FIGURE 6.

Y308F substitution on β₂-AR increases the PTX sensitivity of (R,R′)-aminoFen-induced ERK phosphorylation in HEK stable cell lines. Confluent cultures of HEK-β₂-AR cells and HEK-β₂-AR Y308F cells were deprived of serum overnight. Treatment with PTX (0.3 μg/ml, +) or vehicle (−) was implemented during serum starvation. Cells were then stimulated with ISO (1 μm) or (R,R′)-aminoFen (10⁻⁹ to 10⁻⁶ m) for 5 min at 37 °C as indicated. ERK phosphorylation was determined by immunoblotting. A, immunoblots of p-ERK and total ERK (as protein loading control) in response to agonist stimulation in HEK-β₂-AR cells, and B, averaged data. C, immunoblots of p-ERK and total ERK in response to agonist stimulation in HEK-β₂-AR Y308F cells, and D, averaged data. Data are presented as fold increase over −PTX control (means ± S.E. in 3–4 independent experiments). *, p < 0.05; **, p < 0.01; ***, p < 0.001 versus vehicle controls; #, p < 0.05 versus −PTX group.