Whitt M A, Buonocore L, Prehaud C, Rose J K
Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510.
Virology. 1991 Dec;185(2):681-8. doi: 10.1016/0042-6822(91)90539-n.
The spike glycoprotein (G protein) of rabies virus (CVS strain) expressed in HeLa cells from cloned cDNA mediated membrane fusion after exposure to pHs of 6.1 or below. Chemical crosslinking showed that the rabies G protein, like the vesicular stomatitis virus (VSV) G protein, could be crosslinked to dimers and trimers, indicating that rabies G protein is a trimer. However, unlike the VSV G protein, rabies G protein trimers were not stable to sedimentation in sucrose gradients, even at a mildly acidic pH which stabilizes the VSV G protein trimers. In addition, we report that the expressed rabies virus G protein was functional because it could assemble into VSV particles (tsO45) lacking VSV G protein and rescue infectivity. These VSV (rabies) pseudotypes were neutralized only by an antibody to the rabies G protein. We also examined the properties of a hybrid protein containing the extracellular domain of the rabies virus glycoprotein and the transmembrane and cytoplasmic domains of the VSV G protein. This protein was transported to the cell surface and could be crosslinked to form dimers and trimers, but had little or no detectable membrane fusion activity. The lack of fusion activity was paradoxical because the hybrid protein could rescue VSV infectivity, although the titers were lower than those obtained with the wild-type rabies G protein.
在HeLa细胞中由克隆cDNA表达的狂犬病病毒（CVS毒株）的刺突糖蛋白（G蛋白）在暴露于pH 6.1或更低的pH值后介导膜融合。化学交联显示，狂犬病G蛋白与水泡性口炎病毒（VSV）G蛋白一样，可以交联形成二聚体和三聚体，表明狂犬病G蛋白是三聚体。然而，与VSV G蛋白不同，即使在能稳定VSV G蛋白三聚体的轻度酸性pH条件下，狂犬病G蛋白三聚体在蔗糖梯度中沉降时也不稳定。此外，我们报道所表达的狂犬病病毒G蛋白具有功能，因为它可以组装到缺乏VSV G蛋白的VSV颗粒（tsO45）中并拯救感染性。这些VSV（狂犬病）假型仅被抗狂犬病G蛋白的抗体中和。我们还研究了一种杂合蛋白的特性，该杂合蛋白包含狂犬病病毒糖蛋白的胞外结构域以及VSV G蛋白的跨膜和胞质结构域。这种蛋白被转运到细胞表面并且可以交联形成二聚体和三聚体，但几乎没有或没有可检测到的膜融合活性。融合活性的缺乏是自相矛盾的，因为尽管滴度低于野生型狂犬病G蛋白所获得的滴度，但该杂合蛋白可以拯救VSV感染性。
