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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
Summary
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.
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