title: TNF-alpha represses connexin43 expression in HaCat keratinocytes via activation of JNK signaling.
abstract: We used both pharmacological and gene knockout approaches to elucidate the specific roles played by the Jun-N-terminal kinase (JNK) and NFkappaB pathways downstream of TNF-alpha in the context of connexin43 (Cx43) gene expression. We demonstrate that TNF-alpha reduces the expression of Cx43 in HaCat cell lines at the protein and mRNA levels, and transcriptionally. We also demonstrate that TNF-alpha decreases gap junctional intercellular communication (GJIC) between HaCat cells. Using pharmacological inhibitors of the NFkappaB signaling pathway, we determined that the NFkappaB signaling cascade is not implicated in TNF-alpha effect on Cx43 expression and in the subsequent decrease of GJIC. Conversely, in NFkappaB essential modulator (NEMO(-)) fibroblasts, lack of NFkappaB activation did not influence both the effect of TNF-alpha on Cx43 expression and on GJIC. In contrast, pharmacologic inhibition of JNK abolishes TNF-alpha-driven repression of Cx43 gene expression and GJIC between HaCat cells. Using JNK(1) (-/-)-JNK(2) (-/-) (JNK(-/-)) fibroblasts, we demonstrate that similar regulatory mechanisms take place in fibroblasts. Together, these results identify JNK and not NFkappaB, as a critical mediator of TNF-alpha repressory effect on Cx43 gene expression.
authors.affiliation: INSERM U697, Paris, France.
authors.forename: Chalotte
authors.initials: C
authors.lastname: Tacheau
authors.forename: Julien
authors.initials: J
authors.lastname: Laboureau
authors.forename: Alain
authors.initials: A
authors.lastname: Mauviel
authors.forename: Franck
authors.initials: F
authors.lastname: Verrecchia
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000502:physiology; D002460:Cell Line; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D017629:Gap Junctions / Q000378:metabolism; D005786:Gene Expression Regulation; D018390:Gene Targeting; D017930:Genes, Reporter; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015603:Keratinocytes / Q000166:cytology / Q000502:physiology*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
chemical_list: D018031:Connexin 43; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D048031:JNK Mitogen-Activated Protein Kinases