Distinct pathways for MR1 antigen presentation upon infection with intracellular versus extracellular pathogens

项目摘要 受非经典I类分子MR 1限制的效应CD 8 + T细胞（MAIT细胞）是一种保守的T细胞， 在人类中普遍存在的细胞亚群。因为CD 8 + T细胞识别并破坏受感染的靶细胞， 病原体，肺部驻留的亚群，如MAIT细胞，可能是重要的早期遏制细菌感染 的气道。事实上，我们发现MAIT细胞在气道中高度富集， 对细菌感染的气道上皮细胞（AEC）作出反应。MAIT细胞识别小分子配体 由许多细胞类型（包括AEC）在MR 1上呈现的细菌代谢途径产生。的 MAIT细胞在粘膜组织中的流行，MR 1的普遍表达，以及推测的丰度 小分子配体的表达表明，MR 1受到严格调控，以防止不适当的MAIT细胞活化。 有趣的是，我们发现AEC可以将来自细胞内和细胞外病原体的抗原呈递给 MAIT细胞。此外，我们证明了来自细胞内感染的配体通过以下方式呈递在MR 1上： 与细胞外病原体产生的途径不同。对于这个应用程序，我们提出 来自细胞内病原体的MR 1配体的呈递涉及内体再循环的证据， 需要调节内体运输的蛋白质，如Rab 6。相反，外源性添加的 配体通过Rab 6非依赖性机制发生。因此，本建议的重点是界定不同的 MR 1抗原呈递机制与细胞内与细胞外肺病原体感染。 确定这些配体的不同呈递机制可能是理解MAIT细胞如何 采样气道环境并被激活。 该项目有两个目标： 具体目标1。定义Rab 6如何调节来自细胞内肺的MR 1配体的呈递 病原菌M.结核我们将确定Rab 6如何调节MR 1在人类中的表达或定位。 AEC.此外，我们将确定Rab 6在调节Mtb内体成熟中的作用， 在人类AEC中。 具体目标2。鉴定和验证Rab 6-独立的机制，用于从细胞中呈递MR 1配体。 细胞外肺病原体肺炎链球菌和金黄色葡萄球菌。我们将确定 AEC中的转运分子，对来自细胞外病原体的配体的呈递至关重要， 确定这些分子如何影响细菌感染和MR 1的细胞定位。

Project Summary Effector CD8+ T cells restricted by the non-classical Class I-like molecule MR1 (MAIT cells) are a conserved T cell subset prevalent in humans. Because CD8+ T cells recognize and destroy target cells infected with pathogens, lung-resident subsets like MAIT cells may be important for early containment of bacterial infections of the airway. In fact, we find that MAIT cells are highly enriched in the airways, positioning them to rapidly respond to bacterially infected airway epithelial cells (AEC). MAIT cells recognize small molecule ligands generated by bacterial metabolic pathways that are presented on MR1 by many cell types, including AEC. The prevalence of MAIT cells in mucosal tissues, the ubiquitous expression of MR1, and the presumed abundance of small molecule ligands suggest that MR1 is tightly regulated to prevent inappropriate MAIT cell activation. Interestingly, we found that AEC can present antigen from both intracellular and extracellular pathogens to MAIT cells. Furthermore, we demonstrate that ligands from intracellular infection are presented on MR1 by different pathways than those generated from extracellular pathogens. For this application, we present evidence that presentation of MR1 ligands from intracellular pathogens involves endosomal recycling and requires proteins that regulate endosomal trafficking like Rab6. In contrast, presentation of exogenously added ligands occurs through Rab6-independent mechanisms. This proposal is thus focused on defining distinct mechanisms for MR1 antigen presentation upon infection with intracellular versus extracellular lung pathogens. Defining distinct mechanisms for presentation of these ligands may be key to understanding how MAIT cells sample the airway environment and become activated. This project contains two Aims: Specific Aim 1. Define how Rab6 regulates presentation of MR1 ligands derived from the intracellular lung pathogen M. tuberculosis. We will determine how Rab6 regulates expression or localization of MR1 in human AEC. Additionally, we will determine the role of Rab6 in regulating the maturation of the Mtb endosomal compartment in human AEC. Specific Aim 2. Identify and validate Rab6-independent mechanisms for presentation of MR1 ligands from the extracellular lung pathogens Streptococcus pneumoniae and Staphylococcus aureus. We will identify trafficking molecules in AEC that are critical to presentation of ligands from extracellular pathogens and determine how these molecules impact bacterial infection and cellular localization of MR1.