Garner Joseph N, Joshi Bhavesh, Jagus Rosemary
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, MD 21202, USA.
Dev Comp Immunol. 2003 Mar;27(3):217-31. doi: 10.1016/s0145-305x(02)00096-4.
The cDNAs of rainbow trout and zebrafish eIF2alpha have been isolated and found to encode proteins of similar molecular weight and isoelectric point to the alpha-subunit of the human translational initiation factor, eIF2. The rainbow trout (36.0kDa) and zebrafish (36.2kDa) eIF2alphas share 93 and 91% identity to the human protein, respectively, and are recognized by antibodies raised to the human form. In mammals, the phosphorylation of the alpha-subunit of eIF2 plays a key role in the regulation of protein synthesis in response to a range of cellular stresses. Regions corresponding to the human phosphorylation and kinase-docking sites are identical in the proteins of both fish species, as are residues that interact with the eIF2 recycling factor, eIF2B. Moreover, both recombinant rainbow trout and zebrafish eIF2alphas can be phosphorylated in vitro by the mammalian heme-sensitive eIF2alpha-kinase, HRI/HCR, as well as the interferon-inducible, dsRNA sensitive kinase, PKR. Phosphorylation of rainbow trout and zebrafish eIF2alpha can also occur in vivo. RTG-2 and ZFL cells subjected to endoplasmic reticulum (ER) stress by treatment with the Ca(2+)-ionophore A23187 showed increased levels of eIF2alpha phosphorylation, suggesting similarity between the ER stress response in fish and other higher eukaryotes. Furthermore, RTG-2 cells responded to treatment with poly(I).poly(C) or to infection by infectious pancreatic necrosis virus, IPNV, by increasing eIF2alpha phosphorylation. These data imply that RTG-2 cells express the interferon-induced eIF2alpha-kinase, PKR and suggests that the interferon/eIF2alpha/PKR response to virus infection may be a conserved vertebrate characteristic. Overall these data are consistent with the premise that fish are able to regulate protein synthesis in response to cellular stresses through phosphorylation of eIF2alpha.
虹鳟鱼和斑马鱼eIF2α的cDNA已被分离出来，发现它们编码的蛋白质分子量和等电点与人类翻译起始因子eIF2的α亚基相似。虹鳟鱼（36.0 kDa）和斑马鱼（36.2 kDa）的eIF2α与人类蛋白质分别具有93%和91%的同一性，并且能被针对人类形式产生的抗体识别。在哺乳动物中，eIF2的α亚基磷酸化在响应一系列细胞应激时对蛋白质合成的调节中起关键作用。两种鱼类蛋白质中与人类磷酸化和激酶对接位点相对应的区域是相同的，与eIF2循环因子eIF2B相互作用的残基也是相同的。此外，重组虹鳟鱼和斑马鱼的eIF2α在体外都能被哺乳动物血红素敏感的eIF2α激酶HRI/HCR以及干扰素诱导的双链RNA敏感激酶PKR磷酸化。虹鳟鱼和斑马鱼eIF2α的磷酸化在体内也会发生。用钙离子载体A23187处理使RTG - 2和ZFL细胞遭受内质网（ER）应激，结果显示eIF2α磷酸化水平升高，这表明鱼类和其他高等真核生物在内质网应激反应方面具有相似性。此外，RTG - 2细胞对聚（I）·聚（C）处理或感染传染性胰腺坏死病毒（IPNV）的反应是eIF2α磷酸化增加。这些数据表明RTG - 2细胞表达干扰素诱导的eIF2α激酶PKR，并提示干扰素/eIF2α/PKR对病毒感染的反应可能是脊椎动物的一个保守特征。总体而言，这些数据与鱼类能够通过eIF2α磷酸化来响应细胞应激从而调节蛋白质合成这一前提一致。
