Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111.
Department of Oral Microbiology, Asahi University School of Dentistry, Mizuho, 501-0296 Gifu, Japan.
Proc Natl Acad Sci U S A. 2020 Dec 29;117(52):33561-33569. doi: 10.1073/pnas.2015368117. Epub 2020 Dec 21.
is a leading cause of pneumonia and invasive disease, particularly, in the elderly. lung infection of aged mice is associated with high bacterial burdens and detrimental inflammatory responses. Macrophages can clear microorganisms and modulate inflammation through two distinct lysosomal trafficking pathways that involve 1A/1B-light chain 3 (LC3)-marked organelles, canonical autophagy, and LC3-associated phagocytosis (LAP). The pore-forming toxin pneumolysin (PLY) triggers an autophagic response in nonphagocytic cells, but the role of LAP in macrophage defense against or in age-related susceptibility to infection is unexplored. We found that infection of murine bone-marrow-derived macrophages (BMDMs) by PLY-producing triggered Atg5- and Atg7-dependent recruitment of LC3 to -containing vesicles. The association of LC3 with -containing phagosomes required components specific for LAP, such as Rubicon and the NADPH oxidase, but not factors, such as Ulk1, FIP200, or Atg14, required specifically for canonical autophagy. In addition, was sequestered within single-membrane compartments indicative of LAP. Importantly, compared to BMDMs from young (2-mo-old) mice, BMDMs from aged (20- to 22-mo-old) mice infected with were not only deficient in LAP and bacterial killing, but also produced higher levels of proinflammatory cytokines. Inhibition of LAP enhanced survival and cytokine responses in BMDMs from young but not aged mice. Thus, LAP is an important innate immune defense employed by BMDMs to control infection and concomitant inflammation, one that diminishes with age and may contribute to age-related susceptibility to this important pathogen.
是肺炎和侵袭性疾病的主要病因，尤其是在老年人中。老年小鼠的肺部感染与高细菌负荷和有害炎症反应有关。巨噬细胞可以通过两种不同的溶酶体运输途径清除微生物并调节炎症，这两种途径涉及 1A/1B-轻链 3（LC3）标记的细胞器、经典自噬和 LC3 相关的吞噬作用（LAP）。成孔毒素肺炎球菌溶血素（PLY）在非吞噬细胞中触发自噬反应，但 LAP 在巨噬细胞防御 或与年龄相关的易感性感染中的作用尚未被探索。我们发现，PLY 产生的 感染小鼠骨髓来源的巨噬细胞（BMDMs）会触发 Atg5 和 Atg7 依赖性 LC3 募集到含有 -的囊泡。LC3 与含有 -的吞噬体的关联需要特定于 LAP 的成分，例如 Rubicon 和 NADPH 氧化酶，但不需要经典自噬所需的特定因素，例如 Ulk1、FIP200 或 Atg14。此外，被隔离在单膜隔室内，表明存在 LAP。重要的是，与来自年轻（2 个月大）小鼠的 BMDMs 相比，来自年老（20-22 个月大）小鼠的 BMDMs 不仅在 LAP 和细菌杀伤方面存在缺陷，而且还产生更高水平的促炎细胞因子。在年轻但不是年老的 BMDMs 中，抑制 LAP 增强了 的存活和细胞因子反应。因此，LAP 是 BMDMs 控制 感染和伴随炎症的重要先天免疫防御机制，随着年龄的增长而减弱，可能导致对这种重要病原体的年龄相关易感性。
