Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA.
J Innate Immun. 2013;5(5):427-33. doi: 10.1159/000351979. Epub 2013 Jun 11.
With regard to cell biology, one area of focus that has shifted back and forth over the years has been the relative emphasis on catabolic versus anabolic processes: the breakdown of glucose, the synthesis of DNA, the oxidation of pyruvate, the biogenesis of membranes, protein degradation, and protein synthesis. Historically, the majority of studies concerned with degradation dealt with the production of energy; however, the analysis of the ubiquitin-proteasome system revealed the importance of protein degradation for controlling various aspects of cell physiology. The ubiquitin-proteasome system is limited primarily to targeting individual proteins for destruction, but cells also have to deal with larger structures that are damaged, potentially toxic or superfluous, and these substrates, including entire organelles, are the purview of autophagy. As a general definition, autophagy encompasses a range of processes in which the cell degrades parts of itself within the lysosome (or the analogous organelle, the vacuole, in yeast and plants), followed by the release and reuse of the breakdown products. Thus, autophagy is in part a mechanism for cellular recycling, but such a definition belies the importance of the different autophagic processes in cell and organismal function and homeostasis. Indeed, defects in autophagy are associated with many human diseases and metabolic disorders. Here, we provide a brief overview of the mechanism of autophagy and some of the physiological roles in which this process is involved.
就细胞生物学而言,多年来一个关注的焦点是在分解代谢和合成代谢过程之间的相对侧重:葡萄糖的分解、DNA 的合成、丙酮酸的氧化、膜的生物发生、蛋白质降解和蛋白质合成。从历史上看,大多数与降解有关的研究都涉及能量的产生;然而,对泛素-蛋白酶体系统的分析揭示了蛋白质降解在控制细胞生理学各个方面的重要性。泛素-蛋白酶体系统主要局限于靶向单个蛋白质进行破坏,但细胞还必须处理受损的、潜在有毒的或多余的较大结构,这些底物包括整个细胞器,都属于自噬的范畴。作为一个一般定义,自噬包含一系列过程,其中细胞在溶酶体(或在酵母和植物中类似的细胞器液泡)内降解自身的部分,然后释放和再利用降解产物。因此,自噬在一定程度上是细胞回收的一种机制,但这种定义掩盖了不同自噬过程在细胞和生物体功能和动态平衡中的重要性。事实上,自噬缺陷与许多人类疾病和代谢紊乱有关。在这里,我们简要概述了自噬的机制以及该过程所涉及的一些生理作用。