activity: low-Km GTPase studies.
Human beta-endorphin 1-31 (beta-END) stimulated low-Km GTPase activity in a concentration-dependent and saturable manner in membranes prepared from the delta opioid receptor-containing hybrid cell line NG108-15 and from the mu opioid receptor-enriched human neuroblastoma cell line SK-N-SH. Naloxone and the delta-selective antagonist, ICI 174,864, blocked the stimulation of the GTPase activity produced by beta-END in NG108-15 cell membranes, whereas only naloxone inhibited the beta-END-induced stimulation in SK-N-SH cell membranes, suggesting that beta-END was acting through both mu and delta opioid receptors. Treatment of the cells with Bordetella pertussis toxin before the preparation of membranes blocked the stimulation of low-Km GTPase by beta-END in both cell lines. Activation of NG108-15 and SK-N-SH low-Km GTPase by beta-END was sodium-dependent, and lithium and potassium were poor promoters of this activation. These results demonstrate that beta-END stimulates the interaction of both mu and delta opioid receptors with B. pertussis toxin-sensitive G-proteins in SK-N-SH and NG108-15 cell membranes, respectively.
Selley
D E
DE
Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, New York.
Bidlack
J M
JM
D002462:Cell Membrane / Q000187:drug effects; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D009292:Narcotic Antagonists / Q000494:pharmacology; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D017465:Receptors, Opioid, delta / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D001615:beta-Endorphin / Q000494:pharmacology*
D009292:Narcotic Antagonists; D010446:Peptide Fragments; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D001615:beta-Endorphin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins