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Bharadwaj AG, Kempster E, Waisman DM. The ANXA2/S100A10 Complex—Regulation of the Oncogenic Plasminogen Receptor. Biomolecules 2021; 11:biom11121772. [PMID: 34944416 PMCID: PMC8698604 DOI: 10.3390/biom11121772] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 11/18/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022] Open
Abstract
The generation of the serine protease plasmin is initiated by the binding of its zymogenic precursor, plasminogen, to cell surface receptors. The proteolytic activity of plasmin, generated at the cell surface, plays a crucial role in several physiological processes, including fibrinolysis, angiogenesis, wound healing, and the invasion of cells through both the basement membrane and extracellular matrix. The seminal observation by Albert Fischer that cancer cells, but not normal cells in culture, produce large amounts of plasmin formed the basis of current-day observations that plasmin generation can be hijacked by cancer cells to allow tumor development, progression, and metastasis. Thus, the cell surface plasminogen-binding receptor proteins are critical to generating plasmin proteolytic activity at the cell surface. This review focuses on one of the twelve well-described plasminogen receptors, S100A10, which, when in complex with its regulatory partner, annexin A2 (ANXA2), forms the ANXA2/S100A10 heterotetrameric complex referred to as AIIt. We present the theme that AIIt is the quintessential cellular plasminogen receptor since it regulates the formation and the destruction of plasmin. We also introduce the term oncogenic plasminogen receptor to define those plasminogen receptors directly activated during cancer progression. We then discuss the research establishing AIIt as an oncogenic plasminogen receptor-regulated during EMT and activated by oncogenes such as SRC, RAS, HIF1α, and PML-RAR and epigenetically by DNA methylation. We further discuss the evidence derived from animal models supporting the role of S100A10 in tumor progression and oncogenesis. Lastly, we describe the potential of S100A10 as a biomarker for cancer diagnosis and prognosis.
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Affiliation(s)
- Alamelu G. Bharadwaj
- Departments of Pathology, Dalhousie University, Halifax, NS B3H 1X5, Canada; (A.G.B.); (E.K.)
- Departments of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 1X5, Canada
| | - Emma Kempster
- Departments of Pathology, Dalhousie University, Halifax, NS B3H 1X5, Canada; (A.G.B.); (E.K.)
| | - David M. Waisman
- Departments of Pathology, Dalhousie University, Halifax, NS B3H 1X5, Canada; (A.G.B.); (E.K.)
- Departments of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 1X5, Canada
- Correspondence: ; Tel.: +1-(902)-494-1803; Fax: +1-(902)-494-1355
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Ni R, Neves MAD, Wu C, Cerroni SE, Flick MJ, Ni H, Weitz JI, Gross PL, Kim PY. Activated thrombin-activatable fibrinolysis inhibitor (TAFIa) attenuates fibrin-dependent plasmin generation on thrombin-activated platelets. J Thromb Haemost 2020; 18:2364-2376. [PMID: 32506822 PMCID: PMC7719609 DOI: 10.1111/jth.14950] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 05/29/2020] [Accepted: 05/29/2020] [Indexed: 12/16/2022]
Abstract
BACKGROUND Thrombin-activated platelets can promote fibrinolysis by binding plasminogen in a fibrinogen-dependent manner and enhancing its activation by tissue-type plasminogen activator (t-PA). Whether t-PA also binds to activated platelets and the mechanism for regulation of platelet-dependent fibrinolysis remain unknown. OBJECTIVES Determine the mechanism of plasminogen and t-PA binding on thrombin-activated platelets and its regulation by activated thrombin-activatable fibrinolysis inhibitor (TAFIa). METHODS Plasminogen and t-PA binding with or without TAFIa treatment was quantified using flow cytometry. Plasmin generation on platelets was quantified using a plasmin-specific substrate. Mass spectrometry analyses identified fibrinogen as a potential target of TAFIa. Thrombus formation was studied in mice lacking fibrinogen (Fg-/- ) using intravital microscopy. RESULTS Plasminogen and t-PA bind to platelets activated by thrombin but not by other agonists, including protease-activated receptor agonists (PAR-AP). Plasminogen binds via its kringle domains because ε-aminocaproic acid eliminates binding, whereas t-PA binds via its finger and kringle domains. Plasminogen binding is fibrinogen-dependent because it is abolished on (a) Fg-/- platelets, and (b) thrombi in Fg-/- mice. Binding requires thrombin-mediated fibrinogen modification because addition of batroxobin to PAR-AP activated platelets has no effect on plasminogen binding but induces t-PA binding. TAFIa reduces plasminogen and t-PA binding to thrombin-activated platelets and attenuates plasmin generation in a concentration-dependent manner. Mass spectrometry identified K556 on the fibrinogen alpha-chain as a potential thrombin cleavage site that generates a TAFIa sensitive C-terminal lysine residue. CONCLUSION These findings provide novel mechanistic insights into how platelets activated by thrombin at sites of vascular injury can influence fibrinolysis.
