Mechanism of increased PLD1 gene expression during early adipocyte differentiation process of mouse cell line 3T3-L1.
A mouse cell line 3T3-L1 is differentiated into adipocytes when treated with an inducer cocktail (IDX) (insulin, dexametahsone, and a cAMP phosphodiesterase inhibitor of isobutyl-methylxanthine (IBMX)). Here, we report that PLD1, but not PLD2, mRNA and protein increased during the early differentiation process. Our analysis shows that IDX resulted in a sequential induction of C/EBPbeta, PLD1, and C/EBPalpha which is a key transcription factor of late adipocyte differentiation. Among the three inducers, IBMX + any other inducer induced mild adipocyte differentiation, whereas insulin + dexamethasone did not. IBMX increased PLD1 but not PLD2 mRNA. Forskolin, an adenylate cyclase activator, and dbcAMP also increased PLD1 mRNA, suggesting the cellular cAMP as the inducer of both adipocyte differentiation and PLD1 transcription. We focused on the regulatory mechanism of PLD1 transcription during this differentiation process. IDX or a combination of inducers including IBMX increased PLD1 promoter activity, which is consistent with mRNA analysis. Promoter analysis identified two adjacent C/EBP motifs located between -338 and -231 bp from the first exon as the IBMX responsive elements. Furthermore, overexpression of C/EBPbeta, but not C/EBPalpha, increased PLD1 mRNA and PLD1 5' promoter activity. EMSA and chromatin immunoprecipitation assay confirmed the direct binding of C/EBPbeta, but not C/EBPalpha, to these C/EBP motifs of PLD1 5' promoter. Our results show that PLD1 is a target gene of C/EBPbeta through the increased cellular cAMP during early adipocyte differentiation of 3T3-L1 cells.
Gao
Siqiang
S
Department of Medical Technology, Nagoya University Graduate School of Health Sciences, Nagoya, Japan.
Ito
Hiromi
H
Murakami
Masashi
M
Yoshida
Kayo
K
Tagawa
Yoko
Y
Hagiwara
Kazumi
K
Takagi
Akira
A
Kojima
Tetsuhito
T
Suzuki
Motoshi
M
Banno
Yoshiko
Y
Ohguchi
Kenji
K
Nozawa
Yoshinori
Y
Murate
Takashi
T
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D050156:Adipogenesis / Q000235:genetics*; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010739:Phospholipase D / Q000235:genetics* / Q000378:metabolism; D020218:Response Elements
D022763:CCAAT-Enhancer-Binding Protein-alpha; D022782:CCAAT-Enhancer-Binding Protein-beta; D007328:Insulin; D010726:Phosphodiesterase Inhibitors; D003907:Dexamethasone; D000242:Cyclic AMP; C105606:phospholipase D2; D010739:Phospholipase D; C106801:phospholipase D1; D015056:1-Methyl-3-isobutylxanthine