J E Sadler

Washington University in St. Louis, San Luis, Missouri, United States

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Publications (161)1214.77 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: von Willebrand factor (VWF) strings are removed from the endothelial surface by ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type-1 repeats)-mediated proteolysis. To visualize how single ADAMTS13 molecules bind to these long strings, we built a customized single molecule fluorescence (SMF) microscope and developed single particle tracking software. Extensive analysis of over 6,000 single inactive ADAMTS13E225Q enzymes demonstrated that 20% of these molecules could be detected in at least two consecutive 60ms frames and followed two types of trajectories. ADAMTS13E225Q molecules either decelerated in the vicinity of VWF strings while sometimes making brief contact with the VWF string before disappearing again or readily bound to the VWF strings and this for 120 ms or longer. These interactions were observed at several sites along the strings. Control experiments using an IgG protein revealed that only the second type of trajectory reflected a specific interaction of ADAMTS13 with the VWF string. In conclusion, we developed a dedicated SMF microscope for detecting single ADAMTS13 molecules (nm scale) on their long, flow-stretched VWF substrates (μm scale) anchored on living cells. Comprehensive analysis of all detected enzymes showed a random interaction mechanism for ADAMTS13 with many available binding sites on the VWF strings.
    Journal of Biological Chemistry 02/2014; · 4.65 Impact Factor
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    ABSTRACT: BACKGROUND: Most ADAMTS13 assays use non-physiological conditions (low ionic strength, low pH, barium chloride), are subject to interference from plasma proteins, hemoglobin and bilirubin, and have limited sensitivity, especially for inhibitors. OBJECTIVES: We addressed these constraints by designing a substrate that can be used in undiluted plasma. METHODS: A polypeptide was expressed in E. coli that corresponds to von Willebrand factor Gln(1599) -Arg(1668) , with mutations N1610C and K1617R and an N-terminal Gly. Substrate FRETS-rVWF71 was prepared by modifying Cys(1610) with DyLight 633 (abs 638 nm, em 658 nm) and the N-terminus with IRDye QC-1 (abs 500-800 nm). Assays were performed at pH 7.4 in 150 mM NaCl, 10 mM CaCl2 . RESULTS: Serum and plasma anticoagulated with citrate or heparin had equivalent ADAMTS13 activity with FRETS-rVWF71. Neither bilirubin (≤20 mg/dL) nor hemoglobin (≤20 g/L) interfered with product detection. Assays with FRETS-rVWF71 and FRETS-VWF73 gave similar results (R(2) = 0.95) for plasma from 80 subjects with thrombotic microangiopathy, 22 subjects with other causes of thrombocytopenia, and 20 healthy controls. The limit of detection with FRETS-rVWF71 for ADAMTS13 activity was ≤0.3%. Inhibitor assays with FRETS-rVWF71 gave titers ~2.5-fold higher than with FRETS-VWF73 and clearly distinguished patients with and without inhibitors. CONCLUSIONS: FRETS-rVWF71 is suitable for ADAMTS13 assays in minimally diluted plasma or serum without interference from proteins, bilirubin or free hemoglobin in plasma. Optimized detection of ADAMTS13 inhibitors will facilitate the monitoring of antibody responses during the treatment of thrombotic thrombocytopenic purpura. This article is protected by copyright. All rights reserved.
    Journal of Thrombosis and Haemostasis 06/2013; · 6.08 Impact Factor
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    ABSTRACT: Shiga toxin (Stx) causes diarrhea-associated hemolytic uremic syndrome by damaging renal microvascular endothelium. The pentameric B subunits of Stx types 1 and 2 (Stx1B and Stx2B) are sufficient to stimulate acute VWF secretion from endothelial cells, but Stx1B and Stx2B exert distinct effects on Ca(2+) and cAMP pathways. Therefore, we investigated other signaling components in StxB-induced VWF exocytosis. Incubation of HUVECs with StxB transiently increased phospholipase D (PLD) activity. Inhibition of PLD activity or shRNA-mediated PLD1 knockdown abolished StxB-induced VWF secretion. In addition, treatment with StxB triggered actin polymerization, enhanced endothelial monolayer permeability, and activated RhoA. PLD activation and VWF secretion induced by Stx1B were abolished on protein kinase Cα (PKCα) inhibition or gene silencing but were only moderately reduced by Rho or Rho kinase inhibitors. Conversely, PLD activation and VWF exocytosis induced by Stx2B were reduced by Rho/Rho kinase inhibitors and dominant-negative RhoA, whereas attenuation of PKCα did not affect either process. Another PLD1 activator, ADP-ribosylation factor 6, was involved in VWF secretion induced by Stx1B or Stx2B, but not histamine. These data indicate that Stx1B and Stx2B induce acute VWF secretion in a PLD1-dependent manner but do so by differentially modulating PKCα, RhoA, and ADP-ribosylation factor 6.
