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Protease-activated receptor 4 causes Akt phosphorylation independently of PI3 kinase pathways

Carol Dangelmaier1, Satya P Kunapuli1

  • 1Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA.

Platelets
|August 20, 2020
PubMed

Insights

Phosphoinositide 3-kinase (PI3K) regulates platelet activation. This study reveals distinct pathways for Akt phosphorylation induced by Protease-activated receptor 1 (PAR1) versus Protease-activated receptor 4 (PAR4) agonists.

Area of Science:

  • Biochemistry
  • Hematology
  • Molecular Biology

Background:

  • Phosphoinositide 3-kinase (PI3K) is crucial for platelet activation, primarily via RASA3 regulation.
  • Akt phosphorylation serves as a key indicator of PI3K activity within platelets.

Purpose of the Study:

  • To elucidate the specific signaling pathways responsible for Akt phosphorylation in platelets.
  • To differentiate the mechanisms of Akt activation by various platelet agonists.

Main Methods:

  • Concentration-response experiments using LY294002, a PI3K inhibitor, were conducted on human and mouse platelets.
  • Platelet aggregation and Akt phosphorylation levels were measured following stimulation with agonists like 2MeSADP, SFLLRN, and AYPGKF.

Main Results:

  • Low LY294002 concentrations (3.12 µM) inhibited Akt phosphorylation induced by 2MeSADP and SFLLRN (PAR1 agonists).
  • Higher LY294002 concentrations (12.5–25 µM) were required to inhibit Akt phosphorylation induced by AYPGKF (PAR4 agonist), irrespective of P2Y12 receptor status.
  • These findings suggest that PI3K isoforms are inhibited at low LY294002 concentrations, while higher doses may affect alternative pathways.

Conclusions:

  • Protease-activated receptor 4 (PAR4) mediates Akt phosphorylation through signaling cascades distinct from those activated by Protease-activated receptor 1 (PAR1).
  • The study highlights the differential regulation of Akt phosphorylation in platelets by various receptor pathways.
Keywords:
LY294002PARPI-3 kinaseplatelet Aggregationplatelets

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