Activated Gsα but not Giα prevents the thermal inactivation of adenylyl cyclase in plasma membranes derived from S49 lymphoma cells

AbstractThe thermal inactivation of adenylyl cyclase was studied in plasma membranes isolated from wild-type and the mutant cell strain cyc− of S49 lymphoma. The half-life of adenylyl cyclase activity at 30°C was decreased from 14.2 min to 3.4 min by the presence of detergents. ATP as well as forskolin prevented the adenylyl cyclase inactivation in a dose-response manner independent of the utilized type of cell membranes. Activation of G-proteins by GTPγS or by AlF−4 in wild-type membranes but not in cyc− membranes partially prevented adenylyl cyclase inactivation. Adenylyl cyclase activity in cyc− membranes was preserved in the presence of GTPγS or AlF4 from the observed detergent-induced inactivation by complementation of these membranes with an extract from wild-type membranes. ADP-ribosylation of Giα in a cyc− membranes did not influence the kinetics of the inactivation process of adenylyl cyclase, whereas ADP-ribosylated Gsα, protein protected adenylyl cyclase more effectively than non-ribosylated Gsα in wild-type plasma membranes when GTP was used as an activator