BIOSYNTHESIS AND SECRETION OF FACTOR-VII, PROTEIN-C, PROTEIN-S, AND THE PROTEIN-C INHIBITOR FROM A HUMAN HEPATOMA-CELL LINE

  • 1 January 1986
    • journal article
    • research article
    • Vol. 67  (1) , 64-70
Abstract
Using specific radioimmunoassays 8 day cultures of Hep G2 cells were shown to contain in their supernatants 16, 74, and 828 ng/mL and in their cell lysates, 8, 55, and 48 ng/2 .times. 108 cells of factor VII, protein C, and protein S, respectively. These proteins and the protein C inhibitor were functionally active, and each of these activities was neutralized by their respective polyclonal antibodies. Although vitamin K had a modest effect, warfarin decreased the activity of secreted factor VII, protein C, and protein S by 50% to 90%. Protein C and protein S antigens were reduced three-to fourfold by warfarin. The protein C inhibitor antigen and activity were unaffected by vitamin K or warfarin treatment. Intrinsic labeling and immunoprecipitation indicated that factor VII, protein S, and the protein C inhibitor were secreted at 52,000, 77,000, and 58,000 molecular weight (mol wt) proteins, respectively. Protein C was secreted as a single-chain protein of about 65,000 mol wt, indicating that all of the vitamin K-dependent proteins are translated and secreted as single-chain molecules. Each of the four protein counterparts structurally, functionally, and immunochemically. Thus, all of the known soluble components of the protein C pathway are produced by liver parenchymal cells.