scholarly journals Identification of an alpha-1 antitrypsin variant with enhanced specificity for factor XIa by phage display, bacterial expression, and combinatorial mutagenesis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Varsha Bhakta ◽  
Mostafa Hamada ◽  
Amy Nouanesengsy ◽  
Jessica Lapierre ◽  
Darian L. Perruzza ◽  
...  
Keyword(s):  
Phage Display ◽  
Activated Protein C ◽  
Coagulation Factor ◽  
Bacterial Expression ◽  
Antithrombotic Agent ◽  
Expression Library ◽  
Factor Xia ◽  
Combinatorial Mutagenesis ◽  
Alpha 1 Antitrypsin

AbstractCoagulation Factor XIa (FXIa) is an emerging target for antithrombotic agent development. The M358R variant of the serpin alpha-1 antitrypsin (AAT) inhibits both FXIa and other proteases. Our aim was to enhance the specificity of AAT M358R for FXIa. We randomized two AAT M358R phage display libraries at reactive centre loop positions P13-P8 and P7-P3 and biopanned them with FXIa. A bacterial expression library randomized at P2′-P3′ was also probed. Resulting novel variants were expressed as recombinant proteins in E. coli and their kinetics of FXIa inhibition determined. The most potent FXIa-inhibitory motifs were: P13-P8, HASTGQ; P7-P3, CLEVE; and P2-P3′, PRSTE (respectively, novel residues bolded). Selectivity for FXIa over thrombin was increased up to 34-fold versus AAT M358R for these single motif variants. Combining CLEVE and PRSTE motifs in AAT-RC increased FXIa selectivity for thrombin, factors XIIa, Xa, activated protein C, and kallikrein by 279-, 143-, 63-, 58-, and 36-fold, respectively, versus AAT M358R. AAT-RC lengthened human plasma clotting times less than AAT M358R. AAT-RC rapidly and selectively inhibits FXIa and is worthy of testing in vivo. AAT specificity can be focused on one target protease by selection in phage and bacterial systems coupled with combinatorial mutagenesis.

scholarly journals Stepwise Reversion of Multiply Mutated Recombinant Antitrypsin Reveals a Selective Inhibitor of Coagulation Factor XIa as Active as the M358R Variant

2021 ◽  
Vol 8 ◽  
Author(s):  
Mostafa Hamada ◽  
Varsha Bhakta ◽  
Sara N. Andres ◽  
William P. Sheffield
Keyword(s):  
Activated Protein C ◽  
Coagulation Factor ◽  
Fold Increase ◽  
Bleeding Tendency ◽  
Reactive Center ◽  
Nickel Chelate ◽  
Factor Xia ◽  
Combinatorial Mutagenesis ◽  
Alpha 1 Antitrypsin ◽  
Natural Target

Alpha-1 antitrypsin (AAT, also known as alpha-1 proteinase inhibitor or SERPINA1) is the most abundant member of the serpin superfamily found in human plasma. The naturally occurring variant AAT M358R, altered at the P1 position of the critical reactive center loop (RCL), is re-directed away from inhibition of AAT's chief natural target, neutrophil elastase, and toward accelerated inhibition of thrombin (FIIa), kallikrein (Kal), and other proteases such as factor XIa (FXIa). FXIa is an emerging target for the development of antithrombotic agents, since patients with FXI deficiency are protected from thromboembolic disease and do not exhibit a strong bleeding tendency. Previously, we used phage display, bacterial lysate screening, and combinatorial mutagenesis to identify AAT-RC, an engineered AAT M358R with additional changes between RCL positions P7-P3', CLEVEPR-STE [with changes bolded and the P1-P1' (R358-S359) reactive center shown as R-S]. AAT-RC was 279- and 16-fold more selective for FXIa/IIa or FXIa/Kal than AAT M358R; the increased selectivity came at a cost of a 2.3-fold decrease in the rate of FXIa inhibition and a 3.3-fold increase in the stoichiometry of inhibition (SI). Here, we asked which alterations in AAT-RC were most important for the observed increases in selectivity for FXIa inhibition. We back-mutated AAT-RC to AAT-RC-1 (P7-P3' FLEVEPRSTE), AAT-RC-2 (P7-P3' FLEAEPRSTE), and AAT RC-3 (P7-P3' FLEAIPR-STE). Proteins were expressed as cleavable, hexahistidine-tagged glutathione sulfotransferase fusion proteins in E. coli and purified by proteolytic elution from glutathione agarose, with polishing on nickel chelate agarose. Selectivity for FXIa over Kal of AAT-RC-1, −2, and −3 was 14, 21, and 2.3, respectively. AAT-RC-2 inhibited FXIa 31% more rapidly than AAT M358R, with the same SI, and enhanced selectivity for FXIa over Kal, FXa, FXIIa, activated protein C, and FIIa of 25-, 130-, 420-, 440-, and 470-fold, respectively. Structural modeling of the AAT-RC-2/FXIa encounter complex suggested that both E (Glu) substitutions at P3 and P3' may promote FXIa binding via hydrogen bonding to K192 in FXIa. AAT-RC-2 is the most selective and active AAT variant reported to date for FXIa inhibition and will be tested in animal models of thrombosis and bleeding.

