Article: article from journal or magazin.
Stimulated platelets use serotonin to enhance their retention of procoagulant proteins on the cell surface.
Publication types: Journal Article Publication Status: ppublish
Activated platelets bind numerous adhesive and procoagulant proteins by receptor-mediated processes. Although there is little evidence to suggest that these processes are heterogeneous in platelets, we previously found that platelets co-stimulated with collagen and thrombin express functional alpha-granule factor V only on a subpopulation of cells. Here we show that these cells, referred to as 'COAT-platelets', bind additional alpha-granule proteins, including fibrinogen, von Willebrand factor, thrombospondin, fibronectin and alpha2-antiplasmin. These proteins are all transglutaminase substrates, and inhibitors of transglutaminase prevent the production of COAT-platelets. A synthetic transglutaminase substrate (CP15) also binds to COAT-platelets, and analysis by high performance liquid chromatography/mass spectrometry shows that a product is formed with a relative molecular mass (Mr) equal to CP15 plus 176. Serotonin, an abundant component of platelet-dense granules, has an Mr of 176, and fibrinogen isolated from COAT-platelets contains covalently linked serotonin. Synthetic bovine serum albumin-(serotonin)6 binds selectively to COAT-platelets and also inhibits the retention of procoagulant proteins on COAT-platelets. These data indicate that COAT-platelets use serotonin conjugation to augment the retention of procoagulant proteins on their cell surface through an as yet unidentified serotonin receptor.
Amino Acid Sequence, Animals, Biotin/metabolism, Blood Coagulation, Blood Coagulation Factors, Blood Platelets/metabolism, Cell Membrane/metabolism, Factor V/metabolism, Factor XIII/metabolism, Fibrinogen, Humans, Molecular Sequence Data, Peptides/metabolism, Platelet Activation, Platelet Glycoprotein GPIb-IX Complex/metabolism, Protein Binding, Serotonin, Transglutaminases/metabolism
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