OTULIN allies with LUBAC to govern angiogenesis by editing ALK1 linear polyubiquitin

Mol Cell. 2021 Aug 5;81(15):3187-3204.e7. doi: 10.1016/j.molcel.2021.05.031. Epub 2021 Jun 21.


OTULIN coordinates with LUBAC to edit linear polyubiquitin chains in embryonic development, autoimmunity, and inflammatory diseases. However, the mechanism by which angiogenesis, especially that of endothelial cells (ECs), is regulated by linear ubiquitination remains unclear. Here, we reveal that constitutive or EC-specific deletion of Otulin resulted in arteriovenous malformations and embryonic lethality. LUBAC conjugates linear ubiquitin chains onto Activin receptor-like kinase 1 (ALK1), which is responsible for angiogenesis defects, inhibiting ALK1 enzyme activity and Smad1/5 activation. Conversely, OTULIN deubiquitinates ALK1 to promote Smad1/5 activation. Consistently, embryonic survival of Otulin-deficient mice was prolonged by BMP9 pretreatment or EC-specific ALK1Q200D (constitutively active) knockin. Moreover, mutant ALK1 from type 2 hereditary hemorrhagic telangiectasia (HHT2) patients exhibited excessive linear ubiquitination and increased HOIP binding. As such, a HOIP inhibitor restricted the excessive angiogenesis of ECs derived from ALK1G309S-expressing HHT2 patients. These results show that OTULIN and LUBAC govern ALK1 activity to balance EC angiogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activin Receptors, Type II / genetics*
  • Activin Receptors, Type II / metabolism*
  • Adult
  • Animals
  • Endopeptidases / genetics*
  • Endopeptidases / metabolism
  • Endothelial Cells / drug effects
  • Endothelial Cells / metabolism
  • Female
  • Growth Differentiation Factor 2 / pharmacology
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Male
  • Mice, Mutant Strains
  • Multiprotein Complexes / metabolism*
  • Mutation
  • Neovascularization, Pathologic / drug therapy
  • Neovascularization, Pathologic / genetics*
  • Neovascularization, Pathologic / metabolism
  • Neovascularization, Physiologic / genetics
  • Polyubiquitin / metabolism*
  • Smad1 Protein / genetics
  • Smad1 Protein / metabolism
  • Smad5 Protein / genetics
  • Smad5 Protein / metabolism
  • Telangiectasia, Hereditary Hemorrhagic
  • Ubiquitin-Protein Ligases / metabolism


  • Growth Differentiation Factor 2
  • Multiprotein Complexes
  • Smad1 Protein
  • Smad1 protein, mouse
  • Smad5 Protein
  • Smad5 protein, mouse
  • Polyubiquitin
  • RNF31 protein, human
  • Ubiquitin-Protein Ligases
  • ACVRL1 protein, human
  • Activin Receptors, Type II
  • Acvrl1 protein, mouse
  • Endopeptidases
  • gumby protein, mouse

Supplementary concepts

  • Osler-rendu-weber syndrome 2