Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
Microb Pathog. 2011 Sep;51(3):101-9. doi: 10.1016/j.micpath.2011.05.002. Epub 2011 May 13.
The chlamydia-specific hypothetical protein CT311 was detected both inside and outside of the chlamydial inclusions in Chlamydia trachomatis-infected cells. The extra-inclusion CT311 molecules were distributed in the host cell cytoplasm with a pattern similar to that of CPAF, a known Chlamydia-secreted protease. The detection of CT311 was specific since the anti-CT311 antibody labeling was only removed by absorption with CT311 but not CPAF fusion proteins. In addition, both anti-CT311 and anti-CPAF antibodies only detected their corresponding endogenous proteins without cross-reacting with each other or any other antigens in the whole cell lysates of C. trachomatis-infected cells. Although both CT311 and CPAF proteins were first detected 12 h after infection, localization of CT311 into host cell cytosol was delayed until 24 h while CPAF secretion into host cell cytosol was already obvious by 18 h after infection. The host cell cytosolic localization of CT311 was further confirmed in human primary cells. CT311 was predicted to contain an N-terminal secretion signal sequence and the CT311 signal sequence directed secretion of PhoA into bacterial periplasmic region in a heterologous assay system, suggesting that a sec-dependent pathway may play a role in the secretion of CT311 into host cell cytosol. This hypothesis is further supported by the observation that secretion of CT311 in Chlamydia-infected cells was blocked by a C16 compound known to inhibit signal peptidase I. These findings have provided important molecular information for further understanding the C. trachomatis pathogenic mechanisms.
沙眼衣原体感染细胞中的衣原体包涵体内、外均检测到衣原体特异性假定蛋白 CT311。包涵体外的 CT311 分子分布在宿主细胞质中，模式与已知的衣原体分泌蛋白酶 CPAF 相似。由于抗 CT311 抗体的标记仅被 CT311 吸收而不是 CPAF 融合蛋白吸收所去除，因此 CT311 的检测是特异性的。此外，抗 CT311 和抗 CPAF 抗体仅检测其相应的内源性蛋白，而不会与沙眼衣原体感染细胞的整个细胞裂解物中的彼此或任何其他抗原发生交叉反应。尽管 CT311 和 CPAF 蛋白均在感染后 12 小时首次检测到，但 CT311 定位到宿主细胞胞质溶胶的时间延迟到 24 小时，而 CPAF 分泌到宿主细胞胞质溶胶在感染后 18 小时已经很明显。在人原代细胞中进一步证实了 CT311 定位于宿主细胞胞质溶胶。预测 CT311 含有一个 N 端分泌信号序列，并且 CT311 信号序列在异源测定系统中指导 PhoA 分泌到细菌周质区域，这表明 sec 依赖性途径可能在 CT311 分泌到宿主细胞胞质溶胶中起作用。这一假设进一步得到了以下观察结果的支持：在衣原体感染的细胞中，CT311 的分泌被一种已知抑制信号肽酶 I 的 C16 化合物阻断。这些发现为进一步了解沙眼衣原体的致病机制提供了重要的分子信息。
