Kaplan A H, Swanstrom R
Department of Medicine, University of North Carolina, Chapel Hill 27599-7295.
Proc Natl Acad Sci U S A. 1991 May 15;88(10):4528-32. doi: 10.1073/pnas.88.10.4528.
The structural proteins of the retroviral capsid are translated as a polyprotein (the Gag precursor) that is cleaved by a virally encoded protease. Processing of the human immunodeficiency virus type 1 Gag precursor Pr55 was analyzed through a combination of pulse-chase labeling, cell fractionation, and immunoprecipitation. We observed a membrane-associated processing pathway for the Gag precursor that gives rise to virions. In addition, we found that a significant amount of processing occurs in the cytoplasm of infected cells resulting in the intracellular accumulation of appropriately processed viral proteins. This observation suggests the viral protease is active in the cytoplasmic compartment of the cell. Processing of the Gag protein was blocked in both compartments by the addition of a viral protease inhibitor. A comparison of the amount of cytoplasmic processing seen in lytically infected cells with that seen in chronically infected cells showed that cytoplasmic processing was associated with the lytic infection. These observations raise the possibility that activation of the human immunodeficiency virus type 1 protease in the cytoplasm of lytically infected cells might result in the cleavage of cellular proteins and thus contribute to cytotoxicity.
逆转录病毒衣壳的结构蛋白作为一种多聚蛋白（Gag前体）进行翻译，该多聚蛋白由病毒编码的蛋白酶切割。通过脉冲追踪标记、细胞分级分离和免疫沉淀相结合的方法，对1型人类免疫缺陷病毒Gag前体Pr55的加工过程进行了分析。我们观察到了一条与膜相关的Gag前体加工途径，该途径产生病毒粒子。此外，我们发现大量的加工过程发生在受感染细胞的细胞质中，导致经过适当加工的病毒蛋白在细胞内积累。这一观察结果表明病毒蛋白酶在细胞的细胞质区室中具有活性。通过添加病毒蛋白酶抑制剂，Gag蛋白在两个区室中的加工均被阻断。对裂解感染细胞与慢性感染细胞中细胞质加工量的比较表明，细胞质加工与裂解感染有关。这些观察结果增加了一种可能性，即1型人类免疫缺陷病毒蛋白酶在裂解感染细胞的细胞质中被激活，可能导致细胞蛋白的切割，从而导致细胞毒性。
