What is the mechanism of autophagy?

Autophagy is a complex but tightly regulated cellular process in which malformed and dysfunctional cellular components are encapsulated, broken down and recycled within the cell, thus helping to maintain nutrient and energy homeostasis. 

The mechanism of autophagy involves the creation of a specialized double-membrane structure known as autophagosome. The autophagosome encapsulates and breaks down certain cellular components such as aged and misfolded proteins and organelles. The process is orchestrated by a complex network of autophagy-related (Atg) proteins and two ubiquitin-like conjugation systems, ultimately leading to the fusion of autophagosomes and lysosomes for degradation and recycling within the cell. 

The autophagy process takes place over 5 distinct phases, which include initiation, vesicle nucleation, vesicle elongation, vesicle fusion and cargo degradation.