Human subtilase SKI-1/S1P is a master regulator of the HCV lifecycle and a potential host cell target for developing indirect-acting antiviral agents

Hcv infection is a major risk factor for liver cancer and liver transplantation worldwide. overstimulation of host lipid metabolism in the liver by hcv-encoded proteins during viral infection creates a favorable environment for virus propagation and pathogenesis. in this study,we hypothesize that targeting cellular enzymes acting as master regulators of lipid homeostasis could represent a powerful approach to developing a novel class of broad-spectrum antivirals against infection associated with human flaviviridae viruses such as hepatitis c virus (hcv),whose assembly and pathogenesis depend on interaction with lipid droplets (lds). one such master regulator of cholesterol metabolic pathways is the host subtilisin/kexin-isozyme-1 (ski-1) - or site-1 protease (s1p). ski-1/s1p plays a critical role in the proteolytic activation of sterol regulatory element binding proteins (srebps),which control expression of the key enzymes of cholesterol and fatty-acid biosynthesis. here we report the development of a ski-1/s1p-specific protein-based inhibitor and its application to blocking the srebp signaling cascade. we demonstrate that ski-1/s1p inhibition effectively blocks hcv from establishing infection in hepatoma cells. the inhibitory mechanism is associated with a dramatic reduction in the abundance of neutral lipids,lds,and the ld marker: adipose differentiation-related protein (adrp)/perilipin 2. reduction of ld formation inhibits virus assembly from infected cells. importantly,we confirm that ski-1/s1p is a key host factor for hcv infection by using a specific active,site-directed,small-molecule inhibitor of ski-1/s1p: pf-429242. our studies identify ski-1/s1p as both a novel regulator of the hcv lifecycle and as a potential host-directed therapeutic target against hcv infection and liver steatosis. with identification of an increasing number of human viruses that use host lds for infection,our results suggest that ski-1/s1p inhibitors may allow development of novel broad-spectrum biopharmaceuticals that could lead to novel indirect-acting antiviral options with the current standard of care. © 2012 olmstead et al.