title: Synthesis and secretion of protein C inhibitor by the human hepatoma-derived cell line, Hep G2.
abstract: The site of synthesis of protein C inhibitor, a recently identified human plasma inhibitor against activated protein C, is not known. We have studied the production and secretion of protein C inhibitor by an established human liver cell line derived from hepatocellular carcinoma (Hep G2). The concentration of protein C inhibitor, as measured by a specific radioimmunoassay, increased in the medium of Hep G2 cells with time. There was no evidence for a significant intracellular pool of this protein. Protein C inhibitor secreted from Hep G2 cells (G2 protein C inhibitor) inhibited the activity of purified activated protein C in a functional assay. De novo synthesis of protein C inhibitor was demonstrated by the presence of specific immunoprecipitable radioactivity in the medium after 5 h of labeling of the cells with [35S]methionine. Analysis of the immunoprecipitates by SDS-polyacrylamide gel electrophoresis showed a peak of radioactivity corresponding to Mr 57 000. These results indicate that the liver is a site of protein C inhibitor production.
authors.forename: F
authors.initials: F
authors.lastname: Morito
authors.forename: H
authors.initials: H
authors.lastname: Saito
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: S
authors.initials: S
authors.lastname: Hashimoto
mesh_terms: D001798:Blood Proteins / Q000096:biosynthesis* / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002460:Cell Line; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D018046:Protein C Inhibitor
chemical_list: D001798:Blood Proteins; D003470:Culture Media; D018046:Protein C Inhibitor; D008715:Methionine