title: Differential surface activation of the A1 domain of von Willebrand factor.
abstract: The clotting protein von Willebrand factor (VWF) binds to platelet receptor glycoprotein Ibα (GPIbα) when VWF is activated by chemicals, high shear stress, or immobilization onto surfaces. Activation of VWF by surface immobilization is an important problem in the failure of cardiovascular implants, but is poorly understood. Here, the authors investigate whether some or all surfaces can activate VWF at least in part by affecting the orientation or conformation of the immobilized GPIbα-binding A1 domain of VWF. Platelets binding to A1 adsorbed onto polystyrene surfaces translocated rapidly at moderate and high flow, but detached at low flow, while platelets binding to A1 adsorbed onto glass or tissue-culture treated polystyrene surfaces translocated slowly, and detached only at high flow. Both x-ray photoelectron spectroscopy and conformation independent antibodies reported comparable A1 amounts on all surfaces. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and near-edge x-ray absorption fine structure spectra suggested differences in orientation on the three surfaces, but none that could explain the biological data. Instead, ToF-SIMS data and binding of conformation-dependent antibodies were consistent with the stabilization of an alternative more activated conformation of A1 by tissue culture polystyrene and especially glass. These studies demonstrate that different material surfaces differentially affect the conformation of adsorbed A1 domain and its biological activity. This is important when interpreting or designing in vitro experiments with surface-adsorbed A1 domain, and is also of likely relevance for blood-contacting biomaterials.
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195.
authors.forename: Elaine H
authors.initials: EH
authors.lastname: Tronic
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195.
authors.forename: Olga
authors.initials: O
authors.lastname: Yakovenko
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195.
authors.forename: Tobias
authors.initials: T
authors.lastname: Weidner
authors.affiliation: Department of Chemical Engineering, University of Washington, Seattle, Washington 98195.
authors.forename: Joe E
authors.initials: JE
authors.lastname: Baio
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Penkala
authors.affiliation: Departments of Bioengineering and Chemical Engineering, University of Washington, Seattle, Washington 98195.
authors.forename: David G
authors.initials: DG
authors.lastname: Castner
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195.
authors.forename: Wendy E
authors.initials: WE
authors.lastname: Thomas
mesh_terms: D001792:Blood Platelets / Q000502:physiology*; D002448:Cell Adhesion; D005898:Glass; D006801:Humans; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism*; D011137:Polystyrenes; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013499:Surface Properties; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D019038:Platelet Glycoprotein GPIb-IX Complex; D011137:Polystyrenes; D014841:von Willebrand Factor