    Blood 06/2012; 120(5):1143-9. · 9.78 Impact Factor
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    ABSTRACT: ADAMTS proteases typically employ some combination of ancillary C-terminal disintegrin-like, thrombospondin-1, cysteine-rich, and spacer domains to bind substrates and facilitate proteolysis by an N-terminal metalloprotease domain. We constructed chimeric proteases and substrates to examine the role of C-terminal domains of ADAMTS13 and ADAMTS5 in the recognition of their physiological cleavage sites in von Willebrand factor (VWF) and aggrecan, respectively. ADAMTS5 cleaves Glu(373)-Ala(374) and Glu(1480)-Gly(1481) bonds in bovine aggrecan but does not cleave VWF. Conversely, ADAMTS13 cleaves the Tyr(1605)-Met(1606) bond of VWF, which is exposed by fluid shear stress but cannot cleave aggrecan. Replacing the thrombospondin-1/cysteine-rich/spacer domains of ADAMTS5 with those of ADAMTS13 conferred the ability to cleave the Glu(1615)-Ile(1616) bond of VWF domain A2 in peptide substrates or VWF multimers that had been sheared; native (unsheared) VWF multimers were resistant. Thus, by recombining exosites, we engineered ADAMTS5 to cleave a new bond in VWF, preserving physiological regulation by fluid shear stress. The results demonstrate that noncatalytic thrombospondin-1/cysteine-rich/spacer domains are principal modifiers of substrate recognition and cleavage by both ADAMTS5 and ADAMTS13. Noncatalytic domains may perform similar functions in other ADAMTS family members.
    Journal of Biological Chemistry 06/2012; 287(32):26944-52. · 4.65 Impact Factor
  • The Lancet 02/2012; 379(9815):516; author reply 516-7. · 39.21 Impact Factor
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    J Evan Sadler
    Clinical advances in hematology & oncology: H&O 09/2011; 9(9):673-4.
  • Fang Liu, Jing Huang, J Evan Sadler
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    ABSTRACT: Diarrhea-associated hemolytic uremic syndrome (D(+)HUS) is caused by the ingestion of Escherichia coli that produce Shiga toxin (Stx), which is composed of a cytotoxic A subunit and pentameric B subunits that bind globotriaosylceramide on susceptible cells. Stx occurs in 2 types, Stx1 and Stx2. B subunits of either type stimulate von Willebrand factor (VWF) secretion from human umbilical vein endothelial cells (HUVECs), and Stx2B can cause thrombotic microangiopathy in Adamts13(-/-) mice. We have now determined that Stx1B and Stx2B activate different signaling pathways in HUVECs. VWF secretion induced by Stx1B is associated with a transient rise in intracellular Ca(2+) level that is blocked by chelation with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, removal of extracellular Ca(2+), the phospholipase C inhibitor U73122, the protein kinase inhibitor staurosporine, or small interfering RNA knockdown of protein kinase Cα. In contrast, Stx2B-induced VWF secretion is associated with activation of protein kinase A (PKA) and is blocked by the PKA inhibitor H89 or small interfering RNA knockdown of PKA. Stx2B does not increase cAMP levels and may activate PKA by a cAMP-independent mechanism. The activation of distinct signaling pathways may be relevant to understanding why E coli that express Stx2 are more likely to cause D(+)HUS than are E coli expressing only Stx1.
    Blood 08/2011; 118(12):3392-8. · 9.78 Impact Factor
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    ABSTRACT: Von Willebrand Factor (VWF) is a multimeric plasma glycoprotein that mediates platelet adhesion and aggregation, a process critical for both hemostasis and thrombosis. Under normal conditions, VWF binds to platelets at sites of vascular injury or damage, leading to blood clot formation and wound healing. VWF contains four types of repeating domains in the following sequence: D1-D2-D’-D3-A1-A2-A3-D4-B1-B2-B3-C1-C2-CK (CK: cystine knot). It is synthesized and secreted into plasma by endothelial cells and megakaryocytes. Many newly-secreted VWF multimers are huge in size, thus they are termed ultra-large VWF (ULVWF). ULVWF is thrombogenic, so it is reduced to smaller VWF multimers by ADAMTS13, a metalloprotease that cleaves the Tyr1605-Met1606 bond in the A2 domain of VWF. Proper ULVWF cleavage and subsequent VWF cleavage result in appropriate size distribution of VWF in plasma, which is required for its hemostatic function. On the one hand, insufficient cleavage of ULVWF leads to thrombotic thrombocytopenic purpura (TTP), a disease characterized by microvascular thrombosis; on the other hand, excessive cleavage of VWF leads to Von Willebrand disease (VWD), a potentially-fatal bleeding disorder manifested by lack of large VWF multimers in plasma [1]. Therefore, understanding VWF cleavage by ADAMTS13 is crucial for understanding VWF function and its related diseases.
