Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.7 (plasmin)
9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, we demonstrated that the Heymann nephritis autoantigen, gp330, can serve as a receptor site for plasminogen. This binding was not significantly inhibited by the lysine analogue epsilon-amino caproic acid (EACA), indicating that plasminogen binding was not just through lysine binding sites as suggested for other plasminogen binding sites. We now report that once plasminogen is bound to gp330, it can be converted to its active form of plasmin by urokinase. This conversion of plasminogen to plasmin proceeds at a faster rate when plasminogen is first prebound to gp330. Although there is a proportional increase in the Vmax of the urokinase-catalyzed reaction with increasing gp330 concentrations, no change in Km was observed. Once activated, plasmin remains bound to gp330 in an active state capable of cleaving the chromogenic tripeptide, S-2251. The binding of plasmin to gp330 did not significantly change its enzymatic activity; however, gp330 did have a stabilizing effect on plasmin activity at 37 degrees C. While bound to gp330, plasmin is protected from inactivation by its natural inhibitor alpha 2-antiplasmin. The binding of plasmin to gp330 as analyzed by ELISA was shown to be time dependent, reversible, saturable, and specific for gp330. Inhibition of binding of both plasminogen and plasmin to gp330 by benzamidine was similar, although EACA inhibited the binding of plasmin to gp330 slightly more than the binding of plasminogen to gp330. These results indicate that the binding of plasminogen to gp330 serves as an effective means of increasing the rate of plasmin production on the glomerular and tubular epithelial cell surface while protecting the active plasmin from natural inhibitors.
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PMID:Analysis of plasmin binding and urokinase activation of plasminogen bound to the Heymann nephritis autoantigen, gp330. 128 65

Previous results have shown that the autoantibody eluted from the glomeruli of rats with active Heymann nephritis contain a population of antibodies not only to the putative autoantigen of the disease, gp330, but also to plasminogen. Since gp330 has been shown to serve as a receptor for plasminogen, we have analyzed the effects of autoantibody on plasminogen-binding to gp330 and activation of plasminogen to plasmin by urokinase. Autoantibody does not inhibit the binding of plasminogen to gp330. The binding of autoantibody to plasminogen was shown to be very specific for the compact conformation of glu-plasminogen. The change in the conformation of plasminogen when its lysine-binding sites are occupied or after conversion to plasmin results in a significant decrease in autoantibody-binding. The most significant effect of autoantibody on this system is the inhibition of plasminogen activation to plasmin by urokinase. The binding of autoantibody to plasminogen acts as a competitive inhibitor of the reaction by apparently blocking access of urokinase to plasminogen's activation site. These results indicate that autoantibody obtained from the immune deposits in the glomeruli of rats with active Heymann nephritis does not inhibit the binding of plasminogen to gp330 but does significantly alter the urokinase catalyzed activation of plasminogen to plasmin.
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PMID:Effect of the nephritogenic autoantibody of Heymann's nephritis on plasminogen-binding to gp330 and activation by urokinase. 824 Dec 86

Rat proximal tubular epithelial cells derived from Wistar-Kyoto and spontaneously hypertensive rats were grown to confluency on semipermeable tissue culture inserts, and the plasminogen system of these cells was analyzed using enzyme assays, Western analysis, zymography, and reverse transcriptase-polymerase chain reaction. The tubular epithelial cells are capable of activating exogenous plasminogen to plasmin by endogenous plasminogen activators. The cells produce tissue-plasminogen activator, urokinase-plasminogen activator, plasminogen activator inhibitor-1, and urokinase-plasminogen activator receptor. These cells also produce the Heymann nephritis autoantigen, gp330 (megalin), and an associated protein of 45 kd (RAP). Incubation with transforming growth factor-beta 1 resulted in a decrease in plasminogen activation, primarily because of an increase in plasminogen activator inhibitor-1 RNA and protein and a decrease in u-PA RNA as noted by quantitative reverse transcriptase-polymerase chain reaction, Western analysis, and zymography. Incubation of these cells with tumor necrosis factor-alpha resulted in an increase in plasminogen activating ability, presumably through an increase in urokinase. Gp330 and the associated 45-kd protein (RAP) RNA were decreased in cells treated with tumor necrosis factor-alpha. The data presented indicates that these transformed proximal tubular epithelial cells may be used to study changes that may occur during Heymann nephritis with respect to the plasminogen system and the autoantigen gp330.
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PMID:Effect of TGF-beta 1 and TNF-alpha on the plasminogen system of rat proximal tubular epithelial cells. 904 36

