Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A kininogen binding protein(s), a putative receptor, was identified on endothelial cells. A 54-kDa protein was isolated by a biotin-high molecular mass kininogen (HK) affinity column that, on aminoterminal sequencing of tryptic digests, was identified as cytokeratin 1. Multiple antibodies directed to cytokeratin 1 reacted with a 54-kDa band on immunoblot of lysates of endothelial cells. On laser scanning confocal microscopy, cytokeratin 1 antigen was found on the surface of endothelial cells. Cytokeratin 1 antigen also was detected on endothelial cell membranes by flow cytometry. Moreover, an antipeptide antibody to a sequence unique to cytokeratin 1 also specifically bound to nonpermeabilized endothelial cells. Biotin-HK specifically bound to cytokeratin only in the presence of Zn2+, and cytokeratin blocked biotin-HK binding to endothelial cells. Further, HK and low molecular mass kininogen, but not factor XII, blocked biotin-HK binding to cytokeratin, and peptides of each cell binding region of HK on domains 3,4, and 5 blocked biotin-HK binding to cytokeratin. gC1qR and soluble urokinase-like plasminogen activator receptor also inhibited biotin-HK binding to cytokeratin. These investigations identify a new function for cytokeratin 1 as a kininogen binding protein. Cytokeratins, members of the family of intermediate filament proteins, may represent a new class of receptors.
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PMID:Identification of cytokeratin 1 as a binding protein and presentation receptor for kininogens on endothelial cells. 952 Apr 14

A new hypothesis for activation of the contact system of plasma proteolysis (i.e., the plasma kallikrein/kinin system) is presented. Kininogens have a multiprotein receptor on endothelial cells which consists of at least cytokeratin 1, urokinase plasminogen activator receptor, and gC1qR. When contact proteins (high molecular weight kininogen followed by prekallikrein) assemble on the kininogen receptor on endothelial cells, an endothelial cell membrane cysteine protease is expressed to activate prekallikrein to kallikrein. On endothelial cells, prekallikrein activation is independent of factor XIIa activation. Activation of prekallikrein on endothelial cells results in kallikrein cleaving its receptor high molecular weight kininogen to liberate bradykinin. Bradykinin liberation stimulates release of tissue-type plasminogen activator from endothelial cells. Kallikrein formation also results in kinetically favorable pro-urokinase activation on endothelial cells with subsequent plasminogen activation. In addition to stimulating cellular fibrinolysis, kininogens contribute to the constitutive anticoagulant nature of the intravascular compartment. Kininogens block calpain's participation in forming the heterodimeric complex of platelet integrin alpha IIb beta 3. Kininogens also block thrombin from binding to the thrombin receptor(s) on platelets. Last, kininogens prevent thrombin from cleaving protease activated receptor 1 after arginine41. These combined data indicate a biologic system for activation of the plasma kallikrein/kinin system and physiologic consequences as result of this activation.
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PMID:Plasma contact activation: a revised hypothesis. 983 May 13

The cellular localization of human cytokeratin 1 (CK1), urokinase plasminogen activator receptor (uPAR), and gC1qR, high-molecular-weight kininogen (HK)-binding proteins on endothelial cells, was determined. CK1 was found on the external membrane of nonpermeabilized endothelial cells by immunoperoxidase staining, immunofluorescence, and transmission electron microscopy using immunogold. Human umbilical vein endothelial cells (HUVECs) had 7.2 +/- 0.2 x 10(4) specific CK1 membrane sites/cell by (125)I-F(ab')(2) anti-CK1 antibody binding. Flow cytometry studies confirmed the presence of CK1, uPAR, and gC1qR on HUVECs. On laser scanning confocal microscopy and transmission electron microscopy, CK1 and uPAR, but not gC1qR, colocalized on the cell surface of HUVECs. The HUVEC surface distribution of these proteins was distinctly different from that for von Willebrand factor. In competitive inhibition experiments, anti-CK1, anti-uPAR, or anti-gC1qR blocked both biotin-HK binding and prekallikrein (PK) activation on HUVECs with an inhibitory concentration of 50% (IC(50)) of 300 to 350 nM, 50 to 60 nM, or 35 to 100 nM, respectively. Also, antibodies to uPAR and gC1qR each inhibited 86% of kallikrein-mediated, 2-chain urokinase plasminogen activation, whereas antibodies to CK1 only inhibited 24% of plasminogen activation. On HUVECs, CK1 and uPAR, but not gC1qR, colocalized to be a multiprotein receptor complex for HK binding, PK activation, and 2-chain urokinase plasminogen activation.
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PMID:Expression and colocalization of cytokeratin 1 and urokinase plasminogen activator receptor on endothelial cells. 1129 May 96

