Lum Julian J, DeBerardinis Ralph J, Thompson Craig B
Abramson Family Cancer Research Institute, Department of Cancer Biology, University of Pennsylvania School of Medicine, Philadelphia, Philadelphia 19104, USA.
Nat Rev Mol Cell Biol. 2005 Jun;6(6):439-48. doi: 10.1038/nrm1660.
Cells require a constant supply of macromolecular precursors and oxidizable substrates to maintain viability. Unicellular eukaryotes lack the ability to regulate nutrient concentrations in their extracellular environment. So when environmental nutrients are depleted, these organisms catabolize existing cytoplasmic components to support ATP production to maintain survival, a process known as autophagy. By contrast, the environment of metazoans normally contains abundant extracellular nutrients, but a cell's ability to take up these nutrients is controlled by growth factor signal transduction. Despite evolving the ability to maintain a constant supply of extracellular nutrients, metazoans have retained a complete set of autophagy genes. The physiological relevance of autophagy in such species is just beginning to be explored.
细胞需要持续供应大分子前体和可氧化底物以维持生存能力。单细胞真核生物缺乏调节细胞外环境中营养物质浓度的能力。因此，当环境营养物质耗尽时，这些生物体会分解现有的细胞质成分以支持ATP的产生来维持生存，这一过程称为自噬。相比之下，后生动物的环境通常含有丰富的细胞外营养物质，但细胞摄取这些营养物质的能力受生长因子信号转导的控制。尽管后生动物已经进化出维持细胞外营养物质持续供应的能力，但它们仍保留了一整套自噬基因。自噬在这类物种中的生理相关性才刚刚开始被探索。
