Plasma hyaluronan-binding protein is a serine protease

Nucleosome-releasing factor: a new role for factor VII-activating protease (FSAP)

Plasma proteins such as early complement components and IgM are involved in the removal of late apoptotic or secondary necrotic (sn) cells. We have recently described how a plasma protease that could be inhibited by the protease inhibitor aprotinin was essential to remove nucleosomes from sn cells. An obvious candidate, plasmin, did indeed have nucleosome-releasing factor (NRF) activity. However, recalcified plasma (r-plasma) retained its NRF activity after plasminogen depletion, which suggests the existence of another protease responsible for NRF activity in plasma. In this study we have used size-exclusion and anion-exchange chromatography to purify the protease responsible for NRF activity in plasma. SDS-PAGE analysis of chromatography fractions containing NRF activity revealed a protein band corresponding with NRF activity. Sequence analysis showed this band to be factor VII-activating protease (FSAP). We developed monoclonal antibodies to FSAP and were able to completely inhibit NRF activity in plasma with monoclonal antibodies to FSAP. Using affinity chromatography we were able to purify single-chain (sc) FSAP from r-plasma. Purified scFSAP efficiently removes nucleosomes from sn cells. We report that factor VII-activating protease may function in cellular homeostasis by catalyzing the release of nucleosomes from secondary necrotic cells.

Factor VII activating protease (FSAP): a novel protease in hemostasis

Recently a novel serine protease in human plasma was described and was named PHBP, PHBSP or factor seven activating protease (FSAP), respectively, the latter according to the finding that it can support coagulation by factor VII activation. Later on FSAP was identified as a potent activator of single chain plasminogen activators, in particular of prourokinase, as well. The physiological role of FSAP is still speculative, but recent studies suggest a contribution to hemostasis. Due to its affinity to glycosaminoglycans a role in cell-associated or extracellular proteolytic events is also likely. The impact of a very recently uncovered frequent polymorphism impairing the prourokinase activation potential of FSAP needs to be investigated in more detail.

Hepatic injury-specific conversion of mouse plasma hyaluronan binding protein to the active hetero-dimer form

Plasma hyaluronan binding protein (PHBP) is produced only in liver and kidney in mouse. The induction of PHBP mRNA and the conversion of pro PHBP to the active hetero-dimer form were studied after CCl4, D-galactosamine, HgCl2 or turpentine administration and after partial hepatectomy. The results indicated that the administrations of CCl4 and D-galactosamine, which caused hepatic failure, and the partial hepatectomy enhanced the conversion of pro PHBP to the active two-chain form in the plasma. On the other hand, HgCl2 which injured kidney and turpentine which led to inflammation were not involved in the activation of PHBP. The weak induction and suppression of PHBP mRNA were observed in the liver at 3 h and 12 h, respectively, after the CCl4 administration. However, HgCl2 and turpentine did not influence the amount of PHBP mRNA. These results suggested the hepatic injury-specific activation of PHBP in plasma. PHBP may act as an early factor in the cascade for the tissue remodeling in liver following hepatic injury, i.e., PHBP activates urokinase, urokinase activates matrix metalloproteinases (MMPs) and MMPs degrade extracellular matrix for liver regeneration.