title: Opposing adenine nucleotide-dependent pathways regulate guanylyl cyclase C in rat intestine.
abstract: Opposing adenine nucleotide-dependent pathways regulating guanylyl cyclase C (GC-C) in rat intestinal membranes have been identified and characterized. ATP analogues substituted in the 2-position were potent inhibitors of basal and Escherichia coli heat-stable enterotoxin (ST)-stimulated GC-C, independent of the metal cation cofactor present. Inhibition of GC-C was associated with large changes in Vmax but only small changes in the S0.5, suggesting a noncompetitive mechanism. Also, inhibition of GC-C was associated with a concentration-dependent shift from positive to negative cooperativity when manganese served as the cation cofactor. These data support the existence of a noncompetitive allo steric regulatory mechanism mediating adenine nucleotide-dependent inhibition of GC-C. Adenine nucleotides not substituted in the 2-position potentiated the activation of GC-C by ST in intestinal membranes. The potentiating and inhibitory pathways regulating GC-C enzyme activity were separate and distinct. A specific inhibitor (2-chloroadenosine 5'-triphosphate (2ClATP)), was without effect on the potency of a selective activator (adenosine 5'-O-thiomonophosphate (AMPS)) of GC-C. Similarly, AMPS was without effect on the potency of 2ClATP to inhibit GC-C. These data suggest that adenine nucleotide-dependent activation and inhibition are mediated by independent sites which may modulate the second messenger response of GC-C to ST.
authors.affiliation: Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: S J
authors.initials: SJ
authors.lastname: Parkinson
authors.forename: S L
authors.initials: SL
authors.lastname: Carrithers
authors.forename: S A
authors.initials: SA
authors.lastname: Waldman
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D004768:Enterotoxins / Q000494:pharmacology; D029968:Escherichia coli Proteins; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000378:metabolism* / Q000502:physiology; D007413:Intestinal Mucosa / Q000201:enzymology*; D007421:Intestine, Small; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000502:physiology
chemical_list: D000227:Adenine Nucleotides; D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D007527:Isoenzymes; D018000:Receptors, Peptide; C034151:heat stable toxin (E coli); D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled