title: Regulation of uridine diphosphate-glucuronosyltransferase 1A3 activity by protein phosphorylation.
abstract: Protein phosphorylation is a vital post-translational modification. This study investigated the effect of phosphorylation on human uridine diphosphate (UDP)-glucuronosyltransferase 1A3 (UGT1A3) activity. Curcumin and calphostin C suppressed the activity and phosphorylation of recombinant UGT1A3 expressed in Sf9 cells. These results indicate that UGT1A3 undergoes phosphorylation, which is required for its catalytic activity. Calphostin C is a highly specific protein kinase C (PKC) inhibitor, so three predicted PKC phosphorylation sites in UGT1A3 were examined. Site-directed mutation analysis at residues 28, 43 and 436 (from serine to glycine) was conducted. Compared with the wild-type, the S43G-mutant showed significantly decreased UGT1A3 catalytic activity. Furthermore, the UGT1A3 activity of wild-type and S43G-mutant was down-regulated by calphostin C, whereas the calphostin C inhibitory effect was much weaker on the S43G-mutant than the wild-type. In conclusion, phosphorylation plays an important role in UGT1A3 activity, and the serine at site 43 in UGT1A3 is most likely a phosphorylation site.
authors.affiliation: Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Huidi
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Millennium Pharmaceuticals, Inc., Cambridge, MA, USA.
authors.forename: Chuan
authors.initials: C
authors.lastname: Lu
authors.affiliation: Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Su
authors.initials: S
authors.lastname: Zeng
authors.affiliation: Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China.
authors.forename: Lushan
authors.initials: L
authors.lastname: Yu
mesh_terms: D000818:Animals; D002460:Cell Line; D003106:Colon / Q000166:cytology; D003474:Curcumin / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D014453:Glucuronosyltransferase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D016297:Mutagenesis, Site-Directed; D009281:Naphthalenes / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011994:Recombinant Proteins; D012694:Serine / Q000378:metabolism; D061987:Sf9 Cells; D014162:Transfection
chemical_list: D004791:Enzyme Inhibitors; D009281:Naphthalenes; D011994:Recombinant Proteins; D012694:Serine; C122075:UDP-glucuronosyltransferase, UGT1A3; D014453:Glucuronosyltransferase; D011493:Protein Kinase C; C058819:calphostin C; D003474:Curcumin
keywords: PKC; UGT1A3; calphostin C; curcumin; phosphorylation