chapter  1
Autophagy: An Overview
Pages 10

As can be seen in the above paragraph, there are many types of degradative processes. These are described in detail in the following chapters. For a brief overview, I refer the reader to (Fig. 1), which shows the various pathways used for delivery of proteins and organelles to the lysosome or the analogous yeast organelle, the vacuole. The best characterized of these pathways is macroautophagy, which typically involves the formation of a double-membrane cytosolic vesicle. Through most of the book, the term “autophagy” is used synonymously with macroautophagy except where otherwise specified. The degradation of organelles such as peroxisomes, by a process termed pexophagy, can occur by a macroautophagy-like process. However, organelle degradation, and possibly that of bulk cytosol, can also occur through a microautophagic pro­ cess. In this case, uptake occurs at the surface of the lysosome/vacuole and presumably does not involve a separate membrane (although the role of an additional membrane source cannot be ruled out). As described below, other degradative processes involve direct translocation across the lysosome membrane or sequestration within single-membrane cytosolic vesicles. Thus, there are many variations on the mechanisms used for subcellular degradation.