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Affiliation(s)
- Ran Ni
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
| | - Miguel A. D. Neves
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto Platelet Immunobiology Group, Toronto, ON, Canada
| | - Chengliang Wu
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
| | | | - Matthew J. Flick
- Division of Experimental Hematology and Cancer Biology, Cancer and Blood Diseases Institute, Cincinnati Children’s Research Foundation, Cincinnati, OH, USA
| | - Heyu Ni
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto Platelet Immunobiology Group, Toronto, ON, Canada
- Canadian Blood Services Centre for Innovation, Toronto, ON, Canada
- Department of Medicine and Physiology, University of Toronto, Toronto, ON, Canada
| | - Jeffrey I. Weitz
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
| | - Peter L. Gross
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
| | - Paul Y. Kim
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
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Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen on the surface of vascular endothelial and smooth muscle cells. Thromb Res 2018; 169:1-7. [DOI: 10.1016/j.thromres.2018.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 05/31/2018] [Accepted: 07/03/2018] [Indexed: 11/24/2022]
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Kim PY, Vu TT, Leslie BA, Stafford AR, Fredenburgh JC, Weitz JI. Reduced plasminogen binding and delayed activation render γ'-fibrin more resistant to lysis than γA-fibrin. J Biol Chem 2014; 289:27494-503. [PMID: 25128532 DOI: 10.1074/jbc.m114.588640] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fibrin (Fn) clots formed from γ'-fibrinogen (γ'-Fg), a variant with an elongated γ-chain, are resistant to lysis when compared with clots formed from the predominant γA-Fg, a finding previously attributed to differences in clot structure due to delayed thrombin-mediated fibrinopeptide (FP) B release or impaired cross-linking by factor XIIIa. We investigated whether slower lysis of γ'-Fn reflects delayed plasminogen (Pg) binding and/or activation by tissue plasminogen activator (tPA), reduced plasmin-mediated proteolysis of γ'-Fn, and/or altered cross-linking. Clots formed from γ'-Fg lysed more slowly than those formed from γA-Fg when lysis was initiated with tPA/Pg when FPA and FPB were both released, but not when lysis was initiated with plasmin, or when only FPA was released. Pg bound to γ'-Fn with an association rate constant 22% lower than that to γA-Fn, and the lag time for initiation of Pg activation by tPA was longer with γ'-Fn than with γA-Fn. Once initiated, however, Pg activation kinetics were similar. Factor XIIIa had similar effects on clots formed from both Fg isoforms. Therefore, slower lysis of γ'-Fn clots reflects delayed FPB release, which results in delayed binding and activation of Pg. When clots were formed from Fg mixtures containing more than 20% γ'-Fg, the upper limit of the normal level, the delay in lysis was magnified. These data suggest that circulating levels of γ'-Fg modulate the susceptibility of clots to lysis by slowing Pg activation by tPA and provide another example of the intimate connections between coagulation and fibrinolysis.
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Affiliation(s)
- Paul Y Kim
- From the Departments of Medicine, the Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada
| | - Trang T Vu
- the Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada Biomedical Sciences, and
| | - Beverly A Leslie
- From the Departments of Medicine, the Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada
| | - Alan R Stafford
- From the Departments of Medicine, the Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada
| | - James C Fredenburgh
- From the Departments of Medicine, the Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada
| | - Jeffrey I Weitz
- From the Departments of Medicine, the Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario L8L 2X2, Canada Biomedical Sciences, and Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4L8 and
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Foley JH, Kim PY, Mutch NJ, Gils A. Insights into thrombin activatable fibrinolysis inhibitor function and regulation. J Thromb Haemost 2013; 11 Suppl 1:306-15. [PMID: 23809134 DOI: 10.1111/jth.12216] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fibrinolysis is initiated when the zymogen plasminogen is converted to plasmin via the action of plasminogen activators. Proteolytic cleavage of fibrin by plasmin generates C-terminal lysine residues capable of binding both plasminogen and the plasminogen activator, thereby stimulating plasminogen activator-mediated plasminogen activation and propagating fibrinolysis. This positive feedback mechanism is regulated by activated thrombin activatable fibrinolysis inhibitor (TAFIa), which cleaves C-terminal lysine residues from the fibrin surface, thereby decreasing its cofactor activity. TAFI can be activated by thrombin alone, but the rate of activation is accelerated when in complex with thrombomodulin. Plasmin is also known to activate TAFI. TAFIa has no known physiologic inhibitors and consequently, its primary regulatory mechanism involves its intrinsic thermal instability. The rate of TAFI activation and stability of the active form, TAFIa, function in maintaining its concentration above the threshold value required to down-regulate fibrinolysis. Although all methods to quantify TAFI or TAFIa have their limitations, epidemiologic studies have indicated that elevated TAFI levels are correlated with an increased risk of venous thrombosis. Major efforts have been made to develop TAFI inhibitors that can either directly interfere with TAFIa activity or impair its activation. However, the anti-inflammatory properties of TAFIa might complicate the development and application of a TAFIa inhibitor that aims to increase the efficiency of thrombolytic therapy.
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Affiliation(s)
- J H Foley
- Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada
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Foley JH, Nesheim ME, Rivard GE, Brummel-Ziedins KE. Thrombin activatable fibrinolysis inhibitor activation and bleeding in haemophilia A. Haemophilia 2011; 18:e316-22. [PMID: 21933309 DOI: 10.1111/j.1365-2516.2011.02648.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Individuals with haemophilia A exhibit bleeding tendencies that are not always predicted by their factor (F)VIII level. It has been suggested that bleeding in haemophilia is due not only to defective prothrombin activation but also aberrant fibrinolysis. Thrombin activatable fibrinolysis inhibitor (TAFI) activation was measured in tissue factor (TF)-initiated blood coagulation in blood samples of 28 haemophiliacs and five controls. Reactions were quenched over time with FPRck and citrate and assayed for TAFIa and thrombin-antithrombin (TAT). The TAFIa potential (TP), TAFI activation rate and the TAFIa level at 20 min (TAFIa(20 min)) was extracted from the TAFI activation progress curve. In general, the time course of TAFI activation follows thrombin generation regardless of FVIII activity and as expected the rate of TAFI activation and TP decreases as FVIII decreases. The magnitude of TP was similar among the control subjects and subjects with <11% FVIII. In severe subjects with <1% FVIII at the time of blood collection, the TAFIa(20 min) was inversely and significantly correlated with haemarthrosis (-0.77, P = 0.03) and total bleeds (-0.75, P = 0.03). In all cases, TAFIa(20 min) was more strongly correlated with bleeding than TAT levels at 20 min. Overall, this study shows that TAFI activation in whole blood can be quantified and related to the clinical bleeding phenotype. Measuring TAFIa along with thrombin generation can potentially be useful to evaluate the differential bleeding phenotype in haemophilia A.
