title: Inhibition of proinflammatory RANTES expression by TGF-beta1 is mediated by glycogen synthase kinase-3beta-dependent beta-catenin signaling.
abstract: TGF-β1 is a pleiotropic cytokine with potent anti-inflammation property. However, the mechanisms underlying TGF-β1 suppression of inflammation remain largely unexplored. In this study, we demonstrated that TGF-β1 inhibited TNF-α- or IL-1-induced RANTES expression in human kidney tubular epithelial cells (HKC-8). To delineate the mechanism by which TGF-β1 inhibits RANTES expression, we examined the potential signal pathway activated by TGF-β1 in suppressing NF-κB signaling. TGF-β1 affected neither TNF-α-induced IκBα phosphorylation and subsequent degradation, nor p65 NF-κB phosphorylation and its nuclear translocation. However, TGF-β1 could inhibit p65 and p50 binding to the κB site in human RANTES promoter as revealed by chromatin immunoprecipitation assay and protein-DNA binding assay. We found that TGF-β1 induced glycogen synthase kinase-3β (GSK-3β) phosphorylation on Ser-9 in HKC-8 cells, leading to its inactivation. Knockdown of GSK-3β mimicked TGF-β1 and inhibited RANTES induction, whereas overexpression of GSK-3β abolished the inhibitory effect of TGF-β1 and completely restored RANTES expression. Furthermore, TGF-β1 induced the dephosphorylation and activation of β-catenin, a major downstream target of GSK-3β. Ectopic expression of constitutively active β-catenin mimicked the TGF-β1 effect and completely suppressed RANTES expression induced by TNF-α. Interestingly, TGF-β1 induced a physical interaction between β-catenin and p65 NF-κB, which prevented p65 binding to the κB site, sequestered its trans-activating activity, and repressed p65-mediated gene transcription. We conclude that TGF-β1 inhibition of proinflammatory RANTES expression is mediated by β-catenin-triggered blockade of NF-κB signaling.
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Chunsun
authors.initials: C
authors.lastname: Dai
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wen
authors.forename: Weichun
authors.initials: W
authors.lastname: He
authors.forename: Youhua
authors.initials: Y
authors.lastname: Liu
mesh_terms: D001665:Binding Sites / Q000276:immunology; D002478:Cells, Cultured; D018946:Chemokine CCL5 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology; D016328:NF-kappa B / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D051176:beta Catenin / Q000378:metabolism*
chemical_list: C483024:CCL5 protein, human; C495270:CTNNB1 protein, human; D018946:Chemokine CCL5; D016328:NF-kappa B; D034741:RNA, Small Interfering; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D051176:beta Catenin; D038362:Glycogen Synthase Kinase 3