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Hjazi A, Maroto CG, Appiah M, Rodriguez-Gutierrez ME, Ignat A, Mobayen G, Page T, McKinnon TAJ. The Proteasome Inhibitor Carfilzomib exerts anti-inflammatory and anti-thrombotic effects on the endothelium. J Thromb Haemost 2024:S1538-7836(24)00183-1. [PMID: 38608731 DOI: 10.1016/j.jtha.2024.03.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 03/06/2024] [Accepted: 03/29/2024] [Indexed: 04/14/2024]
Abstract
BACKGROUND Carfilzomib (CFZ) is a second-generation proteasome inhibitor used to treat multiple myeloma. Potent inhibition of the proteasome results in chronic proteotoxic endoplasmic reticulum (ER) stress, leading to apoptosis. While CFZ has improved survival rates in multiple myeloma, it is associated with an increased risk of cardiovascular adverse effects. While this has been putatively linked to cardiotoxicity, CFZ could potentially also exhibit adverse effects on the endothelium. OBJECTIVE To investigate the effects of CFZ on the endothelium METHODS: HUVECs were treated with CFZ and expression of relevant markers of ER stress, inflammation and thrombosis measured and functionally assessed. RESULTS CFZ failed to induce ER stress in HUVECs, but induced the expression of KLF-4, eNOS, tPA and thrombomodulin and reduced TNFα mediated ICAM-1 and tissue factor expression, suggesting a potential protective effect on the endothelium. Consistent with these observations, CFZ reduced leukocyte adhesion under shear stress and reduced Factor Xa generation and fibrin clot formation on the endothelium following TNFα treatment and inhibited Von Willebrand Factor (VWF) and Angiopoietin-2 exocytosis from Webiel-Palade bodies. Subsequently CFZ inhibited the formation of VWF-platelet strings and moreover, media derived from myeloma cell lines induced VWF release, a process also inhibited by CFZ. CONCLUSION(S) This data demonstrates that CFZ is unable to induce ER stress in confluent resting endothelial cells and can conversely attenuate the pro-thrombotic effects of TNFα on the endothelium. This study suggests that CFZ does not negatively alter HUVECs, and proteasome inhibition of the endothelium may offer a potential way to prevent thrombosis.
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Affiliation(s)
- Ahmed Hjazi
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom; Dept. of Mediacal Laboratory Sciences, College of Applied Medical Sciences, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia.
| | - Celia Gonzalez Maroto
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom
| | - Michael Appiah
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom
| | - Maria Elena Rodriguez-Gutierrez
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom
| | - Ana Ignat
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom
| | - Golzar Mobayen
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom
| | - Theresa Page
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom
| | - Thomas A J McKinnon
- Dept. of Immunology and Inflammation, Centre for Haematology, Imperial College Academic Health Science Centre, Hammersmith Hospital, London W12 0NN, United Kingdom.
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Mobayen G, Smith K, Ediriwickrema K, Starke RD, Solomonidis EG, Laffan MA, Randi AM, McKinnon TAJ. von Willebrand factor binds to angiopoietin-2 within endothelial cells and after release from Weibel-Palade bodies. J Thromb Haemost 2023; 21:1802-1812. [PMID: 37011710 DOI: 10.1016/j.jtha.2023.03.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 03/20/2023] [Accepted: 03/22/2023] [Indexed: 04/04/2023]
Abstract
BACKGROUND The von Willebrand factor (VWF) is a multimeric plasma glycoprotein essential for hemostasis, inflammation, and angiogenesis. The majority of VWF is synthesized by endothelial cells (ECs) and stored in Weibel-Palade bodies (WPB). Among the range of proteins shown to co-localize to WPB is angiopoietin-2 (Angpt-2), a ligand of the receptor tyrosine kinase Tie-2. We have previously shown that VWF itself regulates angiogenesis, raising the hypothesis that some of the angiogenic activity of VWF may be mediated by its interaction with Angpt-2. METHODS Static-binding assays were used to probe the interaction between Angpt-2 and VWF. Binding in media from cultured human umbilical vein ECs s and in plasma was determined by immunoprecipitation experiments. Immunofluorescence was used to detect the presence of Angpt-2 on VWF strings, and flow assays were used to investigate the effect on VWF function. RESULTS Static-binding assays revealed that Angpt-2 bound to VWF with high affinity (KD,app ∼3 nM) in a pH and calcium-dependent manner. The interaction was localized to the VWF A1 domain. Co-immunoprecipitation experiments demonstrated that the complex persisted following stimulated secretion from ECs and was present in plasma. Angpt-2 was also visible on VWF strings on stimulated ECs. The VWF-Angpt-2 complex did not inhibit the binding of Angpt-2 to Tie-2 and did not significantly interfere with VWF-platelet capture. CONCLUSIONS Together, these data demonstrate a direct binding interaction between Angpt-2 and VWF that persists after secretion. VWF may act to localize Angpt-2; further work is required to establish the functional consequences of this interaction.
