Apoptosis-dependent Externalization and Involvement in Apoptotic Cell Clearance of DmCaBP1, an Endoplasmic Reticulum Protein of Drosophila
Apoptosis-dependent Externalization and Involvement in Apoptotic Cell Clearance of DmCaBP1, an Endoplasmic Reticulum Protein of Drosophila
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DOI：
10.1074/jbc.m111.277921
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发表时间：
2012-01-27
影响因子：
4.8
通讯作者：
Nakanishi, Yoshinobu
中科院分区：
文献类型：
--
作者：
Okada, Ryo;Nagaosa, Kaz;Nakanishi, Yoshinobu
为了阐明德雷珀，一个负责吞噬清除果蝇凋亡细胞的受体的行动，我们分离的蛋白质结合到细胞外区域的德雷珀使用亲和层析。其中一种蛋白质已被鉴定为一种未表征的蛋白质，称为果蝇钙结合蛋白1（DmCaBP 1）。这种含有硫氧还蛋白样结构域的蛋白质存在于内质网中，似乎在果蝇的整个发育过程中普遍表达。DmCaBP1在诱导细胞凋亡后，在染色质浓缩和DNA切割之前，以依赖于半胱天冬酶活性的方式被外化而不截短。重组DmCaBP 1蛋白结合凋亡细胞和表达德雷珀的血细胞衍生细胞系。DmCaBP 1在细胞表面的强制表达使非凋亡细胞易于被吞噬。果蝇DmCaBP1表达缺陷正常发展，并显示Draper介导的修剪幼虫轴突，但在胚胎中的凋亡细胞的吞噬缺陷进行了观察。失去Pretaporter，一个以前确定的配体德雷珀，并没有导致进一步降低吞噬作用的水平在DmCaBP 1缺乏胚胎。这些结果共同表明，内质网蛋白DmCaBP 1的细胞凋亡的诱导后，外部化，并作为一个拴系分子连接凋亡细胞和吞噬细胞的有效吞噬作用发生。
To elucidate the actions of Draper, a receptor responsible for the phagocytic clearance of apoptotic cells in Drosophila, we isolated proteins that bind to the extracellular region of Draper using affinity chromatography. One of those proteins has been identified to be an uncharacterized protein called Drosophila melanogaster calcium-binding protein 1 (DmCaBP1). This protein containing the thioredoxin-like domain resided in the endoplasmic reticulum and seemed to be expressed ubiquitously throughout the development of Drosophila. DmCaBP1 was externalized without truncation after the induction of apoptosis somewhat prior to chromatin condensation and DNA cleavage in a manner dependent on the activity of caspases. A recombinant DmCaBP1 protein bound to both apoptotic cells and a hemocyte-derived cell line expressing Draper. Forced expression of DmCaBP1 at the cell surface made non-apoptotic cells susceptible to phagocytosis. Flies deficient in DmCaBP1 expression developed normally and showed Draper-mediated pruning of larval axons, but a defect in the phagocytosis of apoptotic cells in embryos was observed. Loss of Pretaporter, a previously identified ligand for Draper, did not cause a further decrease in the level of phagocytosis in DmCaBP1-lacking embryos. These results collectively suggest that the endoplasmic reticulum protein DmCaBP1 is externalized upon the induction of apoptosis and serves as a tethering molecule to connect apoptotic cells and phagocytes for effective phagocytosis to occur.