Elucidation of the paratope of scFv-8H9D4, a PAI-1 neutralizing antibody derivative

2003 ◽  
Vol 89 (01) ◽  
pp. 74-82 ◽  
Author(s):  
Koen Verbeke ◽  
Ann Gils ◽  
Jean-Marie Stassen ◽  
Paul Declerck
Keyword(s):  
Rational Design ◽  
Three Dimensional ◽  
Neutralizing Antibody ◽  
Plasminogen Activator Inhibitor ◽  
Site Directed Mutagenesis ◽  
Dimensional Structure ◽  
Single Chain ◽  
Plasminogen Activator Inhibitor 1 ◽  
Activator Inhibitor ◽  
Pai 1

SummaryInterfering with increased levels of plasminogen activator inhibitor-1 (PAI-1) might offer new therapeutic strategies for a variety of cardiovascular diseases. Inactivation of PAI-1 can be accomplished by a number of monoclonal antibodies (MA), including MA-8H9D4. In a previous study, a single-chain variable fragment (scFv-8H9D4) was cloned and found to have the same properties as the parental MA-8H9D4. In the present study, we identified the residues of scFv-8H9D4 that contribute significantly to the paratope. The complementarity determining region 3 from the heavy (H3) and the light (L3) chain were analysed through site-directed mutagenesis. Out of twelve mutations, only four residues appeared to contribute to the paratope. The affinity of scFv-8H9D4-H3-L97D for PAI-1 was 38-fold decreased (KA = 4.8 ± 0.2 × 107 M–1 vs. 1.8 ± 0.7 × 109 M–1 for scFv-8H9D4) whereas scFv-8H9D4-H3-R98Y did not bind to PAI-1. The affinities of scFv-8H9D4-L3-Y91S and scFv-8H9D4-L3-F94D for PAI-1 were 9- and 5-fold reduced, respectively, whereas the combined mutation resulted in an 86-fold decreased affinity (KA = 2.1 ± 0.2 × 107 M–1).In accordance with the affinity data, these mutants had no, or a reduced, PAI-1 inhibitory capacity, confirming that these four particular residues form the major interaction site of scFv-8H9D4 with PAI-1. In combination with the three-dimensional structure, these data contribute to the rational design of PAI-1 neutralizing compounds.

scholarly journals Biochemical mechanism of action of a diketopiperazine inactivator of plasminogen activator inhibitor-1

2003 ◽  
Vol 373 (3) ◽  
pp. 723-732 ◽  
Author(s):  
Anja P. EINHOLM ◽  
Katrine E. PEDERSEN ◽  
Troels WIND ◽  
Paulina KULIG ◽  
Michael T. OVERGAARD ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Therapeutic Target ◽  
Three Dimensional ◽  
Plasminogen Activator Inhibitor ◽  
Dimensional Structure ◽  
Plasminogen Activator Inhibitor 1 ◽  
Biochemical Basis ◽  
Β Sheet ◽  
Activator Inhibitor ◽  
Pai 1

XR5118 [(3Z,6Z)-6-benzylidine-3-(5-(2-dimethylaminoethyl-thio-))-2-(thienyl)methylene-2,5-dipiperazinedione hydrochloride] can inactivate the anti-proteolytic activity of the serpin plasminogen activator inhibitor-1 (PAI-1), a potential therapeutic target in cancer and cardiovascular diseases. Serpins inhibit their target proteases by the P1 residue of their reactive centre loop (RCL) forming an ester bond with the active-site serine residue of the protease, followed by insertion of the RCL into the serpin's large central β-sheet A. In the present study, we show that the RCL of XR5118-inactivated PAI-1 is inert to reaction with its target proteases and has a decreased susceptibility to non-target proteases, in spite of a generally increased proteolytic susceptibility of specific peptide bonds elsewhere in PAI-1. The properties of XR5118-inactivated PAI-1 were different from those of the so-called latent form of PAI-1. Alanine substitution of several individual residues decreased the susceptibility of PAI-1 to XR5118. The localization of these residues in the three-dimensional structure of PAI-1 suggested that the XR5118-induced inactivating conformational change requires mobility of α-helix F, situated above β-sheet A, and is in agreement with the hypothesis that XR5118 binds laterally to β-sheet A. These results improve our understanding of the unique conformational flexibility of serpins and the biochemical basis for using PAI-1 as a therapeutic target.