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Affiliation(s)
- Golzar Mobayen
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom
| | - Koval Smith
- National Heart and Lung Institute (NHLI) Cardiovascular Sciences, Unit Imperial College Academic Health Science Centre, Hammersmith Hospital, London, United Kingdom
| | - Kushani Ediriwickrema
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom
| | - Richard D Starke
- National Heart and Lung Institute (NHLI) Cardiovascular Sciences, Unit Imperial College Academic Health Science Centre, Hammersmith Hospital, London, United Kingdom
| | - Emmanouil Georgios Solomonidis
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom
| | - Michael A Laffan
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom
| | - Anna M Randi
- National Heart and Lung Institute (NHLI) Cardiovascular Sciences, Unit Imperial College Academic Health Science Centre, Hammersmith Hospital, London, United Kingdom
| | - Thomas A J McKinnon
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom.
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McKinnon TAJ. 2B or not 2B: art thou autoinhibitory? Blood 2023; 141:1102-1103. [PMID: 36893008 DOI: 10.1182/blood.2022019577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023] Open
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Ward SE, O'Sullivan JM, Moran AB, Spencer DIR, Gardner RA, Sharma J, Fazavana J, Monopoli M, McKinnon TAJ, Chion A, Haberichter S, O'Donnell JS. Sialylation on O-linked glycans protects von Willebrand factor from macrophage galactose lectin-mediated clearance. Haematologica 2022; 107:668-679. [PMID: 33763999 PMCID: PMC8883566 DOI: 10.3324/haematol.2020.274720] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 03/12/2021] [Indexed: 11/17/2022] Open
Abstract
Terminal sialylation determines the plasma half-life of von Willebrand factor (VWF). A role for macrophage galactose lectin (MGL) in regulating hyposialylated VWF clearance has recently been proposed. In this study, we showed that MGL influences physiological plasma VWF clearance. MGL inhibition was associated with a significantly extended mean residence time and 3-fold increase in endogenous plasma VWF antigen levels (P<0.05). Using a series of VWF truncations, we further demonstrated that the A1 domain of VWF is predominantly responsible for enabling the MGL interaction. Binding of both full-length and VWF-A1-A2-A3 to MGL was significantly enhanced in the presence of ristocetin (P<0.05), suggesting that the MGL-binding site in A1 is not fully accessible in globular VWF. Additional studies using different VWF glycoforms demonstrated that VWF O-linked glycans, clustered at either end of the A1 domain, play a key role in protecting VWF against MGLmediated clearance. Reduced sialylation has been associated with pathological, increased clearance of VWF in patients with von Willebrand disease. Herein, we demonstrate that specific loss of α2-3 linked sialylation from O-glycans results in markedly increased MGL-binding in vitro, and markedly enhanced MGL-mediated clearance of VWF in vivo. Our data further show that the asialoglycoprotein receptor (ASGPR) does not have a significant role in mediating the increased clearance of VWF following loss of O-sialylation. Conversely however, we observed that loss of N-linked sialylation from VWF drives enhanced circulatory clearance predominantly via the ASGPR. Collectively, our data support the hypothesis that in addition to regulating physiological VWF clearance, the MGL receptor works in tandem with ASGPR to modulate enhanced clearance of aberrantly sialylated VWF in the pathogenesis of von Willebrand disease.
