Personne :
Guillemette, Chantal

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Université Laval. Faculté de pharmacie
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Voici les éléments 1 - 8 sur 8
  • Publication
    Accès libre
    UGT genomic diversity : beyond gene duplication
    (Informa Healthcare, 2009-10-26) Lévesque, Éric; Bellemare, Judith.; Harvey, Mario.; Ménard, Vincent; Guillemette, Chantal
    The human uridine diphospho (UDP)-glucuronosyltransferase (UGT) superfamily comprises enzymes responsible for a major biotransformation phase II pathway: the glucuronidation process. The UGT enzymes are located in the endoplasmic reticulum of almost all tissues, where they catalyze the inactivation of several endogenous and exogenous molecules, including bilirubin, sex steroids, numerous prescribed drugs, and environmental toxins. This metabolic pathway is particularly variable. The influence of inheritable polymorphisms in human UGT-encoding genes has been extensively documented and was shown to be responsible for a fraction of the observed phenotypic variability. Other key genomic processes are likely underlying this diversity; these include copy-number variations, epigenetic factors, and newly discovered splicing mechanisms. This review will discuss novel molecular aspects that may be determinant to UGT phenotypes.
  • Publication
    Accès libre
    Crosstalk between alternatively spliced UGT1A isoforms and colon cancer cell metabolism
    (American Society for Pharmacology and Experimental Therapeutics, 2017-01-03) Rouleau, Michèle; Picard, Frédéric; Têtu, Bernard; Roberge, Joannie; Audet-Delage, Yannick; Guillemette, Chantal; Rouleau, Mélanie; Miard, Stéphanie
    Alternative splicing at the human glucuronosyltransferase 1 gene locus (UGT1) produces alternate isoforms UGT1A_i2s that control glucuronidation activity through protein-protein interactions. Here, we hypothesized that UGT1A_i2s function into a complex protein network connecting other metabolic pathways with influence on cancer cell metabolism. This is based on a pathway enrichment analysis of proteomic data that identified several high-confidence candidate interaction proteins of UGT1A_i2 proteins in human tissues, namely the rate-limiting enzyme of glycolysis pyruvate kinase (PKM), which plays a critical role in cancer cell metabolism and tumor growth. The partnership of UGT1A_i2 and PKM2 was confirmed by co-immunoprecipitation in the HT115 colon cancer cells and was supported by a partial co-localization of these two proteins. In support of a functional role for this partnership, depletion of UGT1A_i2 proteins in HT115 cells enforced the Warburg effect with higher glycolytic rate at the expense of mitochondrial respiration, and led to lactate accumulation. Untargeted metabolomics further revealed a significantly altered cellular content of 58 metabolites including many intermediates derived from the glycolysis and TCA cycle pathways. These metabolic changes were associated with a greater migration potential. The potential relevance of our observations is supported by the down-regulation of UGT1A_i2s mRNA in colon tumors compared to normal tissues. Alternate UGT1A variants may thus be part of the expanding compendium of metabolic pathways involved in cancer biology directly contributing to the oncogenic phenotype of colon cancer cells. Findings uncover new aspects of UGT functions diverging from their transferase activity.
  • Publication
    Accès libre
    Quantitative profiling of the UGT transcriptome in human drug metabolizing tissues
    (Nature Publishing Group., 2017-04-25) Rouleau, Michèle; Gilbert, Isabelle; Droit, Arnaud; Tourancheau, Alan; Guillemette, Chantal; Guauque-Olarte, Sandra; Villeneuve, Lyne
    Alternative splicing as a mean to control gene expression and diversify function is suspected to considerably influence drug response and clearance. We report the quantitative expression profiles of the human UGT genes including alternatively spliced variants not previously annotated established by deep RNA-sequencing in tissues of pharmacological importance. We reveal a comprehensive quantification of the alternative UGT transcriptome that differ across tissues and among individuals. Alternative transcripts that comprise novel in-frame sequences associated or not with truncations of the 5′- and/or 3′- termini, significantly contribute to the total expression levels of each UGT1 and UGT2 gene averaging 21% in normal tissues, with expression of UGT2 variants surpassing those of UGT1. Quantitative data expose preferential tissue expression patterns and remodeling in favor of alternative variants upon tumorigenesis. These complex alternative splicing programs have the strong potential to contribute to interindividual variability in drug metabolism in addition to diversify the UGT proteome.
  • Publication
    Accès libre
    Unravelling the transcriptomic landscape of the major phase II UDP-glucuronosyltransferase drug metabolizing pathway using targeted RNA sequencing
    (Nature, 2015-04-14) Lévesque, Éric; Margaillan, Guillaume; Rouleau, Michèle; Gilbert, Isabelle; Droit, Arnaud; Tourancheau, Alan; Guillemette, Chantal; Villeneuve, Lyne
    A comprehensive view of the human UDP-glucuronosyltransferase (UGT) transcriptome is a prerequisite to the establishment of an individual's UGT metabolic glucuronidation signature. Here, we uncover the transcriptome landscape of the 10 human UGT gene loci in normal and tumoral metabolic tissues by targeted RNA next-generation sequencing. Alignment on the human hg19 reference genome identifies 234 novel exon-exon junctions. We recover all previously known UGT1 and UGT2 enzyme-coding transcripts and identify over 130 structurally and functionally diverse novel UGT variants. We further expose a revised genomic structure of UGT loci and provide a comprehensive repertoire of transcripts for each UGT gene. Data also uncover a remodelling of the UGT transcriptome occurring in a tissue- and tumor-specific manner. The complex alternative splicing program regulating UGT expression and protein functions is likely critical in determining detoxification capacity of an organ and stress-related responses, with significant impact on drug responses and diseases.
  • Publication
    Accès libre
    The relative protein abundance of UGT1A alternative splice variants as a key determinant of glucuronidation activity in vitro
    (American Society for Pharmacology and Experimental Therapeutics, etc., 2013-04-01) Roberge, Joannie; Guillemette, Chantal; Falardeau, Sarah-Ann; Rouleau, Mélanie; Villeneuve, Lyne
    Alternative splicing (AS) is one of the most significant components of the functional complexity of human UDP-glucuronosyltransferase enzymes (UGTs), particularly for the UGT1A gene, which represents one of the best examples of a drug-metabolizing gene regulated by AS. Shorter UGT1A isoforms [isoform 2 (i2)] are deficient in glucuronic acid transferase activity but function as negative regulators of enzyme activity through protein-protein interaction. Their abundance, relative to active UGT1A enzymes, is expected to be a determinant of the global transferase activity of cells and tissues. Here we tested whether i2-mediated inhibition increases with greater abundance of the i2 protein relative to the isoform 1 (i1) enzyme, using the extrahepatic UGT1A7 as a model and a series of 23 human embryonic kidney 293 clonal cell lines expressing variable contents of i1 and i2 proteins. Upon normalization for i1, a significant reduction of 7-ethyl-10-hydroxycamptothecin glucuronide formation was observed for i1+i2 clones (mean of 53%) compared with the reference i1 cell line. In these clones, the i2 protein content varied greatly (38–263% relative to i1) and revealed two groups: 17 clones with i2 < i1 (60% ± 3%) and 6 clones with i2 = i1 (153% ± 24%). The inhibition induced by i2 was more substantial for clones displaying i2 = i1 (74.5%; P = 0.001) compared with those with i2 < i1 (45.5%). Coimmunoprecipitation supports a more substantial i1-i2 complex formation when i2 exceeds i1. We conclude that the relative abundance of regulatory i2 proteins has the potential to drastically alter the local drug metabolism in the cells, particularly when i2 surpasses the protein content of i1.
  • Publication
    Accès libre
    Pharmacogenomics of human uridine diphospho-glucuronosyltransferases (UGTs) and clinical implications
    (Wiley, 2014-06-12) Lévesque, Éric; Rouleau, Michèle; Guillemette, Chantal
    Glucuronidation, mediated by UDP-glucuronosyltransferase enzymes (UGTs), is a major phase II biotransformation pathway and, complementary to phase I metabolism and membrane transport, one of the most important cellular defense mechanism responsible for the inactivation of therapeutic drugs, other xenobiotics and numerous endogenous molecules. Individual variability in UGT enzymatic pathways is significant and may have profound pharmacological and toxicological implications. Several genetic and genomic processes are underlying this variability and are discussed in the context of drug metabolism and diseases such as cancer.
  • Publication
    Accès libre
    Dual roles for splice variants of the glucuronidation pathway as regulators of cellular metabolism
    (American Society for Pharmacology and Experimental Therapeutics, etc., 2014-01-01) Bellemare, Judith.; Roberge, Joannie; Guillemette, Chantal; Rouleau, Mélanie
    Transcripts of the UGT1A gene, encoding half of human UDP-glucuronosyltransferase (UGT) enzymes, undergo alternative splicing, resulting in active enzymes named isoforms 1 (i1s) and novel truncated isoforms 2 (i2s). Here, we investigated the effects of depleting endogenous i2 on drug response and attempted to unveil any additional biologic role(s) for the truncated novel UGT proteins. We used an integrated systems biology approach that combines RNA interference with unbiased global genomic and proteomic screens, and used HT115 colorectal cancer cells as a model. Consistent with previous evidence suggesting that i2s negatively regulate i1s through protein-protein interactions, i2-depleted cells were less sensitive to drug-induced cell death (IC50 of 0.45 ± 0.05 µM versus 0.22 ± 0.03 µM; P = 0.006), demonstrating that modulation of i2 levels meaningfully impacts drug bioavailability and cellular response. We also observed reduced production of reactive oxygen species by 30% (P < 0.05), and an enhanced expression (>1.2-fold; P < 0.05) of several proteins, such as hemoglobin α genes and superoxide dismutase 1, that have network functions associated with antioxidant properties. Interaction proteomics analysis of endogenous proteins from the cellular model, mainly in human intestine but also in kidney tissues, further uncovered interactions between i2s (but not i1s) and the antioxidant enzymes catalase and peroxiredoxin 1, which may influence antioxidant potential through sequestration of these novel partners. Our findings demonstrate for the first time dual roles for i2s in the cellular defense system as endogenous regulators of drug response as well as in oxidative stress.
  • Publication
    Posttranscriptional regulation of UGT2B10 hepatic expression and activity by alternative splicing
    (American Society for Pharmacology and Experimental Therapeutics, 2018-02-09) Rouleau, Michèle; Labriet, Adrien; Audet-Delage, Yannick; Guillemette, Chantal; Allain, Eric; Villeneuve, Lyne
    The detoxification enzyme UDP-glucuronosyltransferase UGT2B10 is specialized in the N-linked glucuronidation of many drugs and xenobiotics. Preferred substrates possess tertiary aliphatic amines and heterocyclic amines, such as tobacco carcinogens and several antidepressants and antipsychotics. We hypothesized that alternative splicing (AS) constitutes a means to regulate steady-state levels of UGT2B10 and enzyme activity. We established the transcriptome of UGT2B10 in normal and tumoral tissues of multiple individuals. The highest expression was in the liver, where 10 AS transcripts represented 50% of the UGT2B10 transcriptome in 50 normal livers and 44 hepatocellular carcinomas. One abundant class of transcripts involves a novel exonic sequence and leads to two alternative (alt.) variants with novel in-frame C termini of 10 or 65 amino acids. Their hepatic expression was highly variable among individuals, correlated with canonical transcript levels, and was 3.5-fold higher in tumors. Evidence for their translation in liver tissues was acquired by mass spectrometry. In cell models, they colocalized with the enzyme and influenced the conjugation of amitriptyline and levomedetomidine by repressing or activating the enzyme (40%–70%; P < 0.01) in a cell context–specific manner. A high turnover rate for the alt. proteins, regulated by the proteasome, was observed in contrast to the more stable UGT2B10 enzyme. Moreover, a drug-induced remodeling of UGT2B10 splicing was demonstrated in the HepaRG hepatic cell model, which favored alt. variants expression over the canonical transcript. Our findings support a significant contribution of AS in the regulation of UGT2B10 expression in the liver with an impact on enzyme activity.