The Relationship of Secretion and Activity of Recombinant Factor IX with N-Glycosylation

 Human coagulation factor IX (hFIX) is a glycoprotein with two N-glycosylation sites at the activation peptide. Since the activation peptide is removed in mature hFIX, the exact role of N-glycosylation is unclear. To investigate the role of N-glycosylation in the secretion and activity of hFIX, we inhibited N-glycosylation by tunicamycin in the stable Human Embryonic Kidney (HEK)- coagulation Factor IX (FIX) cells.

 After the treatment of stable FIX-expressing HEK cells in the presence or absence of tunicamycin, the expression and activity of the recombinant FIX (rFIX) were determined in culture medium and cell lysate with enzyme-linked immunosorbent assay and clotting test, respectively.

Based on the data analysis, total concentrations of FIX in stable HEK-FIX was the same in the media with and without tunicamycin. But throughout the post-induction period, the intracellular and secreted levels of FIX in tunicamycin-treated HEK-FIX cells increased and decreased, respectively, compared with those of control HEK-FIX cells, though the results were not significant. These results indicate that disrupting the synthetic process may slightly reduce the FIX levels secreted in HEK-FIX cells.

 Although glycosylation plays a vital role in the folding and secretion of the proteins, it does not affect the secretion of FIX. Besides, the N-glycosylation of the produced FIX failed to play a significant role in its activity.