Disease relevance of ADAMTS13

• ADAMTS13 deficiency is linked to a life-threatening disorder, thrombotic thrombocytopenic purpura (TTP), characterized by platelet-rich thrombi in the microvasculature [1].
• Strikingly, we found that ADAMTS13 down-regulates both platelet adhesion to exposed subendothelium and thrombus formation in injured arterioles [1].
• Thus, the study showed that ADAMTS13 activity is decreased in a substantial proportion of patients with thrombocytopenia of various causes [2].
• von Willebrand factor cleaving protease (ADAMTS13) is deficient in recurrent and familial thrombotic thrombocytopenic purpura and hemolytic uremic syndrome [3].
• A novel nanobody that detects the gain-of-function phenotype of von Willebrand factor in ADAMTS13 deficiency and von Willebrand disease type 2B [4].

Psychiatry related information on ADAMTS13

• Prompt identification of absent or impaired ADAMTS13 activity could prove invaluable to clinical decision-making regarding diagnosis and treatment of suspected TTP patients [5].

High impact information on ADAMTS13

• We show that deficiency of ADAMTS13 is the molecular mechanism responsible for TTP, and suggest that physiologic proteolysis of VWF and/or other ADAMTS13 substrates is required for normal vascular homeostasis [6].
• A predicted gene in the identified interval corresponds to a segment of a much larger transcript, identifying a new member of the ADAMTS family of zinc metalloproteinase genes (ADAMTS13) [6].
• Absence of ADAMTS13 did not promote thrombi formation in alphaIIbbeta3 integrin-inhibited blood [1].
• Recombinant ADAMTS13 reduced platelet adhesion and aggregation in histamine-activated venules and promoted thrombus dissolution in injured arterioles [1].
• An inhibitory antibody to ADAMTS13 infused in wild-type mice prolonged adhesion of platelets to endothelium and induced thrombi formation with embolization in the activated microvenules [1].

Chemical compound and disease context of ADAMTS13

• RESULTS: Discontinuation of cyclosporine and daily plasma exchange increased the ADAMTS13 activity, which was followed by resolution of the microangiopathic hemolysis and improvement of the graft function [7].
• The presence of a consumptive coagulopathy in the setting of thrombocytopenia supports a diagnosis of DIC, not TTP-HUS, and is demonstrated by decreasing serum fibrinogen levels, and increasing TTs, PTs, aPTTs, and fibrin degradation products [8].
• Among secondary alterations in hemostasis, thrombocytopenia, platelet function abnormalities, or factor consumption contribute to the risk of ICH in patients with ITP, TTP, disseminated intravascular coagulation, myeloproliferative or myelodysplastic disorders, and exposure to certain medications [9].

Biological context of ADAMTS13

• The comparison of individual ADAMTS13 genotypes and plasma VWF-CP activities indicated that the R268P, Q449stop, and C508Y mutations abrogated activity of the enzyme, whereas the P475S mutant retained low but significant activity [10].
• Bombay phenotype is associated with reduced plasma-VWF levels and an increased susceptibility to ADAMTS13 proteolysis [11].
• Considerable progress has also been realized toward understanding the role of ADAMTS13 in normal hemostasis, as well as the mechanisms by which ADAMTS13 deficiency contributes to TTP pathogenesis [12].
• Mutation analysis of the ADAMTS13 gene in the patients deficient in VWF-CP by direct sequencing of all 29 exons identified 8 different mutations, suggesting the hereditary form of TTP in 1 patient with ITP, in the patient with Evans syndrome, and in 5 of the 8 patients with TTP [13].
• In a subgroup of patients with TTP or HUS, the ADAMTS13 defect was inherited, as documented by half-normal levels of ADAMTS13 in their asymptomatic parents, consistent with the heterozygous carrier state [3].

