The intracellular survival of the bacterial pathogen Chlamydia trachomatis depends on protein synthesis by the microbe soon after internalization. Pharmacologic inhibition of bacterial translation inhibits early trafficking of the parasitophorous vacuole (inclusion) to the microtubule-organizing center (MTOC) and promotes its fusion with lysosomes, which is normally blocked by Chlamydia. Depletion of cellular tryptophan pools by gamma interferon-inducible indoleamine-2,3-dioxygenase (IDO) is believed to be the major innate immune mechanism controlling C. trachomatis infection in human cells, an action to which the bacteria can respond by converting into a nonreplicating but highly reactivatable persistent state. However, whether severe IDO-mediated tryptophan starvation can be sufficient to fully arrest the chlamydial life cycle and thereby counteract the onset of persistence is unknown. Here we demonstrate that at low exogenous tryptophan concentrations a substantial fraction of C. trachomatis bacteria fail to traffic to the MTOC or to switch into the conventional persistent state in gamma interferon-induced human cells. The organisms stay scattered in the cell periphery, do not retain infectivity, and display only low transcriptional activity. Importantly, the rate at which these aberrant Chlamydia bacteria become reactivated upon replenishment of cellular tryptophan pools is substantially lower. Thus, severe tryptophan depletion in cells with high IDO activity affects chlamydial development more rigorously than previously described.

译文

细菌病原体沙眼衣原体的细胞内存活取决于微生物内化后不久的蛋白质合成。细菌翻译的药理抑制抑制寄生虫液泡 (内含物) 向微管组织中心 (MTOC) 的早期运输,并促进其与溶酶体的融合,溶酶体通常被衣原体阻断。Γ 干扰素诱导的indoleamine-2,3-双加氧酶 (IDO) 对细胞色氨酸池的消耗被认为是控制人细胞中沙眼衣原体感染的主要先天免疫机制,细菌可以通过转化为不可复制但高度可重新激活的持久性状态来对其做出反应。然而,严重的IDO介导的色氨酸饥饿是否足以完全阻止衣原体生命周期,从而抵消持久性的发作尚不清楚。在这里,我们证明了在低外源色氨酸浓度下,大部分沙眼衣原体细菌无法传播到MTOC或无法在 γ 干扰素诱导的人类细胞中切换到常规的持续状态。生物体分散在细胞周围,不保留感染性,仅显示低转录活性。重要的是,这些异常衣原体细菌在补充细胞色氨酸池后重新激活的速率大大降低。因此,具有高IDO活性的细胞中色氨酸的严重耗竭比以前描述的更严格地影响衣原体的发育。

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