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Affiliation(s)
- Soracha E Ward
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland
| | - Jamie M O'Sullivan
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland
| | - Alan B Moran
- Ludger, Ltd., Culham Science Centre, Abingdon, Oxfordshire OX14 3EB, United Kingdom; Leiden University Medical Centre, Centre for Proteomics and Metabolomics, 2300 RC Leiden
| | | | | | - Jyotika Sharma
- Department of Basic Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota
| | - Judicael Fazavana
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland
| | - Marco Monopoli
- Department of Chemistry, RCSI, 123 St. Stephen's Green, Dublin 2
| | - Thomas A J McKinnon
- Faculty of Medicine, Imperial College, Hammersmith Hospital, Ducane Road, London
| | - Alain Chion
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland
| | | | - James S O'Donnell
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland; National Children's Research Centre, Our Lady's Children's Hospital, Dublin, Ireland; National Coagulation Centre, St James's Hospital, Dublin.
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Abstract
The 2019 coronavirus disease (COVID-19) is the disease caused by SARS-CoV-2 infection. Although this infection has been shown to affect the respiratory system, a high incidence of thrombotic events has been observed in severe cases of COVID-19 and in a significant portion of COVID-19 nonsurvivors. Although prior literature has reported on both the coagulopathy and hypercoagulability of COVID-19, the specifics of coagulation have not been fully investigated. Observations of microthrombosis in patients with COVID-19 have brought attention to potential inflammatory endothelial injury. Von Willebrand factor (VWF) and its protease, A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), play an important homeostatic role in responding to endothelial injury. This report provides an overview of the literature investigating the role the VWF/ADAMTS13 axis may have in COVID-19 thrombotic events and suggests potential therapeutic strategies to prevent the progression of coagulopathy in patients with COVID-19.
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Affiliation(s)
- Ryan Seth
- Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania
| | - Thomas A J McKinnon
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College London, London, United Kingdom
| | - X Frank Zhang
- Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania
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O'Brien HER, Zhang XF, Sanz-Hernandez M, Chion A, Shapiro S, Mobayen G, Xu Y, De Simone A, Laffan MA, McKinnon TAJ. Blocking von Willebrand factor free thiols inhibits binding to collagen under high and pathological shear stress. J Thromb Haemost 2021; 19:358-369. [PMID: 33075181 DOI: 10.1111/jth.15142] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 01/04/2023]
Abstract
BACKGROUND Von Willebrand factor (VWF) contains a number of free thiols, the majority of which are located in its C-domains, and these have been shown to alter VWF function, However, the impact of free thiols on function following acute exposure of VWF to collagen under high and pathological shear stress has not been determined. METHODS VWF free thiols were blocked with N-ethylmaleimide and flow assays performed under high and pathological shear rates to determine the impact on platelet capture and collagen binding function. Atomic force microscopy (AFM) was used to probe the interaction of VWF with collagen and molecular simulations conducted to determine the effect of free thiols on the flexibility of the VWF-C4 domain. RESULTS Blockade of VWF free thiols reduced VWF-mediated platelet capture to collagen in a shear-dependent manner, with platelet capture virtually abolished above 5000 s-1 and in regions of stenosis in microfluidic channels. Direct visualization of VWF fibers formed under extreme pathological shear rates and analysis of collagen-bound VWF attributed the effect to altered binding of VWF to collagen. AFM measurements showed that thiol-blockade reduced the lifetime and strength of the VWF-collagen bond. Pulling simulations of the VWF-C4 domain demonstrated that with one or two reduced disulphide bonds the C4 domain has increased flexibility and the propensity to undergo free-thiol exchange. CONCLUSIONS We conclude that free thiols in the C-domains of VWF enhance the flexibility of the molecule and enable it to withstand high shear forces following collagen binding, demonstrating a previously unrecognized role for VWF free thiols.
