RT Journal Article
SR Electronic
T1 Genetic Variants of the Human Dipeptide Transporter PEPT1
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 636
OP 646
DO 10.1124/jpet.105.094615
VO 316
IS 2
A1 Pascale Anderle
A1 Carsten Uhd Nielsen
A1 Julia Pinsonneault
A1 Pernille Lindskov Krog
A1 Birger Brodin
A1 Wolfgang Sadée
YR 2006
UL http://jpet.aspetjournals.org/content/316/2/636.abstract
AB We tested whether genetic polymorphisms affect activity of the dipeptide transporter PEPT1, which mediates bioavailability of peptidomimetic drugs. All 23 exons and adjoining intronic sections of PEPT1 (SLC15A1) were sequenced in 247 individuals of various ethnic origins (Coriell collection). Of 38 single nucleotide polymorphisms (SNPs), 21 occurred in intronic and noncoding regions and 17 in exonic coding region, of which nine were nonsynonymous. Eight nonsynonymous variants were cloned into expression vectors and functionally characterized after transient transfection into Cos7 and Chinese hamster ovary cells. None of the variants had altered transport activity for various ligands, supporting previous results, except for the new, low-frequency PEPT1-F28Y. This variant displayed significantly reduced cephalexin uptake attributable to increased Km. Altered pH dependence of substrate transport suggested a role for F28Y in H+-driven translocation. Haplotype analysis revealed significant differences among ethnic populations. To search for cis-acting polymorphisms affecting transcription and mRNA processing, we measured allelic PEPT1 mRNA expression in human intestinal biopsy samples using a frequent-marker SNP in exon 17. Of 24 heterozygous samples, significant differences in allelic mRNA levels of 20 to 30% were observed in seven tissues. However, the small difference suggests that cis-acting regulatory factors have only limited effects on transporter activity. We also measured the relative formation of a splice variant (PEPT1-RF). PEPT1-RF mRNA levels ranged from 2 to 44% of total PEPT1-related mRNA, with potential consequences for drug absorption. Together with previous results, this study reveals a relatively low level of genetic variability in polymorphisms affecting both protein function and gene regulation. The American Society for Pharmacology and Experimental Therapeutics