The molecular basis for integration of the Chlamydial responses to iron and tryptophan limitation

7.项目总结/摘要 由专性细胞内病原体沙眼衣原体引起的人类生殖道感染是最常见的感染之一。 在美国和国外，性传播感染的报告率最高。无症状衣原体 感染非常普遍，导致经常出现未诊断和未治疗的病人。未处理 衣原体感染可促进妇女出现严重后遗症，包括盆腔炎。 疾病和输卵管因素不孕。尽管有这些严重的后果， 无症状地仍然知之甚少。越来越多的证据表明， 生长表型，称为持久性，在教唆这些慢性疾病。各种各样的，看似无关的 已知刺激促进体外持久性，但不清楚这些不同的损伤是否达到 通过趋同或发散途径的持久性。限制铁对衣原体的可用性 持久性，但很少了解衣原体物种如何应对铁限制。唯一确定的 衣原体中的铁依赖性转录调节因子由YtgR代表，其活性需要 从N-末端通透酶结构域YtgC裂解。简单地将铁限制在C。沙眼显著诱导 唯一的色氨酸（Trp）生物合成基因trpBA的表达，表明以前未描述的铁- C. Trp生物合成的依赖性调控模式沙眼YtgC具有独特的密码子基序 三个连续的Trp残基（WWW），需要Trp的翻译YtgC和YtgR的可用性。 有趣的是，饥饿色氨酸是诱导持久性的主要方法之一，因为它代表了一个关键的 衣原体的营养素因此，由于长期Trp饥饿导致的YtgR的损失可能会导致 YtgR调节子的失调，有助于诱导持久性。为了研究这个假设， 我们建议利用衣原体遗传学的最新进展来阐明铁依赖性和Trp- YtgR的依赖性调节子。首先，我们将定义铁依赖性YtgR调节子，以了解其对细胞增殖的贡献。 这种调节剂的发展，通过铁限制诱导的持久性。第二，我们将阐明 铁依赖性trpBA调节的分子机制。最后，我们将评估 WWW基序在维持YtgR调节子中作为Trp可用性的函数。成功完成本 研究将提供两个独立的持久性刺激物之间的第一个机制联系， 为无症状和慢性衣原体感染的分子基础提供了关键的见解。

7. Project Summary/Abstract Infections of the human genital tract by the obligate intracellular pathogen Chlamydia trachomatis are among the most highly reported sexually transmitted infections both in the U.S. and abroad. Asymptomatic chlamydial infections are highly prevalent and contribute to the frequency of undiagnosed and untreated patients. Untreated chlamydial infections can promote the development of serious sequelae in women, including pelvic inflammatory disease and tubal factor infertility. Despite these severe consequences, how Chlamydia manifest asymptomatically remains poorly understood. A growing body of evidence implicates an aberrant chlamydial growth phenotype, known as persistence, in abetting these chronic diseases. Varied and seemingly unrelated stimuli are known to facilitate persistence in vitro, yet it is unclear whether these various insults arrive at persistence through convergent or divergent pathways. Limiting the availability of iron to Chlamydia promotes persistence, but little is understood about how chlamydial species respond to iron limitation. The only identified iron-dependent transcriptional regulator in Chlamydia is represented by YtgR, the activity of which requires cleavage from an N-terminal permease domain, YtgC. Briefly limiting iron to C. trachomatis significantly induces the expression of the sole tryptophan (Trp) biosynthetic genes trpBA, indicating a previously undescribed iron- dependent mode of regulation controls Trp biosynthesis in C. trachomatis. YtgC possesses a unique codon motif of three sequential Trp residues (WWW), necessitating Trp availability for the translation of YtgC and thus YtgR. Intriguingly, starvation of Trp is one of the principal methods of inducing persistence as it represents a critical nutrient for Chlamydia. It is therefore possible that the loss of YtgR due to chronic Trp starvation would result in the dysregulation of the YtgR regulon, contributing to the induction of persistence. To investigate this hypothesis, we propose to utilize recent advances in chlamydial genetics to elucidate both the iron-dependent and Trp- dependent regulons of YtgR. First, we will define the iron-dependent YtgR regulon to understand the contribution of this regulator to the development of persistence induced via iron limitation. Secondly, we will elucidate the molecular mechanisms underpinning the iron-dependent regulation of trpBA. Finally, we will assess the role of the WWW motif in maintaining the YtgR regulon as a function of Trp availability. Successful completion of this research will provide the first mechanistic link between two separate stimulators of persistence, potentially offering key insights into the molecular basis for asymptomatic and chronic chlamydial infections.