Pathophysiology of von Willebrand factor in the circulation
Biophysics
Final Report Abstract
Von Willebrand factor (VWF) is the glue of our blood, which prevents excessive blood loss in the event of vessel damage. The VWF protein binds to the site of injury and recruits and activates platelets. This process stops bleeding and initiates wound healing. In the absence of injury, VWF travels through the circulation in an inactive form. However, when VWF is bound to an injury of the vessel wall, blood flow tears on VWF thereby stretching the protein. This elongation uncovers binding sites for platelets, which become activated to fulfill their role in primary hemostasis. This defines VWF as a forceactivated protein. We have described a novel interaction between two subdomains of VWF that acts as a regulatory mechanism by which VWF is kept in this state unable to bind platelets until activation is needed. When VWF is not functioning properly, due to mutations, bleeding cannot be stopped or is prolonged. This disorder is called von Willebrand disease (VWD) and is the most common inherited bleeding disorder. For the VWD subtypes 2A IIC, IID and IIE, we have described novel aspects of the mechanisms underlying these different types of VWD under flow conditions. These findings prompted us to develop novel diagnostic tests which could support better differentiation between VWD subtypes. Incorporation of our tests into the clinical routine diagnostics could lead to optimization of personalized treatment options in the future. Not only quantitative and/or functional deficiencies of VWF have pathological consequences. In thrombotic thrombocytopenic purpura (TTP), VWF is hyperactive because the protein, ADAMTS13, which normally inactivates VWF and thus prevents blood vessel occlusion (thrombosis), is absent or non-functional. Currently, diagnostic tests for TTP are performed under static conditions although ADAMTS13 works in the blood under flow conditions. We have developed two novel diagnostic tests, which are conducted under flow and therefore performed closer to the physiological conditions. These methods helped us to understand how mutations in ADAMTS13 disturb VWF inactivation and allow precise and differential determination of ADAMTS13 dysfunction. Summarizing, our new tests are suitable for the diagnosis of VWD and TTP for parameters, which are currently not covered by stateof-the-art diagnostic test panels. Our most significant scientific finding was the identification of genetic variants of VWF with increased force sensitivity. These variants do not induce bleeding but enhance platelet aggregate formation. These data add VWF variants to the list of risk factors for myocardial infarction and possibly also for stroke and thrombosis. These new insights into force-dependent factors influencing development of vascular disease might support advances in treatment and prevention of these common thrombotic complications. By working together in a highly interdisciplinary environment, the SHENC groups were able to bridge the gap between biophysics, biochemistry and clinical findings to enter new paths for the development of novel diagnostic and therapeutic options.
Publications
- “Ultralarge von Willebrand factor fibers mediate luminal Staphylococcus aureus adhesion to an intact endothelial cell layer under shear stress”, Circulation. 2013 Jul 2;128(1):50-9
Pappelbaum KI, Gorzelanny C, Grässle S, Suckau J, Laschke MW, Bischoff M, Bauer C, Schorpp-Kistner M, Weidenmaier C, Schneppenheim R, Obser T, Sinha B, Schneider SW
