Department of Pathogen Biology, University of South China, Hengyang, Hunan, China.
PLoS One. 2013 Jul 24;8(7):e68764. doi: 10.1371/journal.pone.0068764. Print 2013.
Glycogen has been localized both inside and outside Chlamydia trachomatis organisms. We now report that C. trachomatis glycogen synthase (GlgA) was detected in both chlamydial organism-associated and -free forms. The organism-free GlgA molecules were localized both in the lumen of chlamydial inclusions and in the cytosol of host cells. The cytosolic GlgA displayed a distribution pattern similar to that of a known C. trachomatis-secreted protease, CPAF. The detection of GlgA was specific since the anti-GlgA antibody labeling was only removed by preabsorption with GlgA but not CPAF fusion proteins. GlgA was detectable at 12h and its localization into host cell cytosol only became apparent at 24h after infection. The cytosolic localization of GlgA was conserved among all C. trachomatis serovars. However, the significance of the GlgA secretion into host cell cytoplasm remains unclear since, while expression of chlamydial GlgA in HeLa cells increased glycogen stores, it did not affect a subsequent infection with C. trachomatis. Similar to several other C. trachomatis-secreted proteins, GlgA is immunogenic in women urogenitally infected with C. trachomatis, suggesting that GlgA is expressed and may be secreted into host cell cytosol during C. trachomatis infection in humans. These findings have provided important information for further understanding C. trachomatis pathogenic mechanisms.
糖原已在沙眼衣原体生物体内外定位。我们现在报告，沙眼衣原体糖原合酶（GlgA）在衣原体相关和无衣原体形式中均被检测到。无衣原体的 GlgA 分子定位于衣原体包涵体的腔中和宿主细胞的细胞质中。细胞质中的 GlgA 显示出与已知的沙眼衣原体分泌蛋白酶 CPAF 相似的分布模式。GlgA 的检测是特异性的，因为抗 GlgA 抗体标记仅被 GlgA 但不是 CPAF 融合蛋白吸收而去除。在感染后 12 小时即可检测到 GlgA，其定位到宿主细胞细胞质中仅在感染后 24 小时才变得明显。GlgA 在所有沙眼衣原体血清型中均具有保守的细胞质定位。然而，GlgA 分泌到宿主细胞质中的意义尚不清楚，因为虽然在 HeLa 细胞中表达衣原体 GlgA 会增加糖原储存，但它不会影响随后感染沙眼衣原体。类似于其他几种沙眼衣原体分泌的蛋白质，GlgA 在女性泌尿生殖道感染沙眼衣原体时具有免疫原性，这表明 GlgA 在人类感染沙眼衣原体期间表达并可能分泌到宿主细胞质中。这些发现为进一步了解沙眼衣原体发病机制提供了重要信息。
