Abstract
Glutathione S-transferase omega 1 and omega 2 (GSTO1 and GSTO2) catalyze monomethyl arsenate reduction, the rate-limiting reaction in arsenic biotransformation. As a step toward pharmacogenomic studies of these phase II enzymes, we resequenced human GSTO1 and GSTO2 using DNA samples from four ethnic groups. We identified 31 and 66 polymorphisms in GSTO1 and GSTO2, respectively, with four nonsynonymous-coding single nucleotide polymorphisms (cSNPs) in each gene. There were striking variations among ethnic groups in polymorphism frequencies and types. Expression constructs were created for all eight nonsynonymous cSNPs, as well as a deletion of codon 155 in GSTO1, and those constructs were used to transfect COS-1 cells. Quantitative Western blot analysis, after correction for transfection efficiency, showed a reduction in protein level of greater than 50% for the GSTO1 Tyr32 variant allozyme compared with wild type (WT), whereas levels for the Asp140, Lys208, Val236, and codon 155 deletion variant constructs were similar to that of the WT. For GSTO2, the Tyr130 and Ile158 variant allozymes showed 50 and 84% reductions in levels of expression, respectively, compared with WT, whereas the Ile41 and Asp142 allozymes displayed levels similar to that of WT GSTO2. Rabbit reticulocyte lysate degradation studies showed that the GSTO1 Tyr32 and the GSTO2 Tyr130, Ile158, and Asp142/Ile158 variant allozymes were degraded more rapidly than were their respective WT allozymes. These observations raise the possibility of functionally significant pharmacogenomic variation in the expression and function of GSTO1 and GSTO2.
Footnotes
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This work was supported in part by NIH Grants R01 GM28157 (B.M., O.E.S., and R.M.W.) and R01 GM35720 (O.E.S. and R.M.W.) and U01 GM61388, The Pharmacogenetics Research Network (O.E.S., L.L.P., I.M., B.W.E., D.J.S., E.D.W., and R.M.W.).
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The gene resequencing data described in this article have been deposited in the NIH-funded database PharmGKB with submission numbers PS205018, PS205019, PS205020, PS205021, PS205022, PS205026, PS205027, and PS205028 for GSTO1 and PS204659, PS205029, PS205030, PS205031, PS205032, and PS205033 for GSTO2.
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
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doi:10.1124/dmd.106.009613.
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ABBREVIATIONS: GST, glutathione S-glutathione; GSTO, glutathione S-transferase omega; AS3MT, arsenic methyltransferase; NIH, National Institutes of Health; AA, African-American; CA, Caucasian-American; HCA, Han Chinese American; MA, Mexican-American; PCR, polymerase chain reaction; FR, flanking region; UTR, untranslated region; SNP, single nucleotide polymorphism; PAGE, polyacrylamide gel electrophoresis; RRL, rabbit reticulocyte lysate; bp, base pair(s); WT, wild type.
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The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
- Received February 2, 2006.
- Accepted April 19, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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