RT Journal Article
SR Electronic
T1 Long-Term Morphine Treatment Enhances Proteasome-Dependent Degradation of Gβ in Human Neuroblastoma SH-SY5Y Cells: Correlation with Onset of Adenylate Cyclase Sensitization
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 467
OP 476
DO 10.1124/mol.105.013391
VO 68
IS 2
A1 Lionel Moulédous
A1 Jérémie Neasta
A1 Sandrine Uttenweiler-Joseph
A1 Alexandre Stella
A1 Mariette Matondo
A1 Maïthé Corbani
A1 Bernard Monsarrat
A1 Jean-Claude Meunier
YR 2005
UL http://molpharm.aspetjournals.org/content/68/2/467.abstract
AB The initial aim of this study was to identify protein changes associated with long-term morphine treatment in a recombinant human neuroblastoma SH-SY5Y clone (sc2) stably overexpressing the human μ-opioid (MOP) receptor. In MOP receptor-overexpressing sc2 cells, short-term morphine exposure was found to be much more potent and efficacious in inhibiting forskolin-elicited production of cAMP, and long-term morphine exposure was shown to induce a substantially higher degree of opiate dependence, as reflected by adenylate cyclase sensitization, than it did in wild-type neuroblastoma cells. Differential proteomic analysis of detergent-resistant membrane rafts isolated from untreated and chronically morphine-treated sc2 cells revealed long-term morphine exposure to have reliably induced a 30 to 40% decrease in the abundance of five proteins, subsequently identified by mass spectrometry as G protein subunits αi2, αi3, β1, and β2, and prohibitin. Quantitative Western blot analyses of whole-cell extracts showed that long-term morphine treatment-induced down-regulation of Gβ but not of the other proteins is highly correlated (r2 = 0.96) with sensitization of adenylate cyclase. Down-regulation of Gβ and adenylate cyclase sensitization elicited by long-term morphine treatment were suppressed in the presence of carbobenzoxy-l-leucyl-l-leucyl-l-norvalinal (MG-115) or lactacystin. Thus, sustained activation of the MOP receptor by morphine in sc2 cells seems to promote proteasomal degradation of Gβ to sensitize adenylate cyclase. Together, our data suggest that the long-term administration of opiates may elicit dependence by altering the neuronal balance of heterotrimeric G proteins and adenylate cyclases, with the ubiquitin-proteasome pathway playing a pivotal role.