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Affiliation(s)
- J H Foley
- The Department of Biochemistry, University of Vermont, Burlington, VT, USA
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Foley JH, Cook PF, Nesheim ME. Kinetics of activated thrombin-activatable fibrinolysis inhibitor (TAFIa)-catalyzed cleavage of C-terminal lysine residues of fibrin degradation products and removal of plasminogen-binding sites. J Biol Chem 2011; 286:19280-6. [PMID: 21467042 DOI: 10.1074/jbc.m110.215061] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Partial digestion of fibrin by plasmin exposes C-terminal lysine residues, which comprise new binding sites for both plasminogen and tissue-type plasminogen activator (tPA). This binding increases the catalytic efficiency of plasminogen activation by 3000-fold compared with tPA alone. The activated thrombin-activatable fibrinolysis inhibitor (TAFIa) attenuates fibrinolysis by removing these residues, which causes a 97% reduction in tPA catalytic efficiency. The aim of this study was to determine the kinetics of TAFIa-catalyzed lysine cleavage from fibrin degradation products and the kinetics of loss of plasminogen-binding sites. We show that the k(cat) and K(m) of Glu(1)-plasminogen (Glu-Pg)-binding site removal are 2.34 s(-1) and 142.6 nm, respectively, implying a catalytic efficiency of 16.21 μm(-1) s(-1). The corresponding values of Lys(77)/Lys(78)-plasminogen (Lys-Pg)-binding site removal are 0.89 s(-1) and 96 nm implying a catalytic efficiency of 9.23 μm(-1) s(-1). These catalytic efficiencies of plasminogen-binding site removal by TAFIa are the highest of any TAFIa-catalyzed reaction with a biological substrate reported to date and suggest that plasmin-modified fibrin is a primary physiological substrate for TAFIa. We also show that the catalytic efficiency of cleavage of all C-terminal lysine residues, whether they are involved in plasminogen binding or not, is 1.10 μm(-1) s(-1). Interestingly, this value increases to 3.85 μm(-1) s(-1) in the presence of Glu-Pg. These changes are due to a decrease in K(m). This suggests that an interaction between TAFIa and plasminogen comprises a component of the reaction mechanism, the plausibility of which was established by showing that TAFIa binds both Glu-Pg and Lys-Pg.
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Affiliation(s)
- Jonathan H Foley
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada
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Iwaki T, Malinverno C, Smith D, Xu Z, Liang Z, Ploplis VA, Castellino FJ. The generation and characterization of mice expressing a plasmin-inactivating active site mutation. J Thromb Haemost 2010; 8:2341-4. [PMID: 20653841 PMCID: PMC2965814 DOI: 10.1111/j.1538-7836.2010.03995.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Foley JH, Nesheim ME. Soluble thrombomodulin partially corrects the premature lysis defect in FVIII-deficient plasma by stimulating the activation of thrombin activatable fibrinolysis inhibitor. J Thromb Haemost 2009; 7:453-9. [PMID: 19087221 DOI: 10.1111/j.1538-7836.2008.03261.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Previous work by others has shown that premature clot lysis occurs in plasmas deficient in components of the intrinsic pathway, due to a failure to activate thrombin activatable fibrinolysis inhibitor (TAFI). This suggests the hypothesis that bleeding in hemophilia is due not only to defective coagulation but also enhanced fibrinolysis. These studies were carried out to quantify the extent of TAFI activation over time in normal plasma (NP) and factor VIII deficient plasma (FVIII-DP) and to determine whether soluble thrombomodulin (sTM) can correct the lysis defect in FVIII-DP. METHODS The time courses of TAFI activation in both NP and FVIII-DP were monitored after clotting with thrombin, PCPS and Ca(2+), +/- sTM. Clotting and lysis were measured turbidometrically and TAFIa using a functional assay. RESULTS Premature lysis that occurs in FVIII-DP is corrected by mixing deficient plasma with 10% NP. However, this does not fully correct the defect in TAFI activation. FVIII-DP must be mixed with up to 50% NP to attain the same TAFIa potential as NP. In FVIII-DP, sTM can correct the defect in TAFIa-dependent prolongation of lysis at low tPA concentrations and partially correct this defect at high tPA concentrations. CONCLUSIONS TAFI activation increases as the concentration of FVIII increases. FVIII at a level of 10% fully corrects the lysis defect in spite of the extent of TAFI activation being only one half that obtained with 100% FVIII. In addition, sTM increases TAFI activation sufficiently to correct the premature lysis defect in FVIII-DP.
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Affiliation(s)
- J H Foley
- Department of Biochemistry, Queen's University, Kingston, ON, Canada
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10
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Feric NT, Boffa MB, Johnston SM, Koschinsky ML. Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen: a novel mechanism for lipoprotein(a)-mediated inhibition of plasminogen activation. J Thromb Haemost 2008; 6:2113-20. [PMID: 18983515 DOI: 10.1111/j.1538-7836.2008.03183.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Elevated plasma concentrations of lipoprotein(a) [Lp(a)] are associated with an increased risk for thrombotic disorders. Lp(a) is a unique lipoprotein consisting of a low-density lipoprotein-like moiety covalently linked to apolipoprotein(a) [apo(a)], a homologue of the fibrinolytic proenzyme plasminogen. Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu-plasminogen to Lys-plasminogen. OBJECTIVE Using acid-urea gel electrophoresis to resolve the two forms of radiolabeled plasminogen, we determined whether apo(a) is able to inhibit Glu-plasminogen to Lys-plasminogen conversion. METHODS The assays were performed in the absence or presence of different recombinant apo(a) species, including point mutants, deletion mutants and variants that represent greater than 90% of the known apo(a) isoform sizes. RESULTS Apo(a) substantially suppressed Glu-plasminogen conversion. Critical roles were identified for the kringle IV types 5-9 and kringle V; contributory roles for sequences within the amino-terminal half of the molecule were also observed. Additionally, with the exception of the smallest naturally-occurring isoform of apo(a), isoform size was found not to contribute to the inhibitory capacity of apo(a). CONCLUSION These findings underscore a novel contribution to the understanding of Lp(a)/apo(a)-mediated inhibition of plasminogen activation: the ability of the apo(a) component of Lp(a) to inhibit the key positive feedback step of plasmin-mediated Glu-plasminogen to Lys-plasminogen conversion.
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Affiliation(s)
- N T Feric
- Department of Biochemistry, Queen's University, Kingston, ON, Canada
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Foley JH, Kim P, Nesheim ME. Thrombin-activable fibrinolysis inhibitor zymogen does not play a significant role in the attenuation of fibrinolysis. J Biol Chem 2008; 283:8863-7. [PMID: 18252711 DOI: 10.1074/jbc.m800127200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated thrombin-activable fibrinolysis inhibitor (TAFIa) plays a significant role in the prolongation of fibrinolysis. During fibrinolysis, plasminogen is activated to plasmin, which lyses a clot by cleaving fibrin after selected arginine and lysine residues. TAFIa attenuates fibrinolysis by removing the exposed C-terminal lysine residues. It was recently reported that TAFI zymogen possesses sufficient carboxypeptidase activity to attenuate fibrinolysis through a mechanism similar to TAFIa. Here, we show with a recently developed TAFIa assay that when thrombin is used to clot TAFI-deficient plasma supplemented with TAFI, there is some TAFI activation. The extent of activation was dependent upon the concentration of zymogen present in the plasma, and lysis times were prolonged by TAFIa in a concentration-dependent manner. Potato tuber carboxypeptidase inhibitor, an inhibitor of TAFIa but not TAFI, abolished the prolongation of lysis in TAFI-deficient plasma supplemented with TAFI zymogen. In addition, TAFIa but not TAFI catalyzed release of plasminogen bound to soluble fibrin degradation products. The data presented confirm that TAFI zymogen is effective in cleaving a small substrate but does not play a role in the attenuation of fibrinolysis because of its inability to cleave plasmin-modified fibrin degradation products.
