Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, M1C 1A4 Canada.
J Immunol. 2011 Jan 15;186(2):816-25. doi: 10.4049/jimmunol.1002161. Epub 2010 Dec 13.
FcγR-mediated phagocytosis is a cellular event that is evolutionary conserved to digest IgG-opsonized pathogens. Pseudopod formation during phagocytosis is a limiting step in managing the uptake of particles, and in this paper, we show that the conventional kinesin is involved in both receptor and membrane delivery to the phagocytic cup. Expression of a mutant kinesin isoform (GFP dominant negative mutant of kinesin H chain [EGFP-Kif5B-DN]) in RAW264.7 cells significantly reduced binding of IgG-sheep RBCs when macrophages were faced with multiple encounters with opsonized particles. Scanning electron microscopy analysis of EGFP-Kif5B-DN-expressing cells challenged with two rounds of IgG-sheep RBCs showed sparse, extremely thin pseudopods. We saw disrupted Rab11 trafficking to the phagocytic cup in EGFP-Kif5B-DN-transfected cells. Our particle overload assays also implicated phagosome membrane recycling in pseudopod formation. We observed reduced phagosome fission and trafficking in mutant kinesin-expressing cells, as well as reduced cell surface expression of FcγRs and Mac-1 receptors. In conclusion, anterograde trafficking via kinesin is essential for both receptor recycling from the phagosome and delivery of Rab11-containing membrane stores to effect broad and functional pseudopods during FcγR-mediated phagocytosis.
FcγR 介导的吞噬作用是一种进化上保守的细胞事件，可消化 IgG 调理的病原体。吞噬作用过程中的伪足形成是控制颗粒摄取的一个限制步骤，在本文中，我们表明传统的驱动蛋白参与了受体和膜向吞噬杯的传递。在 RAW264.7 细胞中表达突变型驱动蛋白异构体（驱动蛋白 H 链的 GFP 显性负突变体 [EGFP-Kif5B-DN]）时，当巨噬细胞面临多次与调理颗粒的接触时，明显降低了 IgG-绵羊 RBC 的结合。用两轮 IgG-绵羊 RBC 挑战表达 EGFP-Kif5B-DN 的细胞的扫描电子显微镜分析显示，稀疏、极薄的伪足。我们观察到 EGFP-Kif5B-DN 转染细胞中 Rab11 向吞噬杯的运输受到干扰。我们的颗粒过载测定也表明吞噬体膜的再循环参与了伪足的形成。我们观察到在突变型驱动蛋白表达细胞中吞噬体裂变和运输减少，以及 FcγR 和 Mac-1 受体的细胞表面表达减少。总之，通过驱动蛋白的正向运输对于从吞噬体中回收受体以及将含有 Rab11 的膜库递送至 FcγR 介导的吞噬作用中形成广泛而功能的伪足都是必不可少的。
