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Total inhibition of high shear stress induced platelet aggregation by homodimeric von Willebrand factor A1‐loop fragments
Author(s) -
Miura Shuji,
Sakurai Yoshihiko,
Takatsuka Hideo,
Yoshioka Akira,
Matsumoto Masanori,
Yagi Hideo,
Kokubo Tetsuro,
Ikeda Yasuo,
Matsui Taei,
Titani Koiti,
Fujimura Yoshihiro
Publication year - 1999
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.1999.01454.x
Subject(s) - chemistry , von willebrand factor , protein subunit , monomer , platelet , biophysics , glycoprotein ib , recombinant dna , platelet membrane glycoprotein , biochemistry , stereochemistry , microbiology and biotechnology , glycoprotein , biology , organic chemistry , immunology , gene , polymer
Under high shear stress, the binding of von Willebrand factor (VWF) A1‐loop domain to platelet glycoprotein (GP) Ibα occurs as the earliest event in thrombus formation. Therefore recombinant VWF A1‐loop fragments could be of therapeutic use in blocking this interaction as competing ligands. We have prepared three homodimeric VWF A1‐loop fragments [315 kD Fr III (a homodimer of amino acid [aa] residues 1–1365 of the subunit), 220 kD Fr (a homodimer of aa residues 1–708 of the subunit), and 116 kD Fr (a homodimer of aa residues 449–728 of the subunit) and two monomeric fragments [39/34 kD Fr (a monomer of aa residues 480/481–718 of the subunit] and His‐rVWF465–728 (a monomer of aa residues 465–728 of the subunit)], and assessed their potency as inhibitors of botrocetin‐induced VWF binding to GPIbα and high shear stress induced platelet aggregation mediated by intact VWF. All these fragments completely inhibited botrocetin‐induced VWF binding to GPIbα at a final concentration of 40–200 μ m . The homodimeric A1‐loop fragments also totally inhibited high shear stress induced platelet aggregation at a final concentration of 0.45–2.0 μ m in the following order: 315 kD Fr 220 kD Fr ≫ 116 kD Fr. In contrast, the monomeric A1‐loop fragments were only partial inhibitors of high shear stress induced platelet aggregation even at a final concentration of 20 μ m , and their IC 50 s were 13–39 times higher than those of the homodimers. These results indicate that the homodimeric structure of the A1‐loop fragment is important for optimal molecular interaction with GPIbα under high shear stress.