Abstract

Mitophagy is an evolutionarily conserved catabolic process that selectively degrades damaged or superfluous mitochondria via autophagy. Although mitophagy is considered to be critical to maintain cellular homeostasis, detailed mechanisms of mitophagy remain largely unknown. In the budding yeast Saccharomyces cerevisiae, the protein N-terminal acetyltransferase A (NatA) complex is important for transcriptional induction of the pro-mitophagic factor Atg32 and efficient degradation of mitochondria under prolonged respiratory conditions. Overexpression of Atg32 only partially recovers mitophagy in cells lacking NatA, raising the possibility that NatA may contribute to mitophagy via additional mechanisms. Here we demonstrate that Atg32 phosphorylation, which is required for facilitating mitophagy, is altered in respiring NatA-deficient cells. Hyperphosphorylation of Atg32 partially rescues mitophagy in cells lacking NatA. Notably, mitophagy is mostly restored in NatA-null cells overexpressing hyperphosphorylated Atg32. Loss of NatA does not impair the interaction of phosphorylated Atg32 with Atg11, a scaffold protein critical for selective autophagy, suggesting that NatA-dependent Atg32 phosphorylation promotes mitophagy independently of Atg32-Atg11 interactions. We propose that NatA-mediated protein N-terminal acetylation acts in Atg32 expression and phosphorylation to drive mitophagy.

中文翻译：

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蛋白质 N 端乙酰转移酶 A 复合物通过促进 Atg32 的表达和磷酸化促进酵母线粒体自噬

摘要

线粒体自噬是一种进化上保守的分解代谢过程，通过自噬选择性降解受损或多余的线粒体。尽管线粒体自噬被认为是维持细胞稳态的关键，但线粒体自噬的详细机制在很大程度上仍然未知。在萌芽酵母酿酒酵母中，蛋白质 N 末端乙酰转移酶 A (NatA) 复合物对于促线粒体自噬因子 Atg32 的转录诱导和在长时间呼吸条件下线粒体的有效降解很重要。Atg32 的过表达仅部分恢复缺乏 NatA 的细胞中的线粒体自噬，这增加了 NatA 可能通过其他机制促进线粒体自噬的可能性。在这里，我们证明了促进线粒体自噬所需的 Atg32 磷酸化在呼吸 NatA 缺陷细胞中发生了改变。Atg32 的过度磷酸化部分挽救了缺乏 NatA 的细胞中的线粒体自噬。值得注意的是，线粒体自噬主要在过度表达过度磷酸化 Atg32 的 NatA 无效细胞中恢复。NatA 的缺失不会损害磷酸化的 Atg32 与 Atg11 的相互作用，Atg11 是一种对选择性自噬至关重要的支架蛋白，表明 NatA 依赖性 Atg32 磷酸化促进线粒体自噬独立于 Atg32-Atg11 相互作用。我们提出 NatA 介导的蛋白质 N 端乙酰化作用于 Atg32 表达和磷酸化以驱动线粒体自噬。