Escherichia coli enterotoxin-induced steroidogenesis in cultured adrenal tumor cells

A heat-labile, Pronase-sensitive factor has been partially purified from cell-free culture filtrates of enterotoxigenic Escherichia coli. The partially purified factor contains both protein and carbohydrate moieties and appears to be E. coli enterotoxin (ECT). ECT binds to cultured adrenal tumor cells rapidly and irreversibly leads to adenosine 3', 5'-cyclic monophosphate formation and steroidogenesis after a 60-min lag phase. Further studies indicate that it interacts with the cholera toxin receptor site on adrenal cells rather than the adrenocorticotropin receptor to activate adenyl cyclase. Mixed gangliosides block stimulation of steroidogenesis in response to both E. coli and cholera enterotoxin. In contrast to adrenocorticotropin, ECT has no additive effect on cholera toxin-induced steroidogenesis. The protein moiety of ECT is similar to cholera enterotoxin because horse serum anticholeragenoid prevented stimulation of steroidogenesis by either enterotoxin. Cultured adrenal cells provide a quantitative assay system that has facilitated the purification and characterization of E. coli enterotoxin.