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Affiliation(s)
- Harrison E R O'Brien
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College of Science Technology and Medicine, London, UK
- Institute of Structural and Molecular Biology, University College London, London, UK
| | - X Frank Zhang
- Department of Bioengineering, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, USA
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, USA
| | | | - Alain Chion
- Irish Centre for Vascular Biology, Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Susan Shapiro
- Oxford University Hospitals NHS Foundation Trust, Oxford NIHR Biomedical Research Centre, Oxford, UK
- Radcliffe Department of Medicine, Oxford University, Oxford, UK
| | - Golzar Mobayen
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College of Science Technology and Medicine, London, UK
| | - Yan Xu
- Department of Bioengineering, Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, USA
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, USA
| | | | - Michael A Laffan
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College of Science Technology and Medicine, London, UK
| | - Thomas A J McKinnon
- Department of Immunology and Inflammation, Centre for Haematology, Imperial College of Science Technology and Medicine, London, UK
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Nowak AA, O'Brien HER, Henne P, Doerr A, Vanhoorelbeke K, Laffan MA, McKinnon TAJ. ADAMTS-13 glycans and conformation-dependent activity. J Thromb Haemost 2017; 15:1155-1166. [PMID: 28370891 DOI: 10.1111/jth.13688] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Indexed: 11/30/2022]
Abstract
Essentials The impact of N-linked glycosylation on ADAMTS-13 function has not been fully explored. The activity of glycan modified ADAMTS-13 was investigated under static and shear stress conditions. Terminal sialic acid on the metalloprotease domain glycans are important for ADAMTS-13 activity. The CUB domain glycans modulate ADAMTS-13 activity. SUMMARY Background ADAMTS-13 activity can be regulated by its conformation, whereby interactions between the C-terminal CUB domains and the spacer domain maintain ADAMTS-13 in a closed conformation. ADAMTS-13 contains 10 N-linked glycans, with four sites present in theTSP2 through to CUB domains that may contribute to its conformation. Objectives/Methods We hypothesized that glycosylation contributes to ADAMTS-13 conformation and function. The proteolytic activity of glycan-modified ADAMTS-13 was assessed under static and shear stress conditions. Results Enzymatic removal of terminal silaic acid or entire N-linked glycan chains decreased activity against FRETS-VWF73 at pH 7.4 and against full-length von Willebrand factor (VWF) under shear stress. Using truncated ADAMTS-13, we demonstrated that this was attributable to loss of sialic acid from the glycans in the metalloprotease domain and an effect of N-linked glycosylation in the TSP2 through to CUB domains. Mutation of the N-linked glycan sites in the MDTCS domains reduced or abolished protein expression. However, the N707Q, N828Q, N1235Q and N1354Q (TSP2, TSP4, CUB1, and CUB2 domains, respectively) variants were expressed normally. Interestingly, the N707Q and N828Q variants showed reduced activity against FRETS-VWF73, but normal activity under flow conditions. In contrast, the N1235Q and N1354Q variants had enhanced activity against FRETS-VWF73 and VWF under shear stress. Immunoprecipitation experiments confirmed that loss of N-linked glycans in the CUB domains significantly reduced the interaction with the spacer domain and enhanced binding to the 6A6 anti-ADAMTS-13 antibody, which recognizes a cryptic epitope in the metalloprotease domain. Conclusions Together, these data demonstrate that the N-linked glycans of ADAMTS-13 play a crucial role in regulating ADAMTS-13 activity.
