title: Angiopoietin-like 4 regulates epidermal differentiation.
abstract: The nuclear hormone receptor PPARβ/δ is integral to efficient wound re-epithelialization and implicated in epidermal maturation. However, the mechanism underlying the latter process of epidermal differentiation remains unclear. We showed that ligand-activated PPARβ/δ indirectly stimulated keratinocyte differentiation, requiring de novo gene transcription and protein translation. Using organotypic skin cultures constructed from PPARβ/δ- and angiopoietin-like 4 (ANGPTL4)-knockdown human keratinocytes, we showed that the expression of ANGPTL4, a PPARβ/δ target gene, is essential for the receptor mediated epidermal differentiation. The pro-differentiation effect of PPARβ/δ agonist GW501516 was also abolished when keratinocytes were co-treated with PPARβ/δ antagonist GSK0660 and similarly in organotypic skin culture incubated with blocking ANGPTL4 monoclonal antibody targeted against the C-terminal fibrinogen-like domain. Our focused real-time PCR gene expression analysis comparing the skin biopsies from wildtype and ANGPTL4-knockout mice confirmed a consistent down-regulation of numerous genes involved in epidermal differentiation and proliferation in the ANGPTL4-knockout skin. We further showed that the deficiency of ANGPTL4 in human keratinocytes and mice skin have diminished expression of various protein kinase C isotypes and phosphorylated transcriptional factor activator protein-1, which are well-established for their roles in keratinocyte differentiation. Chromatin immunoprecipitation confirmed that ANGPTL4 stimulated the activation and binding of JUNB and c-JUN to the promoter region of human involucrin and transglutaminase type 1 genes, respectively. Taken together, we showed that PPARβ/δ regulates epidermal maturation via ANGPTL4-mediated signalling pathway.
authors.affiliation: School of Biological Sciences, College of Science, Nanyang Technological University, Singapore, Singapore.
authors.forename: Mintu
authors.initials: M
authors.lastname: Pal
authors.forename: Ming Jie
authors.initials: MJ
authors.lastname: Tan
authors.forename: Royston-Luke
authors.initials: RL
authors.lastname: Huang
authors.forename: Yan Yih
authors.initials: YY
authors.lastname: Goh
authors.forename: Xiao Ling
authors.initials: XL
authors.lastname: Wang
authors.forename: Mark Boon Yang
authors.initials: MB
authors.lastname: Tang
authors.forename: Nguan Soon
authors.initials: NS
authors.lastname: Tan
mesh_terms: D000075803:Angiopoietin-Like Protein 4; D042682:Angiopoietins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D015151:Immunoblotting; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D018345:Mice, Knockout; D047494:PPAR delta / Q000819:agonists / Q000378:metabolism; D048068:PPAR-beta / Q000819:agonists / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D013844:Thiazoles / Q000494:pharmacology; D011503:Transglutaminases / Q000235:genetics
chemical_list: C474772:ANGPTL4 protein, human; D000075803:Angiopoietin-Like Protein 4; D042682:Angiopoietins; C407088:Angptl4 protein, mouse; C425931:GW 501516; D047494:PPAR delta; D048068:PPAR-beta; D011498:Protein Precursors; D013844:Thiazoles; C032253:involucrin; D011503:Transglutaminases; C105804:transglutaminase 1