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Papers In Press, published online ahead of print January 10, 2008
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transcriptional activity
Applied Biological Chemistry, Graduate school of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657
Corresponding Author: aroysato{at}mail.ecc.u-tokyo.ac.jp
In the course of an effort to identify the regulators for peroxisome proliferators-activated receptor (PPAR)
-dependent perilipin gene expression, we have found that tribbles homolog 3 (TRB3), containing a single kinase domain without enzymatic activity, downregulates PPAR
transcriptional activities by protein-protein interaction. We examined the role TRB3 plays in adipocyte differentiation in 3T3-L1 cells. TRB3 gene and protein expression was increased during adipocyte differentiation concomitantly with an increase in the mRNA levels of CCAAT/enhancer binding protein homologous protein (CHOP). The physical interaction between TRB3 and PPAR
was also verified in 3T3-L1 adipocytes. Forced TRB3 expression in 3T3-L1 cells decreased the mRNA levels of PPAR
-target genes and intracellular triglyceride levels, while knockdown of TRB3 expression by RNA interference (RNAi) elevated them. TRB3 also inhibits PPAR
-dependent adipocyte differentiation in lentiviral mediated PPAR
-expressing 3T3-L1 cells. These results provide evidence that TRB3 acts as a potent negative regulator of PPAR
, a master regulator of adipocyte differentiation, and tightly controls adipogenesis.
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