Rapid removal of phagosomal ferroportin in macrophages contributes to nutritional immunity
Rapid removal of phagosomal ferroportin in macrophages contributes to nutritional immunity
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DOI：
10.1182/bloodadvances.2020002833
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发表时间：
2021-01-22
期刊：
影响因子：
7.5
通讯作者：
Heinrichs, David E.
中科院分区：
文献类型：
--
作者：
Flannagan, Ronald S.;Farrell, Tayler J.;Heinrichs, David E.
养分封存是宿主先天免疫的一个重要方面。巨噬细胞通过表达铁转运蛋白铁蛋白(FPN)，将铁从细胞质中排出到细胞外环境中，从而在控制铁的可利用性方面发挥关键作用。在吞噬过程中，来自质膜的限制性吞噬体膜可以被FPN装饰，如果起作用，它将把胞浆中的铁转移到吞噬体腔中。这起到了向吞噬微生物提供铁的作用，并会对许多其他已知的宿主机制产生反作用，这些宿主机制会让微生物无法获得这种重要的金属。为了了解FPN在吞噬过程中是如何调节的，我们在巨噬细胞中表达了FPN作为一种绿色荧光蛋白融合蛋白，并监测了它在吞噬各种吞噬靶点的过程中的定位，诱导了金黄色葡萄球菌、沙门氏菌、鼠伤寒沙门氏菌、人红细胞和免疫球蛋白G调理乳胶珠。我们发现，FPN可以独立于Vps34和PI(3)P迅速从早期吞噬小体中移除，并且不遵循调节转铁蛋白受体循环的循环途径。活细胞视频显微镜显示，FPN在吞噬小体上的运动是动态的，在FPN被运输回质膜之前形成点状和管状结构。N-乙基马来酰亚胺敏感因子破坏了可溶性NSF附着蛋白受体(SNARE)介导的膜融合和转运，阻止了FPN从吞噬小体中去除。我们的数据支持这样的假设，即从限制吞噬体膜上去除FPN将在细胞水平上确保铁不能被泵入吞噬小体。我们提出这是宿主营养免疫的另一种机制，以破坏微生物的生长。
Nutrient sequestration is an essential facet of host innate immunity. Macrophages play a critical role in controlling iron availability through expression of the iron transport protein ferroportin (FPN), which extrudes iron from the cytoplasm to the extracellular milieu. During phagocytosis, the limiting phagosomal membrane, which derives from the plasmalemma, can be decorated with FPN and, if functional, will move iron from the cytosol into the phagosome lumen. This serves to feed iron to phagocytosed microbes and would be counterproductive to the many other known host mechanisms working to starve microbes of this essential metal. To understand how FPN is regulated during phagocytosis, we expressed FPN as a green fluorescent protein-fusion protein in macrophages and monitored its localization during uptake of various phagocytic targets, inducting Staphylococcus aureus, Salmonella enterica serovar Typhimurium, human erythrocytes, and immunoglobulin G opsonized latex beads. We find that FPN is rapidly removed, independently of Vps34 and PI(3)P, from early phagosomes and does not follow recycling pathways that regulate transferrin receptor recycling. Live-cell video microscopy showed that FPN movement on the phagosome is dynamic, with punctate and tubular structures forming before FPN is trafficked back to the plasmalemma. N-ethylmaleimide-sensitive factor, which disrupts soluble NSF attachment protein receptor (SNARE)-mediated membrane fusion and trafficking, prevented FPN removal from the phagosome. Our data support the hypothesis that removal of FPN from the limiting phagosomal membrane will, at the cellular level, ensure that iron cannot be pumped into phagosomes. We propose this as yet another mechanism of host nutritional immunity to subvert microbial growth.