Investigation Of Endogenous Inhibitors And Associated Proteins Of Furin

After biosynthesis, peptides and proteins are often activated by intracellular limited proteolysis by proprotein convertases (PCs). Furin is the first identified mammalian PC and the most extensively studied member of the known PCs. Furin play important roles in various biological events such as the activation and secretion of peptide and protein hormones, the maturation of membrane receptors and the activation of plasma proteins. Furin is also involved in many diseases such as the activation of viral glycoproteins and bacterial exotoxins and the metastasis of cancer. Although synthetic and bioengineered inhibitors of furin have been well characterized, its endogenous inhibitor has not been directly purified from mammalian tissue to date. On the other hand, though a few associated proteins of furin were identified and extensively studied in the past years, whether other binding proteins exist and what roles they play in the regulation of furin localization and maturation are still unclear. Searching for and functional investigation of endogenous inhibitors and partners of furin is not only helpful to undestand the function of furin in vivo, but also to develop anti-viral and anti-bacterial drugs. In this study, three potent inhibitors of furin were purified from porcine liver by using biochemical methods and identified to be the C-terminal fragments of histnone H1 with different sizes. Furthermore, we demonstrated that a 14 amino acid peptide of histnone H1 around the reactive site was a potent inhibitor of furin, which will be useful for further drug design, and histone H1 regulated furin activity in vivo. In addition, our results about the associated proteins of furin showed that mint3 interacted with the cytoplasmic domain of furin and regulated the TGN localization of furin, and NMMHC-A participated in the maturation of furin through binding P domain of furin.This dissertation is consisted of two major parts: one part focuses on the endogenous inhibitor of furin (chapter 1: purification and optimization of endogenous inhibitors of furin and chapter 2: histone H1 regulates furin activity in vivo), and the other part is about the associated proteins of furin including mint3 that regulates the localization of furin (chapter 3) and nonmuscle myosin type A heavy chain that regulates the maturation of furin (chapter 4).