PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ADAMTS13 Protein”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed2003

Severe deficiency of the specific von Willebrand factor-cleaving protease (ADAMTS 13) activity in a subgroup of children with atypical hemolytic uremic syndrome.

OBJECTIVE: The von Willebrand factor-cleaving protease (VWF-cp) activity has been reported to be deficient in adults with thrombotic thrombocytopenic purpura (TTP) and generally normal in adults with hemolytic uremic syndrome (HUS). The goal of this study was to determine VWF-cp activity in children with typical postdiarrheal (d+) HUS or atypical non-postdiarrheal (d-) HUS. Study design We measured VWF-cp activity in the plasma of 64 children with either (d+) HUS (n = 41) or (d-) HUS (n = 23). RESULTS: In the acute phase of HUS, VWF-cp activity was normal (>50%) in 54 children and undetectable (<5%) in one (d+) HUS and in 6 (d-) HUS children. After a 3-month remission, the (d+) HUS patient recovered a 100% VWF-cp activity, and the 6 (d-) HUS patients kept an undetectable level. In these 6 (d-) HUS patients, the disease was characterized by a neonatal onset and several relapses (hemolytic anemia, thrombocytopenia, transient acute renal failure, cerebral ischemia), and sometimes the development of arterial hypertension or end stage renal failure. CONCLUSION: A subgroup of pediatric patients with atypical (d-) HUS, with hematologic symptoms starting at birth and a recurrent course progressively involving kidney and brain, is related to VWF-cp deficiency and actually corresponds to Upshaw-Schulman syndrome revisited as congenital TTP.

ADAM Proteins↗
PubMed2006

Characterization of a core binding site for ADAMTS-13 in the A2 domain of von Willebrand factor.

ADAMTS-13, a metalloprotease in plasma, specifically cleaves the Tyr-1605-Met-1606 bond in the A2 domain of von Willebrand factor (VWF) to regulate the polymer distribution of VWF in circulation, which is critical for primary hemostasis. A 73-aa peptide (VWF73) was previously identified as the minimal substrate cleavable by ADAMTS-13. In this study, VWF73 was enzymatically and chemically cleaved into shorter peptides, and the inhibition of cleavage of a VWF73-derived substrate by these purified peptides was measured in competition studies using a quantitative assay we recently reported. A 24-aa peptide encompassing Pro-1645-Lys-1668 (P'40-P'63) and situated 40 aa downstream from the cleavage site was the minimal peptide that could bind to and competitively inhibit ADAMTS-13 (K(i) = 12 microM). This peptide and longer peptides encompassing this core sequence also inhibited the cleavage of multimeric VWF by ADAMTS-13. These results suggest the presence of a complementary extended binding site, or exosite, on ADAMTS-13. Mutation of Asp-1653 and Asp-1663 to Ala in this region significantly reduced the rate of cleavage of the substrate peptide, whereas the Glu1655Ala mutation caused an enhanced rate of cleavage. These results suggest that ionic interactions of the Pro-1645-Lys-1668 region with the exosite on ADAMTS-13 play a significant role in mediating substrate recognition.

ADAM Proteins↗
PubMed2003

ADAMTS-13 metalloprotease interacts with the endothelial cell-derived ultra-large von Willebrand factor.

Thrombotic thrombocytopenic purpura is caused by congenital or acquired deficiency of ADAMTS-13, a metalloprotease that cleaves the endothelium-derived ultra-large multimers of von Willebrand factor (ULVWF). The proteolysis converts hyper-reactive and thrombogenic ULVWF into smaller and less adhesive plasma forms. Activity of ADAMTS-13 is usually measured in a static system under non-physiological conditions that require protein denaturation and prolonged incubation. We have demonstrated previously that ULVWF multimers, upon release from endothelial cells, form platelet-decorated string-like structures that are rapidly cleaved by ADAMTS-13. Here we report the direct interaction between ADAMTS-13 and VWF under both static and flowing conditions. ADAMTS-13-coated beads adhered to both immobilized VWF and ULVWF strings presented by stimulated endothelial cells. These beads adhered to VWF under both venous (2.5 dynes/cm2) and arterial (30 dynes/cm2) shear stresses. We then demonstrated that ADAMTS-13 beads adhered to immobilized recombinant VWF-A1 and -A3 domains, but soluble metalloprotease bound preferentially to the A3 domain, suggesting that the VWF A3 domain may be the primary docking site for the metalloprotease. We suggest that tensile stresses imposed by fluid shear stretch endothelial bound ULVWF multimers to expose binding sites within the A domains for circulating ADAMTS-13. The bound enzyme then cleaves within the A2 domain that lies in close proximity and releases smaller VWF multimers into the plasma. Once released, these cleaved VWF fragments become inaccessible for the metalloprotease to prevent further cleavage.

