What is the process of autophagy?

Autophagy is a highly regulated cellular mechanism that involves 5 distinct stages: 

1. Initiation - Autophagy is initiated when the cell undergoes some sort of stress or due to depletion of nutrients or growth factors in the media. When either of these occur, stress signals prompt the cell to initiate autophagy. These stress signals serve as cellular cues that trigger the commencement of the autophagic process. 
2. Phagophore Formation - Following the initiation phase, the cell initiates the formation of specialized double-membrane structures called phagophores. These phagophores encapsulate damaged and dysfunctional cellular components (cargo) for degradation or recycling. 
3. Autophagosome Formation - Phagophores expand to completely enclose the cargo, developing into fully formed membrane-bound vesicles called autophagosomes. Autophagosomes serve as the primary transport vehicles for the encapsulated cellular material, effectively packaging and sequestering it for subsequent processing.
4. Fusion with Lysosome - Autophagosomes fuse with lysosomes, which are organelles containing powerful degrading enzymes capable of breaking down cellular components. This fusion merges the contents of the autophagosomes to the degrading enzymes present in the lysosomes. 
5. Degradation and Recycling - Within the lysosome, the encapsulated cellular components undergo enzymatic degradation. This process breaks the components down into their constituent molecules, rendering them available for recycling or utilization by the cell. In this last stage, redundant cellular components are efficiently disposed of while valuable biomolecules are recycled.