scholarly journals Turnover of *I-protein C inhibitor and *I-alpha 1-antitrypsin and their complexes with activated protein C

Blood ◽  
1990 ◽  
Vol 76 (11) ◽  
pp. 2290-2295 ◽  
Author(s):  
M Laurell ◽  
J Stenflo ◽  
TH Carlson
Keyword(s):  
Complex Formation ◽  
Protein C ◽  
Activated Protein C ◽  
Human Protein ◽  
Relative Contribution ◽  
Protein C Inhibitor ◽  
The Difference ◽  
Alpha 1 Antitrypsin

Abstract The rates of clearance and catabolism of human protein C inhibitor (PCI) and human alpha 1-antitrypsin (alpha 1-AT) and their complexes with human activated protein C (APC) were studied in the rabbit. The radioiodinated-free inhibitors had biologic half-lives of 23.4 and 62.1 hours, respectively, while the corresponding *I-labeled activated- protein C complexes were cleared with half-lives of 19.6 +/- 3.1 and 72.2 +/- 6.1 minutes. Complex clearances were linked to their catabolism as shown by a correlation between clearance and the appearance of free radioiodine in the plasma. Thus, the difference in the rates of catabolism would result in a fivefold greater amount of alpha 1-AT-APC complex than PCI-APC complex 1 hour after the formation of equal amounts of these in vivo. These results lead to the conclusion that the relative contribution of PCI and alpha 1-AT to the physiologic inhibition of APC cannot be determined only from the rates of the formation of these complexes in vitro, or from measurement of their levels in plasma. The APC-PCI complex is unstable as compared with the APC-alpha 1-AT complex, compounding the problem of estimating rates of complex formation from their levels in plasma.

scholarly journals Funksionele beskrywing van ’n faktor VIIa inhiberende peptied, IP-7, geselekteer deur faagblootleggingstegnologie

2006 ◽  
Vol 25 (4) ◽  
pp. 209-220
Author(s):  
S.M. Meiring ◽  
C.E. Roets ◽  
P.N. Badenhorst
Keyword(s):  
Phage Display ◽  
Tissue Factor ◽  
Factor Viia ◽  
Coagulation Factor ◽  
Competitive Inhibitor ◽  
Factor Vii ◽  
Antithrombotic Agent ◽  
Phage Display Technology ◽  
Current Form ◽  
Coagulation Factor Vii

Die tegniek van faagblootlegging is gebruik om ’n sikliese heptapeptied te selekteer wat met weefselfaktor(WF) kompeteer vir binding aan stollingsfaktor VIIa. Die aminosuurvolgorde van die peptied is Cys-Ala- Trp-Pro-His-Thr-Pro-Asp-Cys (C-AWPHTPD-C) en dit verleng die protrombientyd (PT) op ’n konsentrasie-afhanklike wyse. Die peptied beperk plaatjieklewing aan beide menslike endoteelsel- en weefselfaktormatrikse in ’n vloeikamermodel onder arteriële vloeitoestande. Die peptied funksioneer as ’n volledig mededingende inhibeerder van faktor VIIa met ’n inhibisiekonstante (Ki) van 123,2 μM. In sy huidige vorm is die peptied waarskynlik nie sterk genoeg om verder as antitrombotiese middel ontwikkel te word nie, maar verskillende strategieë kan gevolg word om die werking daarvan te versterk. AbstractFunctional characterisation of a factor VIIa inhibiting peptide, IP-7 selected by phage display technology By using the technique of phage display, we selected a cyclic heptapeptide sequence Cys-Ala-Trp-Pro-His-Thr-Pro-Asp-Cys (C-AWPHTPD-C) that competes with tissue factor for binding to coagulation factor VII. This peptide prolongs the prothrombin time (PT) in a concentration dependent way. It also reduces platelet adhesion to both human endothelial cell and tissue factor matrixes in a flow chamber under arterial flow conditions. Furthermore, it acts as a full competitive inhibitor of factor VIIa with an inhibition constant (Ki) of 123,2 μM. In its current form the peptide is probably not sufficiently potent for development as an antithrombotic agent, but different strategies could be followed to reinforce its performance.