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Affiliation(s)
- Jonathan H Foley
- Departments of Biochemistry and Medicine, Queen's University, Kingston, Ontario, Canada
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12
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Kim PYG, Foley J, Hsu G, Kim PY, Nesheim ME. An assay for measuring functional activated thrombin-activatable fibrinolysis inhibitor in plasma. Anal Biochem 2007; 372:32-40. [PMID: 17967438 DOI: 10.1016/j.ab.2007.09.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Revised: 08/29/2007] [Accepted: 09/25/2007] [Indexed: 10/22/2022]
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI), also called procarboxypeptidase U (proCPU), is a plasma zymogen that can be activated by thrombin, the thrombin-thrombomodulin complex, or plasmin. The activated form of TAFI (TAFIa, CPU) removes C-terminal lysine residues of plasmin-modified fibrin (FN') that mediates a positive feedback mechanism in plasminogen (Pg) activation, thereby attenuating fibrinolysis. The plasma concentration of TAFI is approximately 75 nM. Because the half-maximal effect of TAFIa occurs at 1 nM, only approximately 1.3% of TAFI needs to be activated to exert an effect on clot lysis. The assay is performed by mixing soluble FN' covalently attached to a quencher and fluorescein-labeled Pg. The sample containing TAFIa is then added, and the rate of fluorescence increase due to removal of C-terminal lysine from FN' and loss of Pg binding is measured with a fluorescence plate reader. The assay was shown to be sensitive for TAFIa at a concentration as low as 12 pM. The intraassay variability and interassay variability of the assay were 6.3 and 8.3%, respectively. This assay was not confounded by the naturally occurring TAFI Thr325Leu polymorphism that affects the thermal stability of TAFIa or endogenous plasminogen in plasma.
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Affiliation(s)
- Paula Y G Kim
- Department of Biochemistry, Queen's University, Kingston, ON, K7L 3N6, Canada
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Boffa MB, Koschinsky ML. Curiouser and curiouser: recent advances in measurement of thrombin-activatable fibrinolysis inhibitor (TAFI) and in understanding its molecular genetics, gene regulation, and biological roles. Clin Biochem 2006; 40:431-42. [PMID: 17331488 DOI: 10.1016/j.clinbiochem.2006.10.020] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 10/29/2006] [Indexed: 10/23/2022]
Abstract
The thrombin-activatable fibrinolysis inhibitor (TAFI) pathway defines a novel molecular connection between blood coagulation and both fibrinolysis and inflammation. TAFI is a plasma zymogen that can be activated by thrombin, the thrombin-thrombomodulin complex, or plasmin. The activated form of TAFI (TAFIa) attenuates fibrinolysis by removing the carboxyl-terminal lysine residues from partially degraded fibrin that mediate positive feedback in the fibrinolytic cascade. A role for TAFIa in modulating inflammation is suggested by the ability of this enzyme to down-regulate pericellular plasminogen activation and to inactivate the inflammatory peptides bradykinin and the anaphylatoxins C3a and C5a. The focus of this review is on recent advances in the clinical measurement of the TAFI pathway in human subjects and what this has revealed in terms of the molecular genetics of TAFI, the biological variation in plasma TAFI antigen levels, potential regulators of expression of the gene encoding TAFI, and the TAFI pathway as a risk factor for the development of vascular diseases. Although this field is in its infancy, much recent progress has been made and the available data suggest that the TAFI pathway is an intriguing new player in a variety of physiological and pathophysiological contexts.
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Affiliation(s)
- Michael B Boffa
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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Neill EKT, Stewart RJ, Schneider MM, Nesheim ME. A functional assay for measuring activated thrombin-activatable fibrinolysis inhibitor in plasma. Anal Biochem 2005; 330:332-41. [PMID: 15203340 DOI: 10.1016/j.ab.2004.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2004] [Indexed: 10/26/2022]
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI) is a procarboxypeptidase found in plasma that is activated by thrombin, the thrombin-thrombomodulin complex, or plasmin. The active carboxypeptidase, TAFIa, attenuates fibrinolysis by removing newly exposed carboxy-terminal lysine residues on fibrin. The half-maximal effect of TAFIa on clot lysis occurs at 1 nM and the maximal effect occurs at 20 nM. Since the circulating concentration of the procarboxypeptidase is approximately 75 nM, only a small portion needs to be activated to have a significant effect on clot lysis. Several assays to measure total plasma TAFI levels and plasma TAFIa levels after it is fully activated exist. However, no currently available assay is sufficiently sensitive and specific to measure endogenous TAFIa in plasma. We have devised a new sensitive and specific assay for TAFIa in plasma that is based on physiologic function. This assay is based on the fact that TAFIa decreases the cofactor activity of high-molecular-weight fibrin degradation products in the stimulation of plasminogen cleavage in a concentration-dependent fashion. With this assay, we can measure TAFIa concentrations as low as 10 pM in plasma and it is not affected by variability in other hemostatic factors. This assay is reliable and repeatable with intra- and interassay variabilities of 6.5 and 6.1%, respectively.