    ASME 2011 Summer Bioengineering Conference; 06/2011
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    ABSTRACT: von Willebrand factor (VWF) is a multimeric plasma protein that mediates platelet adhesion to sites of vascular injury. The hemostatic function of VWF depends upon the formation of disulfide-linked multimers, which requires the VWF propeptide (D1D2 domains) and adjacent D'D3 domains. VWF multimer assembly occurs in the trans-Golgi at pH ~ 6.2 but not at pH 7.4, which suggests that protonation of one or more His residues (pK(a) ~6.0) mediates the pH dependence of multimerization. Alignment of 30 vertebrate VWF sequences identified 13 highly conserved His residues in the D1D2D'D3 domains, and His-to-Ala mutagenesis identified His³⁹⁵ and His⁴⁶⁰ in the D2 domain as critical for VWF multimerization. Replacement of His³⁹⁵ with Lys or Arg prevented multimer assembly, suggesting that reversible protonation of this His residue is essential. In contrast, replacement of His⁴⁶⁰ with Lys or Arg preserved normal multimer assembly, whereas Leu, Met, and Gln did not, indicating that the function of His⁴⁶⁰ depends primarily upon the presence of a positive charge. These results suggest that pH sensing by evolutionarily conserved His residues facilitates the assembly and packaging of VWF multimers upon arrival in the trans-Golgi.
    Journal of Biological Chemistry 05/2011; 286(29):25763-9. · 4.65 Impact Factor
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    ABSTRACT: Weibel-Palade bodies (WPBs) are elongated secretory organelles specific to endothelial cells that contain von Willebrand factor (VWF) and a variety of other proteins that contribute to inflammation, angiogenesis, and tissue repair. The remarkable architecture of WPBs is because of the unique properties of their major constituent VWF. VWF is stored inside WPBs as tubules, but on its release, forms strikingly long strings that arrest bleeding by recruiting blood platelets to sites of vascular injury. In recent years considerable progress has been made regarding the molecular events that underlie the packaging of VWF multimers into tubules and the processes leading to the formation of elongated WPBs. Mechanisms directing the conversion of tightly packaged VWF tubules into VWF strings on the surface of endothelial cells are starting to be unraveled. Several modes of exocytosis have now been described for WPBs, emphasizing the plasticity of these organelles. WPB exocytosis plays a role in the pathophysiology and treatment of von Willebrand disease and may have impact on common hematologic and cardiovascular disorders. This review summarizes the major advances made on the biogenesis and exocytosis of WPBs and places these recent discoveries in the context of von Willebrand disease.
    Blood 01/2011; 117(19):5033-43. · 9.78 Impact Factor
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    ABSTRACT: Diarrhea-associated hemolytic uremic syndrome (D+HUS) is the most common cause of acute renal failure among children. Renal damage in D+HUS is caused by Shiga toxin (Stx), which is elaborated by Shigella dysenteriae and certain strains of Escherichia coli, in North America principally E coli O157:H7. Recent studies demonstrate that Stx also induces von Willebrand factor (VWF) secretion by human endothelial cells and causes thrombotic thrombocytopenic purpura, a disease with similarities to D+HUS, in Adamts13(-/-) mice. Stx occurs in 2 variants, Stx1 and Stx2, each of which is composed of 1 catalytically active A subunit that is responsible for cytotoxicity, and 5 identical B subunits that mediate binding to cell-surface globo-triaosylceramide. We now report that B subunits from Stx1 or Stx2 can stimulate the acute secretion of VWF in the absence of the cytotoxic A subunit. This rapid effect requires binding and clustering of globotriaosylceramide, and depends on plasma membrane cholesterol and caveolin-1 but not clathrin. Furthermore, similar to Stx2 holotoxin, the isolated Stx2B subunits induce thrombotic microangiopathy in Adamts13(-/-) mice. These results demonstrate the existence of a novel Stx B-induced lipid raft-dependent signaling pathway in endothelial cells that may be responsible for some of the biological effects attributed previously to the cytotoxic Stx A subunit.
