Identification of a novel anoikis signalling pathway using the fungal virulence factor gliotoxin

Nat Commun. 2018 Aug 30;9(1):3524. doi: 10.1038/s41467-018-05850-w.

Abstract

Anoikis is a form of apoptosis induced by cell detachment. Integrin inactivation plays a major role in the process but the exact signalling pathway is ill-defined. Here we identify an anoikis pathway using gliotoxin (GT), a virulence factor of the fungus Aspergillus fumigatus, which causes invasive aspergillosis in humans. GT prevents integrin binding to RGD-containing extracellular matrix components by covalently modifying cysteines in the binding pocket. As a consequence, focal adhesion kinase (FAK) is inhibited resulting in dephosphorylation of p190RhoGAP, allowing activation of RhoA. Sequential activation of ROCK, MKK4/MKK7 and JNK then triggers pro-apoptotic phosphorylation of Bim. Cells in suspension or lacking integrin surface expression are insensitive to GT but are sensitised to ROCK-MKK4/MKK7-JNK-dependent anoikis upon attachment to fibronectin or integrin upregulation. The same signalling pathway is triggered by FAK inhibition or inhibiting integrin αV/β3 with Cilengitide. Thus, GT can target integrins to induce anoikis on lung epithelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amides
  • Animals
  • Anoikis / genetics
  • Anoikis / physiology*
  • Cell Line
  • Flow Cytometry
  • Gliotoxin / metabolism*
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • MAP Kinase Kinase 4 / genetics
  • MAP Kinase Kinase 4 / metabolism
  • MAP Kinase Kinase 7 / genetics
  • MAP Kinase Kinase 7 / metabolism
  • Mice
  • Mice, Knockout
  • Mutagenesis, Site-Directed
  • Pyridines
  • Signal Transduction / genetics
  • Signal Transduction / physiology*
  • Virulence Factors / metabolism*
  • rho-Associated Kinases / genetics
  • rho-Associated Kinases / metabolism

Substances

  • Amides
  • Pyridines
  • Virulence Factors
  • Y 27632
  • Gliotoxin
  • rho-Associated Kinases
  • MAP Kinase Kinase 4
  • MAP Kinase Kinase 7