scholarly journals Evidence of activation of the protein C pathway during acute vascular damage induced by Mediterranean spotted fever

Blood ◽  
1991 ◽  
Vol 78 (2) ◽  
pp. 416-422
Author(s):  
V Vicente ◽  
F Espana ◽  
D Tabernero ◽  
A Estelles ◽  
J Aznar ◽  
...  
Keyword(s):  
Protein C ◽  
Degradation Products ◽  
Spotted Fever ◽  
Activated Protein C ◽  
Quantitative Information ◽  
Endothelial Damage ◽  
Mediterranean Spotted Fever ◽  
Fibrin Degradation Products ◽  
Alpha 1 Antitrypsin

Mediterranean spotted fever (MSF) is a rickettsiosis that induces widespread microvascular injury. To obtain quantitative information on the in vivo activation and inactivation of the protein C system during the acute phase of endothelial damage, several components of the protein C pathway were studied in 28 MSF patients. Upon admission (day 1), patients showed clear evidence of endothelial damage as reflected by the significant decrease in the ratio VIII:C/vWF:Ag (0.36 +/- 0.14, mean +/- SD) compared with normals (0.98 +/- 0.14), and clinical and laboratory signs of hemostatic alterations such as decreased platelet count, positive fibrinogen/fibrin degradation products, and increased thrombin:antithrombin-III complex levels. Antigenic protein C (72% +/- 18%) and protein C inhibitor (PCI) (41% +/- 20%) were significantly decreased (P less than .001). Complexes of activated protein C (APC) with PCI or with alpha 1-antitrypsin (alpha 1AT) and of plasma kallikrein with PCI (KK:PCI) were measured using sandwich enzyme-linked immunosorbent assays. APC:alpha 1AT complex levels were increased in patients at day 1 (27 +/- 13 ng/mL) compared with controls (7 +/- 2 ng/mL), and APC:PCI and KK:PCI complexes, which were not detectable in any of the controls, were present in 57% and 75% of the 28 MSF patients, with mean levels of 11 +/- 5 and 46 +/- 16 ng/mL, respectively. After remission of the disease (day 30), a trend toward normal values in the majority of the parameters studied was found. This study shows that, in the course of endothelial injury, MSF patients experience a generalized activation of the protein C pathway, resulting in consumption of protein C and PCI, and in the appearance of APC:inhibitor complexes. Moreover, these data provide the evidence that KK:PCI circulating complexes occur in vivo.

Binding of amyloid β precursor protein to coagulation factor XIa in vivo may favour haemorrhagic stroke

1998 ◽  
Vol 245 (2) ◽  
pp. 111-115 ◽  
Author(s):  
M. Bornebroek ◽  
Peter A. Kr. von dem Borne ◽  
Joost Haan ◽  
Joost C. M. Meijers ◽  
William E. Van Nostrand ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Coagulation Factor ◽  
Haemorrhagic Stroke ◽  
Precursor Protein ◽  
Factor Xia

scholarly journals In vivo and in vitro complexes of activated protein C with two inhibitors in baboons

Blood ◽  
1991 ◽  
Vol 77 (8) ◽  
pp. 1754-1760 ◽  
Author(s):  
F Espana ◽  
A Gruber ◽  
MJ Heeb ◽  
SR Hanson ◽  
LA Harker ◽  
...  
Keyword(s):  
Protein C ◽  
Activated Protein C ◽  
Enzyme Linked Immunosorbent Assay ◽  
High Dose ◽  
Immunoblotting Analysis ◽  
Low Concentrations ◽  
Alpha 1 Antitrypsin ◽  
Formation Of Complexes