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Affiliation(s)
- A A Nowak
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - H E R O'Brien
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - P Henne
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - A Doerr
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - K Vanhoorelbeke
- Laboratory for Thrombosis Research, Catholic University Leuven, Leuven, Belgium
| | - M A Laffan
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - T A J McKinnon
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College London, London, UK
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Shapiro SE, Nowak AA, Wooding C, Birdsey G, Laffan MA, McKinnon TAJ. The von Willebrand factor predicted unpaired cysteines are essential for secretion. J Thromb Haemost 2014; 12:246-54. [PMID: 24283831 DOI: 10.1111/jth.12466] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 11/21/2013] [Indexed: 12/18/2022]
Abstract
BACKGROUND von Willebrand factor (VWF) contains free thiols that mass spectroscopy has located to nine cysteines: two in the D3 domain (Cys889 and Cys898) and seven in the C domains (Cys2448, Cys2451, Cys2453, Cys2490, Cys2491, Cys2528, and Cys2533) (J Biol Chem, 7, 2007, 35604; Blood, 118, 5312). It has been suggested that these free thiols function to regulate the self-association of VWF through thiol-disulfide exchange (J Biol Chem, 7, 2007, 35604; Blood, 118, 5312). However, recent structural modeling has predicted that these cysteines are, in fact, disulfide-bonded (Blood, 118, 5312; Blood, 120, 449). OBJECTIVES To use mutation and expression analyses to investigate how these conflicting reports might be compatible with the synthesis and expression of VWF. METHODS AND RESULTS Both full-length VWF and VWF fragments with cysteine to alanine mutations of the nine cysteines and two predicted binding partners (Cys2431 and Cys2468) failed to secrete. Mutation of a cysteine pair, C2431A/C2453A, similarly resulted in a failure to secrete, indicating that this is not secondary to creation of an unpaired thiol. Deletion mutants containing seven of these cysteines, conforming to hypothesized domain boundaries, also failed to secrete: ∆C1C6 (2255-2720), ∆C3C4 (2429-2577), ∆C3 (2429-2496), and ∆C4 (2497-2577). Analysis of cell lysates and immunofluorescence confirmed that the mutants were retained within the endoplasmic reticulum (ER). Coexpression with wild-type VWF rescued secretion of some mutants to a limited extent. CONCLUSIONS These data suggest: first, that pairing of cysteines implicated in free thiol exchange is essential for correct folding of the VWF molecule, and unpairing must occur following exit from the ER or secretion from the cell; and second, that intact C domains are essential for efficient VWF secretion and must interact in the ER.
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Affiliation(s)
- S E Shapiro
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, London, UK
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Nowak AA, McKinnon TAJ, Hughes JM, Chion ACK, Laffan MA. The O-linked glycans of human von Willebrand factor modulate its interaction with ADAMTS-13. J Thromb Haemost 2014; 12:54-61. [PMID: 24406064 DOI: 10.1111/jth.12451] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Indexed: 11/27/2022]
Abstract
BACKGROUND O-linked glycans (OLGs) are clustered on either side of the von Willebrand factor (VWF) A1 domain and modulate its interaction with platelets; however, their influence on the VWF interaction with ADAMTS-13 is unknown. OBJECTIVES To assess the role of the OLGs in VWF susceptibility to ADAMTS-13 proteolysis, which would help to explain their specific distribution. METHODS OLG sites were mutated individually and as clusters on either and both sides of the A1 domain, and expressed in HEK293T cells. First, their proteolysis by ADAMTS-13 was assayed in the presence of urea. Next, a parallel-flow chamber was used to analyze VWF-mediated platelet capture on collagen in the presence and absence of ADAMTS-13 under a shear stress of 1500 s(-1) . The decrease in platelet capture in the presence ADAMTS-13 was used as a measure of VWF proteolysis. RESULTS Initially, we found that, under denaturing conditions, the C-terminal S1486A and Cluster 2 and double cluster (DC) variants were less susceptible to ADAMTS-13 proteolysis than wild-type VWF. Next, we showed that addition of ADAMTS-13 diminished VWF-mediated platelet capture on collagen under flow; surprisingly, this was more pronounced with the S1486A, Cluster 2 and DC variants than with wild-type VWF, indicating that these are proteolyzed more rapidly under shear flow. CONCLUSIONS OLGs provide rigidity to peptide backbones, and our findings suggest that OLG in the A1-A2 linker region regulates VWF conformational changes under shear. Importantly, the impact of OLGs on ADAMTS-13 cleavage under shear stress is the opposite of that under denaturing conditions, highlighting the non-physiologic nature of in vitro cleavage assays.
