Protein expression and fucosylated glycans of the serum haptoglobin-β subunit in hepatitis B virus-based liver diseases

Glycosylation, which regulates the configuration and function of glycoproteins, is the most important post-translational modification. The aim of this study was to observe the differential patterns in glycan and protein parts of the serum haptoglobin-beta subunit (Hp-beta) purified from patients with hepatitis B virus (HBV) infection, liver cirrhosis (LC), or hepatocellular carcinoma (HCC). 2-D gel electrophoresis and multiplexed proteomics staining technique were employed to investigate whether the Hp-beta glycan level was proportional to the protein level. Multilectin blot, high-performance liquid chromatography (HPLC), and western blot analysis were carried out to identify the glycoform of Hp-beta quantitatively. Our experiments showed that the ratio of total serum Hp-beta to the glycosylated form of Hp-beta varied among the patients with different liver diseases. The total Hp-beta protein expression level was much higher in HCC than LC, while an incremental proportion of fucosylated Hp-beta was also observed in LC and HCC patients compared with that in HBV and healthy controls. Differential fucosylation was further identified as a Lewis X structure by HPLC and antihuman Sialyl-Lewis X antibody. In conclusion, the aberrant alternation of Hp-beta glycan and total protein expression may be a promising biomarker for early hepatocarcinogenesis.