Department of Chemistry, Indiana University, Bloomington, Indiana.
Department of Chemistry, Indiana University, Bloomington, Indiana.
Biophys J. 2022 Feb 1;121(3):459-469. doi: 10.1016/j.bpj.2021.12.032. Epub 2021 Dec 29.
Immune cells degrade internalized pathogens in vesicle compartments called phagosomes. Many intracellular bacteria induce homotypic phagosome fusion to survive in host cells, but the fusion interaction between phagosomes and its consequence for phagosome function have scarcely been studied. Here, we characterize homotypic fusion between phagosomes in macrophages and identify how such interactions impact the degradative capacity of phagosomes. By developing a series of particle sensors for measuring biochemical changes of single phagosomes, we show that phagosomes undergo stable fusion, transient "kiss-and-run" fusion, or both in succession. Super-resolution three-dimensional fluorescence microscopy revealed that stably fused phagosomes are connected by membrane "necks" with submicron-sized fusion pores. Furthermore, we demonstrate that, after stable fusion, phagosomes have leaky membranes and thereby impaired degradative functions. Our findings, based on phagosomes that contain synthetic particles, illustrate that homotypic fusion is not exclusive to phagosomes that encapsulate pathogens, as previously believed. The physical process of homotypic fusion is alone sufficient to perturb the degradative functions of phagosomes.
免疫细胞在称为吞噬体的小泡隔室中降解内化的病原体。许多细胞内细菌诱导同源吞噬体融合以在宿主细胞中存活，但吞噬体之间的融合相互作用及其对吞噬体功能的影响几乎没有被研究过。在这里，我们描述了巨噬细胞中吞噬体的同源融合，并确定了这种相互作用如何影响吞噬体的降解能力。通过开发一系列用于测量单个吞噬体生化变化的颗粒传感器，我们表明吞噬体经历稳定融合、短暂的“亲吻-跑开”融合或两者连续发生。超分辨率三维荧光显微镜显示，稳定融合的吞噬体通过亚微米大小的融合孔的膜“颈部”连接。此外，我们证明，在稳定融合后，吞噬体的膜具有渗漏性，因此降解功能受损。我们的研究结果基于含有合成颗粒的吞噬体，表明同源融合不仅限于包含病原体的吞噬体，这与之前的观点不同。同源融合的物理过程本身足以扰乱吞噬体的降解功能。
