Caillet-Fauquet P, Perros M, Brandenburger A, Spegelaere P, Rommelaere J
Département de Biologie Moléculaire, Faculté des Sciences, Université Libre de Bruxelles, Belgium.
EMBO J. 1990 Sep;9(9):2989-95. doi: 10.1002/j.1460-2075.1990.tb07491.x.
Although its dependence on the target cell type is well established, the cytopathogenicity of parvoviruses has remained elusive to date as far as its mechanism is concerned. However, indirect evidence suggested that parvoviral non-structural (NS) proteins may be the cytotoxic effectors. In order to test this hypothesis, a molecular clone of parvovirus MVMp was modified, by replacing the P4 promoter of the NS transcription unit by the glucocorticoid-inducible promoter of the mouse mammary tumour virus. Clones of neoplastic human cells that had incorporated this construct and that were induced to produce NS proteins by dexamethasone, showed a cytopathic effect and eventually died. Our data strongly suggest that the intracellular accumulation of parvoviral NS products jeopardizes the survival of the cells, which cannot be detected unless a threshold protein concentration is reached. Interestingly, a cell variant could be isolated which resisted dexamethasone-induced killing, although it was fully inducible for the production of NS proteins. This variant was also unusually resistant to infection with MVMp virions, thus confirming the essential role played by the NS proteins in the parvoviral cytotoxicity and indicating that the cytocidal activity of the parvoviral NS products is modulated by cellular factors that may vary from one cell to another.
尽管细小病毒对靶细胞类型的依赖性已得到充分证实，但就其机制而言，细小病毒的细胞致病性至今仍不清楚。然而，间接证据表明细小病毒的非结构（NS）蛋白可能是细胞毒性效应物。为了验证这一假设，对细小病毒MVMp的分子克隆进行了改造，用小鼠乳腺肿瘤病毒的糖皮质激素诱导型启动子替换了NS转录单元的P4启动子。整合了该构建体并经地塞米松诱导产生NS蛋白的肿瘤人类细胞克隆，表现出细胞病变效应并最终死亡。我们的数据强烈表明，细小病毒NS产物在细胞内的积累危及细胞的存活，除非达到阈值蛋白浓度，否则无法检测到。有趣的是，可以分离出一种细胞变体，它能抵抗地塞米松诱导的杀伤作用，尽管它能完全被诱导产生NS蛋白。这种变体对MVMp病毒粒子的感染也异常耐药，从而证实了NS蛋白在细小病毒细胞毒性中所起的重要作用，并表明细小病毒NS产物的杀细胞活性受到可能因细胞而异的细胞因子的调节。
