TY - JOUR
T1 - Differential effects of opioid agonists on G protein expression in CHO cells expressing cloned human opioid receptors
AU - Xu, Heng
AU - Wang, Xiaoying
AU - Partilla, John S.
AU - Bishop-Mathis, Kristen
AU - Benaderet, Tova S.
AU - Dersch, Christina M.
AU - Simpson, Denise S.
AU - Prisinzano, Thomas E.
AU - Rothman, Richard B.
N1 - Funding Information:
This research was supported by the Intramural Research Program of the NIH, National Institute on Drug Abuse and funding NIDA grant DA018151 to Dr. Prisinzano.
PY - 2008/9/5
Y1 - 2008/9/5
N2 - Recent evidence indicates that agonist ligands of G protein coupled receptors (GPCR) can activate different signaling systems. Such "agonist-directed" signaling also occurs with opioid receptors. Previous work from our laboratory showed that chronic morphine, but not DAMGO, up-regulates the expression of Gα12 and that both morphine and DAMGO decreased Gαi3 expression in CHO cells expressing the cloned human mu opioid receptor. In this study, we tested the hypothesis that chronic opioid regulation of G protein expression is agonist-directed. Following a 20 h treatment of CHO cells expressing the cloned human mu (hMOR-CHO), delta (hDOR-CHO) or kappa (hKOR-CHO) opioid receptors with various opioid agonists, we determined the expression level of Gα12 and Gαi3 by Western blots. Among five mu agonists (morphine, etorphine, DADLE, DAMGO, herkinorin) tested with hMOR-CHO cells, only chronic morphine and etorphine up-regulated Gα12 expression. All five mu agonists decreased Gαi3 expression. Among six delta agonists (SNC80, DPDPE, deltorphin-1, morphine, DADLE, etorphine) tested with hDOR-CHO cells, all six agonists down-regulated Gαi3 expression or moderately up-regulated Gα12 expression. Among five kappa agonists, ((-)-ethylketocyclazocine, salvinorin A, U69,593, etorphine, (-)-U50,488) tested with hKOR-CHO cells, only chronic (-)-U50,488 and (-)-EKC up-regulated Gα12 expression. All kappa agonists decreased Gαi3 expression. These data demonstrate that chronic opioid agonist regulation of G protein expression depends not only on the agonist tested, but also on the type of opioid receptor expressed in a common cellular host, providing additional evidence for agonist-directed signaling.
AB - Recent evidence indicates that agonist ligands of G protein coupled receptors (GPCR) can activate different signaling systems. Such "agonist-directed" signaling also occurs with opioid receptors. Previous work from our laboratory showed that chronic morphine, but not DAMGO, up-regulates the expression of Gα12 and that both morphine and DAMGO decreased Gαi3 expression in CHO cells expressing the cloned human mu opioid receptor. In this study, we tested the hypothesis that chronic opioid regulation of G protein expression is agonist-directed. Following a 20 h treatment of CHO cells expressing the cloned human mu (hMOR-CHO), delta (hDOR-CHO) or kappa (hKOR-CHO) opioid receptors with various opioid agonists, we determined the expression level of Gα12 and Gαi3 by Western blots. Among five mu agonists (morphine, etorphine, DADLE, DAMGO, herkinorin) tested with hMOR-CHO cells, only chronic morphine and etorphine up-regulated Gα12 expression. All five mu agonists decreased Gαi3 expression. Among six delta agonists (SNC80, DPDPE, deltorphin-1, morphine, DADLE, etorphine) tested with hDOR-CHO cells, all six agonists down-regulated Gαi3 expression or moderately up-regulated Gα12 expression. Among five kappa agonists, ((-)-ethylketocyclazocine, salvinorin A, U69,593, etorphine, (-)-U50,488) tested with hKOR-CHO cells, only chronic (-)-U50,488 and (-)-EKC up-regulated Gα12 expression. All kappa agonists decreased Gαi3 expression. These data demonstrate that chronic opioid agonist regulation of G protein expression depends not only on the agonist tested, but also on the type of opioid receptor expressed in a common cellular host, providing additional evidence for agonist-directed signaling.
KW - Biased agonism
KW - G protein
KW - Opioid
KW - Opioid receptor
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U2 - 10.1016/j.brainresbull.2008.05.003
DO - 10.1016/j.brainresbull.2008.05.003
M3 - Article
C2 - 18639745
AN - SCOPUS:51749106113
SN - 0361-9230
VL - 77
SP - 49
EP - 54
JO - Brain Research Bulletin
JF - Brain Research Bulletin
IS - 1
ER -