Figure 1.

Diagram illustrates three types of autophagy, autophagosome formation, and autophagic signaling. Three types of autophagy, macroautophagy, microautophagy, and chaperon-mediated autophagy (CMA) have been found in eukaryotic cells. Macroautophagy is the most common type found in mammalian cells which proceeds through several steps including initiation, nucleation, expansion/elongation to form autophagosome, and fusion of autophagosome-lysosome to become autolysosome. These steps are performed by autophagy-related (Atg) proteins and other autophagic proteins, and regulated by different types of stress and signals, such as DNA damage, endoplasmic reticulum (ER) stress, growth factors or insulin, hypoxia, and amino acid depletion.