Expression of the glycine transporter type 1 (GlyT-1A) is upregulated by ATF-4 following physiological stress in human intestinal epithelial cells (1109.14)

Downstream of activating transcription factor 4 (ATF-4) in Caco-2 cells in response to stress. In the present study we show that increased expression of the GlyT-1a gene following stress is dependent on elements contained within the 5’untranslated region (UTR). Caco-2 cells transfected with plasmid constructs containing sequences representative of the GlyT-1a proximal promoter and 5’UTR upstream of a beta-galactosidase reporter showed increased reporter activity following treatment with thapsigargin (Tg), tunicamycin (Tu), amino acid (AA) starvation, tertbutylhydroquinone(tBHQ) or Diethyl maleate (DEM). Short labeled DNA probes containing a potential amino acid response element (AARE) located in exon 1 of the GLYT-1a gene demonstrated binding by ATF-4 in gel shift and super shift assays. qPCR assays performed on short genomic DNA fragments isolated from Caco-2 cells by chromatin immunoprecipitation (ChIP) with antibodies against ATF4 demonstrated 9, 5 and 2-fold enrichment of the ATF-4/AARE interaction at the 5’-UTR region of GlyT1a following Tu, AA starvation and DEM treatment respectively. Our data suggests that response elements within the 5’UTR including exon 1 and the first 85 bases of exon 2 are required for transcriptional induction of GlyT1a. We propose the direct interaction of ATF-4 at the identified AARE drives transcriptional up-regulation of GlyT-1a following nutrient, oxidative and endoplasmic reticulum stress.