Biomaterial Database

Formation of protease nexin-thrombin complexes on the platelet surface. 1986

R S Gronke, and T K Curry, and J B Baker

We have recently described a platelet factor that is similar to the fibroblast thrombin inhibitor protease nexin I (PNI). The present manuscript shows that this platelet form of PN (PNp) does not complex [125I]-thrombin that has been blocked at its active site, consistent with the conclusion that it is a thrombin inhibitor. When platelets are incubated with [125I]-thrombin, PNp-[125I]-thrombin complexers accumulate both in the medium and on the platelet surface. In the case of fibroblasts, PNI-[125I]-thrombin complexes that form in solution bind to the cells as a consequence of a receptor-mediated clearance process [Low et al, Proc Natl Acad Sci USA 78:2340, 1981]. We show here that the PNp-[125I]-thrombin complexes that accumulate in platelet-binding incubation medium do not bind to platelets. Thus, the platelet-associated complexes must form by [125I]-thrombin binding to PNp that is associated with the platelet surface. Pretreatment of platelets with heparin markedly increases the number of PNp-[125I]-thrombin complexes that form on platelets. The basis for this increase is unclear. This effect seems incompatible with a heparinlike factor acting as the surface binding site for PNp.

UI	MeSH Term	Description	Entries
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D001792	Blood Platelets	Non-nucleated disk-shaped cells formed in the megakaryocyte and found in the blood of all mammals. They are mainly involved in blood coagulation.	Platelets,Thrombocytes,Blood Platelet,Platelet,Platelet, Blood,Platelets, Blood,Thrombocyte
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D006493	Heparin	A highly acidic mucopolysaccharide formed of equal parts of sulfated D-glucosamine and D-glucuronic acid with sulfaminic bridges. The molecular weight ranges from six to twenty thousand. Heparin occurs in and is obtained from liver, lung, mast cells, etc., of vertebrates. Its function is unknown, but it is used to prevent blood clotting in vivo and vitro, in the form of many different salts.	Heparinic Acid,alpha-Heparin,Heparin Sodium,Liquaemin,Sodium Heparin,Unfractionated Heparin,Heparin, Sodium,Heparin, Unfractionated,alpha Heparin
D006629	Hirudins	Single-chain polypeptides of about 65 amino acids (7 kDa) from LEECHES that have a neutral hydrophobic N terminus, an acidic hydrophilic C terminus, and a compact, hydrophobic core region. Recombinant hirudins lack tyr-63 sulfation and are referred to as 'desulfato-hirudins'. They form a stable non-covalent complex with ALPHA-THROMBIN, thereby abolishing its ability to cleave FIBRINOGEN.	Hirudin
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D013917	Thrombin	An enzyme formed from PROTHROMBIN that converts FIBRINOGEN to FIBRIN.	Thrombase,Thrombin JMI,Thrombin-JMI,Thrombinar,Thrombostat,alpha-Thrombin,beta,gamma-Thrombin,beta-Thrombin,gamma-Thrombin,JMI, Thrombin
D016564	Amyloid beta-Protein Precursor	A single-pass type I membrane protein. It is cleaved by AMYLOID PRECURSOR PROTEIN SECRETASES to produce peptides of varying amino acid lengths. A 39-42 amino acid peptide, AMYLOID BETA-PEPTIDES is a principal component of the extracellular amyloid in SENILE PLAQUES.	Amyloid A4 Protein Precursor,Amyloid Protein Precursor,beta-Amyloid Protein Precursor,Amyloid beta Precursor Protein,Protease Nexin 2,Protease Nexin II,Amyloid beta Protein Precursor,Nexin 2, Protease,Nexin II, Protease,beta Amyloid Protein Precursor,beta-Protein Precursor, Amyloid
D058255	Protease Nexins	Extracellular protease inhibitors that are secreted from FIBROBLASTS. They form a covalent complex with SERINE PROTEASES and can mediate their cellular internalization and degradation.	Nexin, Protease,Nexin, Protease-Associated,Nexin, Protease Associated,Nexins, Protease,Protease Nexin,Protease-Associated Nexin