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Insulin stimulation of SREBP-1c processing in transgenic rat hepatocytes requires p70 S6-kinase

Title
Insulin stimulation of SREBP-1c processing in transgenic rat hepatocytes requires p70 S6-kinase
Authors
Owen J.L.Zhang Y.Bae S.-H.Farooqi M.S.Liang G.Hammer R.E.Goldstein J.L.Brown M.S.
Ewha Authors
배수한
Issue Date
2012
Journal Title
Proceedings of the National Academy of Sciences of the United States of America
ISSN
0027-8424JCR Link
Citation
vol. 109, no. 40, pp. 16184 - 16189
Indexed
SCI; SCIE; SCOPUS scopus
Abstract
Insulin activates sterol regulatory element-binding protein-1c (SREBP-1c) in liver, thereby increasing fatty acid and triglyceride synthesis. We created a line of transgenic rats that produce epitope-tagged human SREBP-1c in liver under control of the constitutive apolipoprotein E promoter/enhancer. This systemallows us to dissect the pathway by which insulin stimulates SREBP-1c processing without interference by the insulin-mediated increase in SREBP-1c mRNA. Rats are used because freshly isolated rat hepatocytes respond much more robustly to insulin than domouse hepatocytes. The data reveal that insulin-mediated stimulation of SREBP-1c processing requires the mechanistic target of rapamycin complex 1 (mTORC1), which also is required for insulin-mediated SREBP-1cmRNA induction. However, in contrast to mRNA induction, insulin stimulation of SREBP-1c processing is blocked by an inhibitor of p70 S6-kinase. The data indicate that the pathways for insulin enhancement of SREBP-1c mRNA and proteolytic processing diverge after mTORC1. Stimulation of processing requires the mTORC1 target p70 S6-kinase, whereas induction of mRNA bypasses this enzyme. Insulin stimulation of both processes is blocked by glucagon. The transgenic rat system will be useful in further defining the molecular mechanism for insulin stimulation of lipid synthesis in liver in normal and diabetic states.
DOI
10.1073/pnas.1213343109
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일반대학원 > 생명·약학부 > Journal papers
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