Single nucleotide polymorphisms in organic anