3. Effect of Cholera Toxin on Adenylyl Cyclase The gram-negative bacterium Vibri

Question

3. Effect of Cholera Toxin on Adenylyl Cyclase The gram-negative bacterium Vibrio cholerae pro- duces a protein, cholera toxin (M 90,000), that is responsible for the characteristic symptoms of cholera: extensive loss of body water and Na through continuous, debilitating diarrhea. If body fluids and Na are not replaced, severe dehydration results; untreated, the disease is often fatal. When the cholera toxin gains access to the human intestinal tract, it binds tightly to specific sites in the plasma membrane of the epithelial cells lining the small intestine, causing adenylyl cyclase to undergo prolonged activation (hours or days) (a) What is the effect of cholera toxin on [cAMP] in the intestinal cells? (b) Based on the information above, suggest how cAMP normally functions in intestinal epithelial cells. (c) Suggest a possible treatment for cholera.

Explanation / Answer

(a) The concentrations levels of cAMP will increase linearly with time until certain steady state is reached
  due to the effect of cholera toxin in the intestinal cells.
(b) cAMP regulates functions of epithelial cells but when this is elevated due to CTX it slows down
the immunity of these cells.
(c) Providing Oral rehydration solutions is the best possible treatment

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