Wang H, Paul R, Burgeson R E, Keene D R, Kabat D
Department of Biochemistry and Molecular Biology, School of Medicine, Oregon Health Sciences University, Portland 97201-3098.
J Virol. 1991 Dec;65(12):6468-77. doi: 10.1128/JVI.65.12.6468-6477.1991.
A retroviral vector was used to express various amounts of the receptor (ecoR) for ecotropic host range murine retroviruses on naturally barren hamster, mink, and human cells. These cells and murine cells were then incubated for 2 h with dilutions of a helper-free ecotropic retrovirus that encodes human growth hormone, and the number of infected cells was later determined by growth hormone-specific immunofluorescence. For all cells under the conditions of these studies, virus adsorption was the limiting step of infection and the cellular capacities for infection were unsaturated either at cell surfaces or at intracellular sites. Thus, infections occurred at low multiplicities of infection per cell and were directly proportional to virus and cell concentrations, and only a small percentage (ca. 5%) of the infectious virions became adsorbed from the medium during the 2-h incubations. Although increasing the adsorption by raising virus or cell concentrations results in more infections in the cultures, increasing adsorption by raising the number of ecoR above a low threshold had no effect on infections. Thus, cells with a low number of ecoR were infected as efficiently as highly adsorbing cells that contained many times more ecoR. To reconcile these results, we conclude that only a small, set number of cell surface ecoR can be functional for infection and that all excess ecoR can only bind virus into an unsalvageable pool. Therefore, retroviral receptors on single cells are functionally diverse. Our results suggest that activity of ecoR in infection requires a limiting second cellular component.
使用逆转录病毒载体在天然无病毒的仓鼠、水貂和人类细胞上表达不同数量的嗜亲性宿主范围小鼠逆转录病毒的受体（ecoR）。然后将这些细胞和小鼠细胞与编码人生长激素的无辅助嗜亲性逆转录病毒的稀释液孵育2小时，随后通过生长激素特异性免疫荧光确定感染细胞的数量。在这些研究条件下，对于所有细胞而言，病毒吸附是感染的限制步骤，并且在细胞表面或细胞内位点，细胞的感染能力均未饱和。因此，感染以每个细胞低感染复数发生，并且与病毒和细胞浓度成正比，在2小时的孵育过程中，只有一小部分（约5%）的感染性病毒粒子从培养基中吸附。虽然通过提高病毒或细胞浓度来增加吸附会导致培养物中更多的感染，但将ecoR数量提高到低阈值以上来增加吸附对感染没有影响。因此，ecoR数量少的细胞与含有多倍于其数量的高吸附性细胞一样有效地被感染。为了协调这些结果，我们得出结论，只有一小部分固定数量的细胞表面ecoR可用于感染，所有多余的ecoR只能将病毒结合到一个无法挽救的池中。因此，单细胞上的逆转录病毒受体在功能上是多样的。我们的结果表明，ecoR在感染中的活性需要一种有限的第二细胞成分。