Identification of a Functional Epitope in Plasminogen Activator Inhibitor-1, not Localized in the Reactive Center Loop

1998 ◽  
Vol 79 (03) ◽  
pp. 597-601 ◽  
Author(s):  
Sophie Debrock ◽  
Paul Declerck
Keyword(s):  
Plasminogen Activator ◽  
Three Dimensional ◽  
Plasminogen Activator Inhibitor ◽  
Dimensional Structure ◽  
Plasminogen Activator Inhibitor 1 ◽  
Antigen Binding Site ◽  
Pharmacological Agents ◽  
Β Sheet ◽  
Activator Inhibitor ◽  
Pai 1

SummaryPlasminogen activator inhibitor-1 (PAI-1) is unique among the ser-pins because of its conformational flexibility. Previously, we have characterized monoclonal antibodies that neutralize PAI-1 activity by switching the active, inhibitory pathway into the non-inhibitory substrate pathway (10). Here, we report the identification of the epitopes for two of these antibodies, i.e. MA-55F4C12 and MA-33H1 and apply this information to explain their functional effects.Using a random PAI-1 epitope library (11), phages displaying specific PAI-1 fragments were isolated after selective screening for binding onto the respective antibodies. Competition experiments with PAI-1 demonstrated that selected phages react with the antigen-binding site of the antibodies. Comparison of the sequences of the different overlapping inserts, encoding the PAI-1 epitope, with the PAI-1 cDNA sequence revealed that both epitopes, even though not identical, are located between amino acids Glu128 and Ala156 in the PAI-1 molecule. Analysis within the three-dimensional structure of PAI-1 showed that these residues completely cover helix F, which is localized close to the major β-sheet A. This localization provides a rational basis for explaining the mechanism of PAI-1 inactivation by both antibodies: upon binding of these antibodies to PAI-1, a stabilizing effect is induced on helix F resulting in a decrease of the kinetics of insertion of the reactive site loop into β-sheet A during interaction with the target proteinase. This forms the molecular basis for the observed functional effects of these antibodies and fully explains why PAI-1, in the presence of these antibodies, has lost its inhibitory properties but remains succeptible to cleavage by its target proteinases. The identification and localization of these functionally important epitopes opens new perspectives for the development of pharmacological agents with PAI-1 modulating properties.

scholarly journals Functional effects of single amino acid substitutions in the region of Phe113 to Asp138 in the plasminogen activator inhibitor 1 molecule

1998 ◽  
Vol 331 (2) ◽  
pp. 409-415 ◽  
Author(s):  
Guang-Chao SUI ◽  
Björn WIMAN
Keyword(s):  
Amino Acid ◽  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Site Directed Mutagenesis ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Plasminogen Activator Inhibitor 1 ◽  
Low Activity ◽  
Activator Inhibitor ◽  
Pai 1

Thirteen amino acid substitutions have been introduced within the stretch Phe113 to Asp138 in the plasminogen activator inhibitor 1 (PAI-1) molecule by site-directed mutagenesis. The different proteins and wild-type (wt) PAI-1 have been overexpressed in Escherichia coliand purified by chromatography on heparin–Sepharose and on anhydrotrypsin–agarose. The PAI-1 variants have been characterized by their reactivity with tissue plasminogen activator (tPA), interactions with vitronectin or heparin, and stability. Most PAI-1 variants, except for Asp125 → Lys, Phe126 → Ser and Arg133 → Asp, displayed a high spontaneous inhibitory activity towards tPA, which did not change greatly on reactivation with 4 M guanidinium chloride, followed by dialysis at pH 5.5. The variants Asp125 → Lys and Arg133 → Asp became much more active after reactivation and they were also more rapidly transformed to inactive forms (t½ 22–31 min) at physiological pH and temperature than the other variants. However, in the presence of vitronectin they were both almost equally stable (t½ 2.3 h) as wtPAI-1 (t½ 3.0 h). The mutant Glu130 → Lys showed an increased stability, both in the absence and in the presence of vitronectin compared with wtPAI-1. Nevertheless a similar affinity between all the active PAI-1 variants and vitronectin was observed. Further, all mutants, including the three mutants with low activity, were to a large extent adsorbed on anhydrotrypsin–agarose and were eluted in a similar fashion. In accordance with these data, the three variants with a low activity were all to a large extent cleaved as a result of their reaction with tPA, suggesting that they occurred predominantly in the substrate conformation. Our results do not support the presence of a binding site for vitronectin in this part of the molecule, but rather that it might be involved in controlling the active PAI-1 to substrate transition. Partly, this region of the PAI-1 molecule (Arg115 to Arg118) seems also to be involved in the binding of heparin to PAI-1.

