Sichuan University of Science and Engineering, 180 Xueyuan Street, Zigong 643000,China.
Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang University, 14 Shengli Road, Urumqi 830046, China.
Gene. 2019 Mar 30;690:21-29. doi: 10.1016/j.gene.2018.12.036. Epub 2018 Dec 26.
Peptidoglycan recognition proteins (PGRPs) widely distributed in invertebrates and vertebrates are pattern-recognition molecules in innate immunity. In the present study, a novel short PGRP gene, designated as ApPGRP was identified from Anatolica polita. The deduced amino acid sequence of ApPGRP is composed of 196 residues and contains a conserved PGRP domain at the C-terminus. The phylogenetic tree showed that ApPGRP shared high homology of amino acid sequence with TcPGRP2 from Tribolium castaneum. The recombinant protein of ApPGRP exhibited binding activity toward Escherichia coli and DAP-type PGN from E. coli. Quantitative real time PCR (RT-qPCR) analysis indicated that the relative expression level of ApPGRP was up-regulated significantly after E. coli and DAP-type PGN challenge in the fifth instar larvae of A. polita. Moreover, the expressions of three antimicrobial peptides (AMPs) (ApAttacin 1, ApAttacin 2 and ApColeoptericin) were significantly increased after E. coli and DAP-type PGN challenge. RNA interference (RNAi) experiments showed that the expressions of three AMPs in the larvae of A. polita were significantly decreased after injection of ApPGRP dsRNA. Furthermore, the expressions of three AMPs in the larvae injected were still significantly decreased after E. coli challenge compared to the control samples without dsRNA injection. The predicted 3D structure showed that the ApPGRP could form the protein core of five β-sheet and three ɑ-helices, which would be involved in specific PGN recognition. These results suggested that ApPGRP may play an important role in the immune response to E. coli infection and function as a receptor for antimicrobial peptide gene induction in Anatolica polita.
肽聚糖识别蛋白（PGRPs）广泛存在于无脊椎动物和脊椎动物中，是先天免疫中的模式识别分子。本研究从黄粉虫中鉴定出一种新型短肽 PGRP 基因，命名为 ApPGRP。ApPGRP 的推导氨基酸序列由 196 个残基组成，在 C 末端含有一个保守的 PGRP 结构域。系统进化树显示，ApPGRP 与来自赤拟谷盗的 TcPGRP2 具有高度的氨基酸序列同源性。重组 ApPGRP 蛋白对大肠杆菌和大肠杆菌 DAP 型 PGN 具有结合活性。定量实时 PCR（RT-qPCR）分析表明，在黄粉虫五龄幼虫中，ApPGRP 的相对表达水平在大肠杆菌和 DAP 型 PGN 刺激后显著上调。此外，三种抗菌肽（AMPs）（ApAttacin 1、ApAttacin 2 和 ApColeoptericin）的表达在大肠杆菌和 DAP 型 PGN 刺激后显著增加。RNA 干扰（RNAi）实验表明，在黄粉虫幼虫中注射 ApPGRP dsRNA 后，三种 AMPs 的表达显著降低。此外，与未注射 dsRNA 的对照样品相比，注射后三种 AMPs 在幼虫中的表达在大肠杆菌刺激后仍显著降低。预测的 3D 结构表明，ApPGRP 可以形成五个β-折叠和三个α-螺旋的蛋白质核心，这可能参与特定的 PGN 识别。这些结果表明，ApPGRP 可能在大肠杆菌感染的免疫反应中发挥重要作用，并作为抗菌肽基因诱导的受体在黄粉虫中发挥作用。
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