title: Autophagy in metazoans: cell survival in the land of plenty.
abstract: Cells require a constant supply of macromolecular precursors and oxidizable substrates to maintain viability. Unicellular eukaryotes lack the ability to regulate nutrient concentrations in their extracellular environment. So when environmental nutrients are depleted, these organisms catabolize existing cytoplasmic components to support ATP production to maintain survival, a process known as autophagy. By contrast, the environment of metazoans normally contains abundant extracellular nutrients, but a cell's ability to take up these nutrients is controlled by growth factor signal transduction. Despite evolving the ability to maintain a constant supply of extracellular nutrients, metazoans have retained a complete set of autophagy genes. The physiological relevance of autophagy in such species is just beginning to be explored.
authors.affiliation: Abramson Family Cancer Research Institute, Department of Cancer Biology, University of Pennsylvania School of Medicine, Philadelphia, Philadelphia 19104, USA.
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Lum
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: DeBerardinis
authors.forename: Craig B
authors.initials: CB
authors.lastname: Thompson
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics / Q000502:physiology; D002470:Cell Survival; D004734:Energy Metabolism; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D046529:Microscopy, Electron, Transmission; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases
chemical_list: D006133:Growth Substances; D011518:Proto-Oncogene Proteins; D011494:Protein Kinases; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases