Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.7 (plasmin)
 9,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycoprotein (GP) IIb-IIIa is the major fibrinogen receptor on platelets and participates in platelet aggregation at the site of a wound. Integrin alpha v beta 3, which contains an identical beta-subunit, is expressed on endothelial cells and also serves as a fibrinogen receptor. Here, we demonstrate by several criteria that purified GPIIb-IIIa and integrin alpha v beta 3 bind to distinct sites on fibrinogen. First, a plasmin-generated fragment of fibrinogen lacking the RGD sequence at residues 572-574 retained the ability to bind GPIIb-IIIa, but failed to bind integrin alpha v beta 3. Second, a monoclonal antibody which exclusively recognizes the RGD sequence at fibrinogen A alpha chain residues 572-574 abolished interaction between integrin alpha v beta 3 and fibrinogen, but had only a minimal effect on fibrinogen binding to GPIIb-IIIa. Finally, we show that the difference in recognition of sites on fibrinogen by these two integrins is probably a consequence of their remarkably different ligand binding properties. Peptides corresponding to fibrinogen gamma chain residues 400-411 effectively blocked RGD sequence and fibrinogen binding by GPIIb-IIIa, but had no effect on the ability of integrin alpha v beta 3 to bind these ligands. We also show that integrin alpha v beta 3 has a higher affinity than GPIIb-IIIa for a synthetic hexapeptide containing the RGD sequence. In fact, this RGD-containing peptide was 150-fold more effective at blocking fibrinogen binding to integrin alpha v beta 3 than to GPIIb-IIIa. Collectively, our results demonstrate that integrins alpha v beta 3 and GPIIb-IIIa display qualitative and quantitative differences in their ligand binding properties, as is evident by their ability to interact with synthetic peptides. The ultimate result of these differences is the recognition of distinct sites on fibrinogen by the two integrins. These observations may have relevance in the processes of hemostasis and wound healing.
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PMID:Interaction of integrins alpha v beta 3 and glycoprotein IIb-IIIa with fibrinogen. Differential peptide recognition accounts for distinct binding sites. 237 93

The C-terminal region of the fibrinogen gamma chain is known to participate in several functional interactions including fibrin polymerization. This part of the molecule is retained on the gamma chain of fragment D (FgD) when fibrinogen is digested by plasmin in the presence of calcium to produce the fragment D-fragment E (FgD X FgE) complex but is lost if FgD is prepared in the absence of calcium. In an attempt to characterize the C-terminal polymerization domain we have used three techniques to examine this further degradation of FgD following the addition of EDTA and plasmin. Analysis of the digestion by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a progressive cleavage of the gamma chain to two small remnants. The polymerization-inhibitory activity of the whole digest was studied using acid-solubilized fibrin. A progressive loss of inhibitory activity was associated with gamma chain shortening, reaching greater than a 120-fold reduction at the end of digestion. The cleavage of peptides was followed by reverse-phase high performance liquid chromatography and the release of a characteristic peptide triplet was associated with gamma chain cleavage. Manual sequencing, amino acid analysis, and fast atom bombardment mass spectrometry established the three peptides as gamma 303-356, 357-373, and 374-405. These peptides have sequences in common with those peptides recently reported by other investigators to be potent polymerization inhibitors. However, when a mixture of the three peptides was added in a 200-fold molar excess to polymerizing fibrin, no inhibitory activity could be demonstrated. It is concluded that the C-terminal polymerization domain of fibrinogen may be an extended region which includes the sequence gamma 303-405, when this is contiguous with the remainder of the gamma chain.
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PMID:Characterization of peptides cleaved by plasmin from the C-terminal polymerization domain of human fibrinogen. 293 34

