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An acquired defect associated with abnormal signaling of the platelet collagen receptor glycoprotein VI

Jianlin Qiao1, Jane F Arthur, Margaret Collecutt

  • 1Australian Centre for Blood Diseases, Monash University, Melbourne, Vic., Australia.

Acta Haematologica
|August 28, 2012
PubMed
Abstract

Insights

Platelet glycoprotein VI (GPVI) signaling can generate reactive oxygen species (ROS) independently of Syk activation. This study reveals novel divergent pathways in GPVI signaling, impacting ROS production and platelet function in a patient with myelodysplastic syndrome.

Area of Science:

  • Hematology
  • Platelet Biology
  • Molecular Signaling

Background:

  • Platelet activation via glycoprotein VI (GPVI) involves Syk-dependent signaling and reactive oxygen species (ROS) generation.
  • Metalloproteinase-mediated shedding of GPVI can occur through various signaling pathways.

Purpose of the Study:

  • To analyze platelet GPVI expression and signaling in a patient with myelodysplastic syndrome (MDS) and a collagen-selective defect.
  • To investigate divergent pathways of ROS generation and Syk phosphorylation in human platelets.

Main Methods:

  • Quantification of GPVI surface expression and ligand-induced ROS generation using flow cytometry.
  • Analysis of GPVI shedding and Syk phosphorylation via Western blot.

Main Results:

  • Platelets exhibited normal GPVI surface expression but lacked aggregation response to collagen or GPVI-selective agonists.
  • Rapid GPVI-dependent, Syk-independent ROS generation and disulfide-dependent GPVI homodimerization were observed.
  • Ligand-induced platelet aggregation and GPVI ectodomain shedding were absent, while Syk phosphorylation occurred gradually.

Conclusions:

  • Platelet GPVI ligation induces ROS production independently of Syk activation.
  • Divergent pathways exist for ROS generation, platelet aggregation, and GPVI ectodomain shedding.

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