Joe A K, Ferrari G, Jiang H H, Liang X H, Levine B
Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
J Virol. 1996 Nov;70(11):7744-51. doi: 10.1128/JVI.70.11.7744-7751.1996.
Mature neurons are more resistant than dividing cells or differentiating neurons to Sindbis virus-induced apoptotic death. Therefore, we hypothesized that mitogenic signal transduction pathways may influence susceptibility to Sindbis virus-induced apoptosis. Since Ras, a 21-kDa GTP-binding protein, plays an important role in cellular proliferation and neuronal differentiation, we investigated the effect of an inducible dominant inhibitory Ras on Sindbis virus-induced death of a rat pheochromocytoma cell line, PC12 cells. Dexamethasone induction of dominant inhibitory Ras (Ha Ras(Asn17)) expression in transfected PC12 cell lines (MMTV-M17-21 and GSrasDN6 cells) resulted in a marked delay in Sindbis virus-induced apoptosis, compared with infected, uninduced cells. The delay in death after Sindbis virus infection in induced versus uninduced PC12 cells was not associated with differences in viral titers or viral infectivity. No delay in Sindbis virus-induced apoptosis was observed in Ha Ras(Asn17)-transfected PC12 cells if dexamethasone induction was initiated less than 12 h before Sindbis virus infection or in wild-type PC12 cells infected with a chimeric Sindbis virus construct that expresses Ha Ras(Asn17). The delay in Sindbis virus-induced apoptosis in induced Ha Ras(Asn17)-transfected PC12 cells was associated with a decrease in cellular DNA synthesis as measured by 5'-bromo-2'-deoxyuridine incorporation. Thus, in PC12 cells, inducible dominant inhibitory Ras inhibits cellular proliferation and delays Sindbis virus-induced apoptosis. These findings suggest that a Ras-dependent signaling pathway is a determinant of neuronal susceptibility to Sindbis virus-induced apoptosis.
成熟神经元比分裂细胞或分化中的神经元对辛德毕斯病毒诱导的凋亡性死亡更具抵抗力。因此，我们推测有丝分裂原信号转导途径可能影响对辛德毕斯病毒诱导凋亡的易感性。由于Ras，一种21 kDa的GTP结合蛋白，在细胞增殖和神经元分化中起重要作用，我们研究了诱导型显性抑制性Ras对大鼠嗜铬细胞瘤细胞系PC12细胞中辛德毕斯病毒诱导死亡的影响。与未诱导的感染细胞相比，在转染的PC12细胞系（MMTV-M17-21和GSrasDN6细胞）中地塞米松诱导显性抑制性Ras（Ha Ras(Asn17)）表达导致辛德毕斯病毒诱导的凋亡明显延迟。诱导型与未诱导型PC12细胞在辛德毕斯病毒感染后死亡延迟与病毒滴度或病毒感染性的差异无关。如果在地塞米松诱导开始于辛德毕斯病毒感染前不到12小时的情况下，在Ha Ras(Asn17)转染的PC12细胞中未观察到辛德毕斯病毒诱导的凋亡延迟，或者在感染表达Ha Ras(Asn17)的嵌合辛德毕斯病毒构建体的野生型PC12细胞中也未观察到。通过5'-溴-2'-脱氧尿苷掺入法测量，诱导型Ha Ras(Asn17)转染的PC12细胞中辛德毕斯病毒诱导凋亡的延迟与细胞DNA合成减少有关。因此，在PC12细胞中，诱导型显性抑制性Ras抑制细胞增殖并延迟辛德毕斯病毒诱导的凋亡。这些发现表明，Ras依赖性信号通路是神经元对辛德毕斯病毒诱导凋亡易感性的决定因素。
