Factor XI in haemostasis and thrombosis: Past, present and future

Seligsohn, Uri

doi:10.1160/th07-04-0246

Cited by 54 publications

(71 citation statements)

References 63 publications

(53 reference statements)

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“…[1][2][3] The protein is a 160-kDa disulfide-linked dimer of identical 607 amino acid subunits, each containing 4 90-or 91-amino acid repeats called apple domains (A1 to A4 from the N-terminus) and a C-terminal trypsin-like catalytic domain. [3][4][5][6][7] The structure is distinctly different from those of the well-characterized vitamin K-dependent coagulation proteases.…”

Section: Introductionmentioning

confidence: 99%

“…2,16,17 Severe deficiency (Ͻ 15% of normal plasma activity) is prevalent in people of Jewish ancestry. 2,16,17,24 The carrier rate is approximately 5% in Ashkenazi Jews, with severe (homozygous) deficiency found in 1 in 450 persons. 16,24 Two mutations account for more than 90% of abnormal alleles in this population.…”

Section: Introductionmentioning

confidence: 99%

“…1 However, newer schemes do not assign FXI a role in early fibrin generation, based largely on the observation that FXI deficiency causes relatively mild bleeding. [1][2][3] FXIa is now postulated to be part of a feedback loop that sustains thrombin generation through FIX activation to consolidate coagulation ( Figure 1). [13][14][15] This appears to be particularly important in tissues with robust fibrinolytic activity, such as the oropharynx and urinary tract, which are common sites of bleeding in FXI-deficient patients.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15] This appears to be particularly important in tissues with robust fibrinolytic activity, such as the oropharynx and urinary tract, which are common sites of bleeding in FXI-deficient patients. 2,[16][17][18][19][20][21][22][23] Congenital FXI deficiency is associated with a variable, mild to moderate bleeding disorder. 2,16,17 Severe deficiency (Ͻ 15% of normal plasma activity) is prevalent in people of Jewish ancestry.…”

mentioning

confidence: 99%

“…2,[16][17][18][19][20][21][22][23] Congenital FXI deficiency is associated with a variable, mild to moderate bleeding disorder. 2,16,17 Severe deficiency (Ͻ 15% of normal plasma activity) is prevalent in people of Jewish ancestry. 2,16,17,24 The carrier rate is approximately 5% in Ashkenazi Jews, with severe (homozygous) deficiency found in 1 in 450 persons.…”

mentioning

confidence: 99%

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Structure and function of factor XI

Emsley

McEwan

Gailani

2010

Blood

194

234

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Factor XI (FXI) is the zymogen of an enzyme (FXIa) that contributes to hemostasis by activating factor IX. Although bleeding associated with FXI deficiency is relatively mild, there has been resurgence of interest in FXI because of studies indicating it makes contributions to thrombosis and other processes associated with dysregulated coagulation. FXI is an unusual dimeric protease, with structural features that distinguish it from vitamin K-dependent coagulation proteases. The recent availability of crystal structures for zymogen FXI and the FXIa catalytic domain have enhanced our understanding of structure-function relationships for this molecule. FXI contains 4 "apple domains" that form a disk structure with extensive interfaces at the base of the catalytic domain. The characterization of the apple disk structure, and its relationship to the catalytic domain, have provided new insight into the mechanism of FXI activation, the interaction of FXIa with the substrate factor IX, and the binding of FXI to platelets. Analyses of missense mutations associated with FXI deficiency have provided additional clues to localization of ligand-binding sites on the protein surface. Together, these data will facilitate efforts to understand the physiology and pathology of this unusual protease, and development of therapeutics to treat thrombotic disorders. (Blood. 2010; 115(13):2569-2577) IntroductionFactor XI (FXI) is the zymogen of a blood coagulation protease, factor XIa (FXIa), that contributes to hemostasis through activation of factor IX (FIX; Figure 1). [1][2][3] The protein is a 160-kDa disulfide-linked dimer of identical 607 amino acid subunits, each containing 4 90-or 91-amino acid repeats called apple domains (A1 to A4 from the N-terminus) and a C-terminal trypsin-like catalytic domain. [3][4][5][6][7] The structure is distinctly different from those of the well-characterized vitamin K-dependent coagulation proteases. 1 FXI circulates in blood as a complex with high molecular weight kininogen (HK). 8 Prekallikrein (PK), the zymogen of the protease ␣-kallikrein, is a monomeric homolog of FXI with the same domain structure 9,10 that also circulates in complex with HK. 11 A recent analysis of vertebrate genomes confirmed that FXI and PK are products of a duplication event during mammalian evolution. 12 The ancestral predecessor is also a protease with 4 apple domains, but its functional properties have not been studied. 12 In the cascade/waterfall models of coagulation that are the basis for the activated partial thromboplastin time (aPTT) assay, FXI activation by FXIIa initiates fibrin formation (Figure 1). 1 However, newer schemes do not assign FXI a role in early fibrin generation, based largely on the observation that FXI deficiency causes relatively mild bleeding. [1][2][3] FXIa is now postulated to be part of a feedback loop that sustains thrombin generation through FIX activation to consolidate coagulation (Figure 1). [13][14][15] This appears to be particularly important in tissues with robust fibrinolytic acti...

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