Rhythmic expression of DEC2 proteinin vitroandin vivo.
Basic helix-loop-helix (bHLH) transcription factor DEC2 (bHLHE41/Sharp1) is one of the clock genes that show a circadian rhythm in various tissues. DEC2 regulates differentiation, sleep length, tumor cell invasion and apoptosis. Although studies have been conducted on the rhythmic expression of DEC2 mRNA in various tissues, the precise molecular mechanism of DEC2 expression is poorly understood. In the present study, we examined whether DEC2 protein had a rhythmic expression. Western blot analysis for DEC2 protein revealed a rhythmic expression in mouse liver, lung and muscle and in MCF-7 and U2OS cells. In addition, AMP-activated protein kinase (AMPK) activity (phosphorylation of AMPK) in mouse embryonic fibroblasts (MEFs) exhibited a rhythmic expression under the condition of medium change or glucose-depleted medium. However, the rhythmic expression of DEC2 in MEF gradually decreased in time under these conditions. The medium change affected the levels of DEC2 protein and phosphorylation of AMPK. In addition, the levels of DEC2 protein showed a rhythmic expressionin vivoand in MCF-7 and U2OS cells. The results showed that the phosphorylation of AMPK immunoreactivity was strongly detected in the liver and lung ofDEC2knockout mice compared with that of wild-type mice. These results may provide new insights into rhythmic expression and the regulation between DEC2 protein and AMPK activity.
Department of Radiation Oncology and Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA; Department of Pathology, Wakayama Medical University School of Medicine, Wakayama 641-8509, Japan.
Fuyuki
F
Sato
Department of Pathology, Wakayama Medical University School of Medicine, Wakayama 641-8509, Japan.
Yasuteru
Y
Muragaki
Department of Dental and Medical Biochemistry, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
Takeshi
T
Kawamoto
Department of Dental and Medical Biochemistry, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
Katsumi
K
Fujimoto
Department of Dental and Medical Biochemistry, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
Yukio
Y
Kato
Department of Radiation Oncology and Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA; Jiangsu Center for the Collaboration and Innovation of Cancer Biotherapy, Cancer Institute, Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China.
Yanping
Y
Zhang
DEC2; circadian rhythm; clock gene; phosphorylation of AMP-activated protein kinase