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Affiliation(s)
- Erin K T Neill
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6
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Kwon M, Yoon CS, Jeong W, Rhee SG, Waisman DM. Annexin A2-S100A10 heterotetramer, a novel substrate of thioredoxin. J Biol Chem 2005; 280:23584-92. [PMID: 15849182 DOI: 10.1074/jbc.m504325200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The binding of plasminogen activators and plasminogen to the cell surface results in the rapid generation of the serine protease plasmin. Plasmin is further degraded by an autoproteolytic reaction, resulting in the release of an angiostatin, A61 (Lys78-Lys468). Previously, we demonstrated that the annexin A2-S100A10 heterotetramer (AIIt) stimulates the release of A61 from plasmin by promoting the autoproteolytic cleavage of the Lys468-Gly469 bond and reduction of the plasmin Cys462-Cys541 disulfide (Kwon, M., Caplan, J. F., Filipenko, N. R., Choi, K. S., Fitzpatrick, S. L., Zhang, L., and Waisman, D. M. (2002) J. Biol. Chem. 277, 10903-10911). Mechanistically, it was unclear if AIIt promoted a conformational change in plasmin, resulting in contortion of the plasmin disulfide, or directly reduced the plasmin disulfide. In the present study, we show that AIIt thiols are oxidized during the reduction of plasmin disulfides, establishing that AIIt directly participates in the reduction reaction. Incubation of HT1080 cells with plasminogen resulted in the rapid loss of thiol-specific labeling of AIIt by 3-(N-maleimidopropionyl)biocytin. The plasminogen-dependent oxidation of AIIt could be attenuated by thioredoxin. Thioredoxin reductase catalyzed the transfer of electrons from NADPH to the oxidized thioredoxin, thus completing the flow of electrons from NADPH to AIIt. Therefore, we identify AIIt as a substrate of the thioredoxin system and propose a new model for the role of AIIt in the redox-dependent processing of plasminogen and generation of an angiostatin at the cell surface.
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Affiliation(s)
- Mijung Kwon
- Cancer Biology Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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16
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Schneider M, Brufatto N, Neill E, Nesheim M. Activated Thrombin-activatable Fibrinolysis Inhibitor Reduces the Ability of High Molecular Weight Fibrin Degradation Products to Protect Plasmin from Antiplasmin. J Biol Chem 2004; 279:13340-5. [PMID: 14715654 DOI: 10.1074/jbc.m313211200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated thrombin-activable fibrinolysis inhibitor (TAFIa) is a carboxypeptidase B-like plasma enzyme that can slow clot lysis by removing lysine residues exposed on fibrin as it is cleaved by plasmin. Previously, it was shown that fibrin treated with TAFIa is less able to promote plasminogen activation by tissue-type plasminogen activator. In this study, the effect of TAFIa modification of a fibrin surface on the rate of plasmin inhibition by antiplasmin was studied using high molecular weight fibrin degradation products (HMw-FDPs) as a soluble model for intact plasmin-modified fibrin. To quantify the inhibition, a novel end point assay was employed where plasmin, antiplasmin, and cofactors were mixed in the presence of a chromogenic substrate and the end point in the substrate hydrolysis reaction was used to measure the second order rate constant of inhibition. When HMw-FDPs were titrated in the presence of plasmin and antiplasmin, the rate constant for inhibition decreased by 16-fold at saturation (9.6 x 10(6) m(-1) s(-1) to 0.59 x 10(6) m(-1) s(-1)). When HMw-FDPs were pretreated with TAFIa, nearly two-thirds of the protective effect was lost. When 730 nm HMw-FDPs were treated for 20 min with TAFIa, the rate constant for plasmin inhibition was increased 3-fold from 1.9 x 10(6) m(-1) s(-1) to 6.2 x 10(6) m(-1) s(-1). Therefore, a novel mechanism was identified whereby TAFIa can modulate plasmin levels by increasing the susceptibility of plasmin to inhibition by antiplasmin.
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Affiliation(s)
- Mark Schneider
- Departments of Biochemistry and Medicine, Queen's University, Kingston Ontario K7L 3N6, Canada
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17
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Schneider M, Nesheim M. A study of the protection of plasmin from antiplasmin inhibition within an intact fibrin clot during the course of clot lysis. J Biol Chem 2004; 279:13333-9. [PMID: 14715655 DOI: 10.1074/jbc.m313164200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous work using soluble fibrin surrogates or very dilute fibrin indicate that inhibition of plasmin by antiplasmin is attenuated by fibrin surrogates; however, this phenomenon has not been quantified within intact fibrin clots. Therefore, a novel system was designed to measure plasmin inhibition by antiplasmin in real time within an intact clot during fibrinolysis. This was accomplished by including the plasmin substrate S2251 and a recombinant fluorescent derivative of plasminogen (S741C-fluorescein) into clots formed from purified components. Steady state plasmin levels were estimated from the rates of S2251 hydrolysis, the rates of plasminogen activation were estimated by fluorescence decrease over time, and residual antiplasmin was deduced from residual fluorescence. From these measurements, the second order rate constant could be inferred at any time during fibrinolysis. Immediately after clot formation, the rate constant for inhibition decreased 3-fold from 9.6 x 10(6) m(-1) s(-1) measured in a soluble buffer system to 3.2 x 10(6) m(-1) s(-1) in an intact fibrin clot. As the clot continued to lyse, the rate constant for inhibition continued to decrease by 38-fold at maximum. To determine whether this protection was the result of plasmin exposure of carboxyl-terminal lysine residues, clots were formed in the presence of activated thrombin-activatable fibrinolysis inhibitor (TAFIa). In the presence of TAFIa, the initial protective effect associated with clot formation occurred; however, the secondary protective effect associated with lysine residue exposure was delayed in a TAFIa concentration-dependent manner. This latter effect represents another mechanism whereby TAFIa attenuates fibrinolysis.
