Gottlieb T A, Gonzalez A, Rizzolo L, Rindler M J, Adesnik M, Sabatini D D
J Cell Biol. 1986 Apr;102(4):1242-55. doi: 10.1083/jcb.102.4.1242.
Previous studies (Rindler, M. J., I. E., Ivanov, H. Plesken, and D. D. Sabatini, 1985, J. Cell Biol., 100: 136-151; Rindler, M. J., I. E. Ivanov, H. Plesken, E. J. Rodriguez-Boulan, and D. D. Sabatini, 1984, J. Cell Biol., 98: 1304-1319) have demonstrated that in polarized Madin-Darby canine kidney cells infected with vesicular stomatitis virus (VSV) or influenza virus the viral envelope glycoproteins G and HA are segregated to the basolateral and apical plasma membrane domains, respectively, where budding of the corresponding viruses takes place. Furthermore, it has been shown that this segregation of the glycoproteins reflects the polarized delivery of the newly synthesized polypeptides to each surface domain. In transfection experiments using eukaryotic expression plasmids that contain cDNAs encoding the viral glycoproteins, it is now shown that even in the absence of other viral components, both proteins are effectively segregated to the appropriate cell surface domain. In transfected cells, the HA glycoprotein was almost exclusively localized in the apical cell surface, whereas the G protein, although preferentially localized in the basolateral domains, was also present in lower amounts, in the apical surfaces of many cells. Using transfected and infected cells, it was demonstrated that, after reaching the cell surface, the G protein, but not the HA protein, undergoes interiorization by endocytosis. Thus, in the presence of chloroquine, a drug that blocks return of interiorized plasma membrane proteins to the cell surface, the G protein was quantitatively trapped in endosome- or lysosome-like vesicles. The sequestration of G was a rapid process that was completed in many cells by 1-2 h after chloroquine treatment. The fact that in transfected cells the surface content of G protein was not noticeably reduced during a 5-h incubation with cycloheximide, a protein synthesis inhibitor that did not prevent the effect of chloroquine, implies that normally, G protein molecules are not only interiorized but are also recycled to the cell surface.
先前的研究（Rindler, M. J., I. E., Ivanov, H. Plesken, and D. D. Sabatini, 1985, 《细胞生物学杂志》, 100: 136 - 151; Rindler, M. J., I. E. Ivanov, H. Plesken, E. J. Rodriguez - Boulan, and D. D. Sabatini, 1984, 《细胞生物学杂志》, 98: 1304 - 1319）表明，在感染水泡性口炎病毒（VSV）或流感病毒的极化的麦迪逊 - 达比犬肾细胞中，病毒包膜糖蛋白G和HA分别被分隔到基底外侧和顶端质膜结构域，相应病毒在此出芽。此外，已表明糖蛋白的这种分隔反映了新合成的多肽向每个表面结构域的极化运输。在使用含有编码病毒糖蛋白cDNA的真核表达质粒的转染实验中，现已表明，即使在没有其他病毒成分的情况下，这两种蛋白也能有效地分隔到适当的细胞表面结构域。在转染细胞中，HA糖蛋白几乎完全定位于顶端细胞表面，而G蛋白虽然优先定位于基底外侧结构域，但在许多细胞的顶端表面也有少量存在。利用转染和感染的细胞证明，到达细胞表面后，G蛋白而非HA蛋白通过内吞作用发生内化。因此，在存在氯喹（一种阻止内化的质膜蛋白返回细胞表面的药物）的情况下，G蛋白被定量捕获在内体或溶酶体样小泡中。G蛋白的隔离是一个快速过程，在氯喹处理后1 - 2小时，许多细胞中该过程就已完成。在用蛋白质合成抑制剂环己酰亚胺进行5小时孵育期间，转染细胞中G蛋白的表面含量没有明显降低，且环己酰亚胺并不阻止氯喹的作用，这一事实表明，正常情况下，G蛋白分子不仅会内化，还会循环回到细胞表面。
