Shiga toxin produced by enterohemorrhagic Escherichia coli inhibits PI3K/NF-kappaB signaling pathway in globotriaosylceramide-3-negative human intestinal epithelial cells.
Shiga toxin (Stx) produced by enterohemorrhagic Escherichia coli (EHEC) binds to endothelial cells expressing globotriaosylceramide-3 (Gb-3) and induces cell death by inhibiting translation. Nonetheless, the effects of Stx on human enterocytes, which lacks receptor Gb-3, remain less known. In this study, we questioned whether EHEC-derived Stx may modulate cellular signalization in the Gb-3-negative human epithelial cell line T84. Stx produced by EHEC was fixed and internalized by the cells. A weak activation of NF-kappaB was observed in T84 cells after EHEC infection. Cells infected with an isogenic mutant lacking stx1 and stx2, the genes encoding Stx, displayed an increased NF-kappaB DNA-binding activity. Consequently, the NF-kappaB-dependent CCL20 and IL-8 gene transcription and chemokine production were enhanced in T84 cells infected with the Stx mutant in comparison to the wild-type strain. Investigating the mechanism by which Stx modulates NF-kappaB activation, we showed that the PI3K/Akt signaling pathway was not induced by EHEC but was enhanced by the strain lacking Stx. Pharmacological inhibition of the PI3K/Akt signalization in EHEC DeltaStx-infected T84 cells yielded to a complete decrease of NF-kappaB activation and CCL20 and IL-8 mRNA expression. This demonstrates that the induction of the PI3K/Akt/NF-kappaB pathway is potentially induced by EHEC, but is inhibited by Stx in Gb-3-negative epithelial cells. Thus, Stx is an unrecognized modulator of the innate immune response of human enterocytes.
Gobert
Alain P
AP
Institut National de la Recherche Agronomique, UR454 Unité de Microbiologie, Centre de Theix, 63122 Saint-Genès-Champanelle, France. agobert@clermont.inra.fr
Vareille
Marjolaine
M
Glasser
Anne-Lise
AL
Hindré
Thomas
T
de Sablet
Thibaut
T
Martin
Christine
C
D002478:Cells, Cultured; D054418:Chemokine CCL20; D019742:Chemokines, CC / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D020382:Interleukin-18 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000737:chemistry / Q000276:immunology* / Q000382:microbiology; D019402:Macrophage Inflammatory Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D022621:Shiga Toxin / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D014281:Trihexosylceramides / Q000032:analysis
D054418:Chemokine CCL20; D019742:Chemokines, CC; D020382:Interleukin-18; D019402:Macrophage Inflammatory Proteins; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012333:RNA, Messenger; D022621:Shiga Toxin; D014281:Trihexosylceramides; C108355:CCL20 protein, human; C018549:globotriaosylceramide