    Blood 11/2010; 116(18):3653-9. · 9.78 Impact Factor
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    ABSTRACT: von Willebrand disease (VWD) Vicenza is characterized by low plasma von Willebrand factor (VWF) levels, the presence of ultra-large (UL) VWF multimers and less prominent satellite bands on multimer gels, and the heterozygous amino acid substitution R1205H in the VWF gene. The pathogenesis of VWD Vicenza has been elusive. Accelerated clearance is implicated as a cause of low VWF level. We addressed the question, whether the presence of ultra-large multimers is a cause, or a result of accelerated VWF clearance, or whether it is an unrelated phenomenon. We studied the detailed phenotype of three Hungarian patients with VWD Vicenza, expressed the mutant VWF-R1205H in 293T cells and developed a mathematical model to simulate VWF synthesis and catabolism. We found that the half-life of VWF after DDAVP was approximately one-tenth of that after the administration of Haemate P, a source of exogenous wild-type (WT) VWF (0.81 + or - 0.2 vs. 7.25 + or - 2.38 h). An analysis of recombinant mutant VWF-R1205H showed that the biosynthesis and multimer structure of WT and mutant VWF were indistinguishable. A mathematical model of the complex interplay of VWF synthesis, clearance and cleavage showed that decreasing VWF half-life to one-tenth of normal reproduced all features of VWD Vicenza including low VWF level, ultra-large multimers and a decrease of satellite band intensity. We conclude that accelerated clearance alone may explain all features of VWD Vicenza.
    Journal of Thrombosis and Haemostasis 06/2010; 8(6):1273-80. · 6.08 Impact Factor
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    ABSTRACT: Von Willebrand factor (VWF) is a multimeric plasma glycoprotein involved in both hemostasis and thrombosis. VWF conformational changes, especially unfolding of the A2 domain, may be required for efficient enzymatic cleavage in vivo. It has been shown that a single A2 domain unfolds at most probable unfolding forces of 7-14 pN at force loading rates of 0.35-350 pN/s and A2 unfolding facilitates A2 cleavage in vitro. However, it remains unknown how much force is required to unfold the A2 domain in the context of a VWF multimer where A2 may be stabilized by other domains like A1 and A3. With the optical trap, we stretched VWF multimers and a poly-protein (A1A2A3)3 that contains three repeats of the triplet A1A2A3 domains at constant speeds of 2000 nm/s and 400 nm/s, respectively, which yielded corresponding average force loading rates of 90 and 22 pN/s. We found that VWF multimers became stiffer when they were stretched and extended by force. After force increased to a certain level, sudden extensional jumps that signify domain unfolding were often observed. Histograms of the unfolding force and the unfolded contour length showed two or three peaks that were integral multiples of approximately 21 pN and approximately 63 nm, respectively. Stretching of (A1A2A3)3 yielded comparable distributions of unfolding force and unfolded contour length, showing that unfolding of the A2 domain accounts for the behavior of VWF multimers under tension. These results show that the A2 domain can be indeed unfolded in the presence of A1, A3, and other domains. Compared with the value in the literature, the larger most probable unfolding force measured in this study suggests that the A2 domain is mechanically stabilized by A1 or A3 although variations in experimental setups and conditions may complicate this interpretation.
    Biophysical Journal 04/2010; 98(8):1685-93. · 3.67 Impact Factor
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    ABSTRACT: ARC1172 is a 41-mer DNA aptamer selected to bind the A1 domain of von Willebrand factor (VWF). A derivative of ARC1172 with modifications to increase intravascular survival inhibits carotid artery thrombosis in a Cynomolgus macaque model and inhibits VWF-dependent platelet aggregation in humans, suggesting that such aptamers may be useful to prevent or treat thrombosis. In the crystal structure of a VWF A1-ARC1172 complex, the aptamer adopts a three-stem structure of mainly B-form DNA with three noncanonical base pairs and 9 unpaired residues, 6 of which are stabilized by base-base or base-deoxyribose stacking interactions. The aptamer-protein interface is characterized by cation-pi interactions involving Arg, Lys, and Gln residues, often stabilized by H-bonds with adjacent bases. The ARC1172 binding site on the A1 domain overlaps with that of botrocetin and clashes with glycoprotein Ibalpha binding at an adjacent site, which accounts for the antithrombotic activity of ARC1172 and related aptamers.
