| الوصف: |
In autophagy a cellular recycling process, excess, or damaged cellular components are shuttled to the lysosome for degradation and their resultant building blocks can be reused. Macro-autophagy, but not micro-autophagy, occurs via autophagosomes and is dependent on a conserved set of autophagy-specific proteins termed Atgs. While autophagy has been studied extensively under stress conditions, it also occurs under normal growth conditions. The endoplasmic reticulum (ER), which spans throughout the cell, is the site where newly synthesized membrane proteins and lipids are inserted into the membrane before being transported to other organelles. A rigorous quality control (QC) mechanism termed ER-associated degradation (ERAD) ensures that only properly folded proteins leave the ER, and autophagy was proposed as a backup mechanism to ERAD. Ten years ago, selective autophagy of the ER, termed ER-phagy or reticulophagy, induced by ER stress, was described in yeast. However, later it became clear that this process is independent of Atgs, and therefore belongs to the micro-autophagy type. Recently, two types of macro-ER-phagy were characterized in yeast and mammalian cells: starvation induced and QC. Here, we summarize what is currently known about the different types of ER-phagy, highlight differences between them, and discuss future questions. |
