Clostridium difficile toxin A attenuates Wnt/β-catenin signaling in intestinal epithelial cells.

Autor:	Bezerra Lima B; Departamento de Fisiologia & Farmacologia, Faculdade de Medicina, Universidade Federal do Ceará (UFC), Fortaleza, Brazil., Faria Fonseca B; Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil., da Graça Amado N; Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil., Moreira Lima D; Departamento de Fisiologia & Farmacologia, Faculdade de Medicina, Universidade Federal do Ceará (UFC), Fortaleza, Brazil., Albuquerque Ribeiro R; Departamento de Fisiologia & Farmacologia, Faculdade de Medicina, Universidade Federal do Ceará (UFC), Fortaleza, Brazil., Garcia Abreu J; Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil., de Castro Brito GA; Departamento de Fisiologia & Farmacologia, Faculdade de Medicina, Universidade Federal do Ceará (UFC), Fortaleza, Brazil Departamento de Morfologia, Faculdade de Medicina, Universidade Federal do Ceará (UFC), Fortaleza, Brazil gerlybrito@hotmail.com.
Jazyk:	angličtina
Zdroj:	Infection and immunity [Infect Immun] 2014 Jul; Vol. 82 (7), pp. 2680-7. Date of Electronic Publication: 2014 Apr 07.
DOI:	10.1128/IAI.00567-13
Abstrakt:	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/β-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 β-catenin and Western blotting for β-catenin and c-Myc (encoded by a Wnt target gene). Moreover, our Western blot analysis showed a decrease in the β-catenin protein levels, which was reversed by z-VAD-fmk, a pan-caspase inhibitor. Nonetheless, TcdA was still able to inhibit the Wnt/β-catenin pathway even in the presence of z-VAD-fmk, lithium chloride (a GSK3β inhibitor), or constitutively active β-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. (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)
Databáze:	MEDLINE
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