Thromb Haemost 2013; 109(03): 532-539
DOI: 10.1160/TH12-06-0404
Platelets and Blood Cells
Schattauer GmbH

Omi/HtrA2 and XIAP are components of platelet apoptosis signalling

Jeannine Winkler
1   Division of Haematology and Children’s Research Center, University Children’s Hospital Zurich, Zurich, Switzerland
2   Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland, University of Zurich, Switzerland
,
Margaret L. Rand
3   Division of Haematology / Oncology, The Hospital for Sick Children, Toronto, Ontario, Canada
,
Markus Schmugge
1   Division of Haematology and Children’s Research Center, University Children’s Hospital Zurich, Zurich, Switzerland
,
Oliver Speer
1   Division of Haematology and Children’s Research Center, University Children’s Hospital Zurich, Zurich, Switzerland
2   Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland, University of Zurich, Switzerland
› Author Affiliations
Financial support: This work was supported by the Theodor und Ida Herzog-Egli Stiftung Zurich, a donation made by UBS AG by order of a client, the EMDO Foundation Zurich and the Children’s Research Center Zurich.
Further Information

Publication History

Received: 15 June 2012

Accepted after major revision: 05 January 2012

Publication Date:
29 November 2017 (online)

Summary

Although platelets possess the hallmarks of apoptosis such as activation of caspases, cytochrome c release and depolarisation of the mitochondrial transmembrane potential (ΔΨm), their entire apoptotic-signalling pathway is not totally understood. Therefore we studied the expression of various apoptotic proteins and found that platelets contain the pro-apoptotic proteins Omi/HtrA2 and Smac/Diablo, as well as their target the X-linked inhibitor of apoptosis XIAP. Omi/HtrA2 and Smac/Diablo were released from mitochondria into the platelet cytosol together with cytochrome c after induction of apoptosis by the Ca2+ ionophore A23187 or the BH3 mimetic ABT-737, and to a lesser extent, after platelet stimulation with collagen and thrombin. Inhibition of Omi/HtrA2 led to decreased levels of activated caspase-3/7 and caspase-9, but did not abolish loss of ΔΨm or prevent release of Omi/HtrA2 from mitochondria. These results indicate that platelets have a functional intrinsic apoptotic-signalling pathway including the pro-apoptotic protease Omi/HtrA2 and its target protein XIAP.

 
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