Regulation of hypoxia-inducible factor 1 in enterocytic cells.
BACKGROUND
Mucosal hypoxia due to intestinal hypoperfusion is characteristic of a number of clinical disorders. An early event in the adaptive response to cellular hypoxia is the binding of hypoxia-inducible factor 1 (HIF-1) to cis-acting regulatory sites in target genes.


METHODS
We characterized the expression of HIF-1 in transformed (Caco-2(BBe) and T84) and nontransformed human (FHs 74 Int) and rat (IEC-6) intestinal epithelial cell lines.


RESULTS
The electrophoretic mobility shift assay detected increased HIF-1 DNA-binding activity in each cell line within 2 h of hypoxia (1% O2). HIF-1 binding was maximal within 4 h and remained stable for 24 h. HIF-1 DNA-binding activity was maximal in the established IEC-6 cell line below 2% oxygen, but HIF-1 DNA-binding activity was not detectable above 0.5% O2 in the primary human FHs 74 Int cell line. The nonspecific protein kinase inhibitor genistein (200 microM) inhibited HIF-1 binding at 4 h. Transfection of Caco-2 cells with a wild-type, but not a mutant, HIF-1-dependent luciferase expression vector resulted in a fourfold induction of reporter gene expression during hypoxia.


CONCLUSIONS
In conclusion, HIF-1 regulates gene expression in enterocytes and an undefined phosphorylation event is important for O2 sensing.
Bertges
Daniel J
DJ
Department of Surgery, Beth Israel Deaconess Medical Center and Harverd Medical School, Boston, MA 02215, USA.
Berg
Sören
S
Fink
Mitchell P
MP
Delude
Russell L
RL
D000818:Animals; D018938:Caco-2 Cells; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D020895:Enterocytes / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007413:Intestinal Mucosa / Q000166:cytology; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; C497444:Hif1a protein, rat; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D047428:Protein Kinase Inhibitors; D014157:Transcription Factors; D019833:Genistein; D010100:Oxygen