Antithrombin action of phosvitin and other phosphate‐containing polyanions is mediated by heparin cofactor II

Church, Frank C.; Pratt, Charlotte W.; Treanor, Rita E.; Whinna, Herbert C.

doi:10.1016/0014-5793(88)80164-9

Cited by 31 publications

(9 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…AT up to 6 lmol L -1 did not bind polyP in surface plasmon resonance studies (S.A. Smith and J.H. Morrissey, unpublished observation), consistent with results reported by Church and coworkers [25].…”

Section: Effects Of Polyanions On At-mediated Inhibition Of Fxiasupporting

confidence: 91%

Factor XI anion‐binding sites are required for productive interactions with polyphosphate

Geng

Verhamme

Smith

et al. 2013

Journal of Thrombosis and Haemostasis

View full text Add to dashboard Cite

Background Conversion of factor XI (FXI) to factor XIa (FXIa) is enhanced by polymers of inorganic phosphate (polyP). This process requires FXI to bind to polyP. Each FXIa subunit contains anion-binding sites (ABSs) on the apple 3 (A3) and catalytic domains that are required for normal heparin-mediated enhancement of FXIa inhibition by antithrombin. Objective To determine the importance of FXI ABSs to polyP–enhancement of FXI activation. Methods Recombinant FXI variants lacking one or both ABSs were tested in polyP-dependent purified protein systems, plasma clotting assays, and a murine thrombosis model. Results In the presence of polyP, activation rates for FXI lacking either ABS were reduced compared to wild type FXI, and FXI lacking both sites had an even greater defect. In contrast to heparin, polyP binding to FXIa did not enhance inhibition by antithrombin, and did not interfere with FXIa activation of factor IX. FXI lacking one or both ABSs does not reconstitute FXI-deficient plasma as well as wild type FXI when polyP was used to initiate coagulation. In FXI-deficient mice, FXI lacking one or more ABSs was inferior to wild type FXI in supporting arterial thrombus formation. Conclusion The ABSs on FXIa that are required for expression of heparin’s cofactor activity during protease inhibition by antithrombin are also required for expression of polyP cofactor activity during FXI activation. These sites may contribute to FXI-dependent thrombotic processes.

show abstract

Section: Effects Of Polyanions On At-mediated Inhibition Of Fxiasupporting

confidence: 91%

Factor XI anion‐binding sites are required for productive interactions with polyphosphate

Geng

Verhamme

Smith

et al. 2013

Journal of Thrombosis and Haemostasis

View full text Add to dashboard Cite

show abstract

“…Factor VIII was repurified from Profilate (from the UNC Hospital's Pharmacy) by gel filtration on Sepharose CL-2B. Antithrombin III was prepared as described previously (Church et al, 1988). Factor VIIa and full-length tissue factor pathway inhibitor were the generous gift of Dr Ulla Hedner (Novo Nordisk, Gentofte, Denmark).…”

Section: Methodsmentioning

confidence: 99%

Platelet activity of high‐dose factor VIIa is independent of tissue factor

et al. 1997

View full text Add to dashboard Cite

High‐dose recombinant factor VIIa has been successfully used as therapy for haemophiliacs with inhibitors. The mechanism by which high‐dose factor VIIa supports haemostasis is the subject of some controversy. Postulating a mechanism in which activity is dependent on tissue factor at the site of injury explains the localization of activity but not the requirement for high doses. Postulating a mechanism in which factor VIIa acts on available lipid independently of tissue factor explains the requirement for high doses but not the lack of systemic procoagulant activity. We report that factor VIIa bound weakly to activated platelets (Kd ∼ 90 nm). This factor VIIa was functionally active and could initiate thrombin generation in the presence of plasma concentrations of prothrombin, factor X, factor V, antithrombin III and tissue factor pathway inhibitor. The activity was not dependent on tissue factor. The concentration of factor VIIa required for detectable thrombin generation agreed well with the lowest concentration of factor VIIa required for efficacy in patients. High‐dose factor VIIa may function on the activated platelets that form the initial haemostatic plug in haemophilic patients. These observations are in agreement with clinical trials which have shown that high‐dose factor VIIa was haemostatically effective without causing systemic activation of coagulation.