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Affiliation(s)
- A A Nowak
- Department of Haematology, Faculty of Medicine, Hammersmith Hospital Campus, Imperial College, London, UK
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Fallah MA, Huck V, Niemeyer V, Desch A, Angerer JI, McKinnon TAJ, Wixforth A, Schneider SW, Schneider MF. Circulating but not immobilized N-deglycosylated von Willebrand factor increases platelet adhesion under flow conditions. Biomicrofluidics 2013; 7:44124. [PMID: 24404057 PMCID: PMC3772935 DOI: 10.1063/1.4819746] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Accepted: 08/13/2013] [Indexed: 05/10/2023]
Abstract
The role of von Willebrand factor (VWF) as a shear stress activated platelet adhesive has been related to a coiled-elongated shape conformation. The forces dominating this transition have been suggested to be controlled by the proteins polymeric architecture. However, the fact that 20% of VWF molecular weight originates from glycan moieties has so far been neglected in these calculations. In this study, we present a systematic experimental investigation on the role of N-glycosylation for VWF mediated platelet adhesion under flow. A microfluidic flow chamber with a stenotic compartment that allows one to mimic various physiological flow conditions was designed for the efficient analysis of the adhesion spectrum. Surprisingly, we found an increase in platelet adhesion with elevated shear rate, both qualitatively and quantitatively fully conserved when N-deglycosylated VWF (N-deg-VWF) instead of VWF was immobilized in the microfluidic channel. This has been demonstrated consistently over four orders of magnitude in shear rate. In contrast, when N-deg-VWF was added to the supernatant, an increase in adhesion rate by a factor of two was detected compared to the addition of wild-type VWF. It appears that once immobilized, the role of glycans is at least modified if not-as found here for the case of adhesion-negated. These findings strengthen the physical impact of the circulating polymer on shear dependent platelet adhesion events. At present, there is no theoretical explanation for an increase in platelet adhesion to VWF in the absence of its N-glycans. However, our data indicate that the effective solubility of the protein and hence its shape or conformation may be altered by the degree of glycosylation and is therefore a good candidate for modifying the forces required to uncoil this biopolymer.
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Affiliation(s)
- M A Fallah
- University of Augsburg, Chair of Experimental Physics I, 86159 Augsburg, Germany ; Department of Biophysical Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - V Huck
- Heidelberg University, Medical Faculty Mannheim, Experimental Dermatology, 68167 Mannheim, Germany
| | - V Niemeyer
- Heidelberg University, Medical Faculty Mannheim, Experimental Dermatology, 68167 Mannheim, Germany
| | - A Desch
- Heidelberg University, Medical Faculty Mannheim, Experimental Dermatology, 68167 Mannheim, Germany
| | - J I Angerer
- University of Augsburg, Chair of Experimental Physics I, 86159 Augsburg, Germany
| | - T A J McKinnon
- Imperial College London, Hammersmith Hospital Campus, Department of Medicine, London W12 0NN, United Kingdom
| | - A Wixforth
- University of Augsburg, Chair of Experimental Physics I, 86159 Augsburg, Germany
| | - S W Schneider
- Heidelberg University, Medical Faculty Mannheim, Experimental Dermatology, 68167 Mannheim, Germany
| | - M F Schneider
- Department of Mechanical Engineering, Boston University, Boston, Massachusetts 02215, USA
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McKinnon TAJ, Nowak AA, Cutler J, Riddell AF, Laffan MA, Millar CM. Characterisation of von Willebrand factor A1 domain mutants I1416N and I1416T: correlation of clinical phenotype with flow-based platelet adhesion. J Thromb Haemost 2012; 10:1409-16. [PMID: 22537243 DOI: 10.1111/j.1538-7836.2012.04760.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Type 2M von Willebrand disease (VWD) results from mutations in the A1 domain of von Willebrand factor (VWF) that reduce its platelet-binding function. However, currently employed VWF functional static assays may not distinguish between clinical phenotype. METHODS Fifteen individuals from five kindreds with VWF-A1 domain mutations I1416T or I1416N, correlated with mild and moderate clinical phenotypes, respectively, were investigated. The mutations were reproduced by site-directed mutagenesis and expressed in HEK293T cells; functional studies of the recombinant mutants, including GPIbα binding using a flow-based assay, were performed. RESULTS Plasma from all individuals demonstrated discordant reductions in VWF antigen and platelet-binding function in the presence of high-molecular-weight VWF multimers consistent with VWD type 2M. There was lowered expression and secretion of both mutants compared with wild type (WT) recombinant (r)VWF as well as a significant reduction in GPIbα binding. Binding to collagen was normal and electrophoretic analysis demonstrated a similar multimer distribution between the mutant proteins and wt-rVWF. GPIbα binding under flow was also significantly reduced for I1416N and I1416T rVWF. Impairment of GPIbα binding was more marked for I1416N rVWF than I1416T under both static and flow conditions: this was in spite of similar VWF:Ristocetin cofactor (RCo) activities in patient plasma and is consistent with a respective clinical phenotype. CONCLUSIONS Our findings have established for the first time that I1416N and I1416T are responsible for a type 2M VWD phenotype and demonstrate that quantification of VWF function under shear stress may provide a more accurate measure of clinical severity than the static functional measurements in current diagnostic use.
