Draper-mediated and phosphatidylserine-independent phagocytosis of apoptotic cells by drosophila hemocytes/macrophages
Draper-mediated and phosphatidylserine-independent phagocytosis of apoptotic cells by drosophila hemocytes/macrophages
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DOI：
10.1074/jbc.m408597200
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发表时间：
2004-11-12
影响因子：
4.8
通讯作者：
Nakanishi, Y
中科院分区：
文献类型：
--
作者：
Manaka, J;Kuraishi, T;Nakanishi, Y
果蝇中吞噬细胞消除垂死细胞的机制知之甚少。本研究旨在探讨果蝇血细胞/巨噬细胞在体内外对凋亡细胞的识别和吞噬作用。在体外分析中，使用l（2）mbn细胞（从肿瘤果蝇突变体的幼虫血细胞建立的细胞系）作为吞噬细胞。当用蜕皮激素20-羟基蜕皮激素处理l（2）mbn细胞时，细胞获得吞噬凋亡的S2细胞（另一种果蝇细胞系）的能力。经历环己酰亚胺诱导凋亡的S2细胞表面暴露了磷脂酰丝氨酸，但它们被l（2）mbn细胞吞噬似乎不是由磷脂酰丝氨酸介导的。果蝇血细胞/巨噬细胞的候选吞噬受体Croquemort的水平在20-羟基蜕皮激素处理后在l（2）mbn细胞中增加，而另一个候选吞噬受体德雷珀的水平保持不变。然而，凋亡细胞的吞噬作用减少时，表达的德雷珀，但不是Croquemort，抑制RNA干扰处理的l（2）mbn细胞。我们接下来使用基于评估dICAD突变胚胎中凋亡细胞的DNA降解（仅在吞噬细胞摄入后发生）的吞噬测定法来检查德雷珀是否负责体内凋亡细胞的吞噬作用。RNA干扰介导的突变果蝇胚胎中德雷珀水平的降低伴随着含有片段化DNA的细胞数量的减少。此外，分散的胚胎细胞的组织化学分析表明，血细胞/巨噬细胞的吞噬凋亡细胞的水平降低时，德雷珀表达被抑制。这些结果表明，果蝇血细胞/巨噬细胞执行Draper介导的吞噬作用，以消除凋亡细胞。
The mechanism of phagocytic elimination of dying cells in Drosophila is poorly understood. This study was undertaken to examine the recognition and engulfment of apoptotic cells by Drosophila hemocytes/macrophages in vitro and in vivo. In the in vitro analysis, l(2)mbn cells (a cell line established from larval hemocytes of a tumorous Drosophila mutant) were used as phagocytes. When l(2) mbn cells were treated with the molting hormone 20-hydroxyecdysone, the cells acquired the ability to phagocytose apoptotic S2 cells, another Drosophila cell line. S2 cells undergoing cycloheximide-induced apoptosis exposed phosphatidylserine on their surface, but their engulfment by l(2) mbn cells did not seem to be mediated by phosphatidylserine. The level of Croquemort, a candidate phagocytosis receptor of Drosophila hemocytes/macrophages, increased in l(2) mbn cells after treatment with 20-hydroxyecdysone, whereas that of Draper, another candidate phagocytosis receptor, remained unchanged. However, apoptotic cell phagocytosis was reduced when the expression of Draper, but not of Croquemort, was inhibited by RNA interference in hormone-treated l(2) mbn cells. We next examined whether Draper is responsible for the phagocytosis of apoptotic cells in vivo using an assay for engulfment based on assessing DNA degradation of apoptotic cells in dICAD mutant embryos (which only occurred after ingestion by the phagocytes). RNA interference-mediated decrease in the level of Draper in embryos of mutant flies was accompanied by a decrease in the number of cells containing fragmented DNA. Furthermore, histochemical analyses of dispersed embryonic cells revealed that the level of phagocytosis of apoptotic cells by hemocytes/macrophages was reduced when Draper expression was inhibited. These results indicate that Drosophila hemocytes/macrophages execute Draper-mediated phagocytosis to eliminate apoptotic cells.