Molecular Biology of Hemophilia B

Roberts, Harold R.

doi:10.1055/s-0038-1646151

Cited by 71 publications

(40 citation statements)

References 30 publications

(10 reference statements)

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“…EGF-like domains are thought to be mediators of protein-protein interactions by conservation of this function from EGF. A physiological contribution of the EGF-like domains is suggested by the finding that mutations occurring within these domains are associated with a bleeding tendency (3,16). There has been a recent interest in further characterizing these domains and determining their contribution to FIX(a) procoagulant functions.…”

Section: Fig 2 Analysis Of Purified Recombinant Fix Proteins By Sdsmentioning

confidence: 99%

“…While an E78K point mutation resulted in an impaired interaction with FVIIIa, an R94D point mutation did not result in a functional deficiency (36). 3 Subsequent investigations have determined that the R94S substitution introduces a carbohydrate modification to this site and accounts for the functional impairment of the R94S substitution (35) in the hemophilia B patient. The normal behavior of FIXaR94D suggests a compensation mechanism that allows the R94D protein to function normally while the E78K protein is impaired.…”

Section: Fig 2 Analysis Of Purified Recombinant Fix Proteins By Sdsmentioning

confidence: 99%

“…Analysis of patient data suggests that residues contained within EGF1 and EGF2 are important for FIX(a) functions. Several point mutations within the EGF-like domains result in dysfunctional FIX(a) activity and a bleeding tendency (3,16). Investigations of the EGF-like domains have found several important functions for these domains.…”

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confidence: 99%

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Residues 88–109 of Factor IXa Are Important for Assembly of the Factor X Activating Complex

Wilkinson¹,

London²,

Walsh³

2002

Journal of Biological Chemistry

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Activated platelets and phospholipid vesicles promote assembly of the intrinsic factor X (FX) activating complex by presenting high-affinity binding sites for blood coagulation FIXa, FVIIIa, and FX. Previous reports suggest that the second epidermal growth factor (EGF) FIXa is a serine protease that participates in the intrinsic pathway of blood coagulation. FIXa activates FX as part of the intrinsic FX activating complex. The FX activating complex consists of FIXa, FVIIIa (a nonenzymatic cofactor), and FX (the normal macromolecular substrate) assembled on a procoagulant surface (8, 9). Under physiological conditions, thrombinactivated platelets or endothelial cells can provide this surface (10 -13). Additionally, synthetic phospholipid vesicles containing phosphatidylserine can also support assembly of the FX activating complex and activation of FX (8, 14). Assembly of the surface-bound FX activating complex results in a dramatic increase (ϳ20 million-fold) in the catalytic efficiency (k cat /K m ) of FX activation versus that of FIXa alone in solution (9, 15). The surface localization of FIXa is a requisite step in the catalytic enhancement of FIXa when assembled in the FX activating complex (9, 14).-Recent investigations have focused on the contributions of the EGF-like domains to FIXa biochemistry. Analysis of patient data suggests that residues contained within EGF1 and EGF2 are important for FIX(a) functions. Several point mutations within the EGF-like domains result in dysfunctional FIX(a) activity and a bleeding tendency (3,16). Investigations of the EGF-like domains have found several important functions for these domains. EGF1 is important for interactions with FVIIa/TF (17), FVIIIa (18), and FX (19,20). EGF1 does not appear to be important for binding to surfaces such as phospholipids (21), platelets, (22), or endothelial cells (23). While EGF2 has not been extensively characterized, experiments have indicated its importance for activation of FX. A chimeric FIXa protein in which both EGF1 and EGF2 domains were replaced by those of FX possessed about 4% clotting activity (24). In contrast, a chimeric protein with the FX EGF1 domain but the wild type FIX EGF2 domain was entirely normal (24), suggesting an essential function for EGF2. More recent experiments from our laboratory have indicated that EGF2 is likely involved in mediating surface binding to both platelets and phospholipids (25,26).To further define the contribution of the EGF2 domain to surface binding, we have prepared several chimeric FIXa proteins (see Fig. 1

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Section: Fig 2 Analysis Of Purified Recombinant Fix Proteins By Sdsmentioning

confidence: 99%

Section: Fig 2 Analysis Of Purified Recombinant Fix Proteins By Sdsmentioning

confidence: 99%

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Residues 88–109 of Factor IXa Are Important for Assembly of the Factor X Activating Complex

Wilkinson¹,

London²,

Walsh³

2002

Journal of Biological Chemistry

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“…[12][13][14] Severe deficiency in FIX leads to bleeding (Hemo-philia B, Christmas disease). 15 Lollar and Fass 16 showed that active-site blocked factor IXa (FIXai) inhibits clot formation in vitro.…”

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confidence: 99%

Antithrombotic Efficacy of a Novel Murine Antihuman Factor IX Antibody in Rats

Feuerstein¹,

Patel²,

Toomey³

et al. 1999

ATVB

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Abstract-A murine antihuman factor IX monoclonal antibody (BC2) has been generated and evaluated for its capacity to prolong the activated partial thromboplastin time (aPTT) in vitro and ex vivo and to prevent arterial thrombosis in a rat model in vivo. BC2 extended aPTT to a maximum of 60 to 80 seconds at 100 to 1000 nmol/L in vitro (rat and human plasma, respectively) and ex vivo (rat) after dosing of rats up to 6 mg/kg in vivo. BC2, administered as bolus (1 to 6 mg/kg) followed by infusion (0.3 to 2 mg ⅐ kg Ϫ1 ⅐ h Ϫ1 ), dose-dependently prevented thrombosis of an injured rat carotid artery (FeCl 3 -patch model), increased time to artery occlusion, and reduced incidence of vessel occlusion. BC2 efficacy in preventing arterial thrombosis exceeded that of heparin (bolus 15 to 120 U/kg followed by infusion 0.5 to 4.0 U ⅐ kg Ϫ1 ⅐ min Ϫ1 ), whereas the latter rendered the blood incoagulable (aPTTϾ1000 seconds). BC2 demonstrated complete antithrombotic efficacy also as a single bolus given either as prevessel or postvessel injury as evidenced by reduction of thrombus mass (from 4.18Ϯ0.49 to 1.80Ϯ0.3 mg, PϽ0.001), increasing vessel patency time (from 14.9Ϯ0.9 minutes to 58.3Ϯ1.7 minutes, PϽ0.001) and decreasing incidence of vessel occlusion from 100% to 0% in vehicle-versus BC2-treated rats, respectively. BC2 (3 mg/kg, IV) administered in a single bolus resulted in 50% reduction in thrombus mass (PϽ0.01), extended vessel patency time (PϽ0.001), extended aPTT only 4-fold, and had no effect on blood loss via a tail surgical wound; heparin, at doses that reduced thrombus mass to a similar extent, extended aPTT beyond 1000 seconds (over 500-fold) and increased blood loss from 1.8Ϯ0.7 to 3.3Ϯ0.6 mL (PϽ0.001). These data suggest that BC2 may provide enhanced therapeutic efficacy in humans at lesser interference with blood hemostasis than heparin.

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“…F9 gene is located on the long arm of chromosome X at band Xq27.1-q27.2. 461-residue pre-pro-protein is translated from 2802bp mRNA and subsequently cleaved to the 415-residue mature protein when undergoes a serial of posttranslational modifications [2,3]. FIX protein compose of c-carboxyglutamic acid-rich (Gla) domain, 2 epidermal growth factor-like domains (EGF1 and EGF2) and serine protease (SP) domain.…”

Section: Introductionmentioning

confidence: 99%