The chlamydial plasmid-encoded protein pgp3 is secreted into the cytosol of Chlamydia-infected cells
The chlamydial plasmid-encoded protein pgp3 is secreted into the cytosol of Chlamydia-infected cells
复制标题
DOI：
10.1128/iai.01377-07
复制
发表时间：
2008-08-01
影响因子：
3.1
通讯作者：
Zhong, Guangming
中科院分区：
文献类型：
--
作者：
Li, Zhongyu;Chen, Ding;Zhong, Guangming
衣原体隐蔽质粒编码8个可能的开放阅读框架(ORF)，命名为pORF1至-8。针对这些ORF蛋白产生的抗体被用来定位衣原体感染期间的内源性蛋白。我们发现，pORF5蛋白(也称为Pgp3)主要在衣原体感染细胞的胞浆中检测到，而其余7种蛋白仅在衣原体包涵体中检测到。Pgp3在宿主细胞胞浆中的分布模式与衣原体蛋白酶/蛋白酶体样活性因子(CPAF)相似，但不重叠。衣原体基因组编码蛋白是一种已知从衣原体包涵体分泌到宿主细胞胞浆的蛋白质。用Pgp3预吸收可以去除抗Pgp3的标记，但不能去除CPAF融合蛋白，反之亦然，这表明Pgp3是一种独特的分泌蛋白。进一步支持这一结论的观察结果是，Pgp3在胞浆组分中高度浓缩，而在衣原体感染细胞制备的含包涵体核组分中只有极少量的存在。Pgp3蛋白最早在感染后12h就被检测到，并且在所有携带隐匿质粒的衣原体物种中都能分泌，这表明在衣原体感染过程中存在维持Pgp3分泌的选择压力。虽然通过转基因在宿主细胞胞浆中表达Pgp3不会改变转基因细胞对随后衣原体感染的敏感性，但纯化的Pgp3蛋白能刺激巨噬细胞释放炎性细胞因子，提示Pgp3可能参与了衣原体的发病。
The chlamydial cryptic plasmid encodes eight putative open reading frames (ORFs), designated pORF1 to -8. Antibodies raised against these ORF proteins were used to localize the endogenous proteins during chlamydial infection. We found that the pORF5 protein (also known as pgp3) was detected mainly in the cytosol of Chlamydia-infected cells, while the remaining seven proteins were found inside the chlamydial inclusions only. The pgp3 distribution pattern in the host cell cytosol is similar to but not overlapping with that of chlamydial protease/proteasome-like activity factor (CPAF), a chlamydial genome-encoded protein known to be secreted from chlamydial inclusions into the host cell cytosol. The anti-pgp3 labeling was removed by preabsorption with pgp3 but not CPAF fusion proteins and vice versa, demonstrating that pgp3 is a unique secretion protein. This conclusion is further supported by the observation that pgp3 was highly enriched in cytosolic fractions and had a minimal presence in the inclusion-containing nuclear fractions prepared from Chlamydia-infected cells. The pgp3 protein was detected as early as 12 h after infection and was secreted by all chlamydial species that carry the cryptic plasmid, suggesting that there is a selection pressure for maintaining pgp3 secretion during chlamydial infection. Although expression of pgp3 in the host cell cytosol via a transgene did not alter the susceptibility of the transfected cells to the subsequent chlamydial infection, purified pgp3 protein stimulated macrophages to release inflammatory cytokines, suggesting that pgp3 may contribute to chlamydial pathogenesis.