Phagoptosis is a frequently occurring nonautonomous cell death pathway in which phagocytes eliminate viable cells. While it is thought that phosphatidylserine (PS) “eat-me” signals on target cells initiate the process, the precise sequence of events is largely unknown. Here, we show that in Drosophila testes, progenitor germ cells are spontaneously removed by neighboring cyst cells through phagoptosis. Using live imaging with multiple markers, we demonstrate that cyst cell–derived early/late endosomes and lysosomes fused around live progenitors to acidify them, before DNA fragmentation and substantial PS exposure on the germ cell surface. Furthermore, the phagocytic receptor Draper is expressed on cyst cell membranes and is necessary for phagoptosis. Significantly, germ cell death is blocked by knockdown of either the endosomal component Rab5 or the lysosomal associated protein Lamp1, within the cyst cells. These data ascribe an active role for phagocytic cyst cells in removal of live germ cell progenitors.

中文翻译：

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果蝇睾丸中的吞噬囊细胞通过吞噬作用消除生殖细胞祖细胞

吞噬作用是一种经常发生的非自主细胞死亡途径，其中吞噬细胞消除活细胞。虽然人们认为靶细胞上的磷脂酰丝氨酸（PS）“吃我”信号启动了这一过程，但事件的确切顺序在很大程度上是未知的。在这里，我们展示了在果蝇睾丸，祖生殖细胞通过吞噬作用被相邻的囊肿细胞自发去除。使用具有多个标记的实时成像，我们证明囊肿细胞衍生的早期/晚期内体和溶酶体在 DNA 断裂和生殖细胞表面大量 PS 暴露之前融合在活祖细胞周围以酸化它们。此外，吞噬受体 Draper 在囊肿细胞膜上表达，是吞噬作用所必需的。重要的是，生殖细胞死亡被囊肿细胞内内体成分 Rab5 或溶酶体相关蛋白 Lamp1 的敲除所阻断。这些数据归因于吞噬囊细胞在去除活生殖细胞祖细胞中的积极作用。