Gigantic macroautophagy in programmed nuclear death of Tetrahymena thermophila
Gigantic macroautophagy in programmed nuclear death of Tetrahymena thermophila
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DOI：
10.4161/auto.6.7.13287
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发表时间：
2010-10-01
期刊：
影响因子：
13.3
通讯作者：
Endoh, Hiroshi
中科院分区：
文献类型：
--
作者：
Akematsu, Takahiko;Pearlman, Ronald E.;Endoh, Hiroshi
四膜虫的程序性核死亡（PND）是一种独特的结合过程，只有亲本细胞核被降解，然后从后代细胞质中消除，而其他共存的细胞核，如新的微核和大核不受影响。考虑到自噬消除在纤毛虫中的重要作用，如废弃细胞器的周转和下一代的产生，预计通过自噬消除的PND将受到严格控制。在这里，我们证明了四膜虫的PND涉及自噬的特殊方面，不同于哺乳动物或酵母的大自噬。当新的大核分化开始时，亲本大核发生了剧烈的变化。单胺尸胺和溶酶体指示剂LysoTracker Red的联合使用表明，在核凝聚之前，亲代大核的包膜改变了其性质，就好像它是一个自噬膜，而没有从细胞质中积累自噬体前结构。随后，溶酶体仅接近亲本大核并定位于包膜，直到最后的吸收阶段。此外，我们发现亲本大核在包膜上显示出某些糖和磷脂酰丝氨酸，这可能是在其他类型的核上没有发现的“攻击我”信号。这些发现表明PND是一个高度复杂的过程，不同于在其他系统中看到的典型的巨噬，它是通过亲代大核膜上的特定分子信号和自噬/溶酶体机制之间的相互作用来完成的。
Programmed nuclear death (PND) in Tetrahymena is a unique process during conjugation, in which only the parental nnacronucleus is degraded and then eliminated from the progeny cytoplasm, but other co-existing nuclei such as new micro- and macronuclei are unaffected. PND through autophagic elimination is expected to be strictly controlled, considering the significant roles in ciliates such as turnover of disused organelles and production of the next generation. Here we demonstrate that PND in Tetrahymena involves peculiar aspects of autophagy, which differ from mammalian or yeast macroautophagy. Drastic change of the parental macronucleus occurs when differentiation of new macronuclei is initiated. Combined use of monodansylcadaverine and a lysosome indicator LysoTracker Red showed that prior to nuclear condensation, the envelope of the parental macronucleus changed its nature as if it is an autophagic membrane, without the accumulation of a pre-autophagosomal structure from the cytoplasm. Subsequently, lysosomes approached only to the parental macronucleus and localized at the envelope until a final resorption stage. In addition, we found that the parental macronucleus exhibits certain sugars and phosphatidylserine on the envelope, which are possible "attack me" signals, that are not found on other types of nuclei. These findings suggest that PND is a highly elaborated process, different from the typical macroautophagy seen in other systems, and is executed through interaction between specific molecular signals on the parental macronuclear envelope and autophagic/lysosomal machineries.