ADAM Proteins↗
PubMed2005

Role of chloride ions in modulation of the interaction between von Willebrand factor and ADAMTS-13.

The degradation of von Willebrand factor (VWF) depends on the activity of a zinc protease (referred to as ADAMTS-13), which cleaves VWF at the Tyr(1605)-Met(1606) peptide bond. Little information is available on the physiological mechanisms involved in regulation of AD-AMTS-13 activity. In this study, the role of ions on the ADAMTS-13/VWF interaction was investigated. In the presence of 1.5 m urea, the protease cleaved multimeric VWF in the absence of NaCl at pH 8.00 and 37 degrees C, with an apparent k(cat)/K(m) congruent with 3.4 x 10(4) M(-1) s(-1), but this value decreased by approximately 10-fold in the presence of 0.15 M NaCl. Using several monovalent salts, the inhibitory effect was attributed mostly to anions, whose potency was inversely related to the corresponding Jones-Dole viscosity B coefficients (ClO(4)(-) > Cl(-) > F(-)). The specific inhibitory effect of anions was due to their binding to VWF, which caused a conformational change responsible for quenching the intrinsic fluorescence of the protein and reducing tyrosine exposition to bulk solvent. Ristocetin binding to VWF could reduce the apparent affinity and reverse the inhibitory effect of chloride. We hypothesize that, after secretion into the extracellular compartment, VWF is bound by chloride ions abundantly present in this milieu, becoming unavailable to proteolysis by AD-AMTS-13. Shear forces, which facilitate GpIbalpha binding (this effect being artificially obtained by ristocetin), can reverse the inhibitory effect of chloride, whose concentration gradient across the cell membrane may represent a simple but efficient strategy to regulate the enzymatic activity of ADAMTS-13.

ADAM Proteins↗
PubMed2006

Molecular mapping of the chloride-binding site in von Willebrand factor (VWF): energetics and conformational effects on the VWF/ADAMTS-13 interaction.

Physiological concentrations of NaCl inhibit the hydrolysis of von Willebrand factor (VWF) by ADAMTS-13. This effect is because of the specific binding of chloride ions to VWF. Urea-induced unfolding was measured in the presence of NaCl, CH3COONa, and NaClO4 at pH 8.0, 25 degrees C, for multimeric VWF, the recombinant A1-A2-A3 VWF domains, and the A1 domain. Chloride stabilizes the folded conformation of the A1-A2-A3 and A1 domains more efficiently than acetate but less strongly than perchlorate. Spectroscopic evidence showed that chloride binds to both the A1 and A1-A2 domain but not to the isolated A2 domain. Binding of Cl- to both wild type (WT) and the natural mutant p.R1306W A1-A2-A3 domains of VWF has a large heat capacity change equal to -1 and -0.4 kcal mol(-1) K(-1) for WT and p.R1306W A1-A2-A3 domains, respectively. This result implies that a burial of a vast apolar surface area is caused by conformational transitions linked to chloride binding. At any temperature, chloride affinity was higher for WT than for the mutant p.R1306W form. Chloride ions inhibit hydrolysis by ADAMTS-13 of the A1-A2-A3 and A1-A2 domains in the presence of either urea or high shear stress, whereas this effect was either absent or negligible in experiments using A2 and A2-A3 domains. These findings show that the A1 domain contains the binding site of chloride ions that control allosterically the proteolysis by ADAMTS-13 of the Tyr1605-Met1606 bond in the A2 domain and that the R1306W mutation of type 2B VWD quenches the binding of chloride ion to the A1 domain.

ADAM Proteins↗
PubMed2002

Remission of thrombotic thrombocytopenic purpura in a patient with compound heterozygous deficiency of von Willebrand factor-cleaving protease by infusion of solvent/detergent plasma.

