Opposing adenine nucleotide-dependent pathways regulate guanylyl cyclase C in rat intestine

J Biol Chem. 1994 Sep 9;269(36):22683-90.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenine Nucleotides / pharmacology*
  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / pharmacology
  • Animals
  • Bacterial Toxins / pharmacology
  • Cell Membrane / enzymology
  • Enterotoxins / pharmacology
  • Escherichia coli Proteins
  • Guanosine Triphosphate / analogs & derivatives
  • Guanosine Triphosphate / pharmacology
  • Guanylate Cyclase / metabolism*
  • Guanylate Cyclase / physiology
  • Intestinal Mucosa / enzymology*
  • Intestine, Small
  • Isoenzymes / metabolism*
  • Kinetics
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Enterotoxin
  • Receptors, Guanylate Cyclase-Coupled
  • Receptors, Peptide / physiology

Substances

  • Adenine Nucleotides
  • Bacterial Toxins
  • Enterotoxins
  • Escherichia coli Proteins
  • Isoenzymes
  • Receptors, Peptide
  • heat stable toxin (E coli)
  • Guanosine Triphosphate
  • Adenosine Triphosphate
  • Guanylate Cyclase
  • Receptors, Enterotoxin
  • Receptors, Guanylate Cyclase-Coupled