黑腹果蝇CED-8同源蛋白调控细胞凋亡PS外翻的分子机制研究

Apoptosis is one of the important ways of programmed cell death. During apoptosis, phosphatidylserine (PS), normally restricted to the inner leaflet of the plasma membrane, is exposed on the surface of apoptotic cells and serves as an ‘eat-me’ signal to trigger phagocytosis. Previous studies have showed that Xkr8 in mammals and its homologue in Caenorhabditis elegans, CED-8 are activated during apoptosis through cleavage by caspase-3(CED-3), that promotes PS externalization in apoptotic cells. However, it is poorly understood how PS exposure is activated in apoptotic cells. In this study, we found that the homologue of Xkr8 in Drosophila melanogaster (CG32579, dCED-8) has no caspase cleavage site. However, dced-8 RNAi treatment to S2 cells significantly interfered PS externalization during apoptosis, which indicated that dCED-8 may regulate PS externalization without caspase activation. We plan to use Drosophila and Drosophila S2 cells as a model, to study how dCED-8 plays role in regulating PS externalization and promotes cell engulfment, thus provide more theoretical basis to study apoptosis and phygocytosis.

细胞凋亡是程序性细胞死亡的重要方式之一。细胞凋亡发生时，磷脂酰丝氨酸（PS）从细胞膜内侧外翻到细胞膜外侧，作为“eat-me”信号招募吞噬细胞识别并清除凋亡细胞。因此，PS外翻对于细胞凋亡的识别及清除非常重要。研究发现哺乳动物Xkr8及秀丽线虫同源蛋白CED-8在凋亡信号启动后被caspase-3(CED-3)特异性切割，切割产物可促进PS外翻，但其具体分子机制尚不清楚。黑腹果蝇中Xkr8的同源蛋白CG32579（dCED-8）上并没有caspase识别位点，但我们的前期工作发现，降低其表达可抑制凋亡发生时的PS外翻，表明黑腹果蝇中dCED-8可能不依赖于caspase调控PS外翻。本研究拟以黑腹果蝇这一优异的模式动物为载体，研究dCED-8调控PS外翻的分子机制及其对凋亡细胞清除的作用，此项课题的完成有助于我们揭示凋亡细胞清除障碍所致疾病的发病机制。

细胞凋亡是程序性细胞死亡的重要方式之一。细胞凋亡发生时，磷脂酰丝氨酸（PS）从细胞膜内侧外翻到细胞膜外侧，作为“eat-me”信号招募吞噬细胞识别并清除凋亡细胞。因此，PS外翻对于细胞凋亡的识别及清除非常重要。研究发现哺乳动物Xkr8及秀丽线虫同源蛋白CED-8在凋亡信号启动后被caspase-3(CED-3)特异性切割，切割产物可促进PS外翻。我们的前期工作发现，黑腹果蝇中Xkr8的同源蛋白CG32579（dCED-8）具有caspase切割位点，其突变可抑制凋亡发生时的PS外翻。本研究还发现黑腹果蝇dCED-8突变体不仅抑制PS外翻，还抑制了吞噬细胞对凋亡细胞的识别。dCED-8通过和跨膜蛋白TM9SF4及PS非囊泡运输相关蛋白Sac1、CG3860、Vap33等相互作用促进细胞凋亡期间的PS外翻及吞噬细胞对凋亡细胞清除的作用，此项课题的完成有助于我们揭示凋亡细胞清除障碍所致疾病的发病机制。

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