Investigations determined if extracellular matrix of endothelial cells (EC) is a platform for HK assembly and PK activation. In buffers containing bovine serum albumin, biotin-HK binding to ECV304 cells or their matrix requires > or = 50 microM added Zn2+. Ortho-phenanthroline or a HK domain 5 peptide blocks HK binding. Binding to umbilical vein EC or matrix, but not ECV304 cells or matrix, is mediated by cytokeratin 1. Biotin-HK binds to ECV304 cells or matrix with a Kd of 15.8 or 9.0 nM and a Bmax of 2.6 x 10(7) or 2.4 x 10(7) sites/cell, respectively. PK activation on ECV304 cells or matrix is blocked by antipain or SBTI and corn trypsin inhibitor partially inhibits kallikrein formation. PK activation occurs on ECV304 cells or matrix prepared without serum or in human factor XII deficient serum, indicating that the PK activator is not factor XIIa. EC matrix promotes plasminogen activation after the assembly of HK, PK and pro-urokinase. These studies indicate that matrix of various EC has the ability to assemble HK allowing for PK activation and subsequent activities.
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PMID:Assembly of high molecular weight kininogen and activation of prekallikrein on cell matrix. 1158 17

This review considers the data of recent years concerning the contact system initiating the activation of blood plasma proteolytic systems, such as hemocoagulation, fibrinolysis, kininogenesis, and also complement and angiotensinogenesis. The main proteins of the contact system are the factors XII and XI, prekallikrein, and high-molecular-weight kininogen. The data on the structure, functions, and biosynthesis of these proteins and on their genes are presented. Studies in detail on the protein-protein interactions during formation of the ensemble of the contact system components on the anionic surface resulted in the postulation of the mechanism of activation of this system associated with generation of the XIIa factor and of kallikrein. This mechanism is traditionally considered a trigger of processes for the internal pathway of the hemocoagulating cascade. However, the absence of direct confirmation of such activation in vivo and the absence of hemorrhagia in the deficiency of these components stimulated the studies designed to find another mechanism of their activation and physiological role outside of the hemostasis system. As a result, a new concept on the contact system activation on the endothelial cell membrane was proposed. This concept is based on the isolation of a complex of proteins, which in addition to the above-mentioned proteins includes cytokeratin 1 and the receptors of the urokinase-like plasminogen activator and of the complement q-component. The ideas on the role of this system in the biology of vessels are developed. Some of our findings on the effect of leukocytic elastase on the key components of the contact system are also presented.
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PMID:Contact system. New concepts on activation mechanisms and bioregulatory functions. 1184 36

Understanding the importance and physiologic activity of the plasma kallikrein/kinin system (KKS) has been thwarted by the absence of an inclusive theory for its assembly and activation. The contact activation hypothesis describes the assembly and activation of this system in test tubes and disease states, but not under physiologic circumstances. Recent investigations have indicated a new cohesive hypothesis for understanding physiologic activation of this system. Prekallikrein (PK) and factor XI (FXI) through high molecular weight kininogen (HK) assemble on a co-localized, multiprotein receptor complex on endothelial cells that consists of at least cytokeratin 1 (CKI), gClqR, and urokinase plasminogen activator receptor (muPAR). When assembled on these proteins, prekallikrein becomes activated to kallikrein by the membrane-expressed enzyme prolylcarboxypeptidase (PRCP). Formed kallikrein then activates factor XII (FXII) for amplification of its activation and single chain urokinase. The plasma kallikrein/kinin system may serve as a physiologic counterbalance to the plasma renin angiotensin system (RAS) by lowering blood pressure and preventing thrombosis. Insights into the integrated role of these two systems may afford the development of novel therapeutic drugs to manage hypertension and thrombosis.
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PMID:Assembly and activation of the plasma kallikrein/kinin system: a new interpretation. 1248 98

