Clostridium difficile toxin A attenuates Wnt/ß-catenin signaling in intestinal epithelial cells.
Infect Immun
; 82(7): 2680-7, 2014 Jul.
Article
in En
| MEDLINE
| ID: mdl-24711571
ABSTRACT
Clostridium difficile toxins A and B (TcdA and TcdB) are homologous glycosyltransferases that inhibit a group of small GTPases within host cells, but several mechanisms underlying their pathogenic activity remain unclear. In this study, we evaluated the effects of TcdA on the Wnt/ß-catenin pathway, the major driving force behind the proliferation of epithelial cells in colonic crypts. IEC-6 and RKO cells stimulated with Wnt3a-conditioned medium were incubated with 10, 50, and 100 ng/ml of TcdA for 24 h, resulting in a dose-dependent inhibition of the Wnt signaling, as demonstrated by a T-cell factor (TCF) reporter assay. This was further confirmed by immunofluorescence staining for nuclear localization of ß-catenin and Western blotting for ß-catenin and c-Myc (encoded by a Wnt target gene). Moreover, our Western blot analysis showed a decrease in the ß-catenin protein levels, which was reversed by z-VAD-fmk, a pan-caspase inhibitor. Nonetheless, TcdA was still able to inhibit the Wnt/ß-catenin pathway even in the presence of z-VAD-fmk, lithium chloride (a GSK3ß inhibitor), or constitutively active ß-catenin, as determined by a TCF reporter assay. Furthermore, preincubation of RKO cells with TcdA for 12 h also attenuated Wnt3a-mediated activation of Wnt signaling, suggesting that inactivation of Rho GTPases plays a significant role in that inhibition. Taken together, these findings suggest that attenuation of the Wnt signaling by TcdA is important for TcdA antiproliferative effects.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Bacterial Toxins
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Enterotoxins
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Epithelial Cells
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Wnt Proteins
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Beta Catenin
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Intestinal Mucosa
Limits:
Animals
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Humans
Language:
En
Journal:
Infect Immun
Year:
2014
Document type:
Article
Affiliation country:
Brazil
Publication country:
EEUU
/
ESTADOS UNIDOS
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ESTADOS UNIDOS DA AMERICA
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EUA
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UNITED STATES
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UNITED STATES OF AMERICA
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US
/
USA