Abstract
Hepatitis B virus (HBV)is a major etiological factor of liver cirrhosis and hepatocellular carcinoma (HCC) in Taiwan. Recently, it has been shown that the presence of pre-S mutant large surface protein (LHBs)-containing ground glass hepatocytes (GGHs) are associated with an increased recurrence of HBV-related HCC after surgery. HBV LHBs pre-S2 mutant (∆S2) may accumulate in endoplasmic reticulum (ER) and thereby activates ER stress. Whether ER stress may play a role in the cell migration and invasion and subsequently contribute to cancer metastasis is not clear. In this study, we aim to investigate whether HBV LHBs-induced ER stress may interfere with hepatocyte morphology and motility, thereby contributing to cell migration. First, we check the mean velocity of hepatocytes on culture dishes by live cell imaging and found that the induction of ER stress enhanced hepatocyte motility. Furthermore, we demonstrated that an increase in calcium in cytoplasm also increased hepatocyte motility. In addition, treatments of calcium chelators (BAPTA-AM) and calpain inhibitors (calpeptin and E64D) blocked ER stress-induced hepatocyte motility. Interestingly, we specifically detected proteolysis of the focal adhesion complex protein, Talin-1 in cells treated with ER stress inducer (Brefeldin A, BFA) or a stable cell line carrying with PreS2 mutant LHBs proteins. Finally, we show that overexpression of talin-L432G reduced hepatocyte motility under ER stress. In conclusion, we propose that ER stress is involved of LHBs-induced motility change in hepatocytes through the regulation of calpain-dependent proteolysis of talin. This mechanism may contribute to the cell migration and regulation upon liver damage as well as cancer metastasis in HBV-related HCC.