Vibrio cholerae ACE stimulates Ca(2+)-dependent Cl(-)/HCO(3)(-) secretion in T84 cells in vitro.
ACE, accessory cholera enterotoxin, the third enterotoxin in Vibrio cholerae, has been reported to increase short-circuit current (I(sc)) in rabbit ileum and to cause fluid secretion in ligated rabbit ileal loops. We studied the ACE-induced change in I(sc) and potential difference (PD) in T84 monolayers mounted in modified Ussing chambers, an in vitro model of a Cl(-) secretory cell. ACE added to the apical surface alone stimulated a rapid increase in I(sc) and PD that was concentration dependent and immediately reversed when the toxin was removed. Ion replacement studies established that the current was dependent on Cl(-) and HCO(3)(-). ACE acted synergistically with the Ca(2+)-dependent acetylcholine analog, carbachol, to stimulate secretion in T84 monolayers. In contrast, the secretory response to cAMP or cGMP agonists was not enhanced by ACE. The ACE-stimulated secretion was dependent on extracellular and intracellular Ca(2+) but was not associated with an increase in intracellular cyclic nucleotides. We conclude that the mechanism of secretion by ACE involves Ca(2+) as a second messenger and that this toxin stimulates a novel Ca(2+)-dependent synergy.
Trucksis
M
M
Center for Vaccine Development, Department of Medicine, University of Maryland School of Medicine, Baltimore 21201, Maryland, USA. mtrucksi@medicine.umaryland.edu
Conn
T L
TL
Wasserman
S S
SS
Sears
C L
CL
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D001427:Bacterial Toxins / Q000494:pharmacology; D001639:Bicarbonates / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels / Q000502:physiology; D002712:Chlorides / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D002772:Cholera Toxin / Q000494:pharmacology*; D018679:Cholinergic Agonists / Q000494:pharmacology; D003022:Clotrimazole / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004594:Electrophysiology; D004768:Enterotoxins / Q000494:pharmacology; D029968:Escherichia coli Proteins; D009712:Nucleotides, Cyclic / Q000502:physiology; D015290:Second Messenger Systems / Q000187:drug effects; D014734:Vibrio cholerae / Q000378:metabolism*
C081530:Ace toxin; D001427:Bacterial Toxins; D001639:Bicarbonates; D018118:Chloride Channels; D002712:Chlorides; D018679:Cholinergic Agonists; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D009712:Nucleotides, Cyclic; C034151:heat stable toxin (E coli); D005576:Colforsin; D002217:Carbachol; D002772:Cholera Toxin; D003022:Clotrimazole; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium