Dubois M F, Galabru J, Lebon P, Safer B, Hovanessian A G
Institut National de la Santé et de la Recherche Médicale, Hopital St- Vincent de Paul, Paris.
J Biol Chem. 1989 Jul 25;264(21):12165-71.
Previous studies have shown that the antiviral response induced by interferon in murine cells could be degraded after a heat shock. Here we have confirmed that a similar effect occurs also in interferon-treated human HeLa cells subjected to a heat shock. In addition, we have investigated the fate of the interferon-induced, double-stranded RNA-dependent protein kinase in heat-shocked cells. This protein kinase is a Mr 68,000 protein (p68 kinase) which, when autophosphorylated, catalyzes phosphorylation of the protein synthesis eukaryotic initiation factor-2, thus mediating inhibition of protein synthesis. After heat shock of interferon-treated HeLa cells, the double-stranded RNA-dependent autophosphorylation of p68 kinase in cytoplasmic extracts is greatly reduced whereas the phosphorylation of other cellular proteins is not affected. In vivo, autophosphorylation of p68 kinase is also reduced in heat-shocked cells whereas there is no apparent effect on the phosphorylation state of other proteins. In such cells, the interferon-mediated antiviral response becomes modified according to the virus challenge, i.e. these cells remain resistant to vesicular stomatitis virus but become partially sensitive to encephalomyocarditis virus (EMCV) infection. The reduction in the activity of p68 kinase is due to its reduced nonionic detergent solubility occurring during the heat shock period. The resultant reduced detergent extractibility of p68 kinase is dependent on the intensity of the thermal stress. In contrast to the effect after a heat shock, arsenite treatment of interferon-treated HeLa cells induces heat shock proteins, but neither modifies the antiviral response nor affects the extractibility of p68 kinase. These results indicate that the degradation of the anti-EMCV response and reduced p68 kinase activity occur in response to heat treatment independently of the induction of heat shock proteins. The role of p68 kinase in the mechanism of the antiviral response against EMCV and vesicular stomatitis virus is discussed.
先前的研究表明，干扰素在鼠细胞中诱导产生的抗病毒反应在热休克后会被降解。在此我们证实，在经干扰素处理并遭受热休克的人HeLa细胞中也会出现类似的效应。此外，我们研究了热休克细胞中干扰素诱导的双链RNA依赖性蛋白激酶的命运。这种蛋白激酶是一种分子量为68,000的蛋白质（p68激酶），自身磷酸化后，催化蛋白质合成真核起始因子-2的磷酸化，从而介导蛋白质合成的抑制。经干扰素处理的HeLa细胞热休克后，细胞质提取物中p68激酶的双链RNA依赖性自身磷酸化显著降低，而其他细胞蛋白质的磷酸化不受影响。在体内，热休克细胞中p68激酶的自身磷酸化也降低，而对其他蛋白质的磷酸化状态没有明显影响。在这类细胞中，干扰素介导的抗病毒反应会根据病毒攻击而发生改变，即这些细胞对水疱性口炎病毒仍具抗性，但对脑心肌炎病毒（EMCV）感染变得部分敏感。p68激酶活性的降低是由于热休克期间其非离子去污剂溶解度降低所致。由此导致的p68激酶去污剂提取率降低取决于热应激的强度。与热休克后的效应相反，用亚砷酸盐处理经干扰素处理的HeLa细胞会诱导热休克蛋白，但既不改变抗病毒反应，也不影响p68激酶的提取率。这些结果表明，抗EMCV反应的降解和p68激酶活性降低是对热处理的反应，与热休克蛋白的诱导无关。文中讨论了p68激酶在针对EMCV和水疱性口炎病毒的抗病毒反应机制中的作用。
