Fig. 5. Heteromerization of MOR and CCKBR inhibited MOR activities in co-transfected HEK293 cells.
a Immunoblot assays showing the ERK1/2 phosphorylation level in cells expressing HA-MOR alone (top) or co-expressing HA-MOR and FLAG-CCKBR (bottom). Cells were exposed to different concentrations of DAMGO for 5 min, and pERK1/2 and total ERK1/2 were determined. Concentrations of DAMGO were indicated above the bands. b Densitometric analysis was quantified by normalizing with total ERK1/2 and expressed as folds of phosphorylated ERK1/2 over basal in vehicle-treated cells. ERK1/2 phosphorylation in cells expressing HA-MOR alone was significantly higher than that in HA-MOR- and FLAG-CCKBR-co-expressing cells at concentrations of 10−10, 10−9, and 10−8 M. *p < 0.05, t-test, n = 4. c Immunoblot assays showing ERK1/2 phosphorylation in HA-MOR-expressing cells (top) or HA-MOR- and FLAG-CCKBR-co-expressing cells (bottom). Time points of DAMGO stimulation are labeled above the bands. d Statistical results. ERK1/2 phosphorylation in cells expressing HA-MOR alone significantly increased compared with that in HA-MOR- and FLAG-CCKBR-co-expressing cells at 5 min after DAMGO exposure. **p < 0.01, t-test, n = 3. Data are represented as the mean ± SEM