Figure 6.

Effect of stable expression of GPR55 on CB₂ receptor-mediated activation of ERK1/2-MAP kinase. (A) HEK-GPR55, HEK-CB₂ receptor and HEK-CB₂R/GPR55 cells were seeded on six-well plates and 24 h post-serum starvation, cells were stimulated with CP 55,940 (100 nM) for 10 min or pretreated for 10 min with CB₂ receptor antagonists SR144528 (250 nM) and AM 630 (250 nM) before agonist treatment. Total ERK1/2 and phosphorylated ERK1/2 in cell lysates were analysed by Western blotting with respective antibodies. One representative blot from three independent experiments is shown. (B) Phosphorylated ERK1/2 and ERK1/2 bands in the blots from panel A were analysed by using the Image Studio software 1.1 (LI-COR Biosciences). Data were normalized to the basal ratio of pERK1/2 to ERK1/2 and are mean ± SEM from three independent experiments. Significant differences were analysed by one-way anova followed by post hoc Tukey's t-test (^##P < 0.01, ^###P < 0.001 compared with control; **P < 0.01 compared with cells treated with CP 55,940).