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Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/17892

Title: Fibrinogen controls human platelet fibronectin internalization and cell-surface retention
Authors: Zhai, Z
Wu, J
Xu, X
Ding, K
Ni, R
Hu, W
Sun, Z
Ni, H
Department: Laboratory Medicine and Pathobiology
St. Michael's Hospital
Keywords: factor XIII
hypofibrinogenemic patient
platelet aggregation
Issue Date: 1-Aug-2007
Publisher: Blackwell Publishing
Citation: Zhai Z et al. Fibrinogen controls human platelet fibronectin internalization and cell-surface retention. J Thromb Haemost. 2007;5(8):1740-6.
Abstract: BACKGROUND: We recently demonstrated that platelet aggregation occurred in fibrinogen-deficient mice. In these animals, platelet fibronectin (Fn) content was increased 3-5 fold, suggesting that Fn may also be involved in platelet aggregation. METHODS AND RESULTS: We compared platelet Fn content from a severe hypofibrinogenemic patient (with approximately 0.5% of normal fibrinogen levels) with his parents (heterozygous) and healthy donors. A significant increase in the patient's platelet Fn content was detected by immunoblot, flow cytometry, and immunoelectron microscopy (IEM). To examine the possible contribution of platelet Fn to platelet aggregation, we examined cell-surface Fn expression after thrombin treatment. Unexpectedly, IEM detected only trace amounts of Fn retained on the patient's platelet surface, and flow cytometry indicated that surface Fn was approximately 6-fold lower than that of his parents and tenfold lower than that of healthy donors. An ELISA further confirmed that the patient's platelet Fn was primarily released into the extracellular medium. To test whether retention of surface Fn was due to fibrin formation on the platelet surface, an antifibrin antibody (T2 G1) was employed. Fibrin was detected on platelets from healthy donors and from the father, but was negligible on the patient's platelets. Consistent with these data, when gel-filtered platelets of healthy donors were treated with thrombin receptor activation peptide (SFLLRN-NH(2); no conversion of fibrinogen to fibrin), little surface Fn was detected. CONCLUSION: Fibrinogen not only competitively inhibits human platelet Fn internalization but also controls platelet-surface Fn retention via fibrin formation. The Fn-fibrin interaction is one possible mechanism to promote Fn interaction with platelets.
URI: http://hdl.handle.net/1807/17892
ISSN: 1538-7933
Appears in Collections:Faculty Publications

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