In vivo complex formation of activated protein C with protein C inhibitor (APC-PCI) and with alpha 1-antitrypsin (APC-alpha 1AT) following infusion of 0.25 or 1.0 mg APC/kg in 1 hour into baboons was studied using immunoblotting and sandwich enzyme-linked immunosorbent assay (ELISA)s. Before APC infusion, detectable plasma levels (about 30 ng/mL) of APC-alpha 1AT complex were found in the baboon plasma. At the lower APC dose, APC-PCI and APC-alpha 1AT complex levels were 1.4 +/- 0.3 (mean +/- SD) and 0.8 +/- 0.1 microgram/mL after 1 hour of infusion. At the higher APC dose, the APC-PCI level was similar to the APC-alpha 1AT level during the first 30 minutes, but after 1 hour of infusion the APC-alpha 1AT level was higher than the APC-PCI level, reaching 4.1 +/- 1.2 and 2.9 +/- 1.2 microgram/mL, respectively. After 24 hours, complex levels had returned to basal conditions. During infusion of protein C (1.0 mg/kg in 1 hour), both complexes were detected in low concentrations. Following bolus injection of APC, half- lives (t1/2) for APC and APC-PCI and APC-alpha 1AT complexes of 10, 40, and 140 minutes, respectively, were observed. After 1-hour incubation with 2.5 micrograms/mL APC, baboon plasma contained 1.0 +/- 0.2 and 0.8 +/- 0.1 microgram/mL of APC-PCI and APC-alpha 1AT, respectively. Addition of 10 micrograms/mL APC to baboon plasma yielded 2.5 and 2.4 micrograms/mL APC-PCI and APC-alpha 1AT after 1 hour, respectively. Immunoblotting analysis also showed in vivo formation of complexes of APC with an auxilliary inhibitor but not in vitro in citrated plasma. These data show that both PCI and alpha 1AT are physiologic inhibitors of APC and suggest that when PCI is depleted by a high dose of APC, alpha 1AT becomes the major inhibitor of APC.

Factor XIa Induced Activation of the Intrinsic Cascade In Vivo

1996 ◽  
Vol 75 (03) ◽  
pp. 445-449 ◽  
Author(s):  
Hugo ten Cate ◽  
Bart J Biemond ◽  
Marcel Levi ◽  
Walter A Wuillemin ◽  
Kenneth Bauer ◽  
...  
Keyword(s):  
Human Factor ◽  
Coagulation Factor ◽  
Thrombin Inhibitor ◽  
Bleeding Tendency ◽  
Loading Dose ◽  
Factor Xi ◽  
Factor Xia ◽  
Initial Activation ◽  
Baseline Values

SummaryCoagulation factor XI is a glycoprotein of the contact factor system. Its deficiency is associated with a highly variable bleeding tendency, thus a role in relation to hemostasis appears to exist. However, the importance of factor XI for stimulating intrinsic coagulation in vivo has not yet been determined. To study the procoagulant effects of human factor Xla in vivo, we infused the purified enzyme into normal chimpanzees (100 Μg) in the absence or presence of the thrombin inhibitor rec-hirudin (1.0 mg/kg loading dose plus 0.3 mg/kg body wt continuous infusion). Factor Xla elicited an immediate activation of factors IX, X, and prothrombin, as measured by their respective activation fragments. However, whereas the activation of factors IX and X was immediate and shortlasting, (peak increments of 6- and 1.4-fold of baseline at 5 minutes after injection), the conversion of prothrombin gradually increased, reaching a summit of 6-fold baseline values after 60 min, and remaining elevated during the course of the experiments. Thrombin-antithrombin complexes also remained elevated during the study period. In the presence of hirudin, the initial activation of factors IX, X, and prothrombin was unchanged, however the further increment in prothrombin fragment FI+2 was markedly inhibited. These results demonstrate that factor Xla is a potential agonist of the intrinsic cascade in vivo, which activity is enhanced in the presence of thrombin.

scholarly journals Evidence of activation of the protein C pathway during acute vascular damage induced by Mediterranean spotted fever