The combined presence of anti-phospholipid Ab (aPL), thrombosis, and/or fetal loss is recognized as the antiphospholipid syndrome (APS). aPL include anti-cardiolipin Ab (aCL) and/or lupus anticoagulants (LAC, detected as Ig that prolong certain in vitro phospholipid (PL)-restricted blood clotting tests); both aCL and LAC are the diagnostic Ab for APS. Studies show that aPL represent a heterogeneous group of Ab, which recognize various PL, PL-binding plasma proteins, and/or PL-protein complexes. Recently, we found that five of seven patient-derived IgG monoclonal aCL react with thrombin, activated protein C, and plasmin. All three proteins are trypsin-like serine proteases (SP), and are highly homologous in their catalytic domains. Importantly, among these SP autoantigens, the reactive aCL bind to plasmin with the highest affinity, suggesting that plasmin may serve as a major driving autoantigen for some aCL in approximately 30% of APS patients who are positive for IgG anti-plasmin Ab. To test this hypothesis, we immunized BALB/c mice with human plasmin and analyzed immune sera for aCL activity and reactivity with relevant SP. We found that some immune sera displayed aCL activity and/or bound to test SP. Subsequently, eight mAb were obtained and studied. The results revealed that one mAb displayed the aCL and the LAC activities and induced fetal loss when injected into pregnant mice. Immunohistological analyses of placentas revealed extensive deposits of activated C3 components. Combined, these data demonstrate that plasmin may serve as a driving Ag for some pathogenic aPL.
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PMID:Some plasmin-induced antibodies bind to cardiolipin, display lupus anticoagulant activity and induce fetal loss in mice. 1740 20

Patients with inflammatory vascular disease caused by anti-neutrophil cytoplasmic autoantibodies (ANCA) can harbor antibodies not only to the autoantigen proteinase 3 (PR3) but also to complementary PR3 (cPR3(105-201)), a recombinant protein translated from the antisense strand of PR3 cDNA. The purpose of this study was to identify potential endogenous targets of anti-cPR3(105-201) antibodies. Patients' plasmapheresis material was tested for the presence of antigens reactive with affinity-purified rabbit and chicken anti-cPR3(105-201) polyclonal antibodies. Antigen-containing fractions were tested with patients' anti-cPR3(105-201) affinity-purified IgG, and putative protein targets were sequenced by mass spectrometry. Unexpectedly, plasminogen was identified as a target of anti-cPR3(105-201). Reactivity of affinity-purified antibodies from two patients was lost when plasminogen was converted to plasmin, indicating restricted specificity. Antiplasminogen antibodies from five patients bound plasminogen at a surface-exposed loop structure within the protease domain. This loop contains an amino acid motif that is also found in a portion of recombinant cPR3(105-201); site-directed mutagenesis of this sequence decreased antibody reactivity by 30%. Functionally, antiplasminogen antibodies delayed the conversion of plasminogen to plasmin and increased the dissolution time of fibrin clots. Serologically, antiplasminogen antibody levels were higher in PR3-ANCA patients (n = 72) than healthy control subjects (n = 63), myeloperoxidase-ANCA patients (n = 34), and patients with idiopathic thrombosis (n = 57; P = 0.001). Of the patients with PR3-ANCA, nine had documented deep venous thrombosis events, five of whom were positive for antiplasminogen antibodies. In summary, capitalizing on interactions with complementary proteins, specifically complementary PR3, this study identified plasminogen as a previously undescribed autoantigen in PR3-ANCA vasculitis.
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PMID:Antibodies with dual reactivity to plasminogen and complementary PR3 in PR3-ANCA vasculitis. 1870 7