    Structure 11/2009; 17(11):1476-84. · 5.99 Impact Factor
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    ABSTRACT: ADAMTS-13 proteolytic activity is controlled by the conformation of its substrate, von Willebrand factor (VWF), and changes in the secondary structure of VWF are essential for efficient cleavage. Substrate recognition is mediated through several non-catalytic domains in ADAMTS-13 distant from the active site. We hypothesized that not all binding sites for ADAMTS-13 in VWF are cryptic and analyzed binding of native VWF to ADAMTS-13. Immunoprecipiation of VWF-ADAMTS-13 complexes using anti-VWF antibodies and magnetic beads was used. Binding was assessed by Western blotting and immunosorbent assays. Co-immunoprecipitation demonstrated that ADAMTS-13 binds to native multimeric VWF (K(d) of 79 +/- 11 nmol L(-1)) with no measurable proteolysis. Upon shear-induced unfolding of VWF, binding increased 3-fold and VWF was cleaved. Binding to native VWF was saturable, time dependent, reversible and did not vary with ionic strength (I of 50-200). Moreover, results with ADAMTS-13 deletion mutants indicated that binding to native VWF is mediated through domains distal to the ADAMTS-13 spacer, probably thrombospondin-1 repeats. Interestingly, this interaction occurs in normal human plasma with an ADAMTS-13 to VWF stoichiometry of 0.0040 +/- 0.0004 (mean +/- SEM, n = 10). ADAMTS-13 binds to circulating VWF and may therefore be incorporated into a platelet-rich thrombus, where it can immediately cleave VWF that is unfolded by fluid shear stress.
    Journal of Thrombosis and Haemostasis 09/2009; 7(12):2088-95. · 6.08 Impact Factor
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    J E Sadler
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    ABSTRACT: During its life history, von Willebrand factor (VWF) experiences a remarkable sequence of conformational changes that are triggered by differences in pH between the endoplasmic reticulum (ER), Golgi and extracellular environments. VWF subunits dimerize in the ER and assemble into disulfide-linked multimers in the trans-Golgi, which lacks known chaperones and has an acidic pH that inhibits disulfide rearrangement. VWF has circumvented these problems by evolving N-terminal domains that function as an oxidoreductase at the low pH of the Golgi. VWF multimers also condense into tightly packed, tubular arrays for storage in the Weibel-Palade bodies of endothelial cells. Like multimer assembly, tubular packing depends on low pH and Ca2+. Upon secretion, exposure to the neutral pH of the extracellular environment allows enormous VWF multimers to uncoil without tangling, which is crucial for hemostasis. Recent studies have identified some of the biochemical and structural properties that underlie these self-organizing behaviors.
    Journal of Thrombosis and Haemostasis 08/2009; 7 Suppl 1:24-7. · 6.08 Impact Factor
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    ABSTRACT: Enteropeptidase, a type II transmembrane serine protease, is localized to the brush border of the duodenal and jejunal mucosa. It is synthesized as a zymogen (proenteropeptidase) that requires activation by another protease, either trypsin or possibly duodenase. Active enteropeptidase then converts the pancreatic precursor, trypsinogen, to trypsin by cleavage of the specific trypsinogen activation peptide, Asp-Asp-Asp-Asp-Lys- Ile that is highly conserved in vertebrates. Trypsin, in turn, activates other digestive zymogens such as chymotrypsinogen, proelastase, procarboxypeptidase and prolipase in the lumen of the gut. The important biological function of enteropeptidase is highlighted by the manifestation of severe diarrhea, failure to thrive, hypoproteinemia and edema as a result of congenital deficiency of enteropeptidase activity in the gut. Conversely, duodenopancreatic reflux of proteolytically active enteropeptidase may cause acute and chronic pancreatitis.
    Frontiers in bioscience (Elite edition) 06/2009; 1:242-9.
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    ABSTRACT: Von Willebrand factor (VWF) mediates blood platelet adhesion and accumulation at sites of blood vessel injury, and also carries coagulation factor VIII (FVIII) that is important for generating procoagulant activity. Von Willebrand disease (VWD), the most common inherited bleeding disorder, affects males and females, and reflects deficiency or defects of VWF that may also cause decreased FVIII. It may also occur less commonly as an acquired disorder (acquired von Willebrand syndrome). This article briefly summarizes selected features of the March 2008 evidence-based clinical and laboratory diagnostic recommendations from the National Heart, Lung, and Blood Institute (NHLBI) Expert Panel for assessment for VWD or other bleeding disorders or risks. Management of VWD is also addressed in the NHLBI guidelines, but is not summarized here. The VWD guidelines are available at the NHLBI Web site (http://www.nhlbi.nih.gov/guidelines/vwd).
