Differential effects of endomorphin-1, endomorphin-2, and Tyr-W-MIF-1 on activation of G-proteins in SH-SY5Y human neuroblastoma membranes.
Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2), peptides recently isolated from bovine and human brain, have high affinity and selectivity for mu opiate receptors. They share sequence similarity with the endogenous opiate-modulating peptide Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2). The efficacies of these endogenous peptides and of the enkephalin analog DAMGO were compared by measuring their effects on the binding of guanosine-5'-O-(-gamma-[35S]thio)triphosphate ([35S]GTPgammaS) to G-proteins in membranes from SH-SYSY human neuroblastoma cells. DAMGO, endomorphin-1, and endomorphin-2 stimulated [35S]GTPgammaS binding dose dependently, with maximal effects of 60 +/- 9%, 47 +/- 9%, and 43 +/- 6% stimulation above basal and ED50 of 49 +/- 8 nM, 38 +/- 8 nM, and 64 +/- 13 nM, respectively. Tyr-W-MIF-1 showed only a small stimulation of binding (5% stimulation above basal, ED50 = 2 microM). When given in combination with the other opioids, however, Tyr-W-MIF-1 attenuated their ability to activate G-proteins. Thus, the endogenous opioids endomorphin-1 and endomorphin-2 activate G-proteins similarly to the synthetic agonist DAMGO, but the structurally similar peptide Tyr-W-MIF-1 produces only minimal stimulation of G-proteins.
Harrison
L M
LM
Tulane University School of Medicine and Veterans Affairs Medical Center, New Orleans, LA 70146, USA.
Kastin
A J
AJ
Zadina
J E
JE
D002462:Cell Membrane / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000187:drug effects*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists; D009447:Neuroblastoma; D009842:Oligopeptides / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000819:agonists; D014407:Tumor Cells, Cultured
D004745:Enkephalins; D009292:Narcotic Antagonists; D009842:Oligopeptides; D011957:Receptors, Opioid; C105293:endomorphin 1; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C077532:tyrosyl-prolyl-tryptophyl-glycinamide; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C105294:endomorphin 2; D009075:MSH Release-Inhibiting Hormone; D019204:GTP-Binding Proteins