Figure 2.

α_s-A³⁶⁶S/G²²⁶A/E²⁶⁸A does not inhibit cAMP accumulation stimulated by constitutively active α_s but does inhibit cAMP accumulation stimulated by constitutively active LH-R. (A and B) COS-7 cells cotransfected with control plasmid pcDNAI or with plasmids encoding HA–α_s-A³⁶⁶S/G²²⁶A/E²⁶⁸A (1.2 μg per 1.6 × 10⁶ cells per 60-mm dish) and a second plasmid without (A) or with (B) a constitutively active α_s mutant, HA–α_s-R²⁰¹C (0.2 μg per 1.6 × 10⁶ cells per 60-mm dish) were incubated at 37°C for 25 min with 100 μM IBMX and 1 μM isoproterenol (shaded bars) or no drug (hatched bars), and cAMP accumulation was measured. (C) COS-7 cells transfected with control plasmid pcDNAI or with plasmids encoding HA–α_s-A³⁶⁶S/G²²⁶A/E²⁶⁸A (1.2 μg per 1.6 × 10⁶ cells per 60-mm dish) without or with a plasmid encoding a constitutively active LH-R (LH-R-D⁵⁷⁸G, 0.2 μg per 1.6 × 10⁶ cells per 60-mm dish) were incubated at 37°C for 25 min with 100 μM IBMX and 75 ng/ml hCG (shaded bars) or no drug (hatched bars), and cAMP accumulation was measured. Values represent means ± SD of triplicate determinations. Each set of results is representative of at least two additional experiments.