cAMP-response element binding protein (CREB) positively regulates mouse adiponectin gene expression in 3T3-L1 adipocytes

Adiponectin is expressed in adipose tissue by adipogenic transcription factors including PPARgamma, C/EBPalpha, and ADD1/SREBP1c. Because cAMP-response element binding protein (CREB) is also a central transcriptional activator of adipocyte differentiation, we evaluated CREB to determine if it stimulates adiponectin gene expression. To accomplish this, we evaluated the effects of activated CREB on the promoter activity of the mouse adiponectin gene, and identified the cAMP-response element (CRE) in the promoter. The constitutively active form of CREB increased the promoter activity of the mouse adiponectin gene. In addition, transfection studies using 5' serial deleted promoters revealed the presence of a putative CRE located between the -1250 and -1000bp region. Furthermore, an electrophoresis mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis demonstrated that CREB bound to the region between -1022 and -995 in the adiponectin promoter. Insulin-like growth factor (IGF-1), which activate CREB, increased the adiponectin promoter activity. However, this stimulation was prevented by the dominant negative form of CREB (ACREB) and pretreatment with PD098059, indicating that IGF-1 stimulate adiponectin expression through CREB phosphorylation via the ERK pathway. Importantly, the transactivation of adiponectin expression by CREB was inhibited by ATF3. Coimmunoprecipitation and GST pull-down assay revealed that ATF3 bound to CREB and prevented CREB phosphorylation induced during differentiation of 3T3-L1 adipocytes. Collectively, these findings demonstrate that CREB is a positive regulator of mouse adiponectin gene expression in adipocytes, which play an important role in the regulation of adiponectin expression in response to growth factor.