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Figure 1. Autophagy. There are three types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy. Macroautophagy is a type of autophagy that delivers cellular contents to the lysosome via the formation of double-membrane structures called autophagosomes which then fuse with lysosomes to form autolysosomes. Macroautophagy takes place in five main steps. Initiation of autophagy occurs in response to metabolic or therapeutic stress and is mediated by ULK1, ATG13, FIP200, and ATG101. During the nucleation step regulated by BECLIN-1, ATG14L, VPS15, and VPS34, the formation of the phagophore occurs. Expansion results in the sequestration of cytosolic contents within the autophagosome and is facilitated by ATG5, ATG12, ATG16L, and LC3-PE. Degradation is the breakdown of autophagosomal contents upon formation of the autolysosome (fusion of autophagosome and lysosome). Microautophagy is a largely non-selective process that facilitates the direct uptake and breakdown of cytosolic cargo by lysosomes. Chaperone-mediated autophagy refers to the chaperone-dependent targeting of specific cytosolic proteins to lysosomes for proteolysis. HSC70 binds to the consensus motif of specific proteins to target them to the lysosome-associated membrane protein type 2A (LAMP-2A) receptor on the lysosomal membrane. Once internalized by the lysosome, these cytosolic proteins are degraded