Molecular mechanisms of translational control in macrophages

巨噬细胞是先天免疫系统的哨兵。因此，它们在宿主抵抗感染的防御中发挥着核心作用，但在病原体清除后的炎症消退和伤口愈合方面也发挥着核心作用。为了完成这些任务，巨噬细胞通过产生不同类型的蛋白质来对环境的变化迅速做出反应，这些蛋白质使它们具有促炎和杀菌作用，或者更确切地说是抗炎作用。翻译控制(调节信使核糖核酸的翻译)允许细胞根据自己的需要通过合成蛋白质来对外部触发或提示做出反应。其优势在于，与其他调节基因表达的机制不同，mRNA翻译的变化可以非常迅速地发生，因为不需要合成新的mRNA来产生蛋白质。令人惊讶的是，我们对翻译调控如何影响巨噬细胞功能的理解存在相当大的差距。因此，我的NSERC研究计划专注于识别巨噬细胞中在翻译水平上受控的mRNAs和细胞过程，并研究它们是如何被入侵的病原体改变的。为此，我们将用弓形虫感染巨噬细胞，弓形虫是一种细胞内的原生动物寄生虫，已知会破坏许多宿主细胞的功能以求生存。除了靶标识别，我们还将定义弓形虫阻断的细胞内信号，以防止正常巨噬细胞反应所需的mRNAs的翻译。为了实现这些目标，我们将在转基因巨噬细胞中采用生化、免疫学和分子生物学的组合方法来改变不同的mRNA翻译调节因子的表达。我们的筛选将通过全基因组RNA测序和生物信息学分析进行，使用一种专门设计的算法来捕捉mRNA翻译的变化。总之，我们的研究将提供关于原生动物寄生虫如何劫持巨噬细胞的mRNA翻译机制的见解，并修改最终有助于感染进展的基因表达程序。更好地了解细胞内病原体与宿主细胞相互作用的分子机制，对于设计安全有效的治疗方法来对抗具有临床意义的感染，从而提高加拿大人的生活质量至关重要。

Macrophages are the sentinels of the innate immune system. As such, they play central roles in host defense against infections but also in the resolution of inflammation and wound healing after pathogen clearance. In order to accomplish these tasks, macrophages swiftly respond to changes in the environment by producing different types of proteins that render them pro-inflammatory and microbicidal or rather anti-inflammatory. Translational control (regulation of mRNA translation) allows cells to react to external triggers or cues by synthesizing proteins according to their needs. The advantage is that in contrast to other mechanisms that regulate gene expression, changes in mRNA translation can occur very rapidly because there is no need to synthesize new mRNA to produce proteins. Surprisingly, there are considerable gaps in our understanding of how translational control impacts macrophage functions. Therefore, my NSERC research program focuses on identifying the mRNAs and the cellular processes that are controlled at the level of translation in macrophages, and to investigate how they altered by invading pathogens. To this end, we will infect macrophages with Toxoplasma gondii, an intracellular protozoan parasite that is known to subvert numerous host cell functions to survive. In addition to target identification, we will define the intracellular signals that are blocked by Toxoplasma gondii in order to prevent translation of mRNAs required for normal macrophage responses. To achieve these goals, we will deploy a combination of biochemical, immunological and molecular biology approaches in macrophages genetically modified to alter the expression of different regulators of mRNA translation. Our screening will be performed by genome-wide RNA sequencing, and bioinformatic analysis using an algorithm specifically designed to capture changes in mRNA translation. Collectively, our study will provide insight on how protozoan parasites hijack the mRNA translation machinery of macrophages, and modify gene expression programs that ultimately contribute to the progression of the infection. A better understanding of the molecular mechanisms underlying the interactions of intracellular pathogens with their host cells is of paramount importance to design safe and efficient treatments to combat infections of clinical relevance, and thereby improve the life quality of Canadians.