title: The SMAD Pathway Is Required for Hepcidin Response During Endoplasmic Reticulum Stress.
abstract: Hepcidin, the iron hormone, is regulated by a number of stimulatory and inhibitory signals. The cAMP responsive element binding protein 3-like 3 (CREB3L3) mediates hepcidin response to endoplasmic reticulum (ER) stress. In this study we asked whether hepcidin response to ER stress also requires the small mother against decapentaplegic (SMAD)-1/5/8 pathway, which has a major role in hepcidin regulation in response to iron and other stimuli. We analyzed hepcidin mRNA expression and promoter activity in response to ER stressors in HepG2 cells in the presence of the bone morphogenetic protein (BMP) type I receptor inhibitor LDN-193189, mutated hepcidin promoter or small interfering RNA against different SMAD proteins. We then used a similar approach in vivo in wild-type, Smad1/5, or Creb3l3-/-animals undergoing ER stress. In vitro, LDN-193189 prevented hepcidin mRNA induction by different ER stressors. Seemingly, mutation of a BMP-responsive element in the hepcidin promoter prevented ER stress-mediated up-regulation. Moreover, in vitro silencing of SMAD proteins by small interfering RNA, in particular SMAD5, blunted hepcidin response to ER stress. On the contrary, hepcidin induction by ER stress was maintained when using antibodies against canonical BMP receptor ligands. In vivo, hepcidin was induced by ER stress and prevented by LDN-193189. In addition, in Smad1/5 knockout mice, ER stress was unable to induce hepcidin expression. Finally, in Creb3l3 knockout mice, in response to ER stress, SMAD1/5 were correctly phosphorylated and hepcidin induction was still appreciable, although to a lesser extent as compared with the control mice. In conclusion, our study indicates that hepcidin induction by ER stress involves the central regulatory SMAD1/5 pathway.
authors.affiliation: Center for Hemochromatosis (S.C., C.V., C.G., G.M., A.P.), University of Modena and Reggio Emilia, University Hospital of Modena, 41100 Modena, Italy; and Program in Anemia Signaling Research (S.C., J.L.B.), Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Susanna
authors.initials: S
authors.lastname: Canali
authors.affiliation: Center for Hemochromatosis (S.C., C.V., C.G., G.M., A.P.), University of Modena and Reggio Emilia, University Hospital of Modena, 41100 Modena, Italy; and Program in Anemia Signaling Research (S.C., J.L.B.), Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Chiara
authors.initials: C
authors.lastname: Vecchi
authors.affiliation: Center for Hemochromatosis (S.C., C.V., C.G., G.M., A.P.), University of Modena and Reggio Emilia, University Hospital of Modena, 41100 Modena, Italy; and Program in Anemia Signaling Research (S.C., J.L.B.), Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Garuti
authors.affiliation: Center for Hemochromatosis (S.C., C.V., C.G., G.M., A.P.), University of Modena and Reggio Emilia, University Hospital of Modena, 41100 Modena, Italy; and Program in Anemia Signaling Research (S.C., J.L.B.), Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Montosi
authors.affiliation: Center for Hemochromatosis (S.C., C.V., C.G., G.M., A.P.), University of Modena and Reggio Emilia, University Hospital of Modena, 41100 Modena, Italy; and Program in Anemia Signaling Research (S.C., J.L.B.), Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Jodie L
authors.initials: JL
authors.lastname: Babitt
authors.affiliation: Center for Hemochromatosis (S.C., C.V., C.G., G.M., A.P.), University of Modena and Reggio Emilia, University Hospital of Modena, 41100 Modena, Italy; and Program in Anemia Signaling Research (S.C., J.L.B.), Division of Nephrology, Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114.
authors.forename: Antonello
authors.initials: A
authors.lastname: Pietrangelo
mesh_terms: D000818:Animals; D059865:Endoplasmic Reticulum Stress; D056945:Hep G2 Cells; D064451:Hepcidins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008810:Mice, Inbred C57BL; D015398:Signal Transduction; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism*
chemical_list: D064451:Hepcidins; D051896:Smad Proteins, Receptor-Regulated