Document Detail


Identification of Akt-independent regulation of hepatic lipogenesis by mammalian target of rapamycin (mTOR) complex 2.
MedLine Citation:
PMID:  22773877     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Mammalian target of rapamycin complex 2 (mTORC2) is a key activator of protein kinases that act downstream of insulin and growth factor signaling. Here we report that mice lacking the essential mTORC2 component rictor in liver (Lrictor(KO)) are unable to respond normally to insulin. In response to insulin, Lrictor(KO) mice failed to inhibit hepatic glucose output. Lrictor(KO) mice also fail to develop hepatic steatosis on a high fat diet and manifest half-normal serum cholesterol levels. This is accompanied by lower levels of expression of SREBP-1c and SREBP-2 and genes of fatty acid and cholesterol biosynthesis. Lrictor(KO) mice had defects in insulin-stimulated Akt Ser-473 and Thr-308 phosphorylation, leading to decreased phosphorylation of Akt substrates FoxO, GSK-3β, PRAS40, AS160, and Tsc2. Lrictor(KO) mice also manifest defects in insulin-activated mTORC1 activity, evidenced by decreased S6 kinase and Lipin1 phosphorylation. Glucose intolerance and insulin resistance of Lrictor(KO) mice could be fully rescued by hepatic expression of activated Akt2 or dominant negative FoxO1. However, in the absence of mTORC2, forced Akt2 activation was unable to drive hepatic lipogenesis. Thus, we have identified an Akt-independent relay from mTORC2 to hepatic lipogenesis that separates the effects of insulin on glucose and lipid metabolism.
Authors:
Minsheng Yuan; Elizabeth Pino; Lianfeng Wu; Michael Kacergis; Alexander A Soukas
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-07-07
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  287     ISSN:  1083-351X     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-08-27     Completed Date:  2012-11-19     Revised Date:  2013-05-07    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  29579-88     Citation Subset:  IM    
Affiliation:
Center for Human Genetics and Diabetes Unit, Department of Medicine, Massachusetts General Hospital, and Department of Medicine, Harvard Medical School, Boston, MA 02114, USA.
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MeSH Terms
Descriptor/Qualifier:
Adaptor Proteins, Signal Transducing / genetics,  metabolism
Animals
Cholesterol / biosynthesis,  genetics
Fatty Acids / genetics,  metabolism
Forkhead Transcription Factors / genetics,  metabolism
GTPase-Activating Proteins / genetics,  metabolism
Gene Expression Regulation / physiology
Glucose / genetics,  metabolism
Glycogen Synthase Kinase 3 / genetics,  metabolism
Hep G2 Cells
Humans
Insulin / genetics,  metabolism
Insulin Resistance / physiology
Lipogenesis / physiology*
Liver / metabolism*
Mice
Mice, Transgenic
Phosphoproteins / genetics,  metabolism
Phosphorylation / physiology
Proto-Oncogene Proteins c-akt / genetics,  metabolism*
Sterol Regulatory Element Binding Protein 1 / genetics,  metabolism
Sterol Regulatory Element Binding Protein 2 / genetics,  metabolism
Trans-Activators / genetics,  metabolism*
Transcription Factors / genetics,  metabolism*
Tumor Suppressor Proteins / genetics,  metabolism
Grant Support
ID/Acronym/Agency:
K08 DK087941/DK/NIDDK NIH HHS; K08DK087941/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/AKT1S1 protein, human; 0/Adaptor Proteins, Signal Transducing; 0/CRTC2 protein, human; 0/Crtc2 protein, mouse; 0/FOXO1 protein, human; 0/Fatty Acids; 0/Forkhead Transcription Factors; 0/Foxo1 protein, mouse; 0/GTPase-Activating Proteins; 0/Insulin; 0/Phosphoproteins; 0/SREBF1 protein, human; 0/SREBF2 protein, human; 0/Srebf1 protein, mouse; 0/Srebf2 protein, mouse; 0/Sterol Regulatory Element Binding Protein 1; 0/Sterol Regulatory Element Binding Protein 2; 0/TBC1D4 protein, human; 0/Tbc1d4 protein, mouse; 0/Trans-Activators; 0/Transcription Factors; 0/Tumor Suppressor Proteins; 0/proline-rich Akt substrate, 40 kDa protein, mouse; 4JG2LF96VF/tuberous sclerosis complex 2 protein; 50-99-7/Glucose; 57-88-5/Cholesterol; EC 2.7.11.1/AKT2 protein, human; EC 2.7.11.1/Akt2 protein, mouse; EC 2.7.11.1/Proto-Oncogene Proteins c-akt; EC 2.7.11.1/glycogen synthase kinase 3 beta; EC 2.7.11.26/Glycogen Synthase Kinase 3

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