Abstract
The equilibrative nucleoside transporter 2 (ENT2; SLC29A2) is a bidirectional transporter that is involved in the disposition of naturally occurring nucleosides as well as a variety of anticancer and antiviral nucleoside analogs. The goal of the current study was to evaluate the function of genetic variants in ENT2 in cellular assays and to determine the haplotype structure of the coding and flanking intronic region of the gene. As part of a large study focused on genetic variation in membrane transporters (Leabman et al., 2003), DNA samples from ethnically diverse populations (100 African-Americans, 100 European-Americans, 30 Asians, 10 Mexicans, and 7 Pacific Islanders) were screened for variants in membrane transporters, including SLC29A2. Fourteen polymorphic sites in SLC29A2 were found, including 11 in the coding region. Five protein-altering variants were identified: three nonsynonymous variants, and two deletions. Each of the protein-altering variants was found at a very low frequency, occurring only once in the sample population. The nonsynonymous variants and the deletions were constructed via site-directed mutagenesis and were subsequently characterized in Xenopus laevis oocytes. All variants were able to take up inosine with the exception of ENT2-Δ845-846, which resulted in a frameshift mutation that prematurely truncated the protein. ENT2 showed very infrequent variation compared with most other transporter proteins studied, and it was found that five haplotypes were sufficient to describe the entire sample set. The low overall genetic diversity in SLC29A2 makes it unlikely that variation in the coding region contributes significantly to clinically observed differences in drug response.
Footnotes
-
This work was funded by National Institutes of Health Grants GM61390 and GM42230.
-
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
-
doi:10.1124/dmd.105.006270.
-
ABBREVIATIONS: CNT, concentrative nucleoside transporter; ENT, equilibrative nucleoside transporter.
- Received July 4, 2005.
- Accepted October 5, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|