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Affiliation(s)
- Mark Schneider
- Departments of Biochemistry and Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada
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18
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Hancock MA, Boffa MB, Marcovina SM, Nesheim ME, Koschinsky ML. Inhibition of plasminogen activation by lipoprotein(a): critical domains in apolipoprotein(a) and mechanism of inhibition on fibrin and degraded fibrin surfaces. J Biol Chem 2003; 278:23260-9. [PMID: 12697748 DOI: 10.1074/jbc.m302780200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Similarity between the apolipoprotein(a) (apo(a)) moiety of lipoprotein(a) (Lp(a)) and plasminogen suggests a potentially important link between atherosclerosis and thrombosis. Lp(a) may interfere with tissue plasminogen activator (tPA)-mediated plasminogen activation in fibrinolysis, thereby generating a hypercoagulable state in vivo. A fluorescence-based system was employed to study the effect of apo(a) on plasminogen activation in the presence of native fibrin and degraded fibrin cofactors and in the absence of positive feedback reactions catalyzed by plasmin. Human Lp(a) and a physiologically relevant, 17-kringle recombinant apo(a) species exhibited strong inhibition with both cofactors. A variant lacking the protease domain also exhibited strong inhibition, indicating that the apo(a)-plasminogen binding interaction mediated by the apo(a) protease domain does not ultimately inhibit plasminogen activation. A variant in which the strong lysine-binding site in kringle IV type 10 had been abolished exhibited substantially reduced inhibition whereas another lacking the kringle V domain showed no inhibition. Amino-terminal truncation mutants of apo(a) also revealed that additional sequences within kringle IV types 1-4 are required for maximal inhibition. To investigate the inhibition mechanism, the concentrations of plasminogen, cofactor, and a 12-kringle recombinant apo(a) species were systematically varied. Kinetics for both cofactors conformed to a single, equilibrium template model in which apo(a) can interact with all three fibrinolytic components and predicts the formation of ternary (cofactor, tPA, and plasminogen) and quaternary (cofactor, tPA, plasminogen, and apo(a)) catalytic complexes. The latter complex exhibits a reduced turnover number, thereby accounting for inhibition of plasminogen activation in the presence of apo(a)/Lp(a).
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Affiliation(s)
- Mark A Hancock
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.
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19
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Peterson EA, Sutherland MR, Nesheim ME, Pryzdial ELG. Thrombin induces endothelial cell-surface exposure of the plasminogen receptor annexin 2. J Cell Sci 2003; 116:2399-408. [PMID: 12724354 DOI: 10.1242/jcs.00434] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Cell-surface annexin 2 (A2) and its ligand p11 have been implicated in fibrinolysis because of their ability to accelerate tissue plasminogen activator (tPA)-mediated activation of plasminogen to plasmin. Because thrombin is a potent cell modulator obligately produced at the site of clot formation, we hypothesized that the amount of cell-surface A2 and p11 might be altered by thrombin with consequent effects on plasmin generation. In support of this hypothesis, immunofluorescence microscopy and hydrophilic biotinylation experiments showed that both A2 and p11 were significantly increased on the surface of human umbilical vein endothelial cells (HUVECs) treated with thrombin (0.8-8 nM) for 5 minutes followed by 1 hour at 37 degrees C. Intracellular immunofluorescence microscopy and immunoblot analyses of whole cell extracts revealed increased p11 but unchanged A2 in response to thrombin, suggesting that transbilayer trafficking of A2 might be controlled by p11. The thrombin receptor-activating peptide (TRAP) similarly affected cells, demonstrating that cell signaling at least involved the type-1 protease activated receptor (PAR-1). An effect on the fibrinolysis pathway after treatment of HUVECs with thrombin was shown by increased fluorescein-labeled plasminogen binding to cells, which was inhibited by an antibody specific for p11. This was confirmed by observing that thrombin pretreatment of HUVECs increased biotin-modified plasminogen binding. Utilizing a chromogenic assay, pretreatment of HUVECs by thrombin further enhanced activation of the Glu and Lys forms of plasminogen by tPA. These data suggest a novel mechanism that links the coagulation and fibrinolysis pathways by thrombin-mediated feedback.
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Affiliation(s)
- Erica A Peterson
- Canadian Blood Services, R&D Department, 1800 Alta Vista Drive, Ottawa, ON K1G 4J5, Canada
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20
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Kornblatt JA, Marchal S, Rezaei H, Kornblatt MJ, Balny C, Lange R, Debey MP, Hui Bon Hoa G, Marden MC, Grosclaude J. The fate of the prion protein in the prion/plasminogen complex. Biochem Biophys Res Commun 2003; 305:518-22. [PMID: 12763023 DOI: 10.1016/s0006-291x(03)00804-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The cellular prion protein (PrP(c)) forms complexes with plasminogen. Here, we show that the PrP(c) in this complex is cleaved to yield fragments of PrP(c). The cleavage is accelerated by plasmin but does not appear to be dependent on it.
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Affiliation(s)
- Jack A Kornblatt
- Concordia University, 1455 de Maisonneuve Blvd., Montreal, Qc, Canada H3G 1M8.
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21
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Schneider M, Boffa M, Stewart R, Rahman M, Koschinsky M, Nesheim M. Two naturally occurring variants of TAFI (Thr-325 and Ile-325) differ substantially with respect to thermal stability and antifibrinolytic activity of the enzyme. J Biol Chem 2002; 277:1021-30. [PMID: 11684677 DOI: 10.1074/jbc.m104444200] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thrombin-activable fibrinolysis inhibitor (TAFI) is a carboxypeptidase B-like zymogen that is activated to TAFIa by plasmin, thrombin, or the thrombin-thrombomodulin complex. The enzyme TAFIa attenuates clot lysis by removing lysine residues from a fibrin clot. Screening of nine human cDNA libraries indicated a common variation in TAFI at position 325 (Ile-325 or Thr-325). This is in addition to the variation at amino acid position 147 (Ala-147 or Thr-147) characterized previously. Thus, four variants of TAFI having either Ala or Thr at position 147 and either Thr or Ile at position 325 were stably expressed in baby hamster kidney cells and purified to homogeneity. The kinetics of activation of TAFI by thrombin/thrombomodulin were identical for all four variants; however, Ile at position 325 extended the half-life of TAFIa from 8 to 15 min at 37 degrees C, regardless of the residue at position 147. In clot lysis assays with thrombomodulin and the TAFI variants, or with pre-activated TAFI variants, the Ile-325 variants exhibited an antifibrinolytic effect that was 60% greater than the Thr-325 variants. Similarly, in the absence of thrombomodulin, the Ile-325 variants exhibited an antifibrinolytic effect that was 30-50% greater than the Thr-325 variants. In contrast, the variation at position 147 had little if any effect on the antifibrinolytic potential of TAFIa. The increased antifibrinolytic potential of the Ile-325-containing TAFI variants reflects the fact that these variants have an increased ability to mediate the release of lysine from partially degraded fibrin and suppress plasminogen activation. These findings imply that individuals homozygous for the Ile-325 variant of TAFI would likely have a longer lived and more potent TAFIa enzyme than those homozygous for the Thr-325 variant.
