The role of protein glycosylation and carbohydrate receptors in macrophage and neutrophil cross-talk during Mycobacterium tuberculosis infection

结核分枝杆菌（M.tb）是导致结核病（TB）的病原体，结核病是世界上最普遍和最致命的人类传染病之一，每年约有20亿人感染，150万人死亡。分枝杆菌与人类一起适应了数万年，留下了一系列工具来修改人类的先天和适应性免疫系统，以便进入宿主并在宿主内生存。宿主的主要目标是空中巡逻的巨噬细胞，它们通常与常驻的中性粒细胞（两种白细胞）一起迅速消灭入侵者，作为先天免疫系统的一部分。然而，结核分枝杆菌避免了先天免疫系统的早期识别和破坏，并能够通过破坏巨噬细胞的杀伤机制在巨噬细胞内繁殖。最终，结核分枝杆菌引起慢性炎症，这有利于病原体的长期生存，甚至在宿主无症状（潜伏）感染数十年后也可能发生传播。有趣的是，只有一小部分结核分枝杆菌感染者会发展为活动性结核。越来越多的证据表明，巨噬细胞和中性粒细胞在结核病的发展中起着核心作用。所谓的糖缀合物是一种含有碳水化合物部分的分子，已知与结核病感染有关。用碳水化合物修饰蛋白质（糖蛋白）或脂质（糖脂）在所有细胞表面都很常见。这些细胞实际上被一层糖涂层覆盖，作为其他细胞的识别标签。碳水化合物基序也可用于通信目的，因为已知结核分枝杆菌利用这些糖蛋白进入宿主，并且细菌能够操纵宿主细胞的糖基化以调节免疫反应。通过结合碳水化合物（聚糖）和它们在细胞表面和大分泌囊泡（微粒）上的特殊受体之间的相互作用，促进免疫系统细胞之间的交流，也可以被结核分枝杆菌劫持。然而，令人惊讶的是，关于糖蛋白在结核分枝杆菌感染期间巨噬细胞和中性粒细胞之间通讯中的确切作用的详细分子知识很少。因此，很明显，更好地了解巨噬细胞和中性粒细胞的糖生物学改变，以及这如何影响结核分枝杆菌感染期间它们的串扰，对于我们开始揭示与结核相关的复杂免疫过程至关重要。本研究旨在阐明结核分枝杆菌感染期间巨噬细胞和中性粒细胞串扰中蛋白糖基化及其相关碳水化合物受体的作用。全系统筛选（质谱联用液相色谱法）之后，将使用分子生物学技术进行更有针对性的研究，以确定这些分子的功能。

Mycobacterium tuberculosis (M.tb) is the pathogen responsible for causing tuberculosis (TB), one of the most prevalent and lethal infectious human diseases worldwide with approximately 2 billion infected individuals and 1.5 million annual deaths. The mycobacterium has adapted alongside humans for tens of thousands of years leaving it with an array of tools to modify the human innate and adaptive immune system in order to gain access and survive within the host. The principal host targets are the air way-patrolling macrophages that normally, together with resident neutrophils, (both white blood cells) quickly eliminate intruders as part of the innate immune system. However, M.tb avoids early recognition and destruction by the innate immune system and is able to reproduce inside the macrophages by compromising their killing mechanisms. Eventually, M.tb causes chronic inflammation that is beneficial for the long-term survival of the pathogen and transmission can happen even after decades of symptom-free (latent) infection of the host.Interestingly, only a subset of M.tb infected individuals develop the active form of TB. There is growing evidence that macrophages and neutrophils are central players in the development of TB. The so-called glycoconjugates, which are molecules containing a carbohydrate portion are known to be intricately involved in TB infection. The modification of proteins (glycoproteins) or lipids (glycolipids) with carbohydrate moieties is common on all cell surfaces. The cells are literally covered in a sugar coating, which serves as an identification tag for other cells. The carbohydrate motifs may also be used for communication purposes as M.tb is known to use these glycoproteins to gain access to the host and the bacterium is able to manipulate the glycosylation of host cells in order to modulate the immune response. The communication between cells of the immune system, which is facilitated through the interaction between the conjugated carbohydrates (glycans) and their specialized receptors on cell surfaces and on large secreted vesicles (microparticles), can also be hijacked by M.tb. However, surprisingly little detailed molecular knowledge has been established regarding the exact role of glycoproteins in the communication between macrophages and neutrophils during M. tb infection.Thus, it is clear that a better understanding of the altered glycobiology of macrophages and neutrophils and how this influences their cross-talk during M.tb infection is essential to allow us to begin to unravel the complex immune processes associated with TB. With this proposal the role of protein glycosylation and their associated carbohydrate receptors in macrophage and neutrophil cross-talk during M.tb infection is meant to be elucidated. System-wide screens (mass spectrometry coupled to liquid chromatography) will be followed up by more targeted studies using molecular biology techniques to determine the function of these molecules.