UNLABELLED: Plasma exchange or plasma infusion is considered to be the therapy of choice in patients with thrombotic thrombocytopenic purpura (TTP) who are deficient in von Willebrand factor-cleaving protease (VWF-CP). Recently, mutations in the ADAMTS 13 gene were identified as being responsible for VWF-CP deficiency in patients with familial TTP (VWF-CP deficiency in the absence of an inhibitor). Here we report on a girl who presented with recurrent thrombocytopenia and anaemia since birth, developing the full pentad of characteristic TTP at the age of 16 y. Congenital TTP was confirmed on the basis of severe VWF-CP deficiency in the absence of an acquired inhibitor. The patient was found to be compound heterozygous for two hitherto undescribed mutations in the ADAMTS 13 gene: a truncating frame shift mutation, 4143insA in exon 29, and the nonsense mutation 3100A >T in exon 24 (R1034X). After infusion of solvent/detergent plasma, the patient went into remission and remained asymptomatic under regular plasma therapy at 2-wk intervals for over two years. CONCLUSION: TTP in childhood may be mild and oligosymptomatic. Determination of VWF-CP activity is helpful in the differential diagnosis of thrombocytopenia.

ADAM Proteins↗
PubMedDate not supplied

Plasma levels of the von Willebrand factor-cleaving protease in physiological and pathological conditions in children.

The hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are rare disorders characterized by thrombocytopenia, hemolytic anemia, and ischemic organ failure due to thrombotic occlusions in arterioles. The recent observation that a von Willebrand factor-cleaving protease (VWF-CP) is low in the plasma of patients with TTP but normal in those with HUS has potentially offered a new specific tool for differential diagnosis. In this study, the authors evaluated the plasma levels of the VWF-CP during the neonatal state and healthy childhood and in some pathological pediatric conditions. The protease was measured in 16 healthy newborns, 20 healthy children aged 5-18 years, patients with diabetes mellitus type 1 (n = 7), acute viral hepatitis (n = 10), chronic viral hepatitis (n = 10), transfusion-dependent beta-thalassemia major (n = 10), acute varicella infection (n = 11), the nephrotic syndrome (n = 11), and familial Mediterranean fever (n = 10). Mean protease levels were significantly lower in newborns than in healthy children (50.5 +/- 16.1% vs. 83.3 +/- 16.3%)(p = .0001). In patients with acute viral hepatitis, protease levels were also significantly reduced (40.2 +/- 27% v s. 83.3 +/- 16.3% in healthy children)(p = .0001). Other patient groups had normal protease levels. In conclusion, low protease levels are far from being a specific beacon for TTP. The current paradigm that a single laboratory test may enable physicians to distinguish TTP from HUS seems to be challenged by these and other findings.

ADAM Proteins↗
PubMed2001

A novel human metalloprotease synthesized in the liver and secreted into the blood: possibly, the von Willebrand factor-cleaving protease?

We identified a novel metalloprotease, which could be responsible for cleaving the Tyr842-Met843 peptide bond of von Willebrand factor (vWF). This metalloprotease was purified from Cohn Fraction-I precipitate of human pooled plasma by the combination of gel filtration, DEAE chromatography, and preparative polyacrylamide gel electrophoresis in the presence of SDS. The NH2-terminal amino acid sequence of the isolated protein was: AAGGILHLELLVAVGPDVFQAHQEDTRRY. Based on this sequence, we searched human genomic and EST databases, and identified compatible nucleotide sequences. These results suggested that this protein is a novel metalloprotease, a member of the family of a disintegrin and metalloprotease with thrombospondin type-1 motifs (ADAMTS), and its genomic DNA was mapped to human chromosome 9q34. Multiple human tissue northern blotting analysis indicated that the mRNA encoding this protease spanned approximately 5 kilobases and was uniquely expressed in the liver. Furthermore, we determined the cDNA sequence encoding this protease, and found that this protease was comprised of a signal peptide, a proregion followed by the putative furin cleavage site, a reprolysin-type zinc-metalloprotease domain, a disintegrin-like domain, a thrombospondin type-1 (TSP1) motif, a cysteine-rich region, a spacer domain, and COOH-terminal TSP1 motif repeats.

ADAM Proteins↗
PubMedDate not supplied

Congenital microangiopathic hemolytic anemia and thrombocytopenia with unusually large von Willebrand factor multimers and von Willebrand factor-cleaving protease.