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Affiliation(s)
- Mark Schneider
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
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22
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Nesheim M, Walker J, Wang W, Boffa M, Horrevoets A, Bajzar L. Modulation of fibrin cofactor activity in plasminogen activation. Ann N Y Acad Sci 2001; 936:247-60. [PMID: 11460482 DOI: 10.1111/j.1749-6632.2001.tb03513.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Fibrin is a cofactor for the formation of plasmin from plasminogen as catalyzed by tissue plasminogen activator. Initial cleavages of fibrin by plasmin upregulates the cofactor activity of fibrin by exposing carboxyl terminal lysine residues. This effect is eliminated by a carboxypeptidase B-like enzyme generated from the precursor, thrombin activatable fibrinolysis inhibitor (TAFI) that is generated by thrombin during the formation of fibrin. Thus, TAFI and its activation to TAFIa create a link between the coagulation and fibrinolytic cascade, such that activation of the former suppresses the latter. Complete solubilization of fibrin results in a family of very large fibrin degradation products. These also have very substantial tissue plasminogen activator cofactor activity that is very highly downregulated by TAFIa.
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Affiliation(s)
- M Nesheim
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada, K7L 3N6.
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23
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Walker JB, Nesheim ME. A kinetic analysis of the tissue plasminogen activator and DSPAalpha1 cofactor activities of untreated and TAFIa-treated soluble fibrin degradation products of varying size. J Biol Chem 2001; 276:3138-48. [PMID: 11069903 DOI: 10.1074/jbc.m005876200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The kinetics of tissue plasminogen activator (t-PA) and DSPAalpha1-catalyzed plasminogen activation using untreated and TAFIa-treated fibrin degradation products (FDPs), ranging in weight average molecular weight (M(w)) from 0.48 x 10(6) to 4.94 x 10(6) g/mol, were modeled according to the steady-state template model. The FDPs served as effective cofactors for both activators. The intrinsic catalytic efficiencies of both t-PA (17.4 x 10(5) m(-1) s(-1)) and DSPAalpha1 (6.0 x 10(5) m(-1) s(-1)) were independent of FDP M(w). The intrinsic catalytic efficiency of t-PA was 12-fold higher than that measured under identical conditions with intact fibrin as the cofactor. At sub-saturating levels of cofactor and substrate, rates were strongly dependent on FDP M(w) with DSPAalpha1 but not t-PA. Loss of activity with decreasing FDP M(w) correlated with loss of finger-dependent binding of the activators to the FDPs. TAFIa treatment of the FDPs resulted in 90- and 215-fold decreases in the catalytic efficiencies of t-PA (0.20 x 10(5) m(-)(1) s(-1)) and DSPAalpha1 (0.028 x 10(5) m(-1) s(-1)), yielding cofactors that were still 30- and 50-fold better than fibrinogen with t-PA and DSPAalpha1, respectively. Our results show that for both activators the products released during fibrinolysis are very effective cofactors for plasminogen activation, and both t-PA and DSPAalpha1 cofactor activity are strongly down-regulated by TAFIa.
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Affiliation(s)
- J B Walker
- Departments of Biochemistry and Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada
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24
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Kornblatt JA. Understanding the fluorescence changes of human plasminogen when it binds the ligand, 6-aminohexanoate: a synthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1481:1-10. [PMID: 10962086 DOI: 10.1016/s0167-4838(00)00119-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
This work attempts to explain several aspects of the response of plasminogen to 6-aminohexanoate (6-AH). These responses include the overall fluorescent changes that occur when plasminogen binds the ligand, the changes shown by the individual domains when they bind the ligand, and the changes in structure shown by the holoprotein when it binds 6-AH. The results have implications for understanding the physicochemical behavior of all kringle based proteins.
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Affiliation(s)
- J A Kornblatt
- Enzyme Research Group, Concordia University, 1455 de Maisonneuve Ouest, Montreal, Quebec, Canada.
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25
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Dekker RJ, Eichinger A, Stoop AA, Bode W, Pannekoek H, Horrevoets AJ. The variable region-1 from tissue-type plasminogen activator confers specificity for plasminogen activator inhibitor-1 to thrombin by facilitating catalysis: release of a kinetic block by a heterologous protein surface loop. J Mol Biol 1999; 293:613-27. [PMID: 10543954 DOI: 10.1006/jmbi.1999.3178] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Substitution of the native variable region-1 (VR1/37-loop) of thrombin by the corresponding VR1 of tissue-type plasminogen activator (thrombin-VR1(tPA)) increases the rate of inhibition by plasminogen activator inhibitor type 1 (PAI-1) by three orders of magnitude, and is thus sufficient to confer PAI-1 specificity to a heterologous serine protease. A structural and kinetical approach to establish the function of the VR1 loop of t-PA in the context of the thrombin-VR1(tPA) variant is described. The crystal structure of thrombin-VR1(tPA) was resolved and showed a conserved overall alpha-thrombin structure, but a partially disordered VR1 loop as also reported for t-PA. The contribution of a prominent charge substitution close to the active site was studied using charge neutralization variants thrombin-E39Q(c39) and thrombin-VR1(tPA)-R304Q(c39), resulting in only fourfold changes in the PAI-1 inhibition rate. Surface plasmon resonance revealed that the affinity of initial reversible complex formation between PAI-1 and catalytically inactive Ser195-->Ala variants of thrombin and thrombin-VR1(tPA) is only increased fivefold, i.e. KD is 652 and 128 nM for thrombin-S195A and thrombin-S195A-VR1(tPA), respectively. We established that the partition ratio of the suicide substrate reaction between the proteases and PAI-1 was largely unaffected in any variant studied. Hirugen allosterically decreases the rate of thrombin inhibition by PAI-1 2.5-fold and of thrombin-VR1(tPA) 20-fold, by interfering with a unimolecular step in the reaction, not by decreasing initial complex formation or by altering the stoichiometry. Finally, kinetic modeling demonstrated that acylation is the rate-limiting step in thrombin inhibition by PAI-1 (k approximately 10(-3) s(-1)) and this kinetic block is alleviated by the introduction of the tPA-VR1 into thrombin (k>1 s(-1)). We propose that the length, flexibility and different charge architecture of the VR1 loop of t-PA invoke an induced fit of the reactive center loop of PAI-1, thereby enhancing the rate of acylation in the Michaelis complex between thrombin-VR1(t-PA) and PAI-1 by more than two orders of magnitude.
