Institute of Biochemistry I, Medical Faculty, University Hospital Cologne, 50931 Cologne, Germany.
Department of Biology, Texas A & M University, Laredo, TX 77843-3474, USA.
Cells. 2019 Jan 19;8(1):72. doi: 10.3390/cells8010072.
Autophagy is a highly conserved intracellular degradative pathway that is crucial for cellular homeostasis. During autophagy, the core autophagy protein ATG12 plays, together with ATG5 and ATG16, an essential role in the expansion of the autophagosomal membrane. In this study we analyzed gene replacement mutants of in AX2 wild-type and ATG16‾ cells. RNA analysis revealed a strong enrichment of, firstly, autophagy genes among the up-regulated genes and, secondly, genes implicated in cell motility and phagocytosis among the down-regulated genes in the generated ATG12‾, ATG16‾ and ATG12‾/16‾ cells. The mutant strains showed similar defects in fruiting body formation, autolysosome maturation, and cellular viability, implying that ATG12 and ATG16 act as a functional unit in canonical autophagy. In contrast, ablation of ATG16 or of ATG12 and ATG16 resulted in slightly more severe defects in axenic growth, macropinocytosis, and protein homeostasis than ablation of only ATG12, suggesting that ATG16 fulfils an additional function in these processes. Phagocytosis of yeast, spore viability, and maximal cell density were much more affected in ATG12‾/16‾ cells, indicating that both proteins also have cellular functions independent of each other. In summary, we show that ATG12 and ATG16 fulfil autophagy-independent functions in addition to their role in canonical autophagy.
自噬是一种高度保守的细胞内降解途径，对细胞内稳态至关重要。在自噬过程中，核心自噬蛋白 ATG12 与 ATG5 和 ATG16 一起，在自噬体膜的扩展中发挥着重要作用。在这项研究中，我们分析了 AX2 野生型和 ATG16‾细胞中 的基因替换突变体。RNA 分析显示，首先，在被上调的基因中，大量富集了自噬基因，其次，在被下调的基因中，与细胞运动和吞噬作用相关的基因也大量富集。在生成的 ATG12‾、ATG16‾和 ATG12‾/16‾细胞中，突变株在子实体形成、自溶酶体成熟和细胞活力方面表现出相似的缺陷，这表明 ATG12 和 ATG16 在经典自噬中作为一个功能单元发挥作用。相比之下，ATG16 的缺失或 ATG12 和 ATG16 的缺失导致在无菌生长、巨胞饮和蛋白质稳态方面的缺陷比仅 ATG12 的缺失略为严重，这表明 ATG16 在这些过程中还具有额外的功能。酵母吞噬作用、孢子活力和最大细胞密度在 ATG12‾/16‾细胞中受到的影响更大，这表明这两种蛋白质在独立于彼此的情况下也具有细胞功能。综上所述，我们表明 ATG12 和 ATG16 除了在经典自噬中发挥作用外，还具有非自噬依赖性的功能。
