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

Mol Endocrinol. 2005 Dec;19(12):3107-25. doi: 10.1210/me.2005-0048. Epub 2005 Jul 28.

Abstract

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.

MeSH terms

  • AMP-Activated Protein Kinases
  • Animals
  • Apolipoprotein A-V
  • Apolipoproteins / genetics*
  • Apolipoproteins A
  • Cells, Cultured
  • Gene Deletion
  • Gene Expression Regulation*
  • Heat-Shock Proteins / metabolism
  • Hepatocyte Nuclear Factor 4 / antagonists & inhibitors
  • Hepatocyte Nuclear Factor 4 / genetics
  • Hepatocyte Nuclear Factor 4 / metabolism*
  • Hepatocytes / metabolism
  • Humans
  • Mice
  • Mice, Mutant Strains
  • Mitogen-Activated Protein Kinases / metabolism
  • Multienzyme Complexes / metabolism
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Promoter Regions, Genetic / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA, Small Interfering / pharmacology
  • Repetitive Sequences, Nucleic Acid
  • Response Elements / genetics*
  • Transcription Factors / metabolism

Substances

  • APOA5 protein, human
  • Apolipoprotein A-V
  • Apolipoproteins
  • Apolipoproteins A
  • Heat-Shock Proteins
  • Hepatocyte Nuclear Factor 4
  • Multienzyme Complexes
  • PPARGC1A protein, human
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • RNA, Small Interfering
  • Transcription Factors
  • Protein-Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinases
  • AMP-Activated Protein Kinases