title: Herpes simplex virus type 1-encoded glycoprotein C contributes to direct coagulation factor X-virus binding.
abstract: The HSV1 (herpes simplex virus type 1) surface has been shown recently to initiate blood coagulation by FVIIa (activated Factor VII)-dependent proteolytic activation of FX (Factor X). At least two types of direct FX-HSV1 interactions were suggested by observing that host cell-encoded tissue factor and virus-encoded gC (glycoprotein C) independently enhance FVIIa function on the virus. Using differential sedimentation to separate bound from free 125I-ligand, we report in the present study that, in the presence of Ca2+, FX binds directly to purified wild-type HSV1 with an apparent dissociation constant (K(d)) of 1.5+/-0.4 muM and 206+/-24 sites per virus at saturation. The number of FX-binding sites on gC-deficient virus was reduced to 43+/-5, and the remaining binding had a lower K(d) (0.7+/-0.2 microM), demonstrating an involvement of gC. Engineering gC back into the deficient strain or addition of a truncated soluble recombinant form of gC (sgC), increased the K(d) and the number of binding sites. Consistent with a gC/FX stoichiometry of approximately 1:1, 121+/-6 125I-sgC molecules were found to bind per wild-type HSV1. In the absence of Ca2+, the number of FX-binding sites on the wild-type virus was similar to the gC-deficient strain in the presence of Ca2+. Furthermore, in the absence of Ca2+, direct sgC binding to HSV1 was insignificant, although sgC was observed to inhibit the FX-virus association, suggesting a Ca2+-independent solution-phase FX-sgC interaction. Cumulatively, these data demonstrate that gC constitutes one type of direct FX-HSV1 interaction, possibly providing a molecular basis for clinical correlations between recurrent infection and vascular pathology.
authors.affiliation: Canadian Blood Services, Research and Development Department, University of British Columbia/Centre for Blood Research, Department of Pathology and Laboratory Medicine, 2350 Health Sciences Mall, Vancouver, BC, Canada, V6T 1Z3.
authors.forename: Joel R
authors.initials: JR
authors.lastname: Livingston
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sutherland
authors.forename: Harvey M
authors.initials: HM
authors.lastname: Friedman
authors.forename: Edward L G
authors.initials: EL
authors.lastname: Pryzdial
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium; D002522:Chlorocebus aethiops; D005170:Factor X / Q000737:chemistry / Q000378:metabolism*; D018259:Herpesvirus 1, Human / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D011991:Receptors, Virus / Q000378:metabolism*; D014709:Vero Cells; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D011991:Receptors, Virus; D014759:Viral Envelope Proteins; C038535:glycoprotein gC, herpes simplex virus type 1; D005170:Factor X; D002118:Calcium