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Affiliation(s)
- R J Dekker
- Department of Biochemistry Academic Medical Center, University of Amsterdam, Amsterdam, 1105 AZ, The Netherlands
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26
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Kornblatt JA, Kornblatt MJ, Clery C, Balny C. The effects of hydrostatic pressure on the conformation of plasminogen. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 265:120-6. [PMID: 10491165 DOI: 10.1046/j.1432-1327.1999.00695.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Plasminogen undergoes a large conformational change when it binds 6-aminohexanoate. Using ultraviolet absorption spectroscopy and native PAGE, we show that hydrostatic pressure brings about the same conformational change. The volume change for this conformational change is -33 mL.mol-1. Binding of ligand and hydrostatic pressure both cause the protein to open up to expose surfaces that had previously been buried in the interior.
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Affiliation(s)
- J A Kornblatt
- Enzyme Research Group, Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada.
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27
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Wang W, Boffa MB, Bajzar L, Walker JB, Nesheim ME. A study of the mechanism of inhibition of fibrinolysis by activated thrombin-activable fibrinolysis inhibitor. J Biol Chem 1998; 273:27176-81. [PMID: 9765237 DOI: 10.1074/jbc.273.42.27176] [Citation(s) in RCA: 279] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TAFI (thrombin-activable fibrinolysis inhibitor) is a recently described plasma zymogen that, when exposed to the thrombin-thrombomodulin complex, is converted by proteolysis at Arg92 to a basic carboxypeptidase that inhibits fibrinolysis (TAFIa). The studies described here were undertaken to elucidate the molecular basis for the inhibition of fibrinolysis. When TAFIa is included in a clot undergoing fibrinolysis induced by tissue plasminogen activator and plasminogen, the time to achieve lysis is prolonged, and free arginine and lysine are released over time. In addition, TAFIa prevents a 2.5-fold increase in the rate constant for plasminogen activation which occurs when fibrin is modified by plasmin in the early course of fibrin degradation. The effect is specific for the Glu- form of plasminogen. TAFIa prevents or at least attenuates positive feedback expressed through Lys-plasminogen formation during the process of fibrinolysis initiated by tissue plasminogen activator and plasminogen. TAFIa also inhibits plasmin activity in a clot and prolongs fibrinolysis initiated with plasmin. We conclude that TAFIa suppresses fibrinolysis by removing COOH-terminal lysine and arginine residues from fibrin, thereby reducing its cofactor functions in both plasminogen activation and the positive feedback conversion of Glu-plasminogen to Lys-plasminogen. At relatively elevated concentrations, it also directly inhibits plasmin.
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Affiliation(s)
- W Wang
- Departments of Biochemistry and Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada
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28
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Kassam G, Choi KS, Ghuman J, Kang HM, Fitzpatrick SL, Zackson T, Zackson S, Toba M, Shinomiya A, Waisman DM. The role of annexin II tetramer in the activation of plasminogen. J Biol Chem 1998; 273:4790-9. [PMID: 9468544 DOI: 10.1074/jbc.273.8.4790] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Annexin II tetramer (AIIt) is a major Ca2+-binding protein of endothelial cells which has been shown to exist on both the intracellular and extracellular surfaces of the plasma membrane. In this report, we demonstrate that AIIt stimulates the activation of plasminogen by facilitating the tissue plasminogen activator (t-PA)-dependent conversion of plasminogen to plasmin. Fluid-phase AIIt stimulated the rate of activation of [Glu]plasminogen about 341-fold compared with an approximate 6-fold stimulation by annexin II. AIIt bound to [Glu]plasminogen(S741C-fluorescein) with a Kd of 1. 26 +/- 0.04 microM (mean +/- S.D., n = 3) and this interaction resulted in a large conformational change in [Glu]plasminogen. Kinetic analysis established that AIIt produces a large increase of about 190-fold in the kcat, app and a small increase in the Km,app which resulted in a 90-fold increase in the catalytic efficiency (kcat/Km) of t-PA for [Glu]plasminogen. AIIt also stimulated the t-PA-dependent activation of [Lys]plasminogen about 28-fold. Furthermore, other annexins such as annexin I, V, or VI did not produce comparable activation of t-PA-dependent conversion of [Glu]plasminogen to plasmin. The stimulation of the activation of [Glu]plasminogen by AIIt was Ca2+-independent and inhibited by epsilon-aminocaproic acid. AIIt bound to human 293 cells potentiated t-PA-dependent plasminogen activation. AIIt that was bound to phospholipid vesicles or heparin also stimulated the activation of [Glu]plasminogen 5- or 11-fold, respectively. Furthermore, immunofluorescence labeling of nonpermeabilized HUVEC revealed a punctated distribution of AIIt subunits on the cell surface. These results therefore identify AIIt as a potent in vitro activator of plasminogen.
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Affiliation(s)
- G Kassam
- Cancer Biology Research Group, Department of Medical Biochemistry, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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29
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Horrevoets AJ, Pannekoek H, Nesheim ME. A steady-state template model that describes the kinetics of fibrin-stimulated [Glu1]- and [Lys78]plasminogen activation by native tissue-type plasminogen activator and variants that lack either the finger or kringle-2 domain. J Biol Chem 1997; 272:2183-91. [PMID: 9036151 DOI: 10.1074/jbc.272.4.2183] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The kinetics of activation of both [Glu1]- and [Lys78]Plg(S741C-fluorescein by native (recombinant) tissue-type plasminogen activator and its deletion variants lacking either the finger or kringle-2 domain were measured by fluorescence within fully polymerized fibrin clots. The kinetics conform to the Michaelis-Menten equation at any fixed fibrin concentration so long as the plasminogen concentration is expressed as either the free or fibrin-bound, but not the total. The apparent kcat and Km values both vary systematically with the concentration of fibrin. Competition kinetics disclosed an active site-dependent interaction between t-Pa and [Glu1]Plg(S741C-fluorescein) in the presence, but not the absence, of fibrin. A steady-state template model having the rate equation v/[A]o = kcat(app).[Plg]/(Km(app) + [Plg]) was derived and used to interpret the data. The model indicates that catalytic efficiency is determined by the stability of the ternary activator-fibrin-plasminogen complex rather than the binding of the activator or plasminogen to fibrin. This implies that efforts to improve the enzymatic properties of t-PA might be more fruitfully directed at enhancing the stability of the ternary complex rather than fibrin binding.
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Affiliation(s)
- A J Horrevoets
- Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
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