Regulation of cellular retinol-binding protein type II gene expression by arachidonic acid analogue and 9-cis retinoic acid in caco-2 cells.
We previously showed that unsaturated fatty acids induced gene expression of cellular retinol-binding protein type II (CRBPII) in rat jejunum [Suruga, K., Suzuki, R., Goda, T. and Takase, S. (1995) J. Nutr. 125, 2039-2044]. In the present study, we investigated this induction mechanism(s) using the human intestinal Caco-2 cell line. The postconfluent mature Caco-2 cells were maintained in serum-free medium containing arachidonic acid or its analogue, 5,8,11, 14-eicosatetraynoic acid (ETYA). Northern blot analysis showed that these compounds induced CRBPII mRNA levels to rise and that this induction was more effective when combined with 9-cis retinoic acid. This effect was independent of cycloheximide and inhibited by actinomycin D. Nuclear run-on assays confirmed that the ETYA and 9-cis retinoic acid-induced increase of CRBPII mRNA levels was due to an increased rate of transcription of its gene. In Caco-2 cells, the transcripts of peroxisome proliferator-activated receptor alpha (PPARalpha) and retinoid X receptor alpha (RXRalpha), which were activated by their ligands ETYA and 9-cis retinoic acid, respectively, were coexpressed. The gel shift study using rat CRBPII gene nuclear receptor response elements (RXRE, RE2, RE3) revealed that several forms of nuclear proteins from Caco-2 cells specifically bound to these elements. Some of these protein/DNA complexes reacted to both anti-RXRalpha and anti-PPAR antibodies. In addition, in-vitro synthesized RXRalpha and PPARalpha cooperatively bound to these elements as a heterodimer and these binding activities were enhanced by addition of ETYA or arachidonic acid but not by addition of 9-cis retinoic acid. These studies suggest that fatty acid or its analogue may regulate CRBPII gene expression through PPAR/RXR heterodimer bound to the nuclear receptor response element(s) of the CRBPII genes.
Suruga
K
K
School of Food and Nutritional Sciences, The University of Shizuoka, Japan.
Mochizuki
K
K
Suzuki
R
R
Goda
T
T
Takase
S
S
D000077556:Alitretinoin; D001095:Arachidonic Acids / Q000494:pharmacology*; D001483:Base Sequence; D018938:Caco-2 Cells; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D047488:Retinoid X Receptors; D012177:Retinol-Binding Proteins / Q000235:genetics*; D054840:Retinol-Binding Proteins, Cellular; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology*
D001095:Arachidonic Acids; D017931:DNA Primers; C518459:RBP2 protein, human; C518461:Rbp2 protein, rat; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; D014157:Transcription Factors; D000077556:Alitretinoin; D014212:Tretinoin