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Thromb Res. 2014 Aug;134(2):418-25. doi: 10.1016/j.thromres.2014.06.001. Epub 2014 Jun 11.

The neutrophil serine protease PR3 induces shape change of platelets via the Rho/Rho kinase and Ca(2+) signaling pathways.

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Department of Nephrology, Qingyuan City Hospital of Jinan University, Guangdong, China; Department of Medical and Health Sciences, Linköping University, Linköping, Sweden(1). Electronic address:
Department of Experimental and Clinical Medicine, Linköping University, Linköping, Sweden.
Department of Medical and Health Sciences, Linköping University, Linköping, Sweden(1).
Department of Medical and Health Sciences, Linköping University, Linköping, Sweden(1); School of Medicine, Örebro University, Örebro, Sweden.



Proteinase 3 (PR3) is released from neutrophil azurophilic granules and exerts complex effects on the inflammatory process. PR3 catalyzes the degradation of a number of macromolecules, but the consequences on blood cells are less well defined. In the present study, the effect of PR3 on human platelets was thoroughly investigated.


The experiments were performed on washed platelets freshly isolated from blood donated by healthy human volunteers. Platelets shape change and aggregation was measured on a Chrono-Log aggregometer. The phosphorylated form of MYPT1 was visualized by immunostaining. Platelet activation was further evaluated by flow cytometry.


PR3 induced platelet shape change but not aggregation. Flow cytometry analysis showed that PR3 induced no P-selectin expression or binding of fibrinogen to the platelets, and it did not change the activation in response to PAR1- or PAR4-activating peptides or to thrombin. Furthermore, Fura-2 measurement and immuno-blotting analysis, respectively, revealed that PR3 stimulated small intracellular Ca(2+) mobilization and Thr696-specific phosphorylation of the myosin phosphatase target subunit 1 (MYPT1). Separate treatment of platelets with the Rho/Rho kinase inhibitor Y-27632 and the intracellular Ca(2+) chelator BAPTA/AM reduced the shape change induced by PR3 whereas concurrent treatment completely inhibited it.


The data shows that the neutrophil protease PR3 is a direct modulator of human platelets and causes shape change through activation of the Rho/Rho kinase and Ca(2+) signaling pathways. This finding highlights an additional mechanism in the complex interplay between neutrophils and platelets.


ANCA-associated vasculitis; Ca(2+) signaling pathway; Platelet shape change; Proteinase PR3; Rho/Rho kinase signaling pathway

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