Blood ◽  
1991 ◽  
Vol 78 (2) ◽  
pp. 416-422 ◽  
Author(s):  
V Vicente ◽  
F Espana ◽  
D Tabernero ◽  
A Estelles ◽  
J Aznar ◽  
...  
Keyword(s):  
Protein C ◽  
Degradation Products ◽  
Spotted Fever ◽  
Activated Protein C ◽  
Quantitative Information ◽  
Endothelial Damage ◽  
Mediterranean Spotted Fever ◽  
Fibrin Degradation Products ◽  
Alpha 1 Antitrypsin

Abstract Mediterranean spotted fever (MSF) is a rickettsiosis that induces widespread microvascular injury. To obtain quantitative information on the in vivo activation and inactivation of the protein C system during the acute phase of endothelial damage, several components of the protein C pathway were studied in 28 MSF patients. Upon admission (day 1), patients showed clear evidence of endothelial damage as reflected by the significant decrease in the ratio VIII:C/vWF:Ag (0.36 +/- 0.14, mean +/- SD) compared with normals (0.98 +/- 0.14), and clinical and laboratory signs of hemostatic alterations such as decreased platelet count, positive fibrinogen/fibrin degradation products, and increased thrombin:antithrombin-III complex levels. Antigenic protein C (72% +/- 18%) and protein C inhibitor (PCI) (41% +/- 20%) were significantly decreased (P less than .001). Complexes of activated protein C (APC) with PCI or with alpha 1-antitrypsin (alpha 1AT) and of plasma kallikrein with PCI (KK:PCI) were measured using sandwich enzyme-linked immunosorbent assays. APC:alpha 1AT complex levels were increased in patients at day 1 (27 +/- 13 ng/mL) compared with controls (7 +/- 2 ng/mL), and APC:PCI and KK:PCI complexes, which were not detectable in any of the controls, were present in 57% and 75% of the 28 MSF patients, with mean levels of 11 +/- 5 and 46 +/- 16 ng/mL, respectively. After remission of the disease (day 30), a trend toward normal values in the majority of the parameters studied was found. This study shows that, in the course of endothelial injury, MSF patients experience a generalized activation of the protein C pathway, resulting in consumption of protein C and PCI, and in the appearance of APC:inhibitor complexes. Moreover, these data provide the evidence that KK:PCI circulating complexes occur in vivo.

scholarly journals Antithrombotic Effects of Montelukast by Targeting Coagulation Factor XIa

2021 ◽  
Author(s):  
Dong Wang ◽  
Yang Zhou ◽  
Yingying Qi ◽  
Meiru Song ◽  
Huiqiao Yao ◽  
...  
Keyword(s):  
Oral Anticoagulants ◽  
Coagulation Factor ◽  
Healthy Individuals ◽  
Prevention Of Thrombosis ◽  
Factor Xia ◽  
Severe Hemorrhage ◽  
Antithrombotic Effects ◽  
Antiasthmatic Drug ◽  
Increase Blood Loss

Abstract Current oral anticoagulants prescribed for the prevention of thrombosis suffer from severe hemorrhagic problems. Coagulation factor XIa (FXIa) has been confirmed as a safer antithrombotic target as intervention with FXIa causes lower hemorrhagic risks. In this study, by a high-throughput virtual screening, we identified Montelukast (MK), an oral antiasthmatic drug, as a potent and specific FXIa inhibitor (IC50 = 0.17 µM). Compared with the two mostly prescribed anticoagulants (Warfarin and Apixaban), MK demonstrated comparable or even higher antithrombotic effects in three independent animal models. More importantly, in contrast to the severe hemorrhage caused by Warfarin or Apixaban, MK did not measurably increase blood loss in vivo. In addition, MK did not affect the hemostatic function in plasma from healthy individuals. In contrast, MK suppressed clot formation in clinical hypercoagulable plasma samples. This study provides a lead compound of anticoagulants targeting FXIa, and suggests the exploratory clinical researches on antithrombotic therapies using MK.

Phenylimidazoles as Potent and Selective Inhibitors of Coagulation Factor XIa with in Vivo Antithrombotic Activity

2014 ◽  
Vol 57 (23) ◽  
pp. 9915-9932 ◽  
Author(s):  
Jon J. Hangeland ◽  
Todd J. Friends ◽  
Karen A. Rossi ◽  
Joanne M. Smallheer ◽  
Cailan Wang ◽  
...  
Keyword(s):  
Coagulation Factor ◽  
Selective Inhibitors ◽  
Antithrombotic Activity ◽  
Factor Xia
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