Vibrio cholerae produces profuse rice-water diarrhea through which primary toxin mechanism?

• A Cholera toxin B subunit irreversibly activates adenylyl cyclase via ADP-ribosylation of Gsα, increasing cAMP and causing chloride secretion via CFTR ✓
• B Cholera toxin increases intracellular cGMP to activate CFTR
• C Cholera toxin directly pores into intestinal epithelial membranes
• D Zot toxin is the primary pathogenic mechanism for fluid secretion

Explanation

Cholera toxin consists of a pentameric B subunit (binding) and an A subunit (active). The B subunit binds GM1 ganglioside on epithelial cells; the A1 subunit (active fragment) ADP-ribosylates the Gsα subunit of adenylyl cyclase, permanently activating it to produce massive cAMP. Elevated cAMP activates CFTR chloride channels in the apical membrane and inhibits NaCl absorption at the brush border, resulting in isotonic secretory diarrhea. cGMP elevation is the mechanism of E. coli heat-stable toxin (STa). Zot (zonula occludens toxin) disrupts tight junctions but is not the primary diarrheal mechanism.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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