PROTEOLYTIC CLEAVAGE OF BOVINE HERPESVIRUS-1 (BHV-1) GLYCOPROTEIN GB IS NOT NECESSARY FOR ITS FUNCTION IN BHV-1 OR PSEUDORABIES VIRUS
PROTEOLYTIC CLEAVAGE OF BOVINE HERPESVIRUS-1 (BHV-1) GLYCOPROTEIN GB IS NOT NECESSARY FOR ITS FUNCTION IN BHV-1 OR PSEUDORABIES VIRUS
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DOI：
10.1128/jvi.68.3.1667-1674.1994
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发表时间：
1994-03-01
影响因子：
5.4
通讯作者：
METTENLEITER, TC
中科院分区：
文献类型：
--
作者：
KOPP, A;BLEWETT, E;METTENLEITER, TC
糖蛋白B同源物代表疱疹病毒糖蛋白中最高度保守的一组。它们以基于二聚体结构的低聚物形式存在。尽管高度的序列和结构保守性，翻译后加工的差异被观察到。而单纯疱疹病毒的gB在寡聚化后不被蛋白水解加工，大多数其他gB同系物被细胞蛋白酶切割成通过二硫键保持连接的亚基。蛋白水解切割对于病毒融合蛋白的活化是常见的，并且已经显示疱疹病毒gB同源物对于感染期间的膜融合事件是必需的，例如，病毒穿透和直接的病毒细胞间传播。为了分析蛋白水解切割对gB同源物功能的重要性，我们分离了一种突变型牛疱疹病毒1型（BHV-1），其表达的BHV-1 gB由于蛋白水解切割位点的缺失而不再被蛋白水解处理，并分析了其在细胞培养中的表型。我们先前基于表达BHV-1 gB的PrV gB阴性PrV重组体的分离，表明BHV-1 gB可以在功能上替代伪狂犬病病毒（PrV）中的同源糖蛋白（A.科普和TC Mettenleiter，J. Virol. 66：2754 - 2762，1992）。因此，我们还分离出一种缺失PrV gB但表达不可裂解的BHV-1 gB的突变型PrV。我们的研究结果表明，裂解的BHV-1 gB是不是必不可少的，它的功能，无论是在BHV-1或PrV背景。与表达可切割BHV-1 gB的PrV重组体相比，重组PrV中切割位点的缺失未显著改变病毒表型，如空斑试验、一步生长动力学和穿透动力学所分析。在BHV-1突变体中，未裂解的BHV-1 gB在穿透方面与野生型蛋白功能相当，与亲本野生型BHV-1相比，仅显示出略微延迟的一步生长动力学。然而，产生的空斑明显较小，表明BHV-1 gB的蛋白水解裂解在BHV-1的细胞间传播中的作用。
Glycoprotein B homologs represent the most highly conserved group of herpesvirus glycoproteins. They exist in oligomeric forms based on a dimeric structure. Despite the high degree of sequence and structural conservation, differences in posttranslational processing are observed. Whereas gB of herpes simplex virus is not proteolytically processed after oligomerization, most other gB homologs are cleaved by a cellular protease into subunits that remain linked via disulfide bonds. Proteolytic cleavage is common for activation of viral fusion proteins, and it has been shown that herpesvirus gB homologs are essential for membrane fusion events during infection, e.g., virus penetration and direct viral cell-to-cell spread. To analyze the importance of proteolytic cleavage for the function of gB homologs, we isolated a mutant bovine herpesvirus 1 (BHV-1) expressing a BHV-1 gB that is no longer proteolytically processed because of a deletion of the proteolytic cleavage site and analyzed its phenotype in cell culture. We showed previously that BHV-1 gB can functionally substitute for the homologous glycoprotein in pseudorabies virus (PrV), based on the isolation of a PrV gB-negative PrV recombinant that expresses BHV-1 gB (A. Kopp and T.C. Mettenleiter, J. Virol. 66:2754-2762, 1992). Therefore, we also isolated a mutant PrV lacking PrV gB but expressing a noncleavable BHV-1 gB. Our results show that cleavage of BHV-1 gB is not essential for its function in either a BHV-1 or a PrV background. Compared with the PrV recombinant expressing cleavable BHV-1 gB, deletion of the cleavage site in the recombinant PrV did not detectably alter the viral phenotype, as analyzed by plaque assays, one-step growth kinetics, and penetration kinetics. In the BHV-1 mutant, the uncleaved BHV-1 gB was functionally equivalent to the wild-type protein with regard to penetration and showed only slightly delayed one-step growth kinetics compared with parental wild-type BHV-1. However, the resulting plaques were significantly smaller, indicating a role for proteolytic cleavage of BHV-1 gB in cell-to-cell spread of BHV-1.