AMP and G Proteins

Cyclic AMP (adenosine-3, 5 -monophosphate, cAMP) is one example of a second messenger. The mode of action starts with binding of a hormone to a specific receptor called a Pj- or P2 adrenergic receptor, which triggers the production 

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A G protein is permanently activated hy cholera toxin, leading to excessive stimulation of adenylate cyclase and chronic elevation of cAMP levels. The main danger in cholera, caused hy the hacterium Vibrio cholerae, is severe dehydration as a result of diarrhea. The unregulated activity of adenylate cyclase in epithelial cells leads to the diarrhea because cAMP in epithehal cells stimulates active transport of Na+. Excessive cAMP in the epithehal cells of the small intestine produces a lai e flow of Na+ and water from the mucosal surface of the epithelial cells into the lumen of the intestine. If the lost fluid and salts can he replaced in cholera victims, the immune system can ehminate the actual infection within a few days. 

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