Kallikrein directly interacts with and activates Factor IX, resulting in thrombin generation and fibrin formation independent of Factor XI (original) (raw)
Related papers
The plasma kallikrein–kinin system: its evolution from contact activation
Journal of Thrombosis and Haemostasis, 2007
The plasma kallikrein-kinin system consists of the proteins factor XII (FXII), prekallikrein (PK), and high molecular weight kininogen. It was first recognized as a surface-activated coagulation system that is activated when blood or plasma interacts with artificial surfaces. Although surfaceactivated contact activation occurs in vivo in the case of tissue destruction or a developing thrombus, the physiologic basis for the activation and function of this system has not been delineated. New investigations indicate that there is a proteolytic pathway on cells for PK activation independent of FXII. This pathway for PK with subsequent FXII activation indicates physiologic activities. These activities include blood pressure regulation and modulation of thrombosis risk independently of hemostasis. Furthermore, they include regulation of endothelial cell proliferation, angiogenesis and apoptosis through a cellularbased, outside-in signaling system. The present characterizations of this system, which incorrectly had been thought to initiate coagulation, represent an evolution of understanding in this field.
The plasma kallikrein-kinin system counterbalances the renin-angiotensin system
Journal of Clinical Investigation, 2002
The plasma kallikrein-kinin system (KKS), first recognized over 40 years ago, was originally believed to contribute to physiologic hemostasis. At the time, factor XII (Hageman factor, FXII) and the related proteins prekallikrein (PK) and high molecular-weight kininogen (HK) were known to be essential for efficient surface-activated blood coagulation, as measured in the activated partial thromboplastin time (APTT) test. Indeed, in this test, autoactivation of FXII in glass tubes promotes thrombin formation. According to the then-current "contact activation" hypothesis, FXII activation on a negatively charged surface was thought to initiate hemostasis in a similar manner by a cascade of proteolytic reactions that culminate in thrombin formation. This model was undermined by the failure to identify such a physiologically relevant surface, coupled with evidence that individuals deficient in FXII, PK, or HK are free of bleeding disorders. In addition, the
Journal of Clinical Investigation, 2008
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikreinkinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
Biomaterials, 2009
Traditional biochemistry of contact activation of blood coagulation suggesting that anionic hydrophilic surfaces are specific activators of the cascade is inconsistent with known trends in protein adsorption. To investigate contact activation reactions, a chromogenic assay was used to measure prekallikrein (PK) hydrolysis to kallikrein (Kal) by activated factor XII (FXIIa) at test hydrophilic (clean glass) and hydrophobic (silanized glass) surfaces in the presence of bovine serum albumin (BSA). Hydrolysis of PK by FXIIa is detected after contact of the zymogen FXII with a test hydrophobic surface only if putatively-adsorbed FXIIa is competitively displaced by BSA. By contrast, FXIIa activity is detected spontaneously following FXII activation by a hydrophilic surface and requires no adsorption displacement. These results (i) show that an anionic hydrophilic surface is not a necessary cofactor for FXIIa-mediated hydrolysis of PK, (ii) indicate that PK hydrolysis does not need to occur by an activation complex assembled directly on an anionic, activating surface, (iii) confirms that contact activation of FXII (autoactivation) is not specific to anionic hydrophilic surfaces, and (iv) demonstrates that protein-adsorption competition is an essential feature that must be included in any comprehensive mechanism of surface-induced blood coagulation.
Activated factor V is a cofactor for the activation of factor XI by thrombin in plasma
Proceedings of the National Academy of Sciences, 2010
The mechanism by which the intrinsic pathway of coagulation contributes to physiological hemostasis is enigmatic. Thrombin activates factor XI, a key zymogen in this pathway, which leads to increased thrombin generation. As thrombin-dependent activation of factor XI in vitro is relatively inefficient, we hypothesized that a physiological cofactor supports this reaction in a plasma environment. We therefore investigated whether the cofactors of coagulation, activated factor V, activated factor VIII, high-molecular weight kininogen, or protein S, influenced activation of factor XI by thrombin. Only activated factor V stimulated activation of factor XI by thrombin in a purified system. Binding studies demonstrated that factor XI specifically interacts with both factor V and factor Va through multiple binding sites. We further investigated this cofactor function of activated factor V in plasma. Depletion of factor V, or the addition of activated protein C, decreased the activation of the intrinsic pathway by thrombin in plasma. However, activated protein C did not exert this effect in the plasma of a homozygous carrier of the prothrombotic factor V Leiden mutation. In conclusion, we propose a role for (activated) factor V as a cofactor in the activation of factor XI by thrombin. These findings offer insights into the coagulation system in both health and disease.