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Affiliation(s)
- T A J McKinnon
- Centre for Haematology, Imperial College London Haemostasis and Thrombosis Molecular Genetics Laboratory, Guy's and St Thomas NHS Foundation Trust, London, UK
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Canis K, McKinnon TAJ, Nowak A, Panico M, Morris HR, Laffan M, Dell A. The plasma von Willebrand factor O-glycome comprises a surprising variety of structures including ABH antigens and disialosyl motifs. J Thromb Haemost 2010; 8:137-45. [PMID: 19874459 DOI: 10.1111/j.1538-7836.2009.03665.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND von Willebrand factor (VWF) is a key component for maintenance of normal hemostasis. Its glycan moieties, accounting for about 20% of its molecular weight, have been shown to affect many of its properties. Previous studies reported correlations between VWF secretion, half-life and the nature or presence of its N-glycans, and more importantly between VWF plasma level and the type of N-linked ABH antigens. Despite the presence of 10 predicted O-glycosylation sites, the O-glycome remains poorly characterized, impairing the complete elucidation of its influence on VWF functions. So far only a single glycan structure, a disialyl core 1 glycan, has been identified. OBJECTIVES To define an exhaustive profile of the VWF O-glycan structures to help the understanding of their role in VWF regulation and properties. METHODS Plasma-derived VWF O-linked sugars were isolated and analyzed using state-of-the-art mass spectrometry methodologies. RESULTS AND CONCLUSIONS We provide here a detailed analysis of the human plasma-derived VWF O-glycome. Eighteen O-glycan structures including both core 1 and core 2 structures are now demonstrated to be present on VWF. Amongst the newly determined structures are unusual tetra-sialylated core 1 O-glycans and ABH antigen-containing core 2 O-glycans. In conjunction with current models explaining VWF activity, knowledge of the complete O-glycome will facilitate research aimed at providing a better understanding of the influence of glycosylation on VWF functions.
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Affiliation(s)
- K Canis
- Division of Molecular Biosciences, Faculty of Natural Sciences, Imperial College, London, UK
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Affiliation(s)
- M Laffan
- Department of Haematology, Imperial College Academic Health Sciences Centre, Hammersmith Hospital, London, UK.
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O'Donnell JS, McKinnon TAJ, Crawley JTB, Lane DA, Laffan MA. Bombay phenotype is associated with reduced plasma-VWF levels and an increased susceptibility to ADAMTS13 proteolysis. Blood 2005; 106:1988-91. [PMID: 15886321 DOI: 10.1182/blood-2005-02-0792] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractABO blood group is an important determinant of plasma von Willebrand factor antigen (VWF:Ag) levels, with lower levels in group O. Previous reports have suggested that ABO(H) sugars affect the susceptibility of VWF to ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type-1 repeats-13) cleavage. To further test this hypothesis, we collected plasma from individuals with the rare Bombay blood group. VWF:Ag levels were significantly lower in Bombay patients (median, 0.69 IU/mL) than in groups AB, A, or B (P < .05) and lower than in group O individuals (median, 0.82 IU/mL). Susceptibility of purified VWF fractions to recombinant ADAMTS13 cleavage, assessed using VWF collagen-binding assay (VWF:CB), was increased in Bombays compared with either group O or AB. Increasing urea concentration (0.5 to 2 M) increased the cleavage rate for each blood group but eliminated the differences between groups. 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.
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Affiliation(s)
- James S O'Donnell
- Haematology Dept, Imperial College London, 5th Floor, Commonwealth Building, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, United Kingdom.
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