Figure 7.

Adenylyl cyclase activation in wild-type and mutant cell lines. (A) Receptor-mediated stimulation of adenylyl cyclase activity. Differentiated cells were stimulated with 10 μM cAMP, lysed at specific time points, and immediately assayed as described in MATERIALS AND METHODS. (B) GTPγS-mediated stimulation of adenylyl cyclase activity. Differentiated cells were lysed with or without GTPγS, or in the presence MnSO₄ as a measure of unregulated enzyme activity, incubated on ice for 4 min, and assayed as described in MATERIALS AND METHODS. The results are expressed as a ratio of the adenylyl cyclase activity to MnSO₄ activity. The absolute MnSO₄ activities are 4.0, 3.9, 2.5, and 2.5 pmol·min⁻¹·mg⁻¹ for wild-type, aleA null, rip3 null, and rip3/aleA null cells, respectively. The results presented are representative of at least two independent experiments.