    American Journal of Hematology 04/2009; 84(6):366-70. · 4.00 Impact Factor
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    J Evan Sadler
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    ABSTRACT: A sufficiently low level of von Willebrand factor (VWF) predisposes to bleeding that can be quite serious, and low VWF is a diagnostic feature of von Willebrand disease (VWD) type 1, which is characterized by partial quantitative deficiency of VWF. Recent groundbreaking studies of patients with VWD type 1 have delineated several pathophysiologic mechanisms that determine the plasma concentration of VWF, but the relationship between VWF level and the likelihood of bleeding remains less well understood. In part, this problem reflects the broad range of VWF levels in the population, so that the distinction between "normal" and "low" is arbitrary. The risk of bleeding certainly increases as the VWF level decreases, but the relationship is not very strong until the VWF level is very low. Furthermore, mild bleeding symptoms are common in apparently healthy populations and have many causes other than defects in VWF, which can make it impossible to attribute bleeding to any single factor, such as low VWF. These difficulties might be resolved by an epidemiologic approach to VWF and other risk factors for bleeding, analogous to how physicians manage multiple risk factors for cardiovascular disease or venous thromboembolism.
    Hematology 01/2009; · 1.49 Impact Factor
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    ABSTRACT: Acutely secreted von Willebrand factor (VWF) multimers adhere to endothelial cells, support platelet adhesion, and may induce microvascular thrombosis. Immunofluorescence microscopy of live human umbilical vein endothelial cells showed that VWF multimers rapidly formed strings several hundred micrometers long on the cell surface after stimulation with histamine. Unexpectedly, only a subset of VWF strings supported platelet binding, which depended on platelet glycoprotein Ib. Electron microscopy showed that VWF strings often consisted of bundles and networks of VWF multimers, and each string was tethered to the cell surface by a limited number of sites. Several approaches implicated P-selectin and integrin alpha(v)beta(3) in anchoring VWF strings. An RGDS peptide or a function-blocking antibody to integrin alpha(v)beta(3) reduced the number of VWF strings formed. In addition, integrin alpha(v) decorated the VWF strings by immunofluorescence microscopy. Furthermore, lentiviral transduction of shRNA against the alpha(v) subunit reduced the expression of cell-surface integrin alpha(v)beta(3) and impaired the ability of endothelial cells to retain VWF strings. Soluble P-selectin reduced the number of platelet-decorated VWF strings in the absence of Ca(2+) and Mg(2+) but had no effect in the presence of these cations. These results indicate that VWF strings bind specifically to integrin alpha(v)beta(3) on human endothelial cells.
    Blood 11/2008; 113(7):1589-97. · 9.78 Impact Factor

Publication Stats

8k Citations
1,214.77 Total Impact Points


  • 1991–2013
    • Washington University in St. Louis
      • • Department of Pediatrics
      • • Department of Biochemistry and Molecular Biophysics
      • • Department of Medicine
      San Luis, Missouri, United States
  • 1990–2012
    • University of Washington Seattle
      • Department of Medicine
      Seattle, WA, United States
  • 1988–2010
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States
  • 2004–2009
    • The Children's Hospital of Philadelphia
      • Department of Pathology and Laboratory Medicine
      Philadelphia, PA, United States
  • 2008
    • Washington & Lee University
      Lexington, Virginia, United States
  • 2005
    • San Bortolo Hospital
      Vicenza, Veneto, Italy
  • 2000
    • Pacific Institute of Bioorganic Chemistry
      Wladiwostok, Primorskiy, Russia
    • University of Milan
      • Department of Internal Medicine
      Milano, Lombardy, Italy
  • 1993–2000
    • Michigan State University
      • Department of Chemistry
      East Lansing, MI, United States
    • Tel Aviv University
      Tell Afif, Tel Aviv, Israel
    • University of Iowa
      • Department of Internal Medicine
      Iowa City, IA, United States
  • 1999
    • Swedish University of Agricultural Sciences
      Uppsala, Uppsala, Sweden
  • 1996
    • Leiden University Medical Centre
      • Department of Hematology
      Leiden, South Holland, Netherlands
  • 1994
    • Sheba Medical Center
      Gan, Tel Aviv, Israel