Maruzuru Yuhei, Koyanagi Naoto, Kato Akihisa, Kawaguchi Yasushi
Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
Division of Viral Infection, Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
J Virol. 2021 Mar 1;95(5). doi: 10.1128/JVI.02172-20. Epub 2020 Dec 9.
AIM2 is a cytosolic DNA sensor of the inflammasome, which induces critical innate immune responses against various invading pathogens. Earlier biochemical studies showed that the binding of AIM2 to DNA triggered the self-oligomerization of AIM2, which is essential for AIM2 inflammasome activation. We recently reported that VP22, a virion tegument protein of herpes simplex virus 1 (HSV-1), inhibited activation of the AIM2 inflammasome in HSV-1-infected cells by preventing AIM2 oligomerization. VP22 binds non-specifically to DNA; however, its role in HSV-1 replication is unclear. We investigated the role of VP22 DNA binding activity in the VP22-mediated inhibition of AIM2 inflammasome activation. We identified a VP22 domain encoded by amino acids 227 to 258 as the minimal domain required for its binding to DNA Consecutive alanine substitutions in this domain substantially impaired the DNA binding activity of VP22 and attenuated the inhibitory effect of VP22 on AIM2 inflammasome activation in an AIM2 inflammasome reconstitution system. The inhibitory effect of VP22 on AIM2 inflammasome activation was completely abolished in macrophages infected with a recombinant virus harboring VP22 with one of the consecutive alanine substitutions, similar to the effect of a VP22-null mutant virus. These results suggested that the DNA binding activity of VP22 is critical for VP22-mediated AIM2 inflammasome activation in HSV1-infected cells. VP22, a major component of the HSV-1 virion tegument, is conserved in alphaherpesviruses and has structural similarity to ORF52, a component of the virion tegument that is well-conserved in gammaherpesviruses. Although the potential DNA binding activity of VP22 was discovered decades ago, its significance in the HSV-1 life cycle is poorly understood. Here, we show that the DNA binding activity of VP22 is critical for the inhibition of AIM2 inflammasome activation induced in HSV-1-infected cells. This is the first report to show a role for the DNA binding activity of VP22 in the HSV-1 life cycle, allowing the virus to evade AIM2 inflammasome activation, which is critical for its replication .
AIM2是炎性小体的一种胞质DNA传感器，可诱导针对各种入侵病原体的关键先天性免疫反应。早期的生化研究表明，AIM2与DNA的结合触发了AIM2的自我寡聚化，这对于AIM2炎性小体的激活至关重要。我们最近报道，单纯疱疹病毒1型（HSV-1）的病毒体被膜蛋白VP22通过阻止AIM2寡聚化来抑制HSV-1感染细胞中AIM2炎性小体的激活。VP22可非特异性地结合DNA；然而，其在HSV-1复制中的作用尚不清楚。我们研究了VP22 DNA结合活性在VP22介导的对AIM2炎性小体激活的抑制作用中的作用。我们确定由氨基酸227至258编码的VP22结构域是其与DNA结合所需的最小结构域。该结构域中的连续丙氨酸替代大大损害了VP22的DNA结合活性，并减弱了VP22在AIM2炎性小体重构系统中对AIM2炎性小体激活的抑制作用。在感染了携带具有连续丙氨酸替代之一的VP22的重组病毒的巨噬细胞中，VP22对AIM2炎性小体激活的抑制作用完全消除，类似于VP22缺失突变病毒的作用。这些结果表明，VP22的DNA结合活性对于HSV1感染细胞中VP22介导的AIM2炎性小体激活至关重要。VP22是HSV-1病毒体被膜的主要成分，在α疱疹病毒中保守，并且与γ疱疹病毒中病毒体被膜的成分ORF52具有结构相似性。尽管几十年前就发现了VP22潜在的DNA结合活性，但其在HSV-1生命周期中的重要性仍知之甚少。在这里，我们表明VP22的DNA结合活性对于抑制HSV-1感染细胞中诱导的AIM2炎性小体激活至关重要。这是首次报道VP22的DNA结合活性在HSV-1生命周期中的作用，使病毒能够逃避对其复制至关重要的AIM2炎性小体激活。
