Effects of cycloheximide and tunicamycin on opiate receptor activities in neuroblastoma X glioma NG108-15 hybrid cells

Ping Yee Law, Harold G. Ungar, Dennis S. Hom, Horace H. Loh

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

The molecular mechanism of opiate receptor down-regulation and desensitization was investigated by studying the effects of cycloheximide and tunicamycin on opiate receptor activities in neuroblastoma X glioma NG108-15 hybrid cells. Cycloheximide inhibited [35S]methionine and [3H]-glucosamine incorporation by hybrid cells, while tunicamycin inhibited [3H]glucosamine incorporation only. Exposing hybrid cells to these two agents did not alter the viability of the cell. Treatment of NG108-15 cells with cycloheximide or tunicamycin produced a decrease in [3H]diprenorphine binding dependent on both time and concentrations of inhibitors, with no measurable modification in the ability of etorphine to regulate intracellular cyclic AMP production. Cycloheximide attenuated [3H]-diprenorphine binding by decreasing both the number of sites, Bmax, and the affinity of the receptor, Kd. Tunicamycin treatment produced a decrease in Bmax with no apparent alteration in Kd values. Cycloheximide and tunicamycin did not potentiate the rate or magnitude of etorphine-induced down-regulation or desensitization of opiate receptor in NG108-15 cells. Furthermore, there was an apparent antagonism in cycloheximide action on receptor down-regulation. The reappearance of opiate binding sites after agonist removal was affected by these two inhibitors. Cycloheximide and tunicamycin eliminated the increase in [3H]diprenorphine binding in the chronic etorphine-treated cells after agonist removal. These two inhibitors did not alter the resensitization of hybrid cells to etorphine. Thus, the site of opiate agonist action to induce receptor down-regulation and desensitization is not at the site of protein synthesis or protein glycosylation. These data substantiate previously reported observations that receptor down-regulation and receptor desensitization are two different cellular adaptation processes.

Original languageEnglish (US)
Pages (from-to)9-17
Number of pages9
JournalBiochemical Pharmacology
Volume34
Issue number1
DOIs
StatePublished - Jan 1 1985

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