Dimeric Organization of Blood Coagulation Factor VIII bound to Lipid Nanotubes

Sci Rep. 2015 Jun 17;5:11212. doi: 10.1038/srep11212.

Abstract

Membrane-bound Factor VIII (FVIII) has a critical function in blood coagulation as the pro-cofactor to the serine-protease Factor IXa (FIXa) in the FVIIIa-FIXa complex assembled on the activated platelet membrane. Defects or deficiency of FVIII cause Hemophilia A, a mild to severe bleeding disorder. Despite existing crystal structures for FVIII, its membrane-bound organization has not been resolved. Here we present the dimeric FVIII membrane-bound structure when bound to lipid nanotubes, as determined by cryo-electron microscopy. By combining the structural information obtained from helical reconstruction and single particle subtomogram averaging at intermediate resolution (15-20 Å), we show unambiguously that FVIII forms dimers on lipid nanotubes. We also demonstrate that the organization of the FVIII membrane-bound domains is consistently different from the crystal structure in solution. The presented results are a critical step towards understanding the mechanism of the FVIIIa-FIXa complex assembly on the activated platelet surface in the propagation phase of blood coagulation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cryoelectron Microscopy
  • Factor VIII / chemistry*
  • Factor VIII / metabolism*
  • Humans
  • Lipids* / chemistry
  • Models, Molecular
  • Nanotubes* / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Multimerization*
  • Tomography / methods

Substances

  • Lipids
  • Factor VIII