Schreurs C, Mettenleiter T C, Zuckermann F, Sugg N, Ben-Porat T
Department of Microbiology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
J Virol. 1988 Jul;62(7):2251-7. doi: 10.1128/JVI.62.7.2251-2257.1988.
One of the major glycoproteins of pseudorabies virus, gIII, is nonessential for growth in cell culture. Mutants defective in gIII, however, consistently yield lower titers of infectious virus (3- to 20-fold) than does wild-type virus. The interactions of gIII- mutants with their host cells were compared with those of wild-type virus in an attempt to uncover the functions of gIII. We show that gIII plays a major role in the stable adsorption of the virus to its host cell; in the absence of gIII, the rate of adsorption is reduced and adsorption is easily reversed by washing. Thus, adsorption of pseudorabies virus can be said to occur in at least the following two ways: (i) a gIII-mediated rapid adsorption or (ii) a slower and more labile adsorption that is independent of gIII. After virions have been complexed with monoclonal antibodies against gIII (but not some monoclonal antibodies against other glycoproteins), both modes of adsorption were inhibited. Glycoprotein gIII affects virus stability and virus release, as well as adsorption. The effect on virus release is marked when the virus is defective in additional functions. Thus, although we found no obvious difference in the release of virus from gIII- or wild-type virus-infected rabbit kidney cells, release of a gIII-/gI- double mutant from the cells occurred less readily than did release of a gI- mutant. The gIII-/gI- and gIII- mutants, however, adsorbed to cells at a similar rate, indicating that the effects of gIII on adsorption and virus release constitute separate functions. The Bartha vaccine strain of pseudorabies virus has a defective gIII gene and is released poorly from rabbit kidney cells. After the resident Bartha gIII gene was replaced by the gIII gene of wild-type virus, virus release was enhanced considerably. Since inactivation of gIII in wild-type pseudorabies virus did not significantly affect virus release, the Bartha strain must be defective in another function which, in conjunction with gIII, significantly affects virus release. These results indicate again that gIII affects virus release in conjunction with other functions. Also, although the Bartha strain was functionally defective in virus release, it adsorbed to cells as well as wild-type virus did, showing that the effects of gIII on virus adsorption and release constitute separate functions. We conclude that gIII is a multifunctional glycoprotein.
伪狂犬病病毒的主要糖蛋白之一gIII，对于在细胞培养中的生长并非必需。然而，gIII缺陷型突变体产生的感染性病毒滴度始终低于野生型病毒（3至20倍）。为了揭示gIII的功能，我们将gIII突变体与其宿主细胞的相互作用与野生型病毒进行了比较。我们发现gIII在病毒与其宿主细胞的稳定吸附中起主要作用；在没有gIII的情况下，吸附速率降低，并且通过洗涤很容易逆转吸附。因此，可以说伪狂犬病病毒的吸附至少以以下两种方式发生：（i）gIII介导的快速吸附或（ii）与gIII无关的较慢且更不稳定的吸附。在病毒粒子与抗gIII单克隆抗体（但不是一些抗其他糖蛋白的单克隆抗体）复合后，两种吸附模式均受到抑制。糖蛋白gIII影响病毒稳定性、病毒释放以及吸附。当病毒在其他功能上存在缺陷时，对病毒释放的影响尤为明显。因此，尽管我们发现从感染gIII或野生型病毒的兔肾细胞中释放病毒没有明显差异，但gIII-/gI-双突变体从细胞中的释放比gI-突变体更不容易。然而，gIII-/gI-和gIII-突变体以相似的速率吸附到细胞上，表明gIII对吸附和病毒释放的影响构成独立的功能。伪狂犬病病毒的Bartha疫苗株具有缺陷的gIII基因，并且从兔肾细胞中的释放较差。在用野生型病毒的gIII基因替换驻留的Bartha gIII基因后，病毒释放显著增强。由于野生型伪狂犬病病毒中gIII的失活并未显著影响病毒释放，因此Bartha株必定在另一种功能上存在缺陷，该功能与gIII共同作用，显著影响病毒释放。这些结果再次表明gIII与其他功能共同影响病毒释放。此外，尽管Bartha株在病毒释放功能上存在缺陷，但它与野生型病毒一样能吸附到细胞上，表明gIII对病毒吸附和释放的影响构成独立的功能。我们得出结论，gIII是一种多功能糖蛋白。
