Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK.
Department of Marine Science and Fisheries, College of Agricultural and Marine Sciences, Sultan Qaboos University, PO Box 34, 123, Al-Khoud, Sultanate of Oman.
Parasit Vectors. 2020 Feb 18;13(1):88. doi: 10.1186/s13071-020-3964-z.
It is hypothesised that being a blood-feeding ectoparasite, Argulus foliaceus (Linnaeus, 1758), uses similar mechanisms for digestion and host immune evasion to those used by other haematophagous ecdysozoa, including caligid copepods (e.g. sea louse). We recently described and characterised glands associated with the feeding appendages of A. foliaceus using histological techniques. The work described in the present study is the first undertaken with the objective of identifying and partially characterising the components secreted from these glands using a proteomic approach.
Argulus foliaceus parasites were sampled from the skin of rainbow trout (Oncorhynchus mykiss), from Loch Fad on the Isle of Bute, Scotland, UK. The proteins from A. foliaceus secretory/excretory products (SEPs) were collected from the supernatant of artificial freshwater conditioned with active adult parasites (n = 5-9 per ml; n = 560 total). Proteins within the SEPs were identified and characterised using LC-ESI-MS/MS analysis. Data are available via ProteomeXchange with identifier PXD016226.
Data mining of a protein database translated from an A. foliaceus dataset using ProteinScape allowed identification of 27 predicted protein sequences from the A. foliaceus SEPs, each protein matching the criteria of 2 peptides with at least 4 contiguous amino acids. Nine proteins had no matching sequence through OmicsBox (Blast2GO) analysis searches suggesting that Argulus spp. may additionally have unique proteins present in their SEPs. SignalP 5.0 software, identified 13 proteins with a signal sequence suggestive of signal peptides and supportive of secreted proteins being identified. Notably, the functional characteristics of identified A. foliaceus proteins/domains have also been described from the salivary glands and saliva of other blood-feeding arthropods such as ticks. Identified proteins included: transporters, peroxidases, metalloproteases, proteases and serine protease inhibitors which are known to play roles in parasite immune evasion/induction (e.g. astacin), immunomodulation (e.g. serpin) and digestion (e.g. trypsin).
To our knowledge, the present study represents the first proteomic analysis undertaken for SEPs from any branchiuran fish louse. Here we reveal possible functional roles of A. foliaceus SEPs in digestion and immunomodulation, with a number of protein families shared with other haematophagous ectoparasites. A number of apparently unique secreted proteins were identified compared to other haematophagous ecdysozoa.
推测以吸血外寄生虫身份存在的鱼怪（Argulus foliaceus）（Linnaeus，1758）在消化和宿主免疫逃避方面使用与其他血食外节肢动物（如桡足类）相似的机制。我们最近使用组织学技术描述和表征了与鱼怪的附肢相关的腺体。本研究的工作是首次使用蛋白质组学方法，旨在鉴定和部分表征从这些腺体分泌的成分。
从苏格兰巴尔特岛洛克法德的虹鳟（Oncorhynchus mykiss）皮肤上采集鱼怪寄生虫。从用活跃成虫寄生虫调节的人工淡水中收集 A. foliaceus 分泌/排泄产物（SEP）的上清液（n=5-9/ml；n=560 个）。使用 LC-ESI-MS/MS 分析鉴定和表征 SEP 中的蛋白质。数据可通过 ProteomeXchange 获得，标识符为 PXD016226。
使用 ProteinScape 从鱼怪数据集翻译的蛋白质数据库的数据挖掘允许从鱼怪 SEP 中鉴定出 27 个预测的蛋白质序列，每个蛋白质都符合具有至少 4 个连续氨基酸的 2 个肽的标准。OmicsBox（Blast2GO）分析搜索没有匹配序列的 9 种蛋白质表明，Argulus spp. 可能还具有其 SEP 中存在的独特蛋白质。SignalP 5.0 软件鉴定出 13 种具有信号序列的蛋白质，暗示存在信号肽，并支持鉴定分泌蛋白。值得注意的是，从其他吸血节肢动物（如蜱）的唾液腺和唾液中也描述了鉴定出的鱼怪蛋白质/结构域的功能特征。鉴定出的蛋白质包括：转运蛋白、过氧化物酶、金属蛋白酶、蛋白酶和丝氨酸蛋白酶抑制剂，它们已知在寄生虫免疫逃避/诱导（如 astacin）、免疫调节（如 serpin）和消化（如 trypsin）中发挥作用。
据我们所知，本研究代表了首次对任何 Branchiuran 鱼虱的 SEP 进行蛋白质组学分析。在这里，我们揭示了 A. foliaceus SEP 在消化和免疫调节中的可能功能作用，其中一些蛋白质家族与其他血食外寄生虫共享。与其他血食外节肢动物相比，鉴定出了一些明显独特的分泌蛋白。
