Analysis of pmpD Expression and PmpD Post-Translational Processing during the Life Cycle of Chlamydia trachomatis Serovars A, D, and L2
Analysis of pmpD Expression and PmpD Post-Translational Processing during the Life Cycle of Chlamydia trachomatis Serovars A, D, and L2
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DOI：
10.1371/journal.pone.0005191
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发表时间：
2009-04-15
期刊：
影响因子：
3.7
通讯作者：
Lampe, Mary F.
中科院分区：
文献类型：
--
作者：
Kiselev, Andrey O.;Skinner, Megan C.;Lampe, Mary F.
背景：衣原体中的多态膜蛋白D(PmpD)在结构上与其他细菌中描述的自身转运蛋白相似，可能参与了对衣原体的细胞和体液保护性免疫。到目前为止，PmpD的翻译后加工机制及其蛋白产物在衣原体感染发病机制中的作用还不是很清楚。方法/主要研究结果：我们研究了沙眼衣原体A、D和L2三个血清型生命周期中pmpD基因蛋白产物的表达和翻译后加工。这三个血清型中的每一个都针对不同的人体器官和组织，并编码不同的pmpD基因核苷酸序列。我们的实时定量逆转录聚合酶链式反应结果表明，pmpD基因在感染后12-24小时上调，与衣原体血清型无关。这种上调与衣原体网状小体(Rb)的指数生长和复制时期相吻合，表明PmpD在衣原体A、D和L2血清型中的功能可能相似。通过质谱分析，我们鉴定了沙眼衣原体L2亚型PmpD翻译后加工的蛋白质产物，并提出了PmpD加工的双途径模型，一个切割位点位于乘客区和自身转运体结构域之间，另一个位于乘客区的中间。值得注意的是，当衣原体感染的培养细胞受到低温(28摄氏度)时，PmpD翻译后加工和分泌在导致的持续感染中被发现是不受抑制的。此外，衣原体感染细胞的共聚焦显微镜证实了我们早先的假设，即PmpD是在衣原体外分泌的，其分泌随着衣原体包涵体的生长而增加。结论/意义：本研究涉及多个衣原体血清型，支持普遍共识，即pmpD基因在中期感染时最大限度地表达，并提供了关于PmpD作为一种自身转运蛋白的新信息，该蛋白在正常和低温诱导的持续衣原体感染期间被翻译后加工并分泌到衣原体外。
Background: The polymorphic membrane protein D (PmpD) in Chlamydia is structurally similar to autotransporter proteins described in other bacteria and may be involved in cellular and humoral protective immunity against Chlamydia. The mechanism of PmpD post-translational processing and the role of its protein products in the pathogenesis of chlamydial infection have not been very well elucidated to date.Methodology/Principal Findings: Here we examined the expression and post-translational processing of the protein product of the pmpD gene during the life cycle of C. trachomatis serovars A, D, and L2. Each of these three serovars targets different human organs and tissues and encodes a different pmpD gene nucleotide sequence. Our quantitative real-time reverse transcription polymerase chain reaction results demonstrate that the pmpD gene is up-regulated at 12-24 hours after infection regardless of the Chlamydia serovar. This up-regulation is coincidental with the period of exponential growth and replication of reticulate bodies (RB) of Chlamydia and indicates a probable similarity in function of pmpD in serovars A, D, and L2 of Chlamydia. Using mass spectrometry analysis, we identified the protein products of post-translational processing of PmpD of C. trachomatis serovar L2 and propose a double pathway model for PmpD processing, with one cleavage site between the passenger and autotransporter domains and the other site in the middle of the passenger domain. Notably, when Chlamydia infected culture cells were subjected to low (28 degrees C) temperature, PmpD post-translational processing and secretion was found to be uninhibited in the resulting persistent infection. In addition, confocal microscopy of cells infected with Chlamydia confirms our earlier hypothesis that PmpD is secreted outside Chlamydia and its secretion increases with growth of the chlamydial inclusion.Conclusion/Significance: The results of this current study involving multiple Chlamydia serovars support the general consensus that the pmpD gene is maximally expressed at mid infection and provide new information about PmpD as an autotransporter protein which is post-translationally processed and secreted outside Chlamydia during normal and low temperature induced persistent chlamydial infection.