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Autophagy, or autophagocytosis, is a process of organelle degradation that takes place inside the cell. It is executed by lysosomes and is part of everyday normal cell growth and development. Its main purpose is to maintain a balance between biogenesis (production) of cell structures, and their degradation and turnover (see Bruce Alberts et al.: Molecular biology of the cell, 3rd edition, Garland Publishing 1994, p. 613 [1] (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=autophagy+AND+cell%5Bbook%5D+AND+7405%5Buid%5D&rid=cell.section.3155#3165)). For example, a liver-cell mitochondrion lasts around ten days before it is degraded and its contents are reused.
The rate of autophagy increases when the cell is subjected to food deprivation, and also when it receives stimuli that result in organelle proliferation.
When autophagy involves the total destruction of the cell, it is called autophagic cell death (also known as cytoplasmic cell death). This is one of the main types of programmed cell death. As such, it is a regulated process of cell death in a multicellular organism, or in a colony of individual cells such as yeast (see Daniel J. Klionsky and Scott D. Emr: "Autophagy as a Regulated Pathway of Cellular Degradation", Science Vol. 290 p.1717, 1 Dec. 2000 [2] (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11099404)).
Both micro and macroautophagy serve fundamental functions in plants and metazoa (multicellular animals), as well as in other eukaryotes such as slime moulds and yeast.
Further reading
- D. J. Klionsky, Editor: Autophagy (Landes Bioscience, Georgetown, Tx, 2004)
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