Reduction of adenylyl cyclase activity by cholera toxin in myeloid cells Long-term down-regulation of Gsα subunits by cholera toxin treatment

AbstractIn IPC-81 cells, the adenylyl-cyclase activation by cholera toxin produces an elevation of cAMP that causes a rapid cytolysis. A resistant clone with deficient cholera toxin-induced cyclase activity (yet sensitive to cAMP) showed a rapid decrease in the amount of membrane-bound Gsα (42–47 kDa) detectable soon after ADP-ribosylation of these proteins; pertussis toxin-sensitive G proteins (41 kDa) were not affected. Resistant cells showed a rapid decrease of Gsα that is consistent with the finding that cAMP did not accumulate in these cells. Cholera toxin treatment of resistant cells had long-lasting effects (several weeks) on the level of Gsα in the cell membrane. The duration of Gsα decrease does not correspond to the probable life of catalytically active cholera toxin in the cells, and suggests a regulated process more complex than a proteolytic degradation targeted on ADP-ribosylated molecules