Hepatocyte nuclear factor-4alpha regulates the human apolipoprotein AV gene: identification of a novel response element and involvement in the control by peroxisome proliferator-activated receptor-gamma coactivator-1alpha, AMP-activated protein kinase, and mitogen-activated protein kinase pathway.
The recently discovered apolipoprotein AV (apoAV) gene has been reported to be a key player in modulating plasma triglyceride levels. Here we identify the hepatocyte nuclear factor-4alpha (HNF-4alpha) as a novel regulator of human apoAV gene. Inhibition of HNF-4alpha expression by small interfering RNA resulted in down-regulation of apoAV. Deletion, mutagenesis, and binding assays revealed that HNF-4alpha directly regulates human apoAV promoter through DR1 [a direct repeat separated by one nucleotide (nt)], and via a novel element for HNF-4alpha consisting of an inverted repeat separated by 8 nt (IR8). In addition, we show that the coactivator peroxisome proliferator-activated receptor-gamma coactivator-1alpha was capable of stimulating the HNF-4alpha-dependent transactivation of apoAV promoter. Furthermore, analyses in human hepatic cells demonstrated that AMP-activated protein kinase (AMPK) and the MAPK signaling pathway regulate human apoAV expression and suggested that this regulation may be mediated, at least in part, by changes in HNF-4alpha. Intriguingly, EMSAs and mice with a liver-specific disruption of the HNF-4alpha gene revealed a species-distinct regulation of apoAV by HNF-4alpha, which resembles that of a subset of HNF-4alpha target genes. Taken together, our data provide new insights into the binding properties and the modulation of HNF-4alpha and underscore the role of HNF-4alpha in regulating triglyceride metabolism.
Prieur
Xavier
X
GlaxoSmithKline, 25 avenue du Québec, 91951 Les Ulis cedex, France.
Schaap
Frank G
FG
Coste
Hervé
H
Rodríguez
Joan C
JC
D055372:AMP-Activated Protein Kinases; D000818:Animals; D000072040:Apolipoprotein A-V; D001053:Apolipoproteins / Q000235:genetics*; D001054:Apolipoproteins A; D002478:Cells, Cultured; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000378:metabolism; D051557:Hepatocyte Nuclear Factor 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D051379:Mice; D008817:Mice, Mutant Strains; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D012091:Repetitive Sequences, Nucleic Acid; D020218:Response Elements / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism
C437704:APOA5 protein, human; D000072040:Apolipoprotein A-V; D001053:Apolipoproteins; D001054:Apolipoproteins A; D006360:Heat-Shock Proteins; D051557:Hepatocyte Nuclear Factor 4; D009097:Multienzyme Complexes; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D034741:RNA, Small Interfering; D014157:Transcription Factors; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D055372:AMP-Activated Protein Kinases