Xu Ji-Dong, Jiang Hai-Shan, Wei Tian-Di, Zhang Ke-Yi, Wang Xian-Wei, Zhao Xiao-Fan, Wang Jin-Xing
Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Shandong, China.
State Key Laboratory of Microbial Technology, School of Life Sciences, Shandong University, Shandong, China.
J Virol. 2017 Feb 14;91(5). doi: 10.1128/JVI.01916-16. Print 2017 Mar 1.
Many types of small GTPases are widely expressed in eukaryotes and have different functions. As a crucial member of the Rho GTPase family, Cdc42 serves a number of functions, such as regulating cell growth, migration, and cell movement. Several RNA viruses employ Cdc42-hijacking tactics in their target cell entry processes. However, the function of Cdc42 in shrimp antiviral immunity is not clear. In this study, we identified a Cdc42 protein in the kuruma shrimp () and named it Cdc42. Cdc42 was upregulated in shrimp challenged by white spot syndrome virus (WSSV). The knockdown of Cdc42 and injection of Cdc42 inhibitors increased the proliferation of WSSV. Further experiments determined that Cdc42 interacted with an arginine kinase (AK). By analyzing the binding activity and enzyme activity of AK and its mutant, ΔAK, we found that AK could enhance the replication of WSSV in shrimp. AK interacted with the envelope protein VP26 of WSSV. An inhibitor of AK activity, quercetin, could impair the function of AK in WSSV replication. Further study demonstrated that the binding of Cdc42 and AK depends on Cys of AK and suppresses the WSSV replication-promoting effect of AK. By interacting with the active site of AK and suppressing its enzyme activity, Cdc42 inhibits WSSV replication in shrimp. Our results demonstrate a new function of Cdc42 in the cellular defense against viral infection in addition to the regulation of actin and phagocytosis, which has been reported in previous studies. The interaction of Cdc42 with arginine kinase plays a crucial role in the host defense against WSSV infection. This study identifies a new mechanism of Cdc42 in innate immunity and enriches the knowledge of the antiviral innate immunity of invertebrates.
多种小GTP酶在真核生物中广泛表达且具有不同功能。作为Rho GTP酶家族的关键成员，Cdc42具有多种功能，如调节细胞生长、迁移和细胞运动。几种RNA病毒在其进入靶细胞的过程中采用劫持Cdc42的策略。然而，Cdc42在对虾抗病毒免疫中的功能尚不清楚。在本研究中，我们在日本对虾（）中鉴定出一种Cdc42蛋白，并将其命名为Cdc42。Cdc42在受到白斑综合征病毒（WSSV）攻击的对虾中表达上调。敲低Cdc42并注射Cdc42抑制剂会增加WSSV的增殖。进一步实验确定Cdc42与一种精氨酸激酶（AK）相互作用。通过分析AK及其突变体ΔAK的结合活性和酶活性，我们发现AK可增强WSSV在对虾中的复制。AK与WSSV的包膜蛋白VP26相互作用。AK活性抑制剂槲皮素可损害AK在WSSV复制中的功能。进一步研究表明，Cdc42与AK的结合依赖于AK的半胱氨酸，并抑制AK促进WSSV复制的作用。通过与AK的活性位点相互作用并抑制其酶活性，Cdc42抑制WSSV在对虾中的复制。我们的结果证明了Cdc42除了在肌动蛋白调节和吞噬作用方面（先前研究已报道）之外，在细胞抗病毒感染防御中的新功能。Cdc42与精氨酸激酶的相互作用在宿主抵御WSSV感染中起关键作用。本研究确定了Cdc42在先天免疫中的新机制，并丰富了无脊椎动物抗病毒先天免疫的知识。