show abstract

“…Inactivation by AT is accelerated up to 50,000-fold by high molecular weight heparin, which acts as a template, by binding to thrombin exosite II and AT helices A and D (4,11). Whereas heparin accelerates thrombin inactivation by both AT and HCII, dermatan sulfate (DS), and other polyanions (5,(12)(13)(14)(15)(16)(17) selectively enhance HCII inhibitory action. The HCII mechanism was initially thought to utilize GAGs as templates between exosite II and HCII helix D (5,12,13), but later hypothesized to involve allosteric, GAG-induced interaction of an acidic N-terminal domain of HCII with exosite I (6, 7, 18 -21).…”

mentioning

confidence: 99%

The Preferred Pathway of Glycosaminoglycan-accelerated Inactivation of Thrombin by Heparin Cofactor II

Verhamme

Bock

Jackson³

2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

Thrombin (T) inactivation by the serpin, heparin cofactor II (HCII), is accelerated by the glycosaminoglycans (GAGs) dermatan sulfate (DS) and heparin (H). Equilibrium binding and thrombin inactivationThe blood clotting proteinase, ␣-thrombin (T), 1 possesses two electropositive sites, exosites I and II (1, 2), that play distinct roles in its covalent inactivation by the serine proteinase inhibitors (serpins), antithrombin (AT), and heparin cofactor II (HCII), in the absence and presence of rate-accelerating glycosaminoglycans (GAGs) (3-8 (9,10). Inactivation by AT is accelerated up to 50,000-fold by high molecular weight heparin, which acts as a template, by binding to thrombin exosite II and AT helices A and D (4, 11). Whereas heparin accelerates thrombin inactivation by both AT and HCII, dermatan sulfate (DS), and other polyanions (5, 12-17) selectively enhance HCII inhibitory action. The HCII mechanism was initially thought to utilize GAGs as templates between exosite II and HCII helix D (5, 12, 13), but later hypothesized to involve allosteric, GAG-induced interaction of an acidic N-terminal domain of HCII with exosite I (6, 7, 18 -21). A synthetic HCII-(54 -75) peptide was shown to compete with hirudin-(54 -65) for thrombin binding (18). Residues 52-75 in HCII contain two hirudin-like repeats, the first of which interacts directly with exosite I (21). The crystal structure of the HCII⅐S195A-thrombin Michaelis complex confirmed this exosite I interaction (22). Deletion of the first HCII acidic repeat (6,19), and mutations in exosite I residues Arg 67 and Arg 73 (20) caused large decreases in the rate constants for the heparin-and DS-catalyzed inactivation, further suggesting the importance of the direct HCII-exosite I interaction. Selective thrombin exosite II mutations did not affect the DS-catalyzed inactivation rate significantly (23,24). Blocking exosite II with HD22, a single-stranded DNA aptamer only had a modest effect on this inactivation rate, and DS with a chain length of 12-20 saccharide units was found to be as effective as higher M r DS in catalyzing thrombin inactivation (25). Whereas some studies report DS binding to thrombin (13,23,26), others postulate that DS does not interact with thrombin (27, 28). These findings, and the assumption that DS template action, like heparin, engages exosite II, led to the proposal of a mechanism in which direct interaction of the HCII N-terminal domain with exosite I is predominant, and GAG template action may be less important, or not even obligatory.In the mechanism of high affinity heparin-catalyzed throm-

show abstract

Antithrombin action of phosvitin and other phosphate‐containing polyanions is mediated by heparin cofactor II

Cited by 31 publications

References 22 publications

Factor XI anion‐binding sites are required for productive interactions with polyphosphate

Factor XI anion‐binding sites are required for productive interactions with polyphosphate

Platelet activity of high‐dose factor VIIa is independent of tissue factor

The Preferred Pathway of Glycosaminoglycan-accelerated Inactivation of Thrombin by Heparin Cofactor II

Contact Info

Product

Resources

About