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Insulin-stimulated phosphorylation of lipin mediated by the mammalian target of rapamycin.

Authors: Huffman, TA  Mothe-Satney, I  Lawrence JC, JR 
Citation: Huffman TA, etal., Proc Natl Acad Sci U S A. 2002 Jan 22;99(2):1047-52. Epub 2002 Jan 15.
Pubmed: (View Article at PubMed) PMID:11792863
DOI: Full-text: DOI:10.1073/pnas.022634399

The phosphorylation of a previously uncharacterized protein of apparent M(r) approximately 140,000 was found to be increased when rat adipocytes were incubated with insulin. The sequences of peptides generated by digesting the protein with trypsin matched perfectly with sequences in mouse lipin. Lipin is the product of the gene that is mutated in fatty liver dystrophy (fld) mice [Peterfy, M., Phan, J., Xu, P. & Reue, K (2001) Nat. Genet. 27, 121-124], which exhibit several phenotypic abnormalities including hyperlipidemia, defects in adipocyte differentiation, impaired glucose tolerance, and slow growth. When immunoblots were prepared with lipin antibodies, both endogenous adipocyte lipin and recombinant lipin overexpressed in HEK293 cells appeared as bands ranging in apparent M(r) from 120,000 to 140,000. Incubating adipocytes with insulin decreased the electrophoretic mobility and stimulated the phosphorylation of both Ser and Thr residues in lipin. The effects of insulin were abolished by inhibitors of phosphatidylinositol 3-OH kinase, and by rapamycin, a specific inhibitor of the mammalian target of rapamcyin (mTOR). The inhibition by rapamycin was blocked by FK506, which competitively inhibits those effects of rapamycin that are mediated by inhibition of mTOR. Moreover, amino acids, which activate mTOR, mimicked insulin by increasing lipin phosphorylation in a rapamycin-sensitive manner. Thus, lipin represents a target of the mTOR pathway, and potentially links this nutrient-sensing pathway to adipocyte development.

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CRRD Object Information
CRRD ID: 1641823
Created: 2007-08-23
Species: All species
Last Modified: 2007-08-23
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.