title: Evaluation of UGT protein interactions in human hepatocytes: effect of siRNA down regulation of UGT1A9 and UGT2B7 on propofol glucuronidation in human hepatocytes.
abstract: Previous experiments performed in recombinant systems have suggested that protein-protein interactions occur between the UGTs and may play a significant role in modulating enzyme activity. However, evidence of UGT protein-protein interactions either in vivo or in more physiologically relevant in vitro systems has yet to be demonstrated. In this study, we examined oligomerization and its ability to affect glucuronidation in plated human hepatocytes. siRNA down regulation experiments and activity studies were used to examine changes in metabolite formation of one UGT isoform due to down regulation of a second UGT isoform. Selective siRNA directed towards UGT1A9 or UGT2B7 resulted in significant and selective decreases in their respective mRNA levels. As expected, the metabolism of the UGT1A9 substrate propofol decreased with UGT1A9 down regulation. Interestingly, UGT1A9 activity, but not UGT1A9 mRNA expression, was also diminished when UGT2B7 expression was selectively inhibited, implying potential interactions between the two isoforms. Minor changes to UGT1A4, UGT2B4 and UGT2B7 activity were also observed when UGT1A9 expression was selectively down regulated. To our knowledge, this represents the first piece of evidence that UGT protein-protein interactions occur in human hepatocytes and suggests that expression levels of UGT2B7 may directly impact the glucuronidation activity of selective UGT1A9 substrates.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, USA.
authors.forename: Camille M
authors.initials: CM
authors.lastname: Konopnicki
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Dickmann
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Tracy
authors.forename: Robert H
authors.initials: RH
authors.lastname: Tukey
authors.forename: Larry C
authors.initials: LC
authors.lastname: Wienkers
authors.forename: Robert S
authors.initials: RS
authors.lastname: Foti
mesh_terms: D015536:Down-Regulation; D020719:Glucuronides / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D015742:Propofol / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics*; D000090264:UDP-Glucuronosyltransferase 1A9
chemical_list: D020719:Glucuronides; D007527:Isoenzymes; D034741:RNA, Small Interfering; C000715591:UGT1A9 protein, human; C491474:UGT2B7 protein, human; D014453:Glucuronosyltransferase; D000090264:UDP-Glucuronosyltransferase 1A9; D015742:Propofol
references.citation: Drug Metab Lett. 2007 Jan;1(1):77-9
references.pmid: 19356023
references.citation: J Biol Chem. 2007 Feb 16;282(7):4821-4829
references.pmid: 17179145
references.citation: Drug Metab Dispos. 2007 Oct;35(10):1781-7
references.pmid: 17620344
references.citation: Biol Pharm Bull. 2003 Feb;26(2):216-9
references.pmid: 12576683
references.citation: Drug Metab Dispos. 2002 Mar;30(3):270-5
references.pmid: 11854144
references.citation: Drug Metab Rev. 2010 Feb;42(1):145-58
references.pmid: 19817679
references.citation: J Biol Chem. 1997 Oct 24;272(43):26913-7
references.pmid: 9341125
references.citation: Biochem Pharmacol. 1994 Oct 18;48(8):1545-9
references.pmid: 7980619
references.citation: J Pharm Sci. 2010 Jan;99(1):442-54
references.pmid: 19475557
references.citation: Annu Rev Pharmacol Toxicol. 2004;44:1-25
references.pmid: 14744236
references.citation: Biochem Pharmacol. 2004 Dec 15;68(12):2443-50
references.pmid: 15548391
references.citation: Biochem Biophys Res Commun. 2000 Jul 14;273(3):1048-52
references.pmid: 10891369
references.citation: Pharmacogenet Genomics. 2007 Feb;17(2):115-26
references.pmid: 17301691
references.citation: Front Biosci. 2005 Jan 01;10:887-95
references.pmid: 15569627
references.citation: Mol Pharmacol. 2005 Jan;67(1):260-2
references.pmid: 15486048
references.citation: Drug Metab Dispos. 2011 Sep;39(9):1546-54
references.pmid: 21697463
references.citation: J Pharmacol Exp Ther. 2002 Apr;301(1):382-90
references.pmid: 11907196
references.citation: Drug Metab Dispos. 2003 Sep;31(9):1086-9
references.pmid: 12920162
references.citation: Biochem Pharmacol. 2009 May 1;77(9):1458-65
references.pmid: 19150343
references.citation: Int Rev Cytol. 2007;260:35-112
references.pmid: 17482904
references.citation: Drug Metab Dispos. 2005 Nov;33(11):1621-7
references.pmid: 16049128
references.citation: Biochemistry. 1997 Jun 10;36(23):7154-61
references.pmid: 9188715
references.citation: Drug Metab Dispos. 2007 Sep;35(9):1679-86
references.pmid: 17576806
references.citation: J Biol Chem. 2003 Feb 7;278(6):3536-44
references.pmid: 12435745
references.citation: Mol Pharmacol. 1995 Jun;47(6):1101-5
references.pmid: 7603447
references.citation: Mol Pharmacol. 2005 Mar;67(3):665-72
references.pmid: 15611481
references.citation: Drug Metab Dispos. 2012 Feb;40(2):336-45
references.pmid: 22071170
references.citation: Adv Drug Deliv Rev. 2009 Jul 25;61(9):746-59
references.pmid: 19389436
references.citation: Biochem Pharmacol. 2011 Dec 15;82(12):2016-23
references.pmid: 21930117
references.citation: Drug Metab Dispos. 2007 May;35(5):747-57
references.pmid: 17293379
references.citation: Drug Metab Pharmacokinet. 2010;25(2):134-48
references.pmid: 20460819
references.citation: Biochem Pharmacol. 2006 May 28;71(11):1531-9
references.pmid: 16455060
references.citation: Mol Pharm. 2007 Nov-Dec;4(6):873-82
references.pmid: 17927138
references.citation: Annu Rev Pharmacol Toxicol. 2000;40:581-616
references.pmid: 10836148
references.citation: Mol Pharmacol. 2006 Mar;69(3):908-20
references.pmid: 16339389
references.citation: Methods Enzymol. 2005;400:104-16
references.pmid: 16399346