Anatomical context of ADAMTS13

• We found that recombinant CUB-1 and CUB-1+2 polypeptides and synthetic peptides derived from CUB-1 partially blocked the cleavage of ULVWF by ADAMTS13 on the surface of endothelial cells under flow [14].
• ADAMTS13 activity was similar in all 4 type I VWD cryodepleted plasmas and comparable to a normal control plasma [15].
• ADAMTS13, the specific von Willebrand factor (VWF)-cleaving metalloprotease, prevents the spontaneous formation of platelet thrombi in the microcirculation by degrading the highly adhesive ultralarge VWF multimers into smaller forms [16].
• In expression experiments using HeLa cells, all mutants showed no or a marginal secretion of ADAMTS13 [17].
• Furthermore, ADAMTS13 was detected immunohistochemically in perisinusoidal cells, whereas no staining was observed in hepatocytes [18].

Associations of ADAMTS13 with chemical compounds

• Digestion of A1A2A3 by plasma ADAMTS13 was enhanced to a similar extent by a recombinant mutant fragment of platelet GPIbalpha that binds with high affinity to domain A1 or by heparin [19].
• We conclude that reduction in the number of terminal sugars on N-linked glycan increases susceptibility of globular VWF to ADAMTS13 proteolysis and is associated with reduced plasma VWF:Ag and VWF:CB levels [11].
• Barium ions stimulated ADAMTS13 activity in citrated plasma but not in citrate-free plasma [20].
• ADAMTS13 could cleave approximately 14% of VWF pretreated with guanidine HCl, suggesting that this substrate is heterogeneous in susceptibility to proteolysis [20].
• ADAMTS13 is a circulating zinc metalloprotease that cleaves the hemostatic glycoprotein von Willebrand factor (VWF) in a shear-dependent manner [21].
• When the expression of protein O-fucosyltransferase 2 (POFUT2), the enzyme that transfers fucose to serines in TSRs, was reduced using siRNA, the secretion of ADAMTS13 decreased [22].

Physical interactions of ADAMTS13

• Therefore, the spacer domain is required for ADAMTS13 binding to von Willebrand factor [23].

Enzymatic interactions of ADAMTS13

• ADAMTS13 cleaved VWF and FRETS-VWF73 with roughly comparable catalytic efficiency of 55 microM(-1) min(-1) and 18 microM(-1) min(-1), respectively [20].

Regulatory relationships of ADAMTS13

• The finding that an amino acid polymorphism in VWF may influence susceptibility to ADAMTS13 has potentially significant implications in diverse areas [15].
• We evaluated whether or not ADAMTS-13 deficiency and autoantibodies inactivating the protease prevalent in patients with the prototypic autoimmune diseases systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) [24].

Other interactions of ADAMTS13

• High levels of ADAMTSs transcripts were also observed in some tumor biopsies and cells lines, including osteosarcomas (ADAMTS19), melanoma and colon carcinoma cells (ADAMTS13) [25].
• To further delineate the binding site in the disintegrin/TSR1/cysteine-rich/spacer region, we prepared additional ADAMTS13 fragments [26].
• Severe deficiency of the von Willebrand Factor (VWF)-cleaving proteinase, ADAMTS13, is associated with the development of thrombotic thrombocytopenic purpura (TTP) [27].
• The first thrombospondin repeat also affects binding, and the C-terminal thrombospondin type 1 and CUB domains of ADAMTS13 may modulate this interaction [23].
• Preincubation of thrombin with soluble thrombomodulin, but not heparin, inhibited the proteolysis of ADAMTS13, suggesting the involvement of thrombin exosite I (and not exosite II) in ADAMTS13 recognition [28].

Analytical, diagnostic and therapeutic context of ADAMTS13

• Surface plasmon resonance demonstrated appreciable reduction in binding affinity between ADAMTS13 and VWF115 mutants (KD up to approximately 1.3 microM), compared with VWF115 (KD 20 nM) [29].
• Using high pressure liquid chromatography analysis, the initial rates of VWF115 cleavage by ADAMTS13 at different substrate concentrations were determined, and from this the kinetic constants were derived (Km 1.61 microM; kcat 0.14 s(-1)), from which the specificity constant kcat/Km was calculated, 8.70 x 10(4) m(-1) s(-1) [29].
• By using real-time RT-PCR, we confirmed that in mice the liver had the highest level of the ADAMTS13 transcript [21].
• Northern blot analysis has shown that ADAMTS13 is expressed primarily in the liver [21].
• The ELISA was more sensitive than the standard functional inhibitor assay for detecting antibodies against ADAMTS13 [30].

References