Novel Defensins of Human Epithelia

描述（由申请人提供）：抗菌肽的发现揭示了以前未被认识的动物宿主防御成分。我们和其他人发现哺乳动物粘膜上皮细胞表达防御肽，使其具有参与粘膜宿主防御的能力。在人小肠中，防御素HD5和HD6在被称为Paneth细胞的分泌性上皮细胞中高度表达。本小组和其他研究人员的研究为Paneth细胞防御蛋白肽在肠道中提供强大的关键防御功能的假设提供了强有力的支持。我们的研究还发现HD5作为一种修饰的前肽储存在Paneth细胞中。我们发现Paneth细胞胰蛋白酶是将proHD5加工成存在于管腔中的活性抗菌剂的蛋白酶。这些数据表明胰酶的蛋白水解活性可能是调节肠道宿主防御的核心。

DESCRIPTION (provided by applicant): The discovery of antimicrobial peptides has unveiled a previously unrecognized component of animal host defense. We and others have discovered that mammalian mucosal epithelial cells express defensin peptides, providing them with the capacity to participate in mucosal host defense. In the human small intestine, defensins HD5 and HD6 are highly expressed in secretory epithelial cells called Paneth cells. Investigations by our group, and those of others, provide strong support for the hypothesis that Paneth cell defensin peptides provide a robust, critical defensive function in the intestine. Our studies have discovered also that HD5 is stored in Paneth cells as a modified propeptide. We identified that Paneth cell trypsin is the protease that processes proHD5 to the active antimicrobial present in the lumen. These data suggest that the proteolytic activity of Paneth call trypsin might be central to the regulation of enteric host defense. It is our hypothesis that 1) HD5 (and possibly HD6) is stored in Paneth cells as a glycosylated propeptide, providing a mechanism for both latent antibiotic activity and decreased toxicity to host cells, 2) HD6 has partially overlapping (or synergistic) antimicrobial functions with HD5 in the small intestine, and 3) once activated, Paneth cell trypsin activity unmasks latent antimicrobials and activates protease-activated receptor-2 (PAR-2) on enterocytes. In three specific aims, we will determine the posttranslational structural modifications of the tissue form of human proHD-5 (aim 1); establish the structure of tissue and luminal forms of HD-6 and determine their in vitro antimicrobial activity (aim 2); characterize Paneth cell trypsin isoforms, identify their key activities including processing of proHD-5 and -6, activation of other latent antimicrobials and activation of PAR-2, and identify the mechanism of Paneth cell protrypsin activation (aim 3). The proposed investigations may provide insights to novel therapeutic targets and approaches to combat infectious and inflammatory disease of the intestine.