Blood, 1998
The consequences of assembling the contact system of proteins on the surface of vascular cells has received little study. We asked whether assembly of these proteins on the surface of cultured human endothelial cells (HUVECs) results in the activation of prekallikrein (PK) and its dependent pathways. Biotinylated PK binds specifically and reversibly to HUVECs in the presence of high molecular weight kininogen (HK) (apparent K d of 23 ؎ 11 nmol/L, B max of 1.7 ؎ 0.5 ؋ 10 7 sites per cell [mean ؎ SD, n ؍ 5 experiments]). Cellassociated PK is rapidly converted to kallikrein. Surprisingly, the activation of cell-associated HK•PK complexes is entirely independent of exogenous factor XII (K m ؍ 30 nmol/L, V max ؍ 12 ؎ 3 pmol/L/min in the absence v K m ؍ 20 nmol/L, V max ؍ 9.2 ؎ 2.1 pmol/L/min in the presence of factor XII). Rather, kallikrein formation is mediated by an endothelial cellassociated, thiol protease. Cell-associated HK is proteolyzed during the course of prekallikrein activation, releasing kallikrein from the surface. Furthermore, activation of PK bound to HK on HUVECs promotes kallikrein-dependent activation of pro-urokinase, resulting in the formation of plasmin. These results indicate the existence of a previously undescribed, factor XII-independent pathway for contact factor activation on HUVECs that regulates the production of bradykinin and may contribute to cell-associated plasminogen activation in vivo. 1998 by The American Society of Hematology. MATERIALS AND METHODS Proteins. HK was purified from plasma using sequential carboxymethyl-papain-Sepharose (CM-papain-Sepharose) and Blue-Sepharose affinity chromatography as previously reported. 28,29 HK migrated as a 120-kD protein on sodium dodecyl sulfate-8% polyacrylamide gel electrophoresis (SDS-PAGE) after reduction with 2% -mercaptoethanol. HK had a specific activity of 12 to 20 U/mg. Purified HK was iodinated with IODOGEN (Pierce, Rockford, IL) as previously reported. 20 Human PK was purchased from Enzyme Research Laboratories (South Bend, IN). The protein migrated as a doublet at 88 and 85 kD on 10% SDS-PAGE under reduced conditions and expressed approximately 1% to 3% of the amidolytic activity of kallikrein. 33 No FXII or its activated forms were found in the HK or PK preparations by immunoblotting using a monospecific goat antisera to human FXII. PK was also iodinated with IODOGEN using identical techniques previously reported for HK. 20,23 Iodinated PK was a doublet at 88 and 85 kD on 10% SDS-PAGE under reducing conditions. FXII, purchased from Enzyme Research Laboratories, migrated predominantly as a single band at 80 kD on 10% SDS-PAGE under reduced conditions and expressed less than 1% of the amidolytic activity of activated FXII. Activated factor XII (␣FXIIa) was purchased from Enzyme Research Laboratories. ␣FXIIa migrated as two bands at 50 and 28 kD on 10%
Frontiers in Medicine, 2016
The contact activation (CAS) and kallikrein/kinin (KKS) systems regulate thrombosis risk in two ways. First, the CAS influences contact activation-induced factor XI activation and thrombin formation through the hemostatic cascade. Second, prekallikrein (PK) and bradykinin of the KKS regulate expression of three vessel wall G-protein-coupled receptors, the bradykinin B2 receptor (B2R), angiotensin receptor 2, and Mas to influence prostacyclin formation. The degree of intravascular prostacyclin formation inversely regulates intravascular thrombosis risk. A 1.5-to 2-fold increase in prostacyclin, as seen in PK deficiency, increases vessel wall Sirt1 and KLF4 to downregulate vessel wall tissue factor which alone is sufficient to lengthen induced thrombosis times. A twofold to threefold increase in prostacyclin, as seen the B2R-deficient mouse, delays thrombosis and produces a selective platelet function defect of reduced GPVI activation and platelet spreading. Regulation of CAS and KKS protein expression has a profound influence on thrombosis-generating mechanisms in the intravascular compartment.
Platelets promote coagulation factor XII-mediated proteolytic cascade systems in plasma
Biological Chemistry, 2006
Blood coagulation factor XII (FXII, Hageman factor) is a plasma serine protease which is autoactivated following contact with negatively charged surfaces in a reaction involving plasma kallikrein and high-molecular-weight kininogen (contact phase activation). Active FXII has the ability to initiate blood clotting via the intrinsic pathway of coagulation and inflammatory reactions via the kallikrein-kinin system. Here we have determined FXII-mediated bradykinin formation and clotting in plasma. Western blotting analysis with specific antibodies against various parts of the contact factors revealed that limited activation of FXII is sufficient to promote plasma kallikrein activation, resulting in the conversion of high-molecular-weight kininogen and bradykinin generation. The presence of platelets significantly promoted FXII-initiated bradykinin formation. Similarly,in vitroclotting assays revealed that platelets critically promoted FXII-driven thrombin and fibrin formation. In summar...
Amidolytic assay of factor XI in human plasma-significance of kallikrein for the activity measured
Thrombosis Research, 1995
Factor XI (FXI) deficiency is associated with an abnormal bleeding state. The extent of bleeding does not correlate well with the plasma concentration of FXI, and it has been suggested that also unknown factors interfere with the bleeding tendency. In a recent paper (Thromb. Res. 74, 477-485, 1994) we found that FXIa activated in human plasma was present in association with part of factor XIIa (FXIIa) and part of kallikrein, influencing their functional activities. Should the activity level of FXIa also be altered by the other contact factors this might provide one approach to the problem of the failure of assays of FXIa to correlate with bleeding tendency. In the present study we have developed an assay procedure for FXIa based on its amidolytic (S-2366) activity, and allowing at the same time a quantification of the amount of FXIa associated to kallikrein. The total amidase activity obtained was separated into two main fractions by use of soybean trypsin inhibtor (STI), corn inhibitor (CI) and lima bean trypsin inhibitor (LTI). One fraction contained free FXIa which could be specifically blocked by LTI. An inhibitor resistant fraction was found to contain FXIa inactive in association with kallikrein. The content of FXIa could be assessed in experiments with mixtures of normal plasma and plasma deficient in prekallikrein, and was taken into account in the calculations. This fraction increased during storage of plasma at-70°C. To obtain stable and comparable assay conditions the method was based on plasma stored for at least four weeks. The specificity of the method was verified by parallel radial immunodiffusion tests. The results imply that the activity level of FXIa is dependent on kallikrein present. If the experimental results has relevance to the situation under physiological conditions, they indicate one possible cause of the failure of assays of FXI to correlate with bleeding tendency. The contact activation system of blood coagulation comprises four proteins,-factor XII (FXII), factor XI (FXI), prekallikrein (PK) and high molecular weight kininogen (HK). In contrast to congenital deficiences of the other contact phase proteins FXI deficiency is associated with an abnormal bleeding state. However, the extent of the bleeding tendency does not correlate well with the plasma concentration of FXI measured in clotting assays or in immunological test procedures (1,2,3,4,5). In a comprehensive study of members of factor XI deficient kindreds the results obtained in radioimmunoassay and in a coagulation test showed a high degree of correlation (5). However, the levels of FXI measured in patients with failing hemostasis were close to those in non-bleeders. It was concluded that the bleeding tendency in FXI deficiency is determined by unknown factors in addition to plasma concentration of FXI. We have previously reported that
Thrombosis Research, 2010
Factor XII (FXII) is a coagulation protein that is essential for surface-activated blood coagulation tests but whose deficiency is not associated with bleeding. For over forty years, investigators in hemostasis have not considered FXII important because its deficiency is not associated with bleeding. It is because there is a dichotomy between abnormal laboratory assay findings due to FXII deficiency and clinical hemostasis that investigators sought explanations for physiologic hemostasis independent of FXII. FXII is a multidomain protein that contains two fibronectin binding consensual sequences, two epidermal growth factor regions, a kringle region, a proline-rich domain, and a catalytic domain that when proteolyzed turns into a plasma serine protease. Recent investigations with FXII deleted mice that are protected from thrombosis indicate that it contributes to the extent of developing thrombus in the intravascular compartment. These findings suggest that it has a role in thrombus formation without influencing hemostasis. Last, FXII has been newly appreciated to be a growth factor that may influence tissue injury repair and angiogenesis. These combined studies suggest that FXII may become a pharmacologic target to reduce arterial thrombosis risk and promote cell repair after injury, without influencing hemostasis. In 1955, Oscar Ratnoff and Joan Colopy described a patient, 37 year old John Hageman, who was found to have a prolonged Lee-White clotting time that was obtained during routine preoperative screening. The patient had no hemorrhagic symptoms even though he had a remarkably prolonged whole blood and plasma clotting times in glass and silicone-coated glass tubes. The prolonged clotting time was corrected by small amounts of plasma from each of the other known clotting factor deficiencies. Ratnoff concluded that his patient was deficient in an unrecognized clotting factor which he named Hageman factor, later known as Factor XII (FXII) [1]. Further experiments indicated that Hageman factor (FXII) circulates as an inactive precursor (zymogen) that becomes "activated" (FXIIa) as clotting commenced. In 1961, Ratnoff and Davie demonstrated that Factor XI (FXI) was activated by FXIIa, contributing to the presentation of their waterfall cascade hypothesis for the blood coagulation system [2]. These studies encompass the major known properties of Factor XII, a protein that autoactivates upon exposure to negatively charged surfaces to become the enzyme Factor XIIa (α-FXIIa), which then activates FXI, prekallikrein (PK), and C1 esterases (C1r, C1s), the first components of the macromolecular complex of C1 and the classic complement cascade. FXIIa