Document Detail

Protein-protein interactions between the bilirubin-conjugating UDP-glucuronosyltransferase UGT1A1 and its shorter isoform 2 regulatory partner derived from alternative splicing.
MedLine Citation:
PMID:  23148825     Owner:  NLM     Status:  MEDLINE    
The oligomerization of UGTs [UDP (uridine diphosphate)-glucuronosyltransferases] modulates their enzyme activities. Recent findings also indicate that glucuronidation is negatively regulated by the formation of inactive oligomeric complexes between UGT1A enzymes [i1 (isoform 1)] and an enzymatically inactive alternatively spliced i2 (isoform 2). In the present paper, we assessed whether deletion of the UGT-interacting domains previously reported to be critical for enzyme function might be involved in i1-i2 interactions. The bilirubin-conjugating UGT1A1 was used as a prototype. We also explored whether intermolecular disulfide bonds are involved in i1-i2 interactions and the potential role of selected cysteine residues. Co-immunoprecipitation assays showed that UGT1A1 lacking the SP (signal peptide) alone or also lacking the transmembrane domain (absent from i2) did not self-interact, but still interacted with i2. The deletion of other N- or C-terminal domains did not compromise i1-i2 complex formation. Under non-reducing conditions, we also observed formation of HMWCs (high-molecular-mass complexes) for cells overexpressing i1 and i2. The presence of UGTs in these complexes was confirmed by MS. Mutation of individual cysteine residues throughout UGT1A1 did not compromise i1-i1 or i1-i2 complex formation. These findings are compatible with the hypothesis that the interaction between i1 and i2 proteins (either transient or stable) involves binding of more than one domain that probably differs from those involved in i1-i1 interactions.
Mélanie Rouleau; Pierre Collin; Judith Bellemare; Mario Harvey; Chantal Guillemette
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Biochemical journal     Volume:  450     ISSN:  1470-8728     ISO Abbreviation:  Biochem. J.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-01-24     Completed Date:  2013-03-28     Revised Date:  2014-03-28    
Medline Journal Info:
Nlm Unique ID:  2984726R     Medline TA:  Biochem J     Country:  England    
Other Details:
Languages:  eng     Pagination:  107-14     Citation Subset:  IM    
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MeSH Terms
Alternative Splicing*
Bilirubin / metabolism
Glucuronosyltransferase / chemistry*,  genetics*,  metabolism
HEK293 Cells
Protein Interaction Domains and Motifs
Protein Isoforms / chemistry,  genetics,  metabolism
Grant Support
//Canadian Institutes of Health Research
Reg. No./Substance:
0/Protein Isoforms; EC 2.4.1.-/UGT1A1 enzyme; EC; RFM9X3LJ49/Bilirubin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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