title: Intron 1 retaining cyclooxygenase 1 splice variant is induced by osmotic stress in human intestinal epithelial cells.
abstract: The biological roles of intron 1 retaining cyclooxygenase (Cox) 1 splice variants Cox-3 and PCox-1a (Cox-1ir) are not known. In humans, Cox-3 transcription has previously been shown to occur in the brain and in the aorta. However, conclusive evidence regarding the existence of a human Cox-3 protein is lacking. We studied the expression of intron 1 retaining cyclooxygenase 1 splice variants in the human colon cancer cell line Caco-2 and in human colonic tissue samples. In Caco-2 cells, their transcription was induced up to 47-fold by osmotic stress. The corresponding protein, however, could not be detected by Western blotting. In human colonic tissue samples derived from intact and inflamed areas, a low level of Cox-1ir mRNA (1500 +/- 1280 copies per 100 ng total RNA; mean+/-standard deviation; n = 20) was also found. In Caco-2 cells, induction of Cox-1ir under osmotic stress was reversed by addition of the organic osmolyte betaine. Under hypertonic but not under isotonic conditions, splice variant-specific degradation of Cox-1ir mRNA using RNA interference resulted in increased production of fully spliced Cox-1 and Cox-2 mRNA (P = 0.002). In summary, our results indicate that the intron 1 retaining Cox-1 splice variant RNA molecules are expressed by human intestinal epithelial cells in a controlled manner, are most likely not translated and play a regulatory role in the cyclooxygenase mediated epithelial osmoregulation.
authors.affiliation: Department of Biotechnology, University of Turku, Finland. jussi.nurmi@utu.fi
authors.forename: J T
authors.initials: JT
authors.lastname: Nurmi
authors.forename: P A
authors.initials: PA
authors.lastname: Puolakkainen
authors.forename: N E
authors.initials: NE
authors.lastname: Rautonen
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D018938:Caco-2 Cells; D015179:Colorectal Neoplasms / Q000201:enzymology*; D051545:Cyclooxygenase 1 / Q000235:genetics*; D051546:Cyclooxygenase 2 / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D014644:Genetic Variation; D006801:Humans; D007438:Introns; D009997:Osmotic Pressure; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; D011451:Prostaglandin-Endoperoxide Synthases