Factor VII activating protease (FSAP): a novel protective factor in liver fibrosis

Factor VII activating protease (FSAP) is a multifunctional serine protease that is mainly synthesized and secreted by hepatocytes. This enzyme is highly evolutionarily conserved and contains three epidermal growth factor like domains, a kringle domain and a trypsin-like serine protease signature at its C-terminus. Animal experimentation and clinical findings indicate that FSAP influences a range of inflammatory fibroproliferative diseases. In particular, recent work demonstrated that FSAP is anti-fibrotic and influences liver fibrosis progression. The relative high physiological concentration, occurrence of gene variants affecting the proteolytic activity of FSAP and eclectic substrate specificity should in principal presuppose this protease to be frequently found in studies in which quantitative proteomics is performed. However, presently there are only a few studies available that have identified FSAP in applications using 2D gels, MS or other proteomic-associated techniques. We summarize here the actual knowledge about FSAP functions in initiation and progression of hepatic fibrosis and comment on proteome studies in which altered expression or activity of FSAP was reported.