Kido Hiroshi, Okumura Yuushi, Takahashi Etsuhisa, Pan Hai-Yan, Wang Siye, Chida Junji, Le Trong Quang, Yano Mihiro
Division of Enzyme Chemistry, Institute for Enzyme Research, The University of Tokushima, Kuramoto-cho 3-18-15, Tokushima 770-8503, Japan.
J Mol Genet Med. 2008 Nov 29;3(1):167-75.
Influenza A virus (IAV) is one of the most common infectious pathogens in humans and causes considerable morbidity and mortality. The recent spread of highly-pathogenic avian IAV H5N1 viruses has reinforced the importance of pandemic preparedness. In the pathogenesis of IAV infection, cellular proteases play critical roles in the process of viral entry into cells that subsequently leads to tissue damage in the infected organs. Since there are no processing protease for the viral membrane fusion glycoprotein hemagglutinin precursor (HA(0)) in IAV, entry of the virus into cells is determined primarily by the host cellular HA(0) processing proteases that proteolytically activate membrane fusion activity. HA(0) of seasonal human IAV has the consensus cleavage site motif Q(E)-T/X-R and is selectively processed by at least seven different trypsin-type processing proteases identified to-date in animal model experiments using mouse-adapted IAV or gene expression system in MDCK cells. As is the case for the highly pathogenic avian influenza (HPAI) A virus, endoproteolytic processing of the HA(0) occurs through ubiquitous cellular processing proteases, which selectively recognize the multi-basic consensus cleavage site motifs, such as R-X-K/R-R, and K-X-K/R-R. The cleavage enzymes for the R-X-K/R-R motif, but not K-X-K/R-R motif, have been reported to be furin and pro-protein convertase (PC)5/6 in the trans-Golgi network. Here we report new members of type II transmembrane serine proteases of the cell membrane, mosaic serine protease large form (MSPL) and its splice variant TMPRSS13, which recognize and cleave both R-X-K/R-R and K-X-K/R-R motifs without calcium. Furthermore, IAV infection significantly up-regulates a latent ectopic pancreatic trypsin, one of the potent HA processing proteases, and pro-matrix metalloprotease-9, in various organs. These proteases may synergistically damage the blood-brain barrier in the brain and basement membrane of blood vessels in various organs, resulting in severe edema and multiple organ failure. In this review, we discuss these proteases as new drug target molecules for IAV treatment acting by inhibition of IAV multiplication and prevention of multiple organ failure, other than anti-viral agents, viral neuraminidase inhibitors.
甲型流感病毒（IAV）是人类最常见的传染性病原体之一，可导致相当高的发病率和死亡率。高致病性禽流感IAV H5N1病毒最近的传播强化了大流行防范的重要性。在IAV感染的发病机制中，细胞蛋白酶在病毒进入细胞的过程中起着关键作用，随后导致受感染器官的组织损伤。由于IAV中没有用于病毒膜融合糖蛋白血凝素前体（HA(0)）的加工蛋白酶，病毒进入细胞主要由宿主细胞的HA(0)加工蛋白酶决定，这些蛋白酶通过蛋白水解激活膜融合活性。季节性人类IAV的HA(0)具有共有切割位点基序Q(E)-T/X-R，并且在使用小鼠适应的IAV的动物模型实验或MDCK细胞中的基因表达系统中已鉴定出至少七种不同的胰蛋白酶型加工蛋白酶对其进行选择性加工。对于高致病性禽流感（HPAI）A病毒也是如此，HA(0)的内切蛋白水解加工通过普遍存在的细胞加工蛋白酶进行，这些蛋白酶选择性识别多碱性共有切割位点基序，如R-X-K/R-R和K-X-K/R-R。据报道，R-X-K/R-R基序的切割酶而非K-X-K/R-R基序的切割酶是反式高尔基体网络中的弗林蛋白酶和前蛋白转化酶（PC）5/6。在这里，我们报告了细胞膜II型跨膜丝氨酸蛋白酶的新成员，镶嵌丝氨酸蛋白酶大形式（MSPL）及其剪接变体TMPRSS13，它们在没有钙的情况下识别并切割R-X-K/R-R和K-X-K/R-R基序。此外，IAV感染显著上调潜伏的异位胰蛋白酶（一种有效的HA加工蛋白酶）和前基质金属蛋白酶-9在各种器官中的表达。这些蛋白酶可能协同破坏大脑中的血脑屏障和各种器官中血管的基底膜，导致严重水肿和多器官衰竭。在这篇综述中，我们讨论这些蛋白酶作为IAV治疗的新药物靶标分子如何通过抑制IAV增殖和预防多器官衰竭发挥作用，而非作为抗病毒药物、病毒神经氨酸酶抑制剂。
