Forms, Crosstalks, and the Role of Phospholipid Biosynthesis in Autophagy
Figure 2
Microautophagy. A direct invagination of a vesicular membrane (lysosome and/or endosome) takes in cytoplasm from the surrounding environment (a). This invagination continues and forms a narrow tube which elongates into the interior of the vacuole (b). This tube is referred to as the autophagic tube and is continuous with the cytoplasm. Entire organelles or compounds within the taken up cytoplasm are degraded within the lumen of the vacuole (if taken in via the lysosome) or fusion with a lysosome occurs, which results in the breakdown of the captured cytosolic components. As the tube reaches the interior of the vacuole, the proximal ends form a bulge referred to as the autophagic body (c). This bulging end is thicker than the tube leading into the vacuole. The walls of the bulging end of the autophagic tube will then fuse, pinching off into the inner portions of the lysosome (d). The cytosolic components trapped within the vesicle are then degraded within the vesicle (lysosome or vacuole) or the vesicle (endosome) will later fuse with a lysosome, where the components are then degraded.
