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Abl-mediated PI3K activation regulates macrophage podosome formation

Yuhuan Zhou1, Zhen Feng1, Fakun Cao1

  • 1School of Biomedical Sciences, Faculty of Medicine, University of Hong Kong, Hong Kong.

Journal of Cell Science
|May 13, 2020
PubMed

Insights

Macrophage podosome formation relies on phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3] lipids, which recruit Wiskott-Aldrich syndrome protein (WASP). This process is regulated by PIK3CB, Abl1, and Src/Hck kinases, controlling cell migration and matrix degradation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Immunology

Background:

  • Podosomes are critical for macrophage functions like adhesion and migration.
  • Wiskott-Aldrich syndrome protein (WASP)-mediated actin polymerization initiates podosome formation.
  • The specific membrane signals activating WASP at macrophage podosomes are not fully understood.

Purpose of the Study:

  • To elucidate the signaling pathways regulating WASP activation and podosome assembly in macrophages.
  • To identify the key lipid species and kinases involved in triggering podosome formation.
  • To understand the role of Abl1 and Src family kinases in orchestrating podosome function.

Main Methods:

  • Lipid analysis to detect phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3] enrichment at podosomes.
  • WASP recruitment assays using wild-type and mutant forms.
  • Kinase inhibition and overexpression studies (PIK3CB, PTEN).
  • Phosphorylation site analysis of Abl1 (Tyr488).
  • Gene silencing (Abl1, Abl2) and rescue experiments.
  • Assessment of macrophage podosome formation, matrix degradation, and chemotactic migration.

Main Results:

  • PI(3,4,5)P3 lipids are enriched at podosomes and recruit WASP.
  • Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit β (PIK3CB) is located at the podosome core and is essential for F-actin polymerization.
  • Src and Hck kinases phosphorylate Abl1 at Tyr488, enabling PI3K regulatory subunit association and PIK3CB activation.
  • Abl1 knockdown, but not Abl2, suppresses the PI3K/Akt pathway.
  • Inhibition of PIK3CB, Abl1, or Src/Hck impairs podosome formation, matrix degradation, and macrophage migration.

Conclusions:

  • Src/Hck-mediated Abl1 Tyr488 phosphorylation initiates PIK3CB-dependent PI(3,4,5)P3 production.
  • This signaling cascade orchestrates the assembly and function of macrophage podosomes, including adhesion, migration, and matrix degradation.
  • The findings reveal a novel signaling pathway crucial for macrophage podosome dynamics and function.
Keywords:
AblPI(3,4,5)P3 lipidPI3KPodosome

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