Infantile or congenital cases of thrombotic microangiopathy have been reported that were familial and characterized by ongoing microangiopathic hemolysis and thrombocytopenia in the absence of regular fresh-frozen plasma transfusions. The authors describe a child with congenital microangiopathic hemolytic anemia and thrombocytopenia (CMHAT) who has received regular fresh-frozen plasma transfusions since infancy and has never had thrombotic complications. von Willebrand factor (vWF)-cleaving protease activity was studied in the patient's pretransfusion and posttransfusion plasma samples as well as in her parents' plasma. The effects of the patient's and a control subject's plasma on human microvascular endothelial cells were also investigated. Unusually large vWF multimers were present in the patient's plasma both before transfusion (thrombocytopenic) and after transfusion. Unlike cases of chronic relapsing thrombotic thrombocytopenic purpura, vWF-cleaving protease activity was present and treatment of cultured human endothelial cells with the patient's plasma did not induce apoptosis. These findings suggest that the patient with CMHAT may represent a different group in the broad spectrum of thrombotic microangiopathies.

ADAM Proteins↗
PubMed2003

Case series of thrombotic thrombocytopenic purpura in children and adolescents.

Thrombotic thrombocytopenic purpura (TTP) is a well-described entity in adults but is rarely observed in children. The authors describe a series of seven children with suspected acquired TTP. Clinical findings included petechiae, purpura, or jaundice ( 6), central nervous system events ( 5), fever ( 3), diarrhea ( 3), renal insufficiency ( 2), and hematuria ( 2). Significant central nervous system events included cerebral vascular accidents ( 2), altered mental status ( 2), seizures ( 1), and hemiparesis ( 1). Patients were treated with daily plasma infusions (1/7) or plasma exchange (5/7). Response was prompt, although relapses were frequent. Decreased vWF-protease activity was found in four of five cases and vWF-protease inhibitors were found in three of five cases. Although rare, TTP is a life-threatening illness that does occur in children and should be considered in the differential diagnosis of thrombocytopenia with hemolytic anemia.

ADAM Proteins↗
PubMed2000

von Willebrand factor and thrombotic thrombocytopenic purpura.

Recent advances in the understanding of platelet-dependent hemostasis and von Willebrand factor (vWF) functional regulation offer new insights into the pathogenesis of thrombotic microangiopathic disorders. The discovery of vWF-cleaving protease activity in normal plasma, and its deficiency in thrombotic thrombocytopenic purpura (TTP) patients, provides additional support for a pathologic role of ultra-large vWF in TTP. Although vWF-cleaving protease deficiency is highly prevalent among TTP patients, the defect has also been detected in individuals without active TTP. Therefore, vWF-cleaving protease deficiency appears to be an important risk factor for thrombotic microangiopathy rather than a specific diagnostic marker of TTP. Recent data indicate that vWF-cleaving protease activity correlates with clinical parameters in thrombotic microangiopathy patients. Therefore, determination of vWF-cleaving protease activity might prove useful in the future care of thrombotic microangiopathy patients and might be a rational basis for future classification of thrombotic microangiopathic disorders.

ADAM Proteins↗
PubMed2005

Cleavage of von Willebrand factor by ADAMTS-13 in vitro: effect of temperature and barium ions on the proteolysis kinetics.

The multimeric size of von Willebrand factor (VWF) is regulated by the specific cleaving metalloprotease, ADAMTS-13. Laboratory assays for ADAMTS-13 are useful for identifying severe protease-deficient activity. ADAMTS-13 activity is currently assayed by prolonged dialysis of plasma at 37 degrees C in low-ionic-strength denaturing buffer. We investigated the effect of temperature and divalent cation supplementation on the kinetics of VWF proteolysis by ADAMTS-13 in vitro. Proteolysis was monitored for 24 h at 37, 22, and 4 degrees C, in the presence or absence of barium ions, by measuring the binding of VWF to collagen. Complete VWF proteolysis was observed at 37 degrees C in the presence of BaCl2, while about 25% VWF still bound to collagen when BaCl2 supplementation was omitted. Proteolysis kinetics at 22 and 4 degrees C was slower but complete, even in the absence of added barium. A subphysiological temperature might influence the proteolysis kinetics by determining minor variations of the ADAMTS-13 structure, or further modification of the VWF substrate. We describe a simple procedure to analyse the kinetics of VWF proteolysis that is suitable for routine diagnostic use. Furthermore, we offer new insight into the biochemistry of ADAMTS-13.

ADAM Proteins↗