Biosynthesis and secretion of factor VII, protein C, protein S, and the Protein C inhibitor from a human hepatoma cell line.
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 X 10(8) 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 as 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 proteins studied represented their plasma protein counterparts structurally, functionally, and immunochemically. Thus, all of the known soluble components of the protein C pathway are produced by liver parenchymal cells.
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D005167:Factor VII / Q000032:analysis / Q000096:biosynthesis*; D006023:Glycoproteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D006801:Humans; D008113:Liver Neoplasms / Q000032:analysis / Q000378:metabolism*; D008970:Molecular Weight; D011486:Protein C; D017293:Protein S; D011817:Rabbits; D011863:Radioimmunoassay; D014812:Vitamin K / Q000494:pharmacology; D014859:Warfarin / Q000494:pharmacology
D006023:Glycoproteins; D011486:Protein C; D017293:Protein S; D014812:Vitamin K; D014859:Warfarin; D005167:Factor VII