General pathology · Cell injury, adaptation and death
Autophagy !
- Process
Autophagy means self-eating: the cell wraps worn-out parts in a membrane and sends them to the lysosome to be recycled.
Updated 2026-11-01
What it is
Autophagy is the cell’s recycling system for old organelles, protein clumps and some microbes. Starvation and stress switch it on, mainly by turning off mTOR and turning on AMPK. It helps cells survive nutrient shortage and keeps them clean; when it fails, damaged proteins and mitochondria accumulate. It is involved in atrophy, aging, neurodegeneration, inflammatory bowel disease and cancer.
Key facts
- Three types: macroautophagy (the main one), microautophagy and chaperone-mediated autophagy.
- In cancer it is double-edged: it suppresses early tumours but helps established tumours survive stress.
- Danon disease (LAMP2 deficiency) shows autophagic vacuoles in heart and skeletal muscle.
- Atrophic cells contain more autophagic vacuoles.
Step by step
- Nutrients fall or the cell is stressed: mTOR is inhibited and AMPK is activated.
- The ULK1 complex starts a cup-shaped membrane, the phagophore, near the ER.
- The Beclin-1 and VPS34 complex expands the membrane; LC3 is attached to it.
- The membrane closes around the cargo to form a double-membrane autophagosome.
- The autophagosome fuses with a lysosome to form an autolysosome.
- Lysosomal enzymes digest the cargo; amino acids and fatty acids return to the cytosol for reuse.
Clinical notes
- mTOR inhibitors (for example in transplant medicine) also stimulate autophagy.
- Failure to clear aggregated proteins by autophagy is a shared theme in Alzheimer, Parkinson and Huntington disease.
Test yourself
Think of the answer, then tap the question to see it.
Which nutrient sensor normally inhibits autophagy?
mTOR; when nutrients are scarce mTOR is inhibited and autophagy starts.
Which protein marks the autophagosome membrane?
LC3, which is lipidated and attached to the growing membrane.
Which gene links autophagy to Crohn disease?
ATG16L1; certain variants raise susceptibility.
Related
- Atrophy
- Endoplasmic reticulum stress and the unfolded protein response
- Pigments in tissue: lipofuscin, hemosiderin, melanin, bilirubin, carbon
- Cellular aging: telomeres, DNA damage, senescence and proteostasis
- Apoptosis: the intrinsic and extrinsic pathways
Related conditions
- Crohn disease
- Parkinson disease
- Alzheimer disease
- Huntington disease
- Pompe disease (glycogen storage disease type II)
- Sarcopenia
Elsewhere in DurgiPedia
- Ubiquitin–proteasome system
- mTOR (mechanistic target of rapamycin)
- AMP-activated protein kinase (AMPK)
- Lysosomal storage diseases
- Cell organelles and their metabolism
- Organelles: nucleus, ER, Golgi, mitochondria, lysosomes, peroxisomes
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Danon disease: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2024); What is a cell?: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2024).
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Representative model, for educational purposes only.