DataSheet_1_Proteome analysis of Ehrlichia chaffeensis containing phagosome membranes revealed the presence of numerous bacterial and host proteins.pdf

Tick-transmitted Ehrlichia chaffeensis, the causative agent for human monocytic ehrlichiosis, resides and multiplies within a host cell phagosome. Infection progression of E. chaffeensis includes internalization into a host cell by host cell membrane fusion events following engulfment leading to the formation of E. chaffeensis containing vacuole (ECV). Revealing the molecular composition of ECV is important in understanding the host cellular processes, evasion of host defense pathways and in defining host-pathogen interactions. ECVs purified from infected host cells were analyzed to define both host and bacterial proteomes associated with the phagosome membranes. About 160 bacterial proteins and 2,683 host proteins were identified in the ECV membranes. The host proteins included predominantly known phagosome proteins involved in phagocytic trafficking, fusion of vesicles, protein transport, Ras signaling pathway and pathogenic infection. Many highly expressed proteins were similar to the previously documented proteins of phagosome vacuole membranes containing other obligate pathogenic bacteria. The finding of many bacterial membrane proteins is novel; they included multiple outer membrane proteins, such as the p28-Omps, the 120 kDa protein, preprotein translocases, lipoproteins, metal binding proteins, and chaperonins, although the presence of ankyrin repeat proteins, several Type I and IV secretion system proteins is anticipated. This study demonstrates that ECV membrane is extensively modified by the pathogen. This study represents the first and the most comprehensive description of ECV membrane proteome. The identity of many host and Ehrlichia proteins in the ECV membrane will be a valuable to define pathogenic mechanisms critical for the replication of the pathogen within macrophages.

蜱传查菲埃立克体（Tick-transmitted Ehrlichia chaffeensis）是人类单核细胞埃立克体病（human monocytic ehrlichiosis）的致病菌，可在宿主细胞吞噬体（host cell phagosome）内定植并增殖。查菲埃立克体的感染进程包括：宿主细胞通过吞噬后的细胞膜融合事件将其内化，进而形成查菲埃立克体包含液泡（E. chaffeensis containing vacuole, ECV）。解析ECV的分子组成，对于理解宿主细胞过程、病原体逃逸宿主防御通路以及明确宿主-病原体互作机制均具有重要意义。
本研究对从感染宿主细胞中纯化得到的ECV进行分析，以鉴定与吞噬体膜相关的宿主及细菌蛋白质组（proteome）。在ECV膜中共鉴定到约160种细菌蛋白质与2683种宿主蛋白质。宿主蛋白质主要包含已知的参与吞噬运输、囊泡融合、蛋白质转运、Ras信号通路（Ras signaling pathway）以及病原体感染过程的吞噬体相关蛋白。
大量高表达蛋白与此前报道的其他专性致病细菌所包含的吞噬体液泡膜蛋白高度相似。本研究发现了多种新型细菌膜蛋白，包括多种外膜蛋白（outer membrane protein），如p28外膜蛋白（p28-Omps）、120 kDa蛋白、前蛋白转运体、脂蛋白、金属结合蛋白以及分子伴侣蛋白；同时也检测到预期存在的锚蛋白重复蛋白（ankyrin repeat protein）、多种I型和IV型分泌系统（Type I and IV secretion system）蛋白。
本研究证实ECV膜被病原体广泛修饰，是目前首个且最全面的ECV膜蛋白质组解析研究。ECV膜中鉴定到的多种宿主及埃立克体蛋白质，将为阐明该病原体在巨噬细胞（macrophages）内复制的关键致病机制提供重要参考价值。