title: Grape extracts inhibit multiple events in the cell biology of cholera intoxication.
abstract: Vibrio cholerae produces cholera toxin (CT), an AB5 protein toxin that is primarily responsible for the profuse watery diarrhea of cholera. CT is secreted into the extracellular milieu, but the toxin attacks its Gsα target within the cytosol of a host cell. Thus, CT must cross a cellular membrane barrier in order to function. This event only occurs after the toxin travels by retrograde vesicular transport from the cell surface to the endoplasmic reticulum (ER). The catalytic A1 polypeptide then dissociates from the rest of the toxin and assumes an unfolded conformation that facilitates its transfer to the cytosol by a process involving the quality control system of ER-associated degradation. Productive intoxication is blocked by alterations to the vesicular transport of CT and/or the ER-to-cytosol translocation of CTA1. Various plant compounds have been reported to inhibit the cytopathic activity of CT, so in this work we evaluated the potential anti-CT properties of grape extract. Two grape extracts currently sold as nutritional supplements inhibited CT and Escherichia coli heat-labile toxin activity against cultured cells and intestinal loops. CT intoxication was blocked even when the extracts were added an hour after the initial toxin exposure. A specific subset of host-toxin interactions involving both the catalytic CTA1 subunit and the cell-binding CTB pentamer were affected. The extracts blocked toxin binding to the cell surface, prevented unfolding of the isolated CTA1 subunit, inhibited CTA1 translocation to the cytosol, and disrupted the catalytic activity of CTA1. Grape extract could thus potentially serve as a novel therapeutic to prevent or possibly treat cholera.
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida, United States of America ; Lake Highland Preparatory School, Orlando, Florida, United States of America.
authors.forename: Srikar
authors.initials: S
authors.lastname: Reddy
authors.forename: Michael
authors.initials: M
authors.lastname: Taylor
authors.forename: Mojun
authors.initials: M
authors.lastname: Zhao
authors.forename: Patrick
authors.initials: P
authors.lastname: Cherubin
authors.forename: Sandra
authors.initials: S
authors.lastname: Geden
authors.forename: Supriyo
authors.initials: S
authors.lastname: Ray
authors.forename: David
authors.initials: D
authors.lastname: Francis
authors.forename: Ken
authors.initials: K
authors.lastname: Teter
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors; D016466:CHO Cells; D002771:Cholera / Q000382:microbiology / Q000517:prevention & control*; D002772:Cholera Toxin / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D003412:Cricetulus; D060746:Endoplasmic Reticulum-Associated Degradation / Q000187:drug effects; D004768:Enterotoxins / Q000037:antagonists & inhibitors; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors; D056604:Grape Seed Extract / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D006367:HeLa Cells; D054884:Host-Pathogen Interactions / Q000187:drug effects*; D006801:Humans; D021381:Protein Transport / Q000187:drug effects; D058767:Protein Unfolding / Q000187:drug effects; D013552:Swine; D014734:Vibrio cholerae / Q000187:drug effects / Q000502:physiology*; D027843:Vitis / Q000737:chemistry
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D056604:Grape Seed Extract; D002772:Cholera Toxin; C027538:heat-labile enterotoxin, E coli
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