Key Laboratory of Animal Epidemiology of the Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, People's Republic of China.
Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA.
J Virol. 2020 Aug 17;94(17). doi: 10.1128/JVI.00231-20.
The envelope glycoprotein I (gI) of herpes simplex virus 1 (HSV-1) is a critical mediator of virus-induced cell-to-cell spread and cell-cell fusion. Here, we report a previously unrecognized property of this molecule. In transfected cells, the HSV-1 gI was discovered to induce rod-shaped structures that were uniform in width but variable in length. Moreover, the gI within these structures was conformationally different from the typical form of gI, as a previously used monoclonal antibody mAb3104 and a newly made peptide antibody to the gI extracellular domain (ECD) (amino acids [aa] 110 to 202) both failed to stain the long rod-shaped structures, suggesting the formation of a higher-order form. Consistent with this observation, we found that gI could self-interact and that the rod-shaped structures failed to recognize glycoprotein E, the well-known binding partner of gI. Further analyses by deletion mutagenesis and construction of chimeric mutants between gI and gD revealed that the gI ECD is the critical determinant, whereas the transmembrane domain served merely as an anchor. The critical amino acids were subsequently mapped to proline residues 184 and 188 within a conserved PXXXP motif. Reverse genetics analyses showed that the ability to induce a rod-shaped structure was not required for viral replication and spread in cell culture but rather correlated positively with the capability of the virus to induce cell fusion in the UL24syn background. Together, this work discovered a novel feature of HSV-1 gI that may have important implications in understanding gI function in viral spread and pathogenesis. The HSV-1 gI is required for viral cell-to-cell spread within the host, but the molecular mechanisms of how gI exactly works have remained poorly understood. Here, we report a novel property of this molecule, namely, induction of rod-shaped structures, which appeared to represent a higher-order form of gI. We further mapped the critical residues and showed that the ability of gI to induce rod-shaped structures correlated well with the capability of HSV-1 to induce cell fusion in the UL24syn background, suggesting that the two events may have an intrinsic link. Our results shed light on the biological properties of HSV-1 gI and may have important implications in understanding viral pathogenesis.
单纯疱疹病毒 1 (HSV-1) 的包膜糖蛋白 I (gI) 是病毒诱导细胞间传播和细胞融合的关键介质。在这里，我们报告了这个分子的一个以前未被认识到的特性。在转染细胞中，发现 HSV-1 gI 诱导形成了一种均匀宽度但长度可变的杆状结构。此外，这些结构中的 gI 与典型的 gI 构象不同，因为先前使用的单克隆抗体 mAb3104 和新制备的针对 gI 细胞外结构域 (ECD) (氨基酸 [aa] 110 至 202) 的肽抗体都不能染色长杆状结构，表明形成了一种高级形式。与这一观察结果一致，我们发现 gI 可以自我相互作用，而杆状结构不能识别糖蛋白 E，糖蛋白 E 是 gI 的众所周知的结合伴侣。通过缺失突变和 gI 与 gD 之间嵌合突变体的构建进行的进一步分析表明，gI ECD 是关键决定因素，而跨膜结构域仅作为锚。随后将关键氨基酸定位到保守的 PXXXP 基序内的脯氨酸 184 和 188。反向遗传学分析表明，在细胞培养物中诱导杆状结构的能力不是病毒复制和传播所必需的，而是与病毒在 UL24syn 背景下诱导细胞融合的能力呈正相关。总的来说，这项工作发现了 HSV-1 gI 的一个新特征，这可能对理解 gI 在病毒传播和发病机制中的功能具有重要意义。HSV-1 gI 是病毒在宿主细胞间传播所必需的，但 gI 的确切作用的分子机制仍知之甚少。在这里，我们报告了该分子的一个新特性，即诱导形成杆状结构，这似乎代表了 gI 的一种高级形式。我们进一步定位了关键残基，并表明 gI 诱导杆状结构的能力与 HSV-1 在 UL24syn 背景下诱导细胞融合的能力很好地相关，表明这两个事件可能存在内在联系。我们的结果揭示了 HSV-1 gI 的生物学特性，这可能对理解病毒发病机制具有重要意义。
