详细分析沙门氏菌蛋白，检测细菌在躲避免疫监视过程中入侵免疫细胞的机制，为药物、疫苗开发和病情诊断提供候选靶标。
沙门氏杆菌(Salmonella)是引起食物性中毒的最常见的杆菌，全世界每年由其引发的死亡事件成百上千。巨噬细胞是肌体用于追踪、消灭入侵外源微生物的一种免疫细胞，沙门氏杆菌反入侵巨噬细胞并在巨噬细胞内繁殖，这种“诡异”现象的幕后机制一直不为人知。
沙门氏菌是怎样逃避巨噬细胞的免疫监视，并将巨噬细胞作为猎物和其侵略同盟军？为解决这个复杂难题，在与维持细胞生理机能有关的数以千计的蛋白中寻找关键成分无啻于海底捞针。
美国能源部西北太平洋国家实验室PNNL(Pacific Northwest National Laboratory)施良（Liang Shi，音译）率领的研究小组采集感染沙门氏菌不超过24小时的小鼠巨噬细胞，利用蛋白组学的高容量分类筛选（high-volume sorting）和分析能力，对这些巨噬细胞中的沙门氏菌的蛋白进行详细检测，发现幕后黑手——STM3117蛋白。研究详细结果刊登于《The Journal of Biological Chemistry》杂志。
敲除编码STM3117蛋白的基因后，沙门氏菌在巨噬细胞中的繁殖能力丧失。史良及其同事发现STM3117和实验中发现的另外两种相关蛋白，与已知的构成、修饰沙门氏菌细胞壁肽聚糖的蛋白的遗传序列相似。
药物和疫苗开发商可以利用从小鼠巨噬细胞得到的信息，以肽聚糖合成过程或者其它与沙门氏菌在巨噬细胞中繁殖相关的过程为研究对象，寻找分子靶标或者关键免疫应答环节。另外，对这些蛋白进行快速检测，有助于医疗工作者对某种未知微生物的毒力进行评定。
利用傅立叶离子回旋变换质谱(Fourier-Transform Mass Spectrometry，FT-MS)技术，STM3117蛋白从联合技术所检测到的315名嫌疑蛋白中脱颖而出。由论文合作者PNNL研究员D.Smith设计的这组FT-MS设备在对蛋白进行快速分离和鉴定的过程中大显神威，甚至能对刚刚受到沙门氏菌感染的巨噬细胞进行检测。
许多候选蛋白都是管家蛋白（house-keeping proteins），相对于其它蛋白而言在感染过程中数量稳定。另外有39种蛋白的数量在沙门氏菌繁殖过程中明显上升，其中包括STM3117在内的为数不多的蛋白，对发挥抵抗微生物感染作用的巨噬细胞蛋白反应明显。Western blot证实，在感染过程中这几种蛋白含量明显上升.
原始出处:
Shi et al.Proteomic Analysis of Salmonella enterica Serovar Typhimurium Isolated from RAW 264.7 Macrophages: IDENTIFICATION OF A NOVEL PROTEIN THAT CONTRIBUTES TO THE REPLICATION OF SEROVAR TYPHIMURIUM INSIDE MACROPHAGES
J. Biol. Chem., Vol. 281, Issue 39, 29131-29140, September 29, 2006
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英文摘要:
To evade host resistance mechanisms, Salmonella enterica serovar Typhimurium (STM), a facultative intracellular pathogen, must alter its proteome following macrophage infection. To identify new colonization and virulence factors that mediate STM pathogenesis, we have isolated STM cells from RAW 264.7 macrophages at various time points following infection and used a liquid chromatography-mass spectrometry-based proteomic approach to detect the changes in STM protein abundance. Because host resistance to STM infection is strongly modulated by the expression of a functional host-resistant regulator, i.e. natural resistance-associated macrophage protein 1 (Nramp1, also called Slc11a1), we have also examined the effects of Nramp1 activity on the changes of STM protein abundances. A total of 315 STM proteins have been identified from isolated STM cells, which are largely housekeeping proteins whose abundances remain relatively constant during the time course of infection. However, 39 STM proteins are strongly induced after infection, suggesting their involvement in modulating colonization and infection. Of the 39 induced proteins, 6 proteins are specifically modulated by Nramp1 activity, including STM3117, as well as STM3118-3119 whose time-dependent abundance changes were confirmed using Western blot analysis. Deletion of the gene encoding STM3117 resulted in a dramatic reduction in the ability of STM to colonize wild-type RAW 264.7 macrophages, demonstrating a critical involvement of STM3117 in promoting the replication of STM inside macrophages. The predicted function common for STM3117-3119 is biosynthesis and modification of the peptidoglycan layer of the STM cell wall.
