Endofin, a novel BMP-SMAD regulator of the iron-regulatory hormone, hepcidin

Sci Rep. 2015 Sep 11;5:13986. doi: 10.1038/srep13986.

Abstract

BMP-SMAD signalling plays a crucial role in numerous biological processes including embryonic development and iron homeostasis. Dysregulation of the iron-regulatory hormone hepcidin is associated with many clinical iron-related disorders. We hypothesised that molecules which mediate BMP-SMAD signalling play important roles in the regulation of iron homeostasis and variants in these proteins may be potential genetic modifiers of iron-related diseases. We examined the role of endofin, a SMAD anchor, and show that knockdown of endofin in liver cells inhibits basal and BMP-induced hepcidin expression along with other BMP-regulated genes, ID1 and SMAD7. We show for the first time, the in situ interaction of endofin with SMAD proteins and significantly reduced SMAD phosphorylation with endofin knockdown, suggesting that endofin modulates hepcidin through BMP-SMAD signalling. Characterisation of naturally occurring SNPs show that mutations in the conserved FYVE domain result in mislocalisation of endofin, potentially affecting downstream signalling and modulating hepcidin expression. In conclusion, we have identified a hitherto unrecognised link, endofin, between the BMP-SMAD signalling pathway, and the regulation of hepcidin expression and iron homeostasis. This study further defines the molecular network involved in iron regulation and provides potential targets for the treatment of iron-related disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bone Morphogenetic Protein 6 / metabolism
  • Bone Morphogenetic Proteins / metabolism*
  • Cell Line
  • Gene Expression Regulation
  • Gene Knockdown Techniques
  • Gene Silencing
  • Hepcidins / genetics
  • Hepcidins / metabolism*
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Iron / metabolism*
  • Models, Biological
  • Mutation
  • Phosphorylation
  • Polymorphism, Genetic
  • Protein Binding
  • Protein Transport
  • Serine Endopeptidases / genetics
  • Serine Endopeptidases / metabolism*
  • Smad Proteins / metabolism*
  • Smad1 Protein / metabolism

Substances

  • Bone Morphogenetic Protein 6
  • Bone Morphogenetic Proteins
  • Hepcidins
  • Intracellular Signaling Peptides and Proteins
  • Smad Proteins
  • Smad1 Protein
  • Iron
  • ZFYVE16 protein, human
  • Serine Endopeptidases