Key Laboratory of Animal Epidemiology of the Ministry of Agriculture and Rural Affairs, China Agricultural Universitygrid.22935.3f College of Veterinary Medicine, Beijing, People's Republic of China.
Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA.
Microbiol Spectr. 2022 Apr 27;10(2):e0265921. doi: 10.1128/spectrum.02659-21. Epub 2022 Mar 29.
The 380-to-393-amino-acid glycoprotein I (gI) encoded by herpes simplex virus 1 (HSV-1) is a critical mediator for viral cell-to-cell spread and syncytium formation. Here we report a previously unrecognized aberrant form of gI in HSV-1-infected cells. Production of this molecule is independent of cell type and viral strains. It had an unexpected gel migration size of approximately 23 kDa, was packaged into viral particles, and could be coimmunoprecipitated by antibodies to both N and C termini of gI. Deep sequencing failed to detect alternative RNA splicing, and the transcribed full-length mRNA gave rise to the 23 kDa protein in transfected cells. Combined mass spectrometry and antibody probing analyses detected peptide information across different regions of gI, suggesting the possibility of a full-length gI but with abnormal migration behavior. In line with this notion, the HA insertion mutagenesis revealed a stable fold in the gI extracellular region aa.38-196 resistant to denaturing conditions, whereas small deletions within this region failed the antibodies to detect the fast, but not the slow-moving species of gI. It is also intriguing that the structure could be perturbed to some extent by a gBsyn mutation, leading to exposure or shielding of the gI epitopes. Thus, the HSV-1 gI apparently adopts a very stable fold in its natural form, rendering it an unusual biophysical property. Our findings provide novel insight into the biological properties of HSV gI and have important implications in understanding the viral spread and pathogenesis. The HSV-1 gI is required for viral cell-to-cell spread within the host, but its behavior during infection has remained poorly defined. Along with the classic 66 kDa product, here we report a previously unrecognized, approximately 23 kDa form of gI. Biochemical and genetics analyses revealed that this molecule represents the full-length form of gI but adopts a stable fold in its extracellular domain that is resistant to denatured conditions, thus contributing to the aberrant migration rate. Our results revealed a novel property of HSV-1 gI and have important implications in understanding viral pathogenesis.
单纯疱疹病毒 1 (HSV-1) 编码的 380 至 393 个氨基酸糖蛋白 I (gI) 是病毒细胞间传播和融合形成的关键介质。在这里，我们报告了 HSV-1 感染细胞中一种以前未被识别的 gI 异常形式。这种分子的产生不依赖于细胞类型和病毒株。它的凝胶迁移大小出人意料地约为 23 kDa，被包装到病毒颗粒中，并可被针对 gI 的 N 和 C 末端的抗体共免疫沉淀。深度测序未能检测到替代 RNA 剪接，并且全长转录 mRNA 在转染细胞中产生 23 kDa 蛋白。质谱分析和抗体探测分析联合检测到 gI 不同区域的肽信息，表明存在全长 gI 的可能性，但迁移行为异常。这一观点与 HA 插入突变体相一致，该突变体揭示了 gI 细胞外区 aa.38-196 稳定的折叠结构，能够抵抗变性条件，而该区域内的小缺失则使抗体无法检测到快速但不移动的 gI 物种。同样有趣的是，gBsyn 突变在某种程度上可以扰乱结构，导致 gI 表位的暴露或屏蔽。因此，HSV-1 gI 显然以其自然形式采用非常稳定的折叠，这是一种不寻常的生物物理特性。我们的发现为 HSV gI 的生物学特性提供了新的见解，并对理解病毒传播和发病机制具有重要意义。HSV-1 gI 是病毒在宿主细胞间传播所必需的，但它在感染过程中的行为仍未得到很好的定义。除了经典的 66 kDa 产物外，我们还报告了一种以前未被识别的、约 23 kDa 的 gI 形式。生化和遗传学分析表明，这种分子代表 gI 的全长形式，但在其细胞外结构域中采用稳定的折叠结构，能够抵抗变性条件，从而导致异常的迁移率。我们的研究结果揭示了 HSV-1 gI 的一个新特性，并对理解病毒发病机制具有重要意义。
