title: Activation of guanylate cyclase by E. coli heat-stable enterotoxin (STa). Modulation by NAD and pertussis toxin.
abstract: The heat-stable enterotoxin (STa) of E. coli activates intestinal guanylate cyclase and leads to increased cGMP levels by an as yet undetermined mechanism. In comparing this cGMP system to other known toxin-mediated alterations in cAMP metabolism, we observed that pertussis toxin caused lower levels of intestinal cGMP synthesis in response to purified STa. Another participant in ADP-ribosylation reactions, NAD, enhanced the ability of STa to activate guanylate cyclase, yet had no effect on basal enzyme activity. Niacinamide and isoniacinamide also had no effect on basal activity, but attenuated the STa activation. These results are discussed in relation to current models of hormone/toxin-sensitive adenylate cyclase, and may suggest an involvement of guanine-nucleotide-binding proteins in intestinal cGMP metabolism.
authors.forename: S A
authors.initials: SA
authors.lastname: Epstein
authors.forename: R A
authors.initials: RA
authors.lastname: Giannella
authors.forename: H J
authors.initials: HJ
authors.lastname: Brandwein
mesh_terms: D037361:Adenylate Cyclase Toxin; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D004768:Enterotoxins / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D005260:Female; D006162:Guanylate Cyclase / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000201:enzymology*; D009243:NAD / Q000494:pharmacology*; D009536:Niacinamide / Q000494:pharmacology; D037342:Pertussis Toxin; D051381:Rats; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D037361:Adenylate Cyclase Toxin; D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D010566:Virulence Factors, Bordetella; C034151:heat stable toxin (E coli); D009243:NAD; D009536:Niacinamide; D037342:Pertussis Toxin; D006162:Guanylate Cyclase