Ziegler, K, Tumova, S, Kerimi, A et al. (1 more author) (2015) Cellular asymmetric catalysis by UDP-glucuronosyltransferase 1A8 shows functional localization to the basolateral plasma membrane. Journal of Biological Chemistry. ISSN 1083-351X
Abstract
UDP-glucuronosyltransferases (UGTs) are highly expressed in liver, intestine and kidney and catalyze the glucuronic acid conjugation of both endogenous compounds and xenobiotics. Using recombinant human UGT isoforms, we show that glucuronic acid conjugation of the model substrate, (-)-epicatechin, is catalyzed mainly by UGT1A8 and UGT1A9. In HepG2 cells, pre-treatment with polyunsaturated fatty acids increased substrate glucuronidation. In the intestinal Caco-2/HT29-MTX co-culture model, overall relative glucuronidation rates were much higher than in HepG2 cells and (-)-epicatechin was much more readily conjugated when applied to the basolateral side of the cell monolayer. Under these conditions, 95% of the conjugated product was effluxed back to the site of application and none of the other phase 2-derived metabolites followed this distribution pattern. HT29-MTX cells contained >1000-fold higher levels of UGT1A8 mRNA than Caco-2 or HepG2 cells. Gene expression of UGT1A8 increased after treatment of cells with docosahexaenoic acid, as did UGT1A protein levels. Immunofluorescence staining and western blotting showed the presence of UGT1A in basal and lateral parts of the plasma membrane of HT29-MTX cells. These results suggest that in HT29-MTX goblet cells at least some of the UGT1A8 enzyme is not endoplasmic reticulum resident but plasma membrane spanning, resulting in much more efficient conjugation of substrate from the basal than from the luminal side, coupled with rapid efflux by functionally-associated basolateral transporters. This novel molecular strategy allows the cell to carry out conjugation without the xenobiotic entering into the interior of the cell.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This research was originally published in Journal of Biological Chemistry. Ziegler, K, Tumova, S, Kerimi, A and Williamson, G (2015) Cellular asymmetric catalysis by UDP-glucuronosyltransferase 1A8 shows functional localization to the basolateral plasma membrane. Journal of Biological Chemistry. © the American Society for Biochemistry and Molecular Biology |
Keywords: | cell polarity; fatty acid; flavonoid; intestinal metabolism; membrane enzyme; polyunsaturated fatty acid (PUFA); Uridine 5'-diphospho-glucuronosyltransferase (UDP-glucuronosyltransferase); xenobiotic |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Food Science and Nutrition (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 24 Feb 2015 16:09 |
Last Modified: | 08 Mar 2016 19:46 |
Published Version: | http://dx.doi.org/10.1074/jbc.m114.634428 |
Status: | Published |
Publisher: | American Society for Biochemistry and Molecular Biology |
Identification Number: | 10.1074/jbc.m114.634428 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:83106 |