title: Platelets and plasminogen activation.
abstract: Platelets serve as a site for assembly of the proteins of the plasminogen activator system. Once bound to the platelet surface, tissue-type plasminogen activator manifests enhanced catalytic activity. Plasmin, once formed, also binds to the platelets surface and, at low concentrations, renders the platelet dysfunctional by cleaving glycoprotein IIIa selectively in the presence of bound fibrinogen. At higher concentrations (approximately 1 caseinolytic unit/ml), plasmin activates the platelet directly. Activated platelets also bind plasminogen and tissue-type plasminogen activator, and manifest enhanced catalytic efficiency of plasminogen activation. These observations suggest that plasminogen activation by tissue-type plasminogen activator is an autocatalytic process on the platelet surface, and that unique reciprocating mechanisms govern the interaction between platelets and the components of the plasminogen activator system.
authors.affiliation: Whitaker Cardiovascular Institute, Evans Department of Medicine, Boston University School of Medicine, MA 02118-2394, USA.
authors.forename: J
authors.initials: J
authors.lastname: Loscalzo
authors.forename: B
authors.initials: B
authors.lastname: Pasche
authors.forename: H
authors.initials: H
authors.lastname: Ouimet
authors.forename: J E
authors.initials: JE
authors.lastname: Freedman
mesh_terms: D001792:Blood Platelets / Q000502:physiology*; D002384:Catalysis; D002462:Cell Membrane / Q000502:physiology; D004789:Enzyme Activation; D005340:Fibrinogen / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D005342:Fibrinolysis / Q000502:physiology; D006801:Humans; D010958:Plasminogen / Q000378:metabolism*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D010959:Tissue Plasminogen Activator / Q000378:metabolism
chemical_list: D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D005340:Fibrinogen; D010958:Plasminogen; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin