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FEBS Lett. 1996 May 13;386(1):82-6.

Proteolysis of thrombospondin during cathepsin-G-induced platelet aggregation: functional role of the 165-kDa carboxy-terminal fragment.

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  • 1INSERM Unité 353, Hôpital Saint-Louis, Paris, France.

Abstract

The serine-proteinase cathepsin G (CG) is a potent agonist of platelet aggregation inducing the release and surface expression of alpha-granule adhesive proteins such as fibrinogen (Fg) and thrombospondin-1 (TSP-1). Because Fg and TSP-1 are potential substrates for the enzymatic activity of CG, we investigated the fate of these proteins during CG-induced platelet aggregation using an immunoblot technique. Only a small proportion of secreted Fg was proteolyzed by CG and platelet aggregation was efficiently inhibited by anti-fibrinogen Fab fragments. In contrast, TSP-1 was extensively proteolyzed on aggregated platelets releasing in the milieu a fragment with Mr approximately 28 000, corresponding to the amino-terminal heparin-binding domain (HBD). Several antibodies, directed against the cell-associated carboxy-terminal TSP-1f fragment (Mr approximately 165000) impaired the formation of stable macroaggregates, indicating that this fragment may contribute to platelet aggregation in the absence of the HBD.

PMID:
8635609
[PubMed - indexed for MEDLINE]
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