In response to nutrient deficiency, eukaryotic cells activate macroautophagy, a degradative process in which proteins, organelles and cytoplasm are engulfed within unique vesicles called autophagosomes. Fusion of these vesicles with the endolysosomal compartment leads to breakdown of the sequestered material into amino acids and other simple molecules, which can be used as nutrient sources during periods of starvation. This process is driven by a group of autophagy-related (Atg) proteins, and is suppressed by TOR (target of rapamycin) signalling under favourable conditions. Several distinct kinase complexes have been implicated in autophagic signalling downstream of TOR. In yeast, TOR is known to control autophagosome formation in part through a multiprotein complex containing the serine/threonine protein kinase Atg1. Recent work in Drosophila and mammalian systems suggests that this complex and its regulation by TOR are conserved in higher eukaryotes, and that Atg1 has accrued additional functions including feedback regulation of TOR itself. TOR and Atg1 also control the activity of a second kinase complex containing Atg6/Beclin 1, Vps (vacuolar protein sorting) 15 and the class III PI3K (phosphoinositide 3-kinase) Vps34. During autophagy induction, Vps34 activity is mobilized from an early endosomal compartment to nascent autophagic membranes, in a TOR- and Atg1-responsive manner. Finally, the well-known TOR substrate S6K (p70 ribosomal protein S6 kinase) has been shown to play a positive role in autophagy, which may serve to limit levels of autophagy under conditions of continuously low TOR activity. Further insight into these TOR-dependent control mechanisms may support development of autophagy-based therapies for a number of pathological conditions.
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February 2009
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Conference Article|
January 20 2009
Nutrient-dependent regulation of autophagy through the target of rapamycin pathway
Yu-Yun Chang;
Yu-Yun Chang
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
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Gábor Juhász;
Gábor Juhász
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
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Pankuri Goraksha-Hicks;
Pankuri Goraksha-Hicks
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
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Andrew M. Arsham;
Andrew M. Arsham
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
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Daniel R. Mallin;
Daniel R. Mallin
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
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Laura K. Muller;
Laura K. Muller
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
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Thomas P. Neufeld
Thomas P. Neufeld
1
1Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, U.S.A.
1To whom correspondence should be addressed (email neufe003@umn.edu).
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Publisher: Portland Press Ltd
Received:
September 30 2008
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2009 Biochemical Society
2009
Biochem Soc Trans (2009) 37 (1): 232–236.
Article history
Received:
September 30 2008
Citation
Yu-Yun Chang, Gábor Juhász, Pankuri Goraksha-Hicks, Andrew M. Arsham, Daniel R. Mallin, Laura K. Muller, Thomas P. Neufeld; Nutrient-dependent regulation of autophagy through the target of rapamycin pathway. Biochem Soc Trans 1 February 2009; 37 (1): 232–236. doi: https://doi.org/10.1042/BST0370232
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