scholarly journals Structural Insights into the Mechanism of a Nanobody That Stabilizes PAI-1 and Modulates Its Activity

2020 ◽  
Vol 21 (16) ◽  
pp. 5859
Author(s):  
Machteld Sillen ◽  
Stephen D. Weeks ◽  
Sergei V. Strelkov ◽  
Paul J. Declerck
Keyword(s):  
Rational Design ◽  
Therapeutic Strategy ◽  
Molecular Mechanisms ◽  
Biochemical Characterization ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Plasminogen Activator Inhibitor 1 ◽  
Structural Insights ◽  
Activator Inhibitor ◽  
Pai 1

Plasminogen activator inhibitor-1 (PAI-1) is the main physiological inhibitor of tissue-type (tPA) and urokinase-type (uPA) plasminogen activators (PAs). Apart from being critically involved in fibrinolysis and wound healing, emerging evidence indicates that PAI-1 plays an important role in many diseases, including cardiovascular disease, tissue fibrosis, and cancer. Targeting PAI-1 is therefore a promising therapeutic strategy in PAI-1 related pathologies. Despite ongoing efforts no PAI-1 inhibitors were approved to date for therapeutic use in humans. A better understanding of the molecular mechanisms of PAI-1 inhibition is therefore necessary to guide the rational design of PAI-1 modulators. Here, we present a 1.9 Å crystal structure of PAI-1 in complex with an inhibitory nanobody VHH-s-a93 (Nb93). Structural analysis in combination with biochemical characterization reveals that Nb93 directly interferes with PAI-1/PA complex formation and stabilizes the active conformation of the PAI-1 molecule.

Plasminogen Activator Inhibitor-1 Is the Primary Inhibitor of Tissue-Type Plasminogen Activator in Pregnancy Plasma

1987 ◽  
Vol 58 (03) ◽  
pp. 872-878 ◽  
Author(s):  
Maja Jørgensen ◽  
Malou Philips ◽  
Sixtus Thorsen ◽  
Johan Selmer ◽  
Jesper Zeuthen
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Single Chain ◽  
Plasminogen Activator Inhibitor 1 ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator ◽  
Activator Inhibitor ◽  
Pai 1 ◽  
In Pregnancy

SummaryThe aim of the present work was to clarify to what extent plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator inhibitor-2 (PAI-2) contribute to the increase in plasma inhibition of tissue-type plasminogen activator (t-PA) observed during pregnancy. It was demonstrated that a monoclonal antibody against PAI-1 almost completely quenched inhibition of single-chain t-PA and most of the inhibition of two-chain t-PA in plasma during the third trimester of piegnancy. The remaining inhibition of two-chain t-PA was to a great extent abolished by a PAI-2 antibody. The second order rate constant (k1) for inhibition of single-chain t-PA by the inhibitor neutralized by the PAI-1 antibody was about 4.8 · 106 M-1 · s-1. The conversion of singlechain t-PA to the two-ehain form increased the reaction rate with the inhibitor about 3-fold. These kinetic data are compaiable with those obtained with TAI-l in non-pregnancy plasma oi with purified PAI-1. From the above results it is concluded that PAI-1 is the primary inhibitor of both single-chain and two chain t PA and that PAI-2 is the secondary inhibitor of two-chain t-PA in pregnancy plasma. The concentration of reactive PAI-1 versus gestation age was assayed in plasma from 6 women by binding of PAI-1 to 125I-labelled single-chain t-PA followed by quantitation of the labelled t-PA-PAI-1 complex after separation by SDS- polyacrylamide gel electrophoresis. It was found that the concentration of PAI-1 increased 4 to 8-fold during the gestation period reaching a level of about 1.4 nM at term. Post partum the plasma concentration declined abruptly within 24 h to the level observed in age-matched non-pregnant women.

