Le VHC infecte les hépatocytes, cellules polarisées du foie. Le cycle de réplication du VHC est dépendant du métabolisme lipidique de la cellule hôte. Mais la relation entre VHC, polarité cellulaire et métabolisme lipidique est mal connue. Nous avons démontré que SHIP2 joue un rȏle important dans l’établissement de la polarité apicobasale des cellules épithéliales. La protéine core du HCV induit la perte de polarité cellulaire et diminue l’expression de la phosphatase SHIP2. La réintroduction de SHIP2 dans les cellules exprimant core restitue la polarité cellulaire et diminue l’expression de core. SHIP2 agit aussi sur l’accumulation et l’organisation des gouttelettes lipidiques qui sont des éléments cellulaires nécessaires à la réplication du VHC. Ces résultats montrent le rôle de SHIP2 dans la polarité cellulaire et le désigne comme une cible intéressante pour des recherches dans la lutte contre les infections du VHC. / HCV infects hepatocytes, polarized cells of the liver. HCV replication cycle is dependent on lipid metabolism of the host cell. But the relationship between HCV cell polarity and lipid metabolism is unknown. We demonstrated that SHIP2 plays an important role in establishment of the apicobasal epithelial cell polarity. The HCV core protein induces loss of cell polarity and decreases the expression of the phosphatase SHIP2. The reintroduction of SHIP2 in cells expressing core restores cell polarity and decreases the expression of core protein. SHIP2 also negatively affect lipid droplets, which are important for HCV replication. These results show the role of SHIP2 in cell polarity and designate it as an attractive target for research in the fight against HCV infection.

Student Number : 9906382M MSc (Med) dissertation - Faculty of Health Sciences / The G1862T mutation in the bulge of the RNA encapsidation signal, in the precore region of hepatitis B virus, results in reduced expression of HBeAg and accumulation of the HBeAg precursor in the endoplasmic reticulum (ER)/Golgi apparatus of the cell. This accumulation can disturb the functioning of the ER and lead to the ER stress response that can affect various cellular pathways, in turn affecting cell viability. The aim of this study was to determine whether apoptosis or necrosis occurred when cultured Huh7 cells were transfected with a plasmid expressing the G1862T mutation. Plasmid constructs, with and without the G1862T mutation, were used to transfect cells. To differentiate between necrosis and apoptosis cells were stained with propidium iodide or YO-PRO-1®, respectively. These were analyzed quantitatively using flow cytometry and qualitatively using confocal microscopy. Confocal microscopy, using monoclonal anti- HBe and the Hoechst stain, was performed to ensure that apoptosis was present as a result of the accumulation of the G1862T mutant HBeAg precursor. Caspase profiling was carried out using a fluorogenic-based assay. When cells were transfected with wild-type plasmid, necrosis predominated over apoptosis. Apoptosis predominated when the cells were transfected with the G1862T mutant plasmid. The highest levels of apoptosis occurred at 72 hours post-transfection. Confocal microscopy revealed the co-localization of aggregates of mutant HBeAg precursor with apoptotic nuclei. Transfection with G1862T mutant plasmids resulted in significant differences in the expression of caspase 3, 8, and 9 relative to the wild-type, at 48 and 72 hours post-transfection. The accumulation of the G1862T mutant HBeAg precursor, in the ER/ Golgi compartment, leads to apoptosis and affects the levels of caspase expression.