Plasmin sensitive sites are found on the A alpha, B beta and gamma chains of fibrinogen at regions joining the two C-terminal D fragments with the central E fragment. We have developed a monoclonal antibody (MoAb) reactive with this plasmin sensitive region on the human fibrinogen gamma chain and mapped its epitope. MoAb J88B reacts with gamma chains of both native as well as with reduced and denatured fibrinogen and fibrin, the CNBr fragment of the fibrinogen central domain, plasmin cleaved fragments D, gamma-gamma dimers, but not with plasmic fragments E. These data indicate that J88B maps to the plasmin sensitive domain localized to gamma 63-78. MoAb J88B failed to react with synthetic peptide gamma 70-78, which suggests that the epitope includes the newly exposed N-terminal residues gamma 63-70 of the early plasmic fragment D1A. As calcium has a marked influence on plasmin cleavage of C-terminal sites on the gamma chain, the effects of calcium on modulating plasmin cleavage of D1A to D1 were assessed in the absence or presence of J88B. The results indicated that calcium delays and J88B (+/- calcium) protects the gamma chain from plasmin cleavage at the N-terminus of D1A, suggesting that this enzymatically labile site is calcium-sensitive. Thus, MoAb J88B should prove useful in studies examining the structure of plasmin cleaved fibrinogen and fibrin.
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PMID:Calcium modulates plasmin cleavage of the fibrinogen D fragment gamma chain N-terminus: mapping of monoclonal antibody J88B to a plasmin sensitive domain of the gamma chain. 894 90

Murine models employing genetically altered mice have the potential to provide important new information about the hemostatic system, but before such data can be extrapolated to humans it is necessary to define the similarities and differences between murine and human hemostasis. After establishing the similarities of murine fibrinogen to human fibrinogen in its pattern of proteolysis in response to plasmin and its cross-linking by factor XIIIa, we studied a new hamster monoclonal antibody (mAb) 7E9 that reacts with the gamma chain of mouse fibrinogen. This antibody inhibits platelet adhesion to fibrinogen, platelet-mediated clot retraction, platelet aggregation, and FXIIIa-mediated cross-linking of fibrin; it also facilitates tissue plasminogen activator (tPA)-mediated lysis of fibrin formed either in the absence or presence of platelets. These data provide evidence that the C-terminus of mouse fibrinogen gamma chain, like that of human fibrinogen, is involved in fibrinogen binding to platelets and FXIIIa-mediated cross-linking of fibrin. Our data raise the possibility that a therapeutic agent that targets the C-terminus of the gamma chain in human fibrinogen might have broad antithrombotic and profibrinolytic effects.
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PMID:A hamster antibody to the mouse fibrinogen gamma chain inhibits platelet-fibrinogen interactions and FXIIIa-mediated fibrin cross-linking, and facilitates thrombolysis. 1168 23

Interaction of lipoprotein(a) with fibrin associated with atherosclerotic lesions promotes its accumulation in the lesions, thereby contributing to the development of atherothrombosis. Numerous studies revealed that this interaction occurs through the apolipoprotein(a) [apo(a)] component of lipoprotein(a) and COOH-terminal Lys residues generated by partial degradation of fibrin with plasmin (a COOH-Lys-dependent mechanism). At the same time, the mechanism of the interaction of apo(a) with intact fibrin(ogen) remained unclear. Our recent study identified the Lys-independent apo(a)-binding sites within the fibrin(ogen) alphaC domains which contribute to an alternative Lys-independent mechanism. In this study, we performed direct measurements of the interaction between apo(a) and various fibrin(ogen) fragments representing the whole fibrin(ogen) molecule except the alphaC regions. The experiments revealed that the apo(a)-binding site, identified previously within fibrinogen gamma chain residues 207-235 [Klose, R., et al. (2000) J. Biol. Chem. 275, 38206-38212], is a high-affinity site and mainly Lys-independent, suggesting that it should also contribute to the Lys-independent mechanism. The experiments also identified a novel Lys-dependent high-affinity apo(a)-binding site within the sequence of gamma chain residues 287-411. This site may provide interaction of apo(a) with intact fibrin(ogen) through another alternative mechanism, which depends on internal Lys residues. Thus, apo(a) may interact with intact fibrin through the Lys-independent and Lys-dependent mechanisms, while the COOH-Lys-dependent mechanism may prevail in the presence of fibrinolytic activity.
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PMID:Interaction of fibrin(ogen) with apolipoprotein(a): further characterization and identification of a novel lysine-dependent apolipoprotein(a)-binding site within the gamma chain 287-411 region. 1693 14