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Protein phosphatase 2A negatively regulates integrin alpha(IIb)beta(3) signaling
Francisca C Gushiken1, Vimal Patel, Yan Liu
1Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
The Journal of Biological Chemistry
|March 13, 2008
Summary
Protein phosphatase 2A catalytic subunit (PP2Ac) directly binds to integrin alpha(IIb)beta(3), negatively regulating platelet activation and adhesion signaling pathways like ERK1/2.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Integrin alpha(IIb)beta(3) activation is crucial for platelet function.
- The role of phosphatases in integrin alpha(IIb)beta(3) signaling is less understood compared to kinases.
Purpose of the Study:
- To investigate the role of protein phosphatase 2A catalytic subunit (PP2Ac) in integrin alpha(IIb)beta(3) signaling.
- To elucidate the mechanism by which PP2Ac regulates integrin-mediated platelet adhesion.
Main Methods:
- Co-immunoprecipitation to demonstrate PP2Ac-integrin alpha(IIb)beta(3) association.
- Site-directed mutagenesis to identify the binding sequence.
- Cell adhesion assays in HEK293 cells and primary megakaryocytes.
- Western blotting to assess protein phosphorylation and signaling pathway activation.
- Small interference RNA (siRNA) mediated knockdown of PP2Ac.
Main Results:
- PP2Ac constitutively associates with integrin alpha(IIb)beta(3) via the KVGFFKR sequence.
- Fibrinogen binding reduces PP2A activity and increases vasodilator-associated phosphoprotein phosphorylation.
- Overexpression of PP2Ac decreases alpha(IIb)beta(3) adhesion; PP2Ac knockdown enhances adhesion and ERK1/2/p38 activation.
- ERK1/2 inhibition reverses the enhanced adhesion in PP2Ac-depleted cells.
- PP2Ac knockdown in megakaryocytes increases soluble fibrinogen binding.
Conclusions:
- PP2Ac negatively regulates integrin alpha(IIb)beta(3) signaling.
- PP2Ac suppresses the ERK1/2 signaling pathway, thereby controlling platelet adhesion.
- This study reveals a novel regulatory mechanism for integrin alpha(IIb)beta(3) function by PP2Ac.
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