Which of the following bacteria manifests its clinical features by increasing cAMP?
Vibrio cholerae secretes an enterotoxin called choleragen (cholera toxin). Choleragen consists of an A (active) subunit and a B (binding) subunit. The B subunit binds to a ganglioside receptor on the surface of the enterocyte. The A subunit is inseed into the cytosol, where it catalyzes the addition of ADP-ribose to the Gs protein. This locks the Gs protein in the "on" position, which causes the persistent stimulation of adenylate cyclase. The resulting overproduction of cyclic AMP activates cyclic AMP-dependent protein kinase, an enzyme that phosphorylates ion transpoers in the cell membrane, resulting in the loss of water and ions from the cell. The watery efflux enters the lumen of the gut, resulting in a massive watery diarrhea that contains neither neutrophils nor red blood cells. Ref: Levinson W. (2012). Chapter 18. Gram-Negative Rods Related to the Enteric Tract. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.
Vibrio cholerae
Staphylococcus aureus
E. coli heat stable toxin
Salmonella