In human hepatocellular carcinoma (HCC), the high expression of urokinase-type plasminogen activator (uPA) is an unfavorable prognostic factor and a therapeutic target. To identify the downstream effects of uPA silencing by RNA interference, we studied proteome modifications of uPA-inhibited SKHep1C3 cells, an HCC-derived cell line. The study with two-dimensional difference gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry showed Lim and SH3 protein 1 (LASP-1), cytokeratin 1 (CK-1), cytokeratin 10 (CK-10), and heterogeneous nuclear ribonucleoprotein H1 down-modulation after uPA inhibition. LASP-1, CK-1, and CK-10 are involved in cytoskeleton dynamics as heterogeneous nuclear ribonucleoprotein H1 takes part in the mRNA processing and stability. We first confirmed the proteomic data by Western blot and immunoflorescence and then explored the link between uPA and LASP-1. The ectopic expression of uPA and LASP-1 supported the proteomic results and showed that uPA up-regulation increased LASP-1 expression and that both were implicated in SKHep1C3 motility. siRNA LASP-1 inhibition showed that LASP-1 was involved in actin microfilaments organization of SKHep1C3 cells. The disruption of the actin microfilaments after LASP-1 depletion increased uPA secretion and SKHep1C3 motility. Our results would suggest the hypothesis that uPA and LASP-1 expression may be coordinated in HCC-derived cells. In summary, the proteomic identification of a set of uPA downstream proteins provides new insight into the function of uPA in HCC cells.
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PMID:Proteomic identification of LASP-1 down-regulation after RNAi urokinase silencing in human hepatocellular carcinoma cells. 1917 5

The plasma bradykinin-forming cascade and the complement pathways share many elements, including cross-activation, common control mechanisms, and shared binding proteins. The C1 inhibitor (C1 INH) is not only the inhibitor of activated C1r and C1s, but it is the key control protein of the plasma bradykinin-forming cascade. It inhibits the autoactivation of Factor XII, the ability of Factor XIIa to activate prekallikrein and Factor XI, the activation of high molecular weight kininogen (HK) by kallikrein, and the feedback activation of Factor XII by kallikrein. Thus in the absence of C1 INH (hereditary angioedema or acquired C1 INH deficiency) there is unimpeded formation of bradykinin leading to angioedema. Activated Factor XII (Factor XIIa, 80,000 kDa) is further cleaved by kallikrein or plasmin to yield Factor XII fragment (Factor XIIf, 30,000 kDa) and Factor XIIf can activate the C1r subcomponent of C1, particularly when C1 INH (which inhibits Factor XIIf) is absent. Once bradykinin is formed, it causes vasodilatation and increased vascular permeability by interaction with constitutively expressed B-2 receptors. However degradation of bradykinin by carboxypeptidase N (in plasma) or carboxypeptidase M (on endothelial cells) yields des-arg-9 (Kerbiriou and Griffin, 1979) bradykinin which interacts with B-1 receptors. B-1 receptors are induced in inflammatory states by cytokines such as Interleukin 1 and its interaction with bradykinin may prolong or perpetuate the vascular response until bradykinin is completely inactivated by angiotensin converting enzyme or aminopeptidase P, or neutral endopeptidase. The entire bradykinin-forming cascade is assembled and can be activated along the surface of endothelial cells in zinc dependent reactions involving gC1qR, cytokeratin 1, and the urokinase plasminogen activated receptor (u-PAR). Although Factors XII and HK can be shown to bind to each one of these proteins, they exist in endothelial cells as two bimolecular complexes; gC1qR-cytokeratin 1, which preferentially binds HK, and cytokeratin 1-u-PAR which preferentially binds Factor XII. The gC1qR, which binds the globular heads of C1q is present in excess and can bind either Factor XII or HK however the binding sites for HK and C1q have been shown to reside at opposite ends of gC1qR. Activation of the bradykinin-forming pathway can be initiated at the cell surface by gC1qR-induced autoactivation of Factor XII or direct activation of the prekallikrein-HK complex by endothelial cell-derived heat-shock protein 90 (HSP 90) or prolylcarboxypeptidase with recruitment or Factor XII by the kallikrein produced.
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PMID:The plasma bradykinin-forming pathways and its interrelationships with complement. 2058 91