核糖核酸酶5在宿主防御中的作用及机制

抗菌肽是机体天然免疫的重要组成部分。核糖核酸酶5（ribonuclease5，RNASE5；又名angiogenin）属于核糖核酸酶A超家族，是一个分泌型小分子蛋白质，广泛分布于机体需要抵御外界病原微生物的组织中。RNASE5对病毒、细菌以及真菌都存在抑制效应，具有广谱抗菌特点，但其表达和活性受到宿主生理状态和外界环境多层次的调控。RNASE5存在多样的抗微生物作用机制，其带正电荷的理化特性破坏微生物细胞壁，而其核糖核酸酶活性则是杀伤真菌所必须的。除了直接作用于微生物外，RNASE5还可作为重要因子调节宿主免疫功能，参与多种病理过程。本文综述了RANSE5的结构、生物活性与功能、作用特点与机制，并讨论了在其研究中存在的问题，以期为今后的研究提供新思路和新方向。

The Role and Working Mechanism of Ribonuclease 5 in Host Defense

Antimicrobial peptides are key components of the innate immune system. Ribonuclease 5 (RNASE5, also named as angiogenin), the fifth member of the ribonuclease A superfamily, is a secreted small protein and widely distributed in the tissues that resist pathogenic microorganisms. As a multifunctional antimicrobial peptide, RNASE5 exhibits broad-spectrum antimicrobial activity, including growth inhibition of viruses, bacteria and fungi. However, its expression and activity are regulated by the physiological states of host and the external environment at multiple levels. Mechanistically, RNASE5 mainly plays its antimicrobial role through its positively charged physicochemical properties and ribonuclease activity. Besides killing microorganisms directly, RNASE5 also regulates host defense and immune functions in a variety of pathological processes. Here, we systematically review the structure and biological activity of RNASE5 in host defense, as well as discuss the existing problems and future directions for further research.