RAX, the PKR activator, sensitizes cells to inflammatory cytokines, serum withdrawal, chemotherapy, and viral infection
RAX, the PKR activator, sensitizes cells to inflammatory cytokines, serum withdrawal, chemotherapy, and viral infection
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DOI：
10.1182/blood-2005-11-006817
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发表时间：
2006-08-01
期刊：
影响因子：
20.3
通讯作者：
May, W. Stratford
中科院分区：
文献类型：
--
作者：
Bennett, Richard L.;Blalock, William L.;May, W. Stratford
虽然干扰素（IFN）诱导的双链RNA（dsRNA）依赖性蛋白激酶PKR的报道，在某些情况下启动细胞凋亡，不同的应激刺激激活PKIR的机制仍然未知。现在我们报道RAX，唯一已知的PKR的细胞激活剂，启动PKR激活响应于广泛的应激，包括血清剥夺，细胞因子，Ic细胞因子或化疗治疗，或病毒感染。因此，使用小干扰RNA（siRNA）将RAX表达敲低80%防止IFN-γ肿瘤坏死因子α（TNF α）诱导的PKR活化和eIF 2 α磷酸化、I κ B降解、IRF-1表达和STAT 1磷酸化，从而导致小鼠胚胎成纤维细胞（MEF）存活增强。相反，外源RAX的表达，而不是非磷酸化的显性负性RAX（S18 A）突变体的表达，使细胞对IFN γ/TNF α，丝裂霉素C（MMC），或血清剥夺与增加PKR活性和凋亡相关。此外，RAX（S18 A）在Fanconi贫血互补组C-无效MEF细胞中的表达不仅阻止PKR活化，而且阻断对IFN-γ/TNF α或丝裂霉素C的超敏反应，从而导致增强的凋亡。此外，降低的RAX表达促进水泡性口炎病毒（VSV）的生产性病毒感染，并促进MEF细胞的贴壁依赖性集落生长。总的来说，这些数据表明，RAX可能作为一个负调节生长所需的激活PKR在响应范围广泛的凋亡诱导的压力。
While the interferon (IFN)-inducible double-stranded RNA (dsRNA)-dependent protein kinase PKR is reported to initiate apoptosis in some instances, the mechanism by which diverse stress stimuli activate PKIR remains unknown. Now we report that RAX, the only known cellular activator for PKR, initiates PKR activation in response to a broad range of stresses including serum deprivation, cytoto),Ic cytokine or chemotherapy treatment, or viral infection. Thus, knockdown of RAX expression by 80% using small interfering RNA (siRNA) prevents IFN-gamma tumor necrosis factor alpha (TNF alpha)- induced PKR activation and eIF2 alpha phosphorylation, I kappa B degradation, IRF-1 expression, and STAT1 phosphorylation, resulting in enhanced murine embryonic fibroblast (MEF) cell survival. In contrast, expression of exogenous RAX, but not of the nonphosphorylatable, dominant-negative RAX(S18A) mutant, sensitizes cells to IFN gamma/TNF alpha, mitomycin C (MMC), or serum deprivation in association with increased PKR activity and apoptosis. Furthermore, RAX(S18A) expression in Fanconi anemia complementation group C-null MEF cells not only prevents PKR activation but also blocks hypersensitivity to IFN-gamma/TNF alpha or mitomycin C that results in enhanced apoptosis. In addition, reduced RAX expression facilitates productive viral infection with vesicular stomatitis virus (VSV) and promotes anchorage-i ndepen dent colony growth of MEF cells. Collectively, these data indicate that RAX may function as a negative regulator of growth that is required to activate PKR in response to a broad range of apoptosis-inducing stress.