Internalization and recycling of XXXX mu opioid receptors expressed in Sf9 insect cells.

@entity1 @entity558 @entity7862 @entity1510 @entity969 @entity1286 @entity72548
Internalization and recycling of G protein-coupled receptors (GPCRs), such as the mu-opioid receptor, largely depend on agonist stimulation. Agonist-promoted internalization of some GPCRs has been shown to mediate receptor desensitization, resensitization, and down-regulation. In this study, we investigated whether different mu opioid agonists displayed different effects in receptor internalization and recycling, the potential mechanisms involved in @entity72548 -induced internalization process. In transfected Sf9 insect cells expressing 6His-tagged wild type mu opioid receptor, exposure to 100 nM @entity72548 caused a maximum internalization of the receptor at 30 min and receptors seemed to reappear at the cell membrane after 60 min as determined by radioligand binding assay. @entity72548 -induced @entity1 mu opioid receptor internalization was concentration-dependent, with about 40% of the receptors internalized following a 30-min exposure to 1 microM @entity72548 . 10 microM @entity1286 and 1 microM @entity7862 could also induce about 40% internalization. The antagonist @entity1510 and pretreatment with pertussis toxin both blocked @entity72548 -induced internalization without affecting internalization themselves. Incubation with @entity969 0.45 M significantly inhibited @entity72548 -induced internalization of the mu receptor. The removal of agonists @entity72548 and @entity1286 resulted in the receptors gradually returning to the cell surface over a 60 min period, while the removal of agonist @entity7862 only partly resulted in the receptor recycling. The results of this study suggest that @entity72548 -induced internalization of @entity1 mu opioid receptor in Sf9 insect cells occurs via Gi/o protein-dependent process that likely involves @entity558 . In addition, the recycling process displays the differential modes of action of different agonists.
