Schematic diagram of autophagic progression. Autophagy induction signal leads to form a sequestering membrane called phagophore. Following a sequence of ubiquitination-like reactions, LC3 conjugates to the sequestering membrane and controls the elongation of phagophore. As the phagophore expands, cytoplasmic constituents, including organelles such as mitochondria and endoplasmic reticulum, aggregated proteins and foreign organisms (bacteria and virus) are enwrapped. At the end of elongation, sequestering membrane closes and results in the formation of a double-membrane vesicle, autophagosome. Once the autophagosome is formed, it is delivered to fuse with lysosome to form autolysosome for degradation. Lysosomal hydrolases degrades the cargo together with the inner membrane of autophagosome, and LC3 from the outer membraneas well as the autophagy-derived nutrients are recycled.This autophagic process can act as a mechanism to keep homeostatic balance and support cell survival. However, it can also cause cell death directly or indirectly.