Colonocyte basolateral membranes contain Escherichia coli heat-stable enterotoxin receptors.
Heat-stable enterotoxin (ST(a)) elaborated by E. coli is a major cause of diarrhea. The transmembrane protein guanylyl cyclase C (GC-C) is the acknowledged receptor for ST(a) and for the mammalian peptides guanylin and uroguanylin. Binding to GC-C results in generation of cGMP, activation of type II cGMP-dependent protein kinase, phosphorylation of CFTR and increased chloride and bicarbonate secretion. We had previously shown that ST(a) receptors (GC-C) are found on the brush border membranes of small intestinal enterocytes and of colonocytes. However, since it has subsequently been shown that the endogenous ligands for these receptors, guanylin and uroguanylin, circulate in blood, we proposed the existence of ST(a) binding sites on the basolateral membranes (BLM) of colonocytes. Specific binding of 125I-ST(a) to rat colonocyte BLM was seen. The kinetics of binding to the BLM were similar to binding to BBM. The nature of the BLM receptor is unknown. This suggests that circulating guanylin and uroguanylin, analogues of ST(a), may also function via the basolateral surface.
Albano
F
F
Division of Digestive Diseases, Veterans Administration Medical Center, Cincinnati, Ohio, USA.
Brasitus
T
T
Mann
E A
EA
Guarino
A
A
Giannella
R A
RA
D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism* / Q000494:pharmacology; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D003106:Colon / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D004768:Enterotoxins / Q000378:metabolism* / Q000494:pharmacology; D029968:Escherichia coli Proteins; D006162:Guanylate Cyclase / Q000378:metabolism*; D008024:Ligands; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000378:metabolism*; D013997:Time Factors
D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D008024:Ligands; D018000:Receptors, Peptide; C034151:heat stable toxin (E coli); D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled