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Rapamycin‐sensitive phase of 3T3‐L1 preadipocyte differentiation after clonal expansion
Author(s) -
Gag Annemarie,
Lau Stephen,
Sorisky Alexander
Publication year - 2001
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1132
Subject(s) - adipogenesis , pi3k/akt/mtor pathway , p70 s6 kinase 1 , biology , microbiology and biotechnology , mechanistic target of rapamycin , protein kinase a , kinase , maturation promoting factor , mtorc1 , cell cycle , biochemistry , signal transduction , cyclin , apoptosis , mesenchymal stem cell
Inhibition of insulin‐induced 3T3‐L1 preadipocyte differentiation by rapamycin has been attributed to a blockade of the early critical clonal expansion phase of the adipogenic program. Rapamycin binds to, and inhibits, mTOR (mammalian target of rapamycin), leading to diminution of p70 S6 kinase activity and eukaryotic initiation factor 4E binding protein 1 (eIF4E‐BP1) function. Our objective was to determine if rapamycin‐sensitive pathways exist subsequent to the clonal expansion phase. We determined that the mitotic clonal expansion was complete by day 4 of the differentiation protocol, based on the response to Ara‐C (cytosine β‐ d ‐arabinofuranoside), which only inhibits differentiation when administered during this phase. Treatment of differentiating 3T3‐L1 cells with rapamycin, starting on day 4, exerted potent negative effects on glycerol phosphate dehydrogenase activity, and triacylglycerol accumulation, as well as on the protein expression of adipogenic transcription factors, C/EBPα and PPARγ. Insulin‐stimulated p70 S6 kinase activity, and its inhibition by rapamycin, were comparable in preadipocytes at day 0 vs. day 4 post‐differentiation. We conclude that a component of the adipogenic program, operating after the completion of clonal expansion, is inhibited by rapamycin, suggesting an ongoing need for mTOR function in this process. © 2001 Wiley‐Liss, Inc.