Inhibition of @entity857 -ribosyltransferase increases synthesis of @entity12820 in neuroblastoma x glioma hybrid cells and reverses iloprost-dependent heterologous loss of XXXX -sensitive adenylate cyclase.

@entity1388 @entity19 @entity1880 @entity12820 @entity13338 @entity857 @entity4571
Exposure of @entity19 cells to 50 mM @entity4571 [an inhibitor of mono( @entity857 - @entity13338 )transferase] for 18 hr led to an increase in membrane associated @entity12820 measured either as cholera toxin substrate or by immunoblotting with a specific antiserum. Prolonged exposure of @entity19 cells to iloprost is followed by homologous loss of iloprost sensitivity, and heterologous loss of @entity1388 -dependent activation of adenylate cyclase. @entity4571 reversed the loss of @entity1388 sensitivity, but failed to restore iloprost-dependent activation of adenylate cyclase. These results with @entity4571 in @entity19 cells contrasted with those from platelets, which also exhibit heterologous desensitization of @entity1388 sensitivity following prolonged exposure to iloprost. Treatment of platelets with 50 mM @entity4571 for 18 hr led to an increase of 75.0 +/- 19.4% in the amount of membrane associated cholera toxin substrate. However, there was no associated increase in the abundance of @entity12820 as determined by immunoblotting. Furthermore, in platelets there was no restoration by @entity4571 of the iloprost-dependent loss of @entity1388 -sensitive adenylate cyclase activity. It follows that heterologous desensitization in platelets is accompanied by inactivation of @entity12820 , which is retained within the plasma membrane in its inactive state. The @entity4571 -dependent increase in the abundance of membrane associated cholera toxin substrate and immunoreactive @entity12820 in @entity19 cells is associated with an increase of 72.0 +/- 20.3% in the levels of mRNA encoding @entity12820 . The capacity of @entity4571 to increase the abundance of membrane associated @entity12820 was reversed when the cells were cultured in the presence of 20 micrograms/mL @entity1880 . These results suggest that the ability of @entity4571 to increase the abundance of @entity12820 in @entity19 cells is mediated by de novo protein synthesis.