Effect of Plasminogen Activator Inhibitor-1 on Tissue-Type Plasminogen Activator-Induced Fibrinolysis

1992 ◽  
Vol 67 (01) ◽  
pp. 106-110 ◽  
Author(s):  
Marcus E Carr ◽  
C Krishnamurti ◽  
B M Alving
Keyword(s):  
Plasminogen Activator ◽  
Degradation Products ◽  
Plasminogen Activator Inhibitor ◽  
Fibrin Clot ◽  
Tissue Type ◽  
Single Chain ◽  
Plasminogen Activator Inhibitor 1 ◽  
Human Thrombin ◽  
Activator Inhibitor ◽  
Pai 1

SummaryThe effect of fibrin on the interaction of human recombinant single-chain tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) was studied in normal rabbit plasma and in plasma with high levels of native PAI-1. t-PA was added to diluted plasma containing calcium (10 mM) and 125I-fibrinogen at 37° C. Clotting was initiated with human thrombin, and lysis was monitored both turbidimetrically and by release of 125I-fibrin degradation products (fdp). The activity of t-PA (50 IU/ml) was rapidly reduced to 15% of the initial value in plasma containing PAI-1 (23 AU/ml). When thrombin and t-PA were added simultaneously to the plasma, more than 70% of the activity was retained through incorporation of t-PA into the fibrin clot. t-PA-induced fibrinolysis in PAI-1 enriched plasma was further delayed when the temperature was reduced from 37 to 25° C. Turbidimet-ric and 125I-fdp release data provided complementary information. The former technique traced fiber dissolution, while the latter reflected network integrity. These results indicate that t-PA-induced fibrinolysis in PAI-1 enriched plasma is modulated by the presence of fibrin and by temperature.

943: Plasminogen Activator Inhibitor 1 (PAI-1) is Increased in Human Peyronie's Disease

2005 ◽  
Vol 173 (4S) ◽  
pp. 255-255 ◽  
Author(s):  
Hugo H. Davila ◽  
Thomas R. Magee ◽  
Freddy Zuniga ◽  
Jacob Rajfer ◽  
Nestor F. GonzalezCadavid
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Peyronie’S Disease ◽  
Plasminogen Activator Inhibitor 1 ◽  
Peyronie's Disease ◽  
Activator Inhibitor ◽  
Pai 1

Relationship of Plasminogen Activator Inhibitor-1 Levels following Thrombolytic Therapy with rt-PA as Compared to Streptokinase and Patency of Infarct Related Coronary Artery

1999 ◽  
Vol 82 (07) ◽  
pp. 104-108 ◽  
Author(s):  
Franck Paganelli ◽  
Marie Christine Alessi ◽  
Pierre Morange ◽  
Jean Michel Maixent ◽  
Samuel Lévy ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Thrombolytic Therapy ◽  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Control Group ◽  
Plasminogen Activator Inhibitor 1 ◽  
Vessel Patency ◽  
Activator Inhibitor ◽  
Pai 1

Summary Background: Type 1 plasminogen activator inhibitor (PAI-1) is considered to be risk factor for acute myocardial infarction (AMI). A rebound of circulating PAI-1 has been reported after rt-PA administration. We investigated the relationships between PAI-1 levels before and after thrombolytic therapy with streptokinase (SK) as compared to rt-PA and the patency of infarct-related arteries. Methods and Results: Fifty five consecutive patients with acute MI were randomized to strep-tokinase or rt-PA. The plasma PAI-1 levels were studied before and serially within 24 h after thrombolytic administration. Vessel patency was assessed by an angiogram at 5 ± 1days. The PAI-1 levels increased significantly with both rt-PA and SK as shown by the levels obtained from a control group of 10 patients treated with coronary angioplasty alone. However, the area under the PAI-1 curve was significantly higher with SK than with rt-PA (p <0.01) and the plasma PAI-1 levels peaked later with SK than with rt-PA (18 h versus 3 h respectively). Conversely to PAI-1 levels on admission, the PAI-1 levels after thrombolysis were related to vessel patency. Plasma PAI-1 levels 6 and 18 h after SK therapy and the area under the PAI-1 curve were significantly higher in patients with occluded arteries (p <0.002, p <0.04 and p <0.05 respectively).The same tendency was observed in the t-PA group without reaching significance. Conclusions: This study showed that the PAI-1 level increase is more pronounced after SK treatment than after t-PA treatment. There is a relationship between increased PAI-1 levels after thrombolytic therapy and poor patency. Therapeutic approaches aimed at quenching PAI-1 activity after thrombolysis might be of interest to improve the efficacy of thrombolytic therapy for acute myocardial infarction.

