Ubiquitin E3 ligase FIEL1 regulates fibrotic lung injury through SUMO-E3 ligase PIAS4

J Exp Med. 2016 May 30;213(6):1029-46. doi: 10.1084/jem.20151229. Epub 2016 May 9.


The E3 small ubiquitin-like modifier (SUMO) protein ligase protein inhibitor of activated STAT 4 (PIAS4) is a pivotal protein in regulating the TGFβ pathway. In this study, we discovered a new protein isoform encoded by KIAA0317, termed fibrosis-inducing E3 ligase 1 (FIEL1), which potently stimulates the TGFβ signaling pathway through the site-specific ubiquitination of PIAS4. FIEL1 targets PIAS4 using a double locking mechanism that is facilitated by the kinases PKCζ and GSK3β. Specifically, PKCζ phosphorylation of PIAS4 and GSK3β phosphorylation of FIEL1 are both essential for the degradation of PIAS4. FIEL1 protein is highly expressed in lung tissues from patients with idiopathic pulmonary fibrosis (IPF), whereas PIAS4 protein levels are significantly reduced. FIEL1 overexpression significantly increases fibrosis in a bleomycin murine model, whereas FIEL1 knockdown attenuates fibrotic conditions. Further, we developed a first-in-class small molecule inhibitor toward FIEL1 that is highly effective in ameliorating fibrosis in mice. This study provides a basis for IPF therapeutic intervention by modulating PIAS4 protein abundance.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bleomycin / adverse effects
  • Bleomycin / pharmacology
  • Cell Line
  • Disease Models, Animal
  • Glycogen Synthase Kinase 3 beta / genetics
  • Glycogen Synthase Kinase 3 beta / metabolism
  • Humans
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Lung / metabolism*
  • Lung / pathology
  • Mice
  • Poly-ADP-Ribose Binding Proteins
  • Protein Inhibitors of Activated STAT / genetics
  • Protein Inhibitors of Activated STAT / metabolism*
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism
  • Protein Kinase C-theta
  • Pulmonary Fibrosis / chemically induced
  • Pulmonary Fibrosis / genetics
  • Pulmonary Fibrosis / metabolism*
  • Pulmonary Fibrosis / pathology
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination*


  • Isoenzymes
  • PIAS4 protein, human
  • Poly-ADP-Ribose Binding Proteins
  • Protein Inhibitors of Activated STAT
  • Bleomycin
  • Ubiquitin-Protein Ligases
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, mouse
  • PRKCQ protein, human
  • Prkcq protein, mouse
  • Protein Kinase C
  • Protein Kinase C-theta

Associated data

  • PDB/2XBF