Direct induction of autophagy by Atg1 inhibits cell growth and induces apoptotic cell death
Direct induction of autophagy by Atg1 inhibits cell growth and induces apoptotic cell death
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DOI：
10.1016/j.cub.2006.10.053
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发表时间：
2007-01-09
期刊：
影响因子：
9.2
通讯作者：
Neufeld, Thomas P.
中科院分区：
文献类型：
--
作者：
Scott, Ryan C.;Juhasz, Gabor;Neufeld, Thomas P.
背景：为了在饥饿和其他形式的应激下生存，真核细胞经历细胞质降解的溶酶体过程，称为自噬。自噬与许多细胞和发育过程有关，包括细胞生长控制和程序性细胞死亡。然而，缺乏自噬在这些过程中因果作用的直接证据，部分原因是信号分子（例如调节自噬的 TOR）的多效性作用。在这里，我们通过自噬特异性蛋白激酶 Atg1 直接操纵果蝇中的自噬率，从而规避了这一困难。结果：我们发现 Atg1 的过度表达足以诱导高水平的自噬，这是野生型 Atg 蛋白中的首次此类证明。与酵母中的发现相反，Atg1 诱导自噬依赖于其激酶活性。我们发现Atg1诱导的自噬水平高的细胞被迅速消除，这表明自噬能够诱导细胞死亡。然而，这种细胞死亡是半胱天冬酶依赖性的，并表现出 DNA 片段化，表明自噬代表细胞凋亡的另一种诱导，而不是一种独特的细胞死亡形式。此外，我们证明Atg1诱导的自噬强烈抑制细胞生长，并且Atg1突变细胞在TOR信号传导减弱的条件下具有相对的生长优势。最后，我们表明 Atg1 表达会导致 TOR 本身活性的负反馈。结论：我们的结果揭示了 Atg1 在协调自噬反应中的核心作用，并证明自噬具有诱导细胞死亡的能力。此外，这项工作将自噬确定为一种关键机制，通过抑制 TOR 信号传导可导致细胞生长减少。
Background: To survive starvation and other forms of stress, eukaryotic cells undergo a lysosomal process of cytoplasmic degradation known as autophagy. Autophagy has been implicated in a number of cellular and developmental processes, including cell-growth control and programmed cell death. However, direct evidence of a causal role for autophagy in these processes is lacking, resulting in part from the pleiotropic effects of signaling molecules such as TOR that regulate autophagy. Here, we circumvent this difficulty by directly manipulating autophagy rates in Drosophila through the autophagy-specific protein kinase Atg1.Results: We find that overexpression of Atg1 is sufficient to induce high levels of autophagy, the first such demonstration among wild-type Atg proteins. In contrast to findings in yeast, induction of autophagy by Atg1 is dependent on its kinase activity. We find that cells with high levels of Atg1-induced autophagy are rapidly eliminated, demonstrating that autophagy is capable of inducing cell death. However, this cell death is caspase dependent and displays DNA fragmentation, suggesting that autophagy represents an alternative induction of apoptosis, rather than a distinct form of cell death. In addition, we demonstrate that Atg1-induced autophagy strongly inhibits cell growth and that Atg1 mutant cells have a relative growth advantage under conditions of reduced TOR signaling. Finally, we show that Atg1 expression results in negative feedback on the activity of TOR itself.Conclusions: Our results reveal a central role for Atg1 in mounting a coordinated autophagic response and demonstrate that autophagy has the capacity to induce cell death. Furthermore, this work identifies autophagy as a critical mechanism by which inhibition of TOR signaling leads to reduced cell growth.