(See online at https://doi.org/10.1161/CIRCULATIONAHA.113.002008) - „Exponential size distribution of von Willebrand factor”, Biophys J. 2013 Sep 3;105(5):1208-16
Lippok S, Obser T, Müller JP, Stierle VK, Benoit M, Budde U, Schneppenheim R, Rädler JO
(See online at https://doi.org/10.1016/j.bpj.2013.07.037) - “Platelet-free shear flow assay facilitates analysis of shear-dependent functions of VWF and ADAMTS13”, Thromb Res. 2014 Dec;134(6):1285-91
Kraus E, Obser T, Kraus K, Oyen F, Klemm U, Schneppenheim R, Brehm MA
(See online at https://doi.org/10.1016/j.thromres.2014.08.013) - “VWD type 2A phenotypes IIC, IID and IIE: A day in the life of shear stressed mutant VWF”, Thromb Haemost. 2014 Jul 3;112(1):96-108
Brehm MA, Huck V, Aponte-Santamaría C, Obser T, Grässle S, Oyen F, Budde U, Schneppenheim S, Baldauf C, Gräter F, Schneider SW, Schneppenheim R
(See online at https://doi.org/10.1160/TH13-11-0902) - “Force-sensitive autoinhibition of the von Willebrand factor mediated by inter-domain interactions”, Biophys J. 2015 May 5;108(9):2312-21
Aponte-Santamaría C, Huck V, Posch S, Bronowska AK, Grässle A, Brehm MA, Obser T, Schneppenheim R, Hinterdorfer P, Schneider SW, Baldauf C, Gräter F
(See online at https://doi.org/10.1016/j.bpj.2015.03.041) - “Identification and characterization of the elusive mutation causing the historical von Willebrand Disease type IIC Miami”, J Thromb Haemost. 2016 Sep;14(9):1725-35
Obser T, Ledford-Kraemer M, Oyen F, Brehm MA, Denis CV, Marschalek R, Montgomery RR, Sadler JE, Schneppenheim S, Budde U, Schneppenheim R
(See online at https://doi.org/10.1111/jth.13398) - “Von Willebrand Factor is dimerized by Protein Disulfide Isomerase”, Blood, 2016 Mar 3;127(9):1183-91
Lippok S, Kolšek K, Löf A, Eggert D, Vanderlinden W, Müller JP, König G, Obser T, Röhrs K, Schneppenheim S, Budde U, Baldauf C, Aponte-Santamaría C, Gräter F, Schneppenheim R, Rädler JO, Brehm MA
(See online at https://doi.org/10.1182/blood-2015-04-641902) - “Von Willebrand factor regulates complement on endothelial cells”, Kidney Int. 2016 Jul;90(1):123-34
Noone DG, Riedl M, Pluthero FG, Bowman ML, Liszewski MK, Lu L, Quan Y, Balgobin S, Schneppenheim R, Schneppenheim S, Budde U, James P, Atkinson JP, Palaniyar N, Kahr WH, Licht C
(See online at https://doi.org/10.1016/j.kint.2016.03.023) - “Enhanced Local Disorder in a Clinically Elusive von Willebrand Factor Provokes High-Affinity Platelet Clumping”, J Mol Biol, 2017, Jul 7;429(14):2161-2177
Tischer A, Machha VR, Frontroth JP, Brehm MA, Obser T, Schneppenheim R, Mayne L, Englander W, Auton M
(See online at https://doi.org/10.1016/j.jmb.2017.05.013) - “Mutual A domain interactions in the force sensing protein von Willebrand factor“, J Struct Biol. 2017 Jan;197(1):57-64
Posch S, Aponte-Santamaría C, Schwarzl R, Karner A, Radtke M, Gräter F, Obser T, König G, Brehm MA, Gruber HJ, Netz RR, Baldauf C, Schneppenheim R, Tampé R, Hinterdorfer P
(See online at https://doi.org/10.1016/j.jsb.2016.04.012) - “Genetic and Functional Characterization of ADAMTS13 Variants in a Patient Cohort with Upshaw-Schulman Syndrome Investigated in Germany” Thromb Haemost. 2018 Apr;118(4):709-722
Hassenpflug WA, Obser T, Bode J, Oyen F, Budde U, Schneppenheim S, Schneppenheim R, Brehm MA
(See online at https://doi.org/10.1055/s-0038-1637749) - Structure and dynamics of the platelet integrin-1 binding C4 domain of von Willebrand factor., Blood
Xu, E.-R.; von Bülow, S.; Chen, P.-C.; Lenting, P.J.; Kolšek, K.; Aponte-Santamaría, C.; Simon, B.; Foot, J.; Obser, T.; Schneppenheim, R.; Gräter, F.; Denis, C.V.; Wilmanns, M.; Hennig J.
(See online at https://doi.org/10.1182/blood-2018-04-843615)
