Inter-isoform Hetero-dimerization of Human UDP-Glucuronosyltransferases (UGTs) 1A1, 1A9 and 2B7 and Impacts on Glucuronidation Activity

Abstract

Human UDP-glucuronosyltransferases (UGTs) play a pivotal role in phase II metabolism by catalyzing the glucuronidation of endobiotics and xenobiotics. The catalytic activities of UGTs are highly impacted by both genetic polymorphisms and oligomerization. The present study aimed to assess the inter-isoform hetero-dimerization of UGT1A1, 1A9, and 2B7, including the wild type (1A1*1, 1A9*1, and 2B7*1) and the naturally occurring (1A1*1b, 1A9*2/*3/*5, and 2B7*71S/*2/*5) variants. The related enzymes were double expressed in Bac-to-Bac systems. The fluorescence resonance energy transfer (FRET) technique and co-immunoprecipitation (Co-IP) revealed stable hetero-dimerization of UGT1A1, 1A9, and 2B7 allozymes. Variable FRET efficiencies and donor-acceptor distances suggested that genetic polymorphisms resulted in altered affinities to the target protein. In addition, the metabolic activities of UGTs were differentially altered upon hetero-dimerization via double expression systems. Moreover, protein interactions also changed the regioselectivity of UGT1A9 for querectin glucuronidation. These findings provide in-depth understanding of human UGT dimerization as well as clues for complicated UGT dependent metabolism in humans.

Hepatic Abundance and Activity of Androgen- and Drug-Metabolizing Enzyme UGT2B17 Are Associated with Genotype, Age, and Sex

“…UGT enzymes belong to distinct subfamilies of more than 26 genes with 19 well characterized functional proteins. The functional isoforms belong to the UGT1 and UGT2 superfamilies, which are further divided into three subfamilies, based on their sequence similarities, into UGT1As (UGT1A1, UGT1A3-UGT1A10), UGT2As (UGT2A1-UGT2A3), and UGT2Bs (UGT2B4, UGT2B7, UGT2B10, UGT2B11, UGT2B15, UGT2B17, and UGT2B28) (Guillemette, 2003;Oda et al, 2015;Yuan et al, 2016).…”

Construction and Verification of Physiologically Based Pharmacokinetic Models for Four Drugs Majorly Cleared by Glucuronidation: Lorazepam, Oxazepam, Naloxone, and Zidovudine

“…Indeed, we recognize the need to extend this work to simulate population variability as an important next step for UGT metabolized drugs due to the frequency and clinical relevance of polymorphisms. UGT1A1 and UGT1A3 are highly polymorphic isoforms (65,66) and polymorphism is also evident for UGT2B7 which might contribute to the variability seen between clinical studies for some of our model drugs (67,68).…”

Advances in the Understanding of Protein-Protein Interactions in Drug Metabolizing Enzymes through the Use of Biophysical Techniques

“…More recently, Yuan et al used FRET to demonstrate that UGT2B7 was able to form homo oligomers with both wild-type and mutant forms of the enzyme, which had the possibility of affecting zidovudine glucuronidation (Yuan et al, 2015 ). Yuan further went on to demonstrate that the UGT isoforms UGT1A1, 1A9, and 2B7 were all able to form heterodimeric complexes, expanding on their previous work that examined homodimerization in this enzyme class (Yuan et al, 2016 ).…”

“…Fluorescence studies have also been useful in the study of the human UGT enzymes (Operana and Tukey, 2007 ; Fujiwara et al, 2016 ; Yuan et al, 2016 ). Turkey et al used FRET to examine UGT1A oligomerization in vivo (Operana and Tukey, 2007 ).…”