Endothelial cell protein C receptor acts as a cellular receptor for factor VIIa on endothelium

J Biol Chem. 2007 Apr 20;282(16):11849-57. doi: 10.1074/jbc.M609283200. Epub 2007 Feb 27.

Abstract

Although factor VII/factor VIIa (FVII/FVIIa) is known to interact with many non-vascular cells, activated monocytes, and endothelial cells via its binding to tissue factor (TF), the interaction of FVII/FVIIa with unperturbed endothelium and the role of this interaction in clearing FVII/FVIIa from the circulation are unknown. To investigate this, in the present study we examined the binding of radiolabeled FVIIa to endothelial cells and its subsequent internalization. (125)I-FVIIa bound to non-stimulated human umbilical vein endothelial cells (HUVEC) in time- and dose-dependent manner. The binding is specific and independent of TF and negatively charged phospholipids. Protein C and monoclonal antibodies to endothelial cell protein C receptor (EPCR) blocked effectively (125)I-FVIIa binding to HUVEC. FVIIa binding to EPCR is confirmed by demonstrating a marked increase in (125)I-FVIIa binding to CHO cells that had been stably transfected with EPCR compared with the wild-type. Binding analysis revealed that FVII, FVIIa, protein C, and activated protein C (APC) bound to EPCR with similar affinity. FVIIa binding to EPCR failed to accelerate FVIIa activation of factor X or protease-activated receptors. FVIIa binding to EPCR was shown to facilitate FVIIa endocytosis. Pharmacological concentrations of FVIIa were found to impair partly the EPCR-dependent protein C activation and APC-mediated cell signaling. Overall, the present data provide convincing evidence that EPCR serves as a cellular binding site for FVII/FVIIa. Further studies are needed to evaluate the pathophysiological consequences and relevance of FVIIa binding to EPCR.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Binding Sites
  • Blood Coagulation Factors / physiology*
  • CHO Cells
  • Cells, Cultured
  • Cricetinae
  • Cricetulus
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism*
  • Factor VII / metabolism*
  • Factor VIIa / metabolism*
  • Factor Xa / metabolism
  • Humans
  • Protein C / metabolism
  • Receptors, Cell Surface / physiology*
  • Signal Transduction
  • Umbilical Veins / cytology

Substances

  • Blood Coagulation Factors
  • Protein C
  • Receptors, Cell Surface
  • activated protein C receptor
  • Factor VII
  • Factor VIIa
  • Factor Xa