The transmembrane serine protease hepsin suppresses type I interferon induction by cleaving STING.

Many viral proteases mediate the evasion of antiviral innate immunity by cleaving adapter proteins in the interferon (IFN) induction pathway. Host proteases are also involved in innate immunity and inflammation. Here, we report that the transmembrane protease hepsin (also known as TMPRSS1), which is predominantly present in hepatocytes, inhibited the induction of type I IFN during viral infections. Knocking out hepsin in mouse embryonic fibroblasts (MEFs) increased the viral infection-induced expression of Ifnb1, an Ifnb1 promoter reporter, and an IFN-sensitive response element promoter reporter. Ectopic expression of hepsin in cultured human hepatocytes and HEK293T cells suppressed the induction of IFNß during viral infections by reducing the abundance of STING. These effects depended on the protease activity of hepsin. We identified a putative hepsin target site in STING and showed that mutating this site protected STING from hepsin-mediated cleavage. In addition to hepatocytes, several hepsin-producing prostate cancer cell lines showed reduced STING-mediated type I IFN induction and responses. These results reveal a role for hepsin in suppressing STING-mediated type I IFN induction, which may contribute to the vulnerability of hepatocytes to chronic viral infections.

A Preconditioning Strategy to Augment Retention and Engraftment Rate of Donor Cells During Hepatocyte Transplantation.

BACKGROUND: Hepatocyte transplantation has been extensively investigated as an alternative to orthotopic liver transplantation. However, its application in routine clinical practice has been restricted because of low initial engraftment and subsequent repopulation. METHODS: Using mice as a model, we have developed a minimally invasive and nontoxic preconditioning strategy based on preadministration of antibodies against hepsin to increase donor hepatocyte retention and engraftment rate. RESULTS: Liver sinusoid diameters decreased significantly with antihepsin pretreatment, and graft cell numbers increased nearly 2-fold in the recipients' liver parenchyma for 20 days after hepatocyte transplantation. Postoperative complications such as hepatic ischemia injury or apparent immune cell accumulation were not observed in recipients. In a hemophilia B mouse model, antihepsin preconditioning enhanced the expression and clotting activity of coagulation factor IX (FIX) to nearly 2-fold that of immunoglobulin G-treated controls and maintained higher plasma FIX clotting activity relative to the prophylactic range for 50 days after hepatocyte transplantation. Antihepsin pretreatment combined with adeno-associated virus-transduced donor hepatocytes expressing human FIX-Triple, a hyperfunctional FIX variant, resulted in plasma FIX levels similar to those associated with mild hemophilia, which protected hemophilia B mice from major bleeding episodes for 50 days after transplantation. Furthermore, antihepsin pretreatment and repeated transplantation resulted in extending the therapeutic period by 30 days relative to the immunoglobulin G control. CONCLUSIONS: Thus, this antihepsin strategy improved the therapeutic effect of hepatocyte transplantation in mice with tremendous safety and minimal invasion. Taken together, we suggest that preconditioning with antihepsin may have clinical applications for liver cell therapy.