Thromb Haemost 2013; 109(06): 1131-1140
DOI: 10.1160/TH12-09-0645
Platelets and Blood Cells
Schattauer GmbH

Dextran sulphate induces fibrinogen receptor activation through a novel Syk-independent PI-3 kinase-mediated tyrosine kinase pathway in platelets

Todd M. Getz
1   Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
3   Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
,
Bhanu Kanth Manne
1   Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
3   Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
,
Lorena Buitrago
1   Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
3   Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
,
Yingying Mao
1   Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
3   Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
,
Satya P. Kunapuli
1   Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
2   Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
3   Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania, USA
› Author Affiliations

Financial support: This work is supported by HL93231 from National Institutes of Health to SPK. TG is supported by NIH training grant in Thrombosis (HL07777). YM is supported by AHA postdoctoral fellowship 10POST3730006.
Further Information

Publication History

Received: 17 September 2012

Accepted after major revision: 01 March 2013

Publication Date:
22 November 2017 (online)

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Summary

In our attempt to find a physiological agonist that activates PAR3 receptors, we screened several coagulation proteases using PAR4 null platelets. We observed that FXIIa and heat inactivated FXIIa, but not FXII, caused platelet aggregation. We have identified a contaminant activating factor in FXIIa preparation as dextran sulfate (DxS), which caused aggregation of both human and mouse platelets. DxS-induced platelet aggregation was unaffected by YM254890, a Gq inhibitor, but abolished by pan-Src family kinase (SFK) inhibitor PP2, suggesting a role for SFKs in this pathway. However, DxS-induced platelet aggregation was unaffected in FcRγ-chain null murine platelets, ruling out the possibility of glycoprotein VI-mediated events. More interesting, OXSI-2 and Go6976, two structurally unrelated inhibitors shown to affect Syk, had only a partial effect on DxS-induced PAC-1 binding. DxS-induced platelet aggregation and intracellular calcium increases were abolished by the pan PI-3 kinase inhibitor LY294002, or an isoform-specific PI-3 kinase β inhibitor TGX-221. Pretreatment of platelets with Syk inhibitors or ADP receptor antagonists had little effect on Akt phosphorylation following DxS stimulation. These results, for the first time, establish a novel tyrosine kinase pathway in platelets that causes fibrinogen receptor activation in a PI-3 kinase-dependent manner without a crucial role for Syk.