title: Interferon regulatory factor 6 differentially regulates Toll-like receptor 2-dependent chemokine gene expression in epithelial cells.
abstract: Epidermal and mucosal epithelial cells are integral to host defense. They not only act as a physical barrier but also utilize pattern recognition receptors, such as the Toll-like receptors (TLRs), to detect and respond to pathogens. Members of the interferon regulatory factor (IRF) family of transcription factors are key components of TLR signaling as they impart specificity to downstream responses. Although IRF6 is a critical regulator of epithelial cell proliferation and differentiation, its role in TLR signaling has not previously been addressed. We show here that IRF6 is activated by IRAK1 as well as by MyD88 but not by TRIF or TBK1. Co-immunoprecipitation experiments further demonstrated that IRF6 can interact with IRAK1. Gene silencing in epithelial cells along with gene promoter reporter assays showed that IRAK1 mediates TLR2-inducible CCL5 gene expression at least in part by promoting IRF6 activation. Conversely, IRAK1 regulated CXCL8 gene expression independently of IRF6, thus identifying a molecular mechanism by which TLR2 signaling differentially regulates the expression of specific chemokines in epithelial cells. Bioinformatics analysis and mutagenesis-based experiments identified Ser-413 and Ser-424 as key regulatory sites in IRF6. Phosphomimetic mutation of these residues resulted in greatly enhanced IRF6 dimerization and trans-activator function. Collectively, our findings suggest that, in addition to its importance for epithelial barrier function, IRF6 also contributes to host defense by providing specificity to the regulation of inflammatory chemokine expression by TLR2 in epithelial cells.
authors.affiliation: From the Oral Health Cooperative Research Centre, Melbourne Dental School, and Bio21 Institute, and Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and.
authors.forename: Mei Qi
authors.initials: MQ
authors.lastname: Kwa
authors.affiliation: Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and.
authors.forename: Thao
authors.initials: T
authors.lastname: Nguyen
authors.affiliation: From the Oral Health Cooperative Research Centre, Melbourne Dental School, and Bio21 Institute, and Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Huynh
authors.affiliation: the Institute for Molecular Bioscience, and Australian Infectious Disease Research Centre, The University of Queensland, Queensland 4072, Australia.
authors.forename: Divya
authors.initials: D
authors.lastname: Ramnath
authors.affiliation: Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and.
authors.forename: Dominic
authors.initials: D
authors.lastname: De Nardo
authors.affiliation: Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and.
authors.forename: Pui Yeng
authors.initials: PY
authors.lastname: Lam
authors.affiliation: From the Oral Health Cooperative Research Centre, Melbourne Dental School, and Bio21 Institute, and.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Reynolds
authors.affiliation: Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and.
authors.forename: John A
authors.initials: JA
authors.lastname: Hamilton
authors.affiliation: the Institute for Molecular Bioscience, and Australian Infectious Disease Research Centre, The University of Queensland, Queensland 4072, Australia.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Sweet
authors.affiliation: From the Oral Health Cooperative Research Centre, Melbourne Dental School, and Bio21 Institute, and Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Victoria 3010, Australia, and glenms@unimelb.edu.au.
authors.forename: Glen M
authors.initials: GM
authors.lastname: Scholz
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D002460:Cell Line; D018946:Chemokine CCL5 / Q000096:biosynthesis* / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D050835:Interferon Regulatory Factors / Q000235:genetics / Q000378:metabolism*; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D020125:Mutation, Missense; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C483024:CCL5 protein, human; C508606:CXCL8 protein, human; D018946:Chemokine CCL5; C109803:IRF6 protein, human; D050835:Interferon Regulatory Factors; D016209:Interleukin-8; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; C470409:TICAM1 protein, human; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; C507768:IRAK1 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human
keywords: Chemokine; Epithelial Cell; Inflammation; Interferon Regulatory Factor (IRF); Interleukin Receptor-associated Kinase; Toll-like Receptor (TLR); Transcription Factor