Fibrinolysis in Normal Subjects - Comparison Between Plasminogen Activator Inhibitor and Other Components of the Fibrinolytic System

1988 ◽  
Vol 59 (02) ◽  
pp. 299-303 ◽  
Author(s):  
Grazia Nicoloso ◽  
Jacques Hauert ◽  
Egbert K O Kruithof ◽  
Guy Van Melle ◽  
Fedor Bachmann
Keyword(s):  
Plasminogen Activator ◽  
Fibrinolytic Activity ◽  
Plasminogen Activator Inhibitor ◽  
Venous Occlusion ◽  
Venous Stasis ◽  
Plasminogen Activator Inhibitor 1 ◽  
Plate Assay ◽  
Fibrin Plate ◽  
Activator Inhibitor ◽  
Pai 1

SummaryWe analyzed fibrinolytic parameters in 20 healthy men and 20 healthy women, aged from 25 to 59, before and after 10 and 20 min venous occlusion. The 10 min post-occlusion fibrinolytic activity measured directly in diluted unfractionated plasma by a highly sensitive 125I-fibrin plate assay correlated well with the activity of euglobulins determined by the classical fibrin plate assay (r = 0.729), but pre-stasis activities determined with these two methods did not correlate (r = 0.084). The enhancement of fibrinolytic activity after venous occlusion was mainly due to an increase of t-PA in the occluded vessels (4-fold increase t-PA antigen after 10 min and 8-fold after 20 min venous occlusion). Plasminogen activator inhibitor (PAI) activity and plasminogen activator inhibitor 1 (PAI-1)1 antigen levels at rest showed considerable dispersion ranging from 1.9 to 12.4 U/ml, respectively 6.9 to 77 ng/ml. A significant increase of PAI-1 antigen levels was observed after 10 and 20 min venous occlusion. At rest no correlation was found between PAI activity or PAI-1 antigen levels and the fibrinolytic activity measured by 125I-FPA. However, a high level of PAI-1 at rest was associated with a high prestasis antigen level of t-PA and a low fibrinolytic response after 10 min of venous stasis. Since the fibrinolytic response inversely correlated with PAI activity at rest, we conclude that its degree depends mainly on the presence of free PAI.

A Specific Immunologic Assay for Functional Plasminogen Activator Inhibitor 1 in Plasma – Standardized Measurements of the Inhibitor and Related Parameters in Patients with Venous Thromboembolic Disease

1992 ◽  
Vol 68 (05) ◽  
pp. 486-494 ◽  
Author(s):  
Malou Philips ◽  
Anne-Grethe Juul ◽  
Johan Selmer ◽  
Bent Lind ◽  
Sixtus Thorsen
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Normal Subjects ◽  
Tissue Type ◽  
Blood Collection ◽  
Plasminogen Activator Inhibitor 1 ◽  
Type Plasminogen Activator ◽  
Significant Difference ◽  
Activator Inhibitor ◽  
Pai 1

SummaryA new assay for functional plasminogen activator inhibitor 1 (PAI-1) in plasma was developed. The assay is based on the quantitative conversion of PAI-1 to urokinase-type plasminogen activator (u-PA)-PAI-l complex the concentration of which is then determined by an ELISA employing monoclonal anti-PAI-1 as catching antibody and monoclonal anti-u-PA as detecting antibody. The assay exhibits high sensitivity, specificity, accuracy, and precision. The level of functional PAI-1, tissue-type plasminogen activator (t-PA) activity and t-PA-PAI-1 complex was measured in normal subjects and in patients with venous thromboembolism in a silent phase. Blood collection procedures and calibration of the respective assays were rigorously standardized. It was found that the patients had a decreased fibrinolytic capacity. This could be ascribed to high plasma levels of PAI-1. The release of t-PA during venous occlusion of an arm for 10 min expressed as the increase in t-PA + t-PA-PAI-1 complex exhibited great variation and no significant difference could be demonstrated between the patients with a thrombotic tendency and the normal subjects.

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