Every cell in our body is equipped with a form of housecleaning machinery
called autophagy. Autophagy is universally present in all
cells from yeast to humans. During nutrient starvation, autophagic processes
promote cell survival by degrading superfluous cytoplasmic proteins and
organelles.
The cytoplasmic cargo is captured by a cup-shaped structure (phagophore),
which elongates and expands to form vesicles called
autophagosomes. These autophagosomes fuse with the
lysosomes, where lysosomal proteases degrade the cargo into basic building
blocks that are then recycled.
Autophagy is not only involved in clearing superfluous and unwanted cellular
components, but is also known to degrade several intracellular pathogens,
including bacteria (Salmonella, Shigella, Mycobacterium, Group A
Streptococcus) and viruses (herpes simplex virus, HIV, etc.).
Autophagy also serves a neuroprotective role, clearing large aggregates of
mutant polyubiquitylated proteins that are resistant to proteasomal
degradation.
Furthermore, beyond neurodegenerative and infectious diseases, autophagy has
been shown to play roles in heart diseases, atherosclerosis, certain
myopathies, immune responses (both innate and adaptive), Crohn's disease,
and cancer.
