Targeting Mechanism of a Novel Liver-targeting Interferon IFN-CSP Involves Liver Heparan Sulfate Proteoglycan

In our previous study, a novel liver-targeting interferon (IFN-CSP) combining IFN α2b with plasmodium region I-plus peptide was successfully designed and prepared with Escherichia coli expression systems. The purified IFN-CSP showed anti-HBV activity and liver-targeting potentiality. The present investigation was designed to investigate the molecular mechanisms responsible for liver-targeting of IFN-CSP.The binding site of IFN-CSP in hepatocytes was assayed by immunofluorescent staining. The correspondence of HSPG distribution and the pattern of IFN-CSP binding in liver tissue were determined using a confocal laser scanning microscope. Both the hepatocytes and liver tissue were using as model to investigate the effect of enzyme and soluble glycosaminoglycan on IFN-CSP binding using flow cytometry and fluorescence microscope.Studies of hepatocytes demonstrated that the localization of IFN-CSP in hepatocytes was the plasma membrane. Studies of liver tissue slices showed that IFN-CSP bound to liver tissue in a pattern similar to the distribution of heparan sulfate proteoglycan (HSPG) immunoreactivity. Pretreatment of hepatocytes and liver slices with heparinase reduced the binding of IFN-CSP to HepG2.2.15 cells and liver slices. Coincubation of IFN-CSP with heparin markedly inhibited IFNCSP binding to HepG2.2.15 cells and liver slices.These results indicate that the molecular mechanisms responsible for IFN-CSP targeting involve binding to HSPG of hepatocytes and liver.