Document Detail

Isolation of hyperactive mutants of mammalian target of rapamycin.
MedLine Citation:
PMID:  18812319     Owner:  NLM     Status:  MEDLINE    
The mammalian target of rapamycin (mTOR) is a Ser/Thr kinase that plays essential roles in the regulation of a wide array of growth-related processes such as protein synthesis, cell sizing, and autophagy. mTOR forms two functionally distinct complexes, termed the mTOR complex 1 (mTORC1) and 2 (mTORC2); only the former of which is inhibited by rapamycin. Based on the similarity between the cellular responses caused by rapamycin treatment and by nutrient starvation, it has been widely accepted that modulation in the mTORC1 activity in response to nutrient status directs these cellular responses, although direct evidence has been scarce. Here we report isolation of hyperactive mutants of mTOR. The isolated mTOR mutants exhibited enhanced kinase activity in vitro and rendered cells refractory to the dephosphorylation of the mTORC1 substrates upon amino acid starvation. Cells expressing the hyperactive mTOR mutant displayed larger cell size in a normal growing condition and were resistant to cell size reduction and autophagy induction in an amino acid-starved condition. These results indicate that the activity of mTORC1 actually directs these cellular processes in response to nutrient status and confirm the biological functions of mTORC1, which had been proposed solely from loss-of-function analyses using rapamycin and (molecular)genetic techniques. Additionally, the hyperactive mTOR mutant did not induce cellular transformation of NIH/3T3 cells, suggesting that concomitant activation of additional pathways is required for tumorigenesis. This hyperactive mTOR mutant will be a valuable tool for establishing physiological consequences of mTOR activation in cells as well as in organisms.
Yoichiro Ohne; Terunao Takahara; Riko Hatakeyama; Tomoko Matsuzaki; Makoto Noda; Noboru Mizushima; Tatsuya Maeda
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-09-23
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  283     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2008 Nov 
Date Detail:
Created Date:  2008-11-10     Completed Date:  2009-01-07     Revised Date:  2013-09-30    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  31861-70     Citation Subset:  IM    
Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Tokyo 113-0032, Japan.
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MeSH Terms
Cell Line
Cell Size
Enzyme Activation
Gene Expression Regulation, Enzymologic
Mutation / genetics
Protein Kinases / genetics,  metabolism*
Proto-Oncogene Proteins c-akt / metabolism
Signal Transduction
TOR Serine-Threonine Kinases
Transcription Factors / metabolism
Reg. No./Substance:
0/Proteins; 0/Transcription Factors; 0/mechanistic target of rapamycin complex 1; EC 2.7.-/Protein Kinases; EC protein, human; EC Serine-Threonine Kinases; EC protein, mouse; EC Proteins c-akt

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