Mechanism for fatty acid "sparing" effect on glucose-induced transcription: regulation of carbohydrate-responsive element-binding protein by AMP-activated protein kinase.
Carbohydrate-responsive element-binding protein (ChREBP) is a new transcription factor that binds to the carbohydrate-responsive element of the l-type pyruvate kinase gene (l-PK). The aim of this study was to investigate the mechanism by which feeding high fat diets results in decreased activity of ChREBP in the liver (Yamashita, H., Takenoshita, M., Sakurai, M., Bruick, R. K., Henzel, W. J., Shillinglaw, W., Arnot, D., and Uyeda, K. (2001) Proc. Natl. Acad. Sci. U.S.A. 98, 9116-9121). We cloned the rat liver ChREBP gene for use throughout this study. Acetate, octanoate, and palmitate inhibited the glucose-induced activation of l-PK transcription in ChREBP-overexpressed hepatocytes. In these hepatocytes, the cytosolic AMP concentration increased 30-fold and AMP-activated protein kinase activity was activated 2-fold. Similarly to the fatty acids, 5-amino-4-imidazolecarboxamide ribotide, a specific activator of AMP-activated protein kinase (AMPK) also inhibited the l-PK transcription activity in ChREBP-overexpressed hepatocytes. Using as a substrate a truncated ChREBP consisting of the C-terminal region, we demonstrated that phosphorylation by AMPK resulted in inactivation of the DNA binding activity. AMPK specifically phosphorylated Ser(568) of ChREBP. A S568A mutant of the ChREBP gene showed tight DNA binding and lost its fatty acid sensitivity, whereas a S568D mutant showed weak DNA binding and inhibited l-PK transcription activity even in the absence of fatty acid. These results strongly suggested that the fatty acid inhibition of glucose-induced l-PK transcription resulted from AMPK phosphorylation of ChREBP at Ser(568), which inactivated the DNA binding activity. AMPK was activated by the increased AMP that was generated by the fatty acid activation.
Kawaguchi
Takumi
T
Department of Biochemistry, Dallas Veterans Affairs Medical Center and University of Texas Southwestern Medical Center, Dallas, Texas 75223, USA.
Osatomi
Kiyoshi
K
Yamashita
Hiromi
H
Kabashima
Tsutomu
T
Uyeda
Kosaku
K
D000595:Amino Acid Sequence; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D003001:Cloning, Molecular; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011770:Pyruvate Kinase / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005227:Fatty Acids; C442825:Mlxipl protein, rat; D011994:Recombinant Proteins; D012265:Ribonucleotides; D014157:Transcription Factors; D000620:Aminoimidazole Carboxamide; D011770:Pyruvate Kinase; D017868:Cyclic AMP-Dependent Protein Kinases; C031143:AICA ribonucleotide; D005947:Glucose