title: The regulation of hepcidin expression by serum treatment: requirements of the BMP response element and STAT- and AP-1-binding sites.
abstract: Expression of hepcidin, a central regulator of systemic iron metabolism, is transcriptionally regulated by the bone morphogenetic protein (BMP) pathway. However, the factors other than the BMP pathway also participate in the regulation of hepcidin expression. In the present study, we show that serum treatment increased hepcidin expression and transcription without inducing the phosphorylation of Smad1/5/8 in primary hepatocytes, HepG2 cells or Hepa1-6 cells. Co-treatment with LDN-193189, an inhibitor of the BMP type I receptor, abrogated this hepcidin induction. Reporter assays using mutated reporters revealed the involvement of the BMP response element-1 (BMP-RE1) and signal transducers and activator of transcription (STAT)- and activator protein (AP)-1-binding sites in serum-induced hepcidin transcription in HepG2 cells. Serum treatment induced the expression of the AP-1 components c-fos and junB in primary hepatocytes and HepG2 cells. Forced expression of c-fos or junB enhanced the response of hepcidin transcription to serum treatment. By contrast, the expression of dominant negative (dn)-c-fos and dn-junB decreased hepcidin transcription. The present study reveals that serum contains factors stimulating hepcidin transcription. Basal BMP activity is essential for the serum-induced hepcidin transcription, although serum treatment does not stimulate the BMP pathway. The induction of c-fos and junB by serum treatment stimulates hepcidin transcription, through possibly cooperation with BMP-mediated signaling. Considering that AP-1 is induced by various stimuli, the present results suggest that hepcidin expression is regulated by more diverse factors than had been previously considered.
authors.affiliation: Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kanamori
authors.affiliation: Laboratory of Molecular Biology, Azabu University School of Veterinary Medicine, Sagamihara 252-5201, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Matsui
authors.affiliation: Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan. Electronic address: mfunaba@kais.kyoto-u.ac.jp.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Funaba
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D019485:Bone Morphogenetic Proteins / Q000235:genetics; D045744:Cell Line, Tumor; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D064451:Hepcidins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D061251:Primary Cell Culture; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D020218:Response Elements / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050791:STAT Transcription Factors / Q000378:metabolism; D044967:Serum / Q000737:chemistry*; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; D003470:Culture Media; D064451:Hepcidins; C554430:LDN 193189; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011720:Pyrazoles; D011743:Pyrimidines; D050791:STAT Transcription Factors; D018808:Transcription Factor AP-1
keywords: AP-1; BMP; Hepcidin; Liver; Serum