Collagen XVII (BP180) and its shed ectodomain represent major autoantigens in dermatoses of the pemphigoid group. The 120 kDa ectodomain is constitutively shed from the cell surface by disintegrin-metalloproteinases (ADAMs). Part of it is further processed to a 97 kDa fragment (LABD97), an autoantigen in linear IgA dermatosis (LAD), but the responsible proteinases remain elusive. In this study, we identified the 120 and the 97 kDa ectodomain in blister fluids of bullous pemphigoid patients using new mAbs. As blister fluids contain significant plasmin-like serine protease activity, HaCaT keratinocytes or purified 120 kDa ectodomain were incubated with several human serine proteases. In vitro, only plasmin generated a stable 97 kDa fragment that was also targeted by LAD sera. Characterization of the plasmin-derived 97 kDa fragment with domain-specific collagen XVII antibodies, heparin binding and N-glycosylation studies indicates that the N-terminus is located approximately at AA 515 and the C-terminus N-terminally from AA 1,421. Interestingly, plasmin-derived LABD97 was also generated in the presence of ADAM inhibitors and remained stable over more than 12 hours incubation at 37 degrees C, indicating that this disease relevant collagen XVII fragment can also arise in an ADAM-independent manner through direct action by plasmin.
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PMID:Plasmin plays a role in the in vitro generation of the linear IgA dermatosis antigen LADB97. 1915 42

Autoimmune processes have been implicated in the development of rheumatoid arthritis (RA); however, specific autoantigens that play a role in the aetiology of RA have been lacking. In this study, we found that sera from RA patients were particularly immunoreactive against the protein tryptase. Compared with osteoarthritis (OA) patients and healthy controls, RA patients had relatively higher levels of tryptase and concomitant anti-tryptase antibodies in their synovial tissues and sera. Similarly, synovial fluid from RA patients, but not from OA patients, contained antibodies that recognized tryptase in vitro. In addition, serum tryptase levels in both early and late RA patients significantly correlated with clinical indices usually used to diagnose RA, such as rheumatoid factor, Disease Activity Score using 28 joint counts and autoantibodies against cyclic citrullinated peptide. Our results identify tryptase as a candidate autoantigen involved in the pathogenesis of RA and monitoring its levels may have diagnostic and prognostic value.
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PMID:Tryptase is a candidate autoantigen in rheumatoid arthritis. 2443 28

Bullous pemphigoid (BP) is a common autoimmune blistering disease in which autoantibodies target the hemidesmosomal components BP180 and/or BP230 in basal keratinocytes. In BP, 80 to 90% of autoantibodies target the juxtamembranous extracellular non-collagenous 16th A (NC16A) domain of BP180. Recently, the administration of dipeptidyl peptidase-IV inhibitors (DPP4i), which are widely used as antihyperglycemic drugs, has been recognized to be a causative factor for BP. DPP4i-associated BP (DPP4i-BP) autoantibodies tend to target epitopes on non-NC16A regions of BP180, and the pathomechanism for the development of the unique autoantibodies remains unknown. To address the characteristics of DPP4i-BP autoantibodies in detail, we performed epitope analysis of 18 DPP4i-BP autoantibodies targeting the non-NC16A domains of BP180 using various domain-specific as well as plasmin-digested polypeptides derived from recombinant BP180. Firstly, Western blotting showed that only one DPP4i-BP serum reacted with the epitopes on the intracellular domain of BP180, and no sera reacted with the C-terminal domain of the molecule. In addition, only 2 DPP4i-BP sera reacted with BP230 as determined by enzyme-linked immunosorbent assay. Thus, DPP4i-BP autoantibodies were found to mainly target the non-NC16A mid-portion of the extracellular domain of BP. Interestingly, Western blotting using plasmin-digested BP180 as a substrate revealed that all of the DPP4i-BP sera reacted more intensively with the 97-kDa processed extracellular domain of BP180, which is known as the LABD97 autoantigen, than full-length BP180 did. All of the DPP4i-BP autoantibodies targeting the LABD97 autoantigen were IgG1, and IgG4 was observed to react with the molecule in only 7 cases (38.9%). In summary, the present study suggests that IgG1-class autoantibodies targeting epitopes on the processed extracellular domain of BP180, i.e., LABD97, are the major autoantibodies in DPP4i-BP.
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PMID:Preferential Reactivity of Dipeptidyl Peptidase-IV Inhibitor-Associated Bullous Pemphigoid Autoantibodies to the Processed Extracellular Domains of BP180. 3119 60

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