Macrophage killing mechanisms for intra-phagosomal mycobacteria

巨噬细胞吞噬病原体形成专门的囊泡，吞噬体。形成后，吞噬体进行通过连续的成熟阶段，包括融合，首先与早期-然后与晚期内吞细胞器;我们的研究表明，后者的融合是由肌动蛋白组装促进的吞噬体膜。完全成熟的吞噬体是一个溶酶体样的、低pH值的、富含水解酶的隔室，潜在病原体的最终消化发生在这里。一些吞噬体内病原体，最突出的是结核分枝杆菌，可以阻断肌动蛋白的吞噬体组装和晚期融合事件，使它们繁殖。申请人研究小组已经表明，向受感染的巨噬细胞中加入促炎脂质可以克服病原体诱导的阻滞，并促进对病原性分枝杆菌的杀灭。本提案的目标是对巨噬细胞杀死吞噬体内病原体的机制进行全面的细胞生物学分析。虽然吞噬体-溶酶体融合足以杀死分枝杆菌的教条，但最近的工作揭示，除了一氧化氮释放外，至少有四种不同的晚期内吞隔室需要与吞噬体融合以杀死分枝杆菌。这些区室，以及它们与吞噬体的融合事件在功能上是不同的，但都受p38 Map激酶的调节。此外，促炎性转录因子NfkB的活化对于病原体杀灭也是必需的。因此，p38和NfkB与与吞噬体融合以促进分枝杆菌杀伤的隔室之间的相互作用也将是该提议的一个重要方面。

Phagocytosis of pathogens by macrophages forms specialised vesicles, phagosomes. After formation, phagosomes proceed through sequential maturation stages involving fusion, first with early- then with late-endocytic organelles; our studies showed that the latter fusion is facilitated by actin assembly by phagosomal membranes. The fully matured phagosome is a lysosome-like, low pH, hydrolase-rich compartment where final digestion of potential pathogens occurs. Some intraphagosomal pathogens, most prominently Mycobacterium tuberculosis can block phagosome assembly of actin and late fusion events, allowing them to multiply. The applicant¿s group has shown that the addition of pro-inflammatory lipids to infected macrophages can overcome the pathogen-induced block and promote killing of pathogenic mycobacteria. The goal of this proposal is to make a global cell biological analysis of the mechanisms by which macrophages kill intraphagosomal pathogens. Although the dogma that phagosome-¿lysosome¿ fusion is sufficient to kill mycobacteria, the recent work has revealed that, in addition to nitric oxide release, at least four different late endocytic compartments need to fuse with phagosomes in order to kill mycobacteria. These compartments, and their fusion events with phagosomes are functionally distinct, but all are regulated by p38 Map kinase. Further, activation of the pro-inflammatory transcription factor NfKB is also essential for pathogen killing. The interactions between p38 and NfkB with the compartments that fuse with phagosomes to facilitate mycobacterial killing will therefore also be an important aspect f the proposal.