cAMP is a second messenger that regulates many diverse cellular functions. In the intestinal lumen, cAMP is responsible for maintaining electrolyte and water balance. Certain bacterial toxins, including one produced by Vibrio cholera, can upset the levels of cAMP, leading to fatal dehydration.

a. Given what you know about the mechanism of Vibrio cholera toxin, label the graph below showing cAMP concentration in (1) normal intestinal epithelial cells treated with a GPCR agonist to activate G_as, and (2) cholera toxin-treated cells stimulated with the same GPCR agonist. Explain how you came to these conclusions.

b. Would you expect lower or higher levels of PKA in cells treated with cholera toxin? Explain how you came to these conclusions.

Transcribed Image Text:

Time GPCR agonist CAMP concentration