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 as a complex protein network connecting other metabolic pathways with an 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 coimmunoprecipitation in the HT115 colon cancer cells and was supported by a partial colocalization 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 a 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 tricarboxylic acid 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_i2 mRNA in colon tumors compared with 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.
- Received July 18, 2016.
- Accepted December 29, 2016.
This work was supported by the Canadian Institutes of Health [CIHR MOP-142318] and the Natural Sciences and Engineering Research Council of Canada [NSERC 342176-2012]. YAD received studentship awards from Centre de Recherche en Endocrinologie Moléculaire et Oncologique et Génomique Humaine (CREMOGH), Laval University and Fonds de Recherche du Québec – Santé (FRQS). MeR and JR received studentship awards from CIHR. CG holds a Canada Research Chair in Pharmacogenomics (Canadian Research Chair Program).
Part of this work was presented as a poster presentation at the following meeting: Audet-Delage Y, Rouleau M, Rouleau M, Roberge J and Guillemette C. (2015) Glucuronosyltransferase splice variant proteins and their roles in cancer cell metabolism and progression. Integrating Metabolism and Tumor Biology Keystone meeting; 2015 Jan 13-18; Vancouver, BC, Canada.
This article has supplemental material available at molpharm.aspetjournals.org.
- Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics