ECTS2016 Poster Presentations Energy metabolism and bone, fat and bone (11 abstracts)
Cyclic AMP/protein kinase A signalling downregulates Dlx5 expression via inducing C/Ebpβ in 3T3-L1 preadipocytes
Jeong-Hwa Baek 1 , Hye-Lim Lee 1 , Abdul Qadir 1 , Hyun Jeong Kim 1 , Jin Chung 2 , Kyung Mi Woo 1 & Hyun-Mo Ryoo 1
1Seoul National University School of Dentistry, Seoul, Republic of Korea; 2Pusan National University School of Dentistry, Yangsan, Republic of Korea.
Distal-less homeobox 5 (Dlx5) is a transcription factor that enhances osteogenic differentiation of mesenchymal stem cells via upregulating the expression of Runx2 and other osteoblast phenotypic genes. We have previously demonstrated that Dlx5 also downregulates adipogenic differentiation of mesenchymal stem cells and that insulin decreases expression levels of Dlx5 via increasing expression levels of miR-124, a microRNA targeting 3′UTR of Dlx5. However, the mechanism of Dlx5 down-regulation by adipogenic stimuli other than insulin has not been clarified yet. In this study, we examined the effect of cAMP/protein kinase A signalling on the expression of Dlx5 in 3T3-L1 preadipocytic cells. Activation of cAMP/protein kinase A signalling by 3-isobutyl-1-methylxanthine (IBMX), 8CPT-cAMP, foskolin or prostacyclin significantly downregulated the expression levels of Dlx5 mRNA and protein. These stimuli induced CREB phosphorylation and increased expression levels of CREB and C/EBPβ. Forced expression of CREB or C/EBPβ suppressed Dlx5 expression, whereas knockdown of C/EBPβ prevented IBMX from downregulating Dlx5 expression. Overexpression of C/EBPβ significantly decreased the luciferase activity of promoter reporter containing 3 kb murine Dlx5 promoter sequence. Chromatin immunoprecipitation assays demonstrated that IBMX treatment or CREB overexpression increased the binding of C/EBPβ but decreased the binding of RNA polymerase II to the Dlx5 promoter region. These results suggest that cAMP/protein kinase A signalling attenuates Dlx5 transcription via enhancing the binding of C/EBPβ to the Dlx5 promoter.
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