Transfection of NG108-15 cells with antisense opioid-binding cell adhesion molecule cDNA alters opioid receptor-G-protein interaction.

We previously reported that transfection of antisense OBCAM (opioid-binding cell adhesion molecule) cDNA into NG108-15 neuroblastoma x glioma hybrid cells, which contain delta-opioid receptors, results in greatly reduced opioid binding (Ann, D. K., Hasegawa, J., Ko, J. L., Chen, S. T., Lee, N. M., and Loh, H. H. (1992) J. Biol. Chem. 267, 7921-7926. Here we report that these cells show altered coupling between opioid receptors and G-proteins. G-proteins were identified using cholera toxin (CTX)-induced ADP-ribosylation and antisera selective for Gi2 and Go alpha subunits. In the presence of delta-opioid agonists, CTX induced the incorporation of [32P]ADP-ribose into a 39-41-kDa protein with the same electrophoretic mobility as Gi2 and Go alpha subunits. This band, which was also a pertussis toxin (PTX) substrate, exhibited decreased CTX-induced ADP-ribosylation in membranes of cells treated chronically with D-Ala2-D-Leu5-enkephalin (DADLE). In cells transfected with antisense cDNA for OBCAM, labeling of this band was also decreased, compared with either sense-transfected or untransfected cells. DADLE inhibition of adenylyl cyclase and DADLE stimulation of GTPase were also greatly impaired in antisense cells, as well as GTP and GppNHp inhibition of basal and forskolin-stimulated adenylyl cyclase. These results provide further evidence for a role of OBCAM in opioid receptor function.