College of Animal Science and Technology, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China.
College of Animal Science and Technology, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China.
Fish Shellfish Immunol. 2018 Jul;78:299-309. doi: 10.1016/j.fsi.2018.04.059. Epub 2018 Apr 27.
Glutaminyl-peptide cyclotransferase (QPCT) catalyzes the posttranslational modification of an N-terminal glutamate of proteins to pyroglutamate. This renders the protein more resistant to protease degradation, more susceptible to hydrophobic interactions, aggregation, and neurotoxic. In this study, we evaluated the influence of QPCT in the crab Scylla paramamosain infected with white spot syndrome virus (WSSV) or with Vibrio alginolyticus. A cDNA clone, encompassing the entire 2445 bp of the S. paramamosain QPCT gene, containing a 1113 bp open reading frame (ORF) encoding a 370 amino acid protein was cloned from S. paramamosain. Real-time PCR indicated that QPCT was primarily expressed in the digestive tract of S. paramamosain, was up-regulated in hemocytes after infection with V. alginolyticus, and down-regulated in hemocytes after infection with WSSV. Knockdown of QPCT expression by double-stranded RNA (QPCT-dsRNA) resulted in down-regulation of prophenoloxidase (proPO) and crustin antimicrobial peptide, whereas myosin-II-essential-light-chain-like-protein was significantly up-regulated in hemocytes at 24 h post QPCT-dsRNA treatment. WSSV challenge in crabs treated with QPCT-dsRNA resulted in a reduction in viral burden and in the apoptotic rate of crab hemocytes, while the phagocytic activity of crab hemocytes and overall mortality rate were increased. This suggests that WSSV might take advantage of QPCT to benefit its replication. In contrast, V. alginolyticus infection in crabs treated with QPCT-dsRNA indicated that the apoptotic rate and phagocytic activity of hemocytes, and overall incidence of mortality, were increased compared to mock-treated animals, indicating that QPCT might be a resistance factor in bacterial infection. These results increase our understanding of the function of QPCT and its role in the innate immunity of S. paramamosain.
谷氨酰胺肽环转移酶（QPCT）催化蛋白质 N 端谷氨酸的翻译后修饰为焦谷氨酸。这使得蛋白质更能抵抗蛋白酶降解，更容易发生疏水相互作用、聚集和神经毒性。在这项研究中，我们评估了 QPCT 在感染白斑综合征病毒（WSSV）或溶藻弧菌的锯缘青蟹中的影响。从锯缘青蟹中克隆了一个 cDNA 克隆，包含 S. paramamosain QPCT 基因的全长 2445 bp，包含一个编码 370 个氨基酸蛋白质的 1113 bp 开放阅读框（ORF）。实时 PCR 表明，QPCT 主要在锯缘青蟹的消化道中表达，在感染溶藻弧菌后在血细胞中上调，在感染 WSSV 后下调。双链 RNA（QPCT-dsRNA）敲低 QPCT 表达导致酚氧化酶原（proPO）和甲壳质抗菌肽下调，而肌球蛋白-II-必需轻链样蛋白在 QPCT-dsRNA 处理后 24 小时血细胞中显著上调。用 QPCT-dsRNA 处理的螃蟹受到 WSSV 攻击后，病毒载量和螃蟹血细胞的凋亡率降低，而螃蟹血细胞的吞噬活性和总体死亡率增加。这表明 WSSV 可能利用 QPCT 来促进其复制。相比之下，用 QPCT-dsRNA 处理的螃蟹感染溶藻弧菌表明，与 mock 处理的动物相比，血细胞的凋亡率和吞噬活性以及总体死亡率增加，表明 QPCT 可能是细菌感染的抗性因素。这些结果增加了我们对 QPCT 功能及其在锯缘青蟹先天免疫中的作用的理解。
