title: Induction of SREBP-1c mRNA by differentiation and LXR ligand in human keratinocytes.
abstract: The epidermis is an active site of lipid metabolism, and the synthesis of fatty acids and cholesterol is required for cutaneous homeostasis. Liver X receptor-alpha (LXRalpha) and LXRbeta are nuclear receptors that are activated by oxysterols and regulate cholesterol and fatty acid metabolism. LXRs, predominantly LXRbeta, have been shown to be involved in keratinocyte differentiation and epidermal permeability barrier function. Although LXR regulates hepatic lipogenesis by inducing sterol-regulatory element-binding protein-1c (SREBP-1c), SREBP-1c induction by LXR in the epidermis has not been studied. In this study, we report that SREBP-1c mRNA increased during differentiation of human keratinocyte HaCaT cells and that LXR agonist effectively induced expression of LXR target genes, including SREBP-1c and ATP-binding cassette transporter A1, in differentiated HaCaT cells. Differentiation-associated and LXR-enhanced expression of SREBP-1c was also observed in malignant human keratinocyte A431 cells and primary human keratinocytes. A synthetic LXR antagonist inhibited confluency-dependent expression of SREBP-1c. Thus, SREBP-1c expression increases during keratinocyte differentiation, and LXR activation enhances its expression.
authors.affiliation: Division of Biochemistry, Department of Biomedical Sciences, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Yokoyama
authors.forename: Makoto
authors.initials: M
authors.lastname: Makishima
authors.forename: Mihwa
authors.initials: M
authors.lastname: Choi
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Cho
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nishida
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: Tadashi
authors.initials: T
authors.lastname: Terui
mesh_terms: D001692:Biological Transport; D002454:Cell Differentiation; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004817:Epidermis / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D008024:Ligands; D050356:Lipid Metabolism; D000071518:Liver X Receptors; D008954:Models, Biological; D057093:Orphan Nuclear Receptors; D010539:Permeability; D012333:RNA, Messenger / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D051780:Sterol Regulatory Element Binding Protein 1 / Q000096:biosynthesis*
chemical_list: D004268:DNA-Binding Proteins; D005227:Fatty Acids; D008024:Ligands; D000071518:Liver X Receptors; C000605213:NR1H3 protein, human; D057093:Orphan Nuclear Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D051780:Sterol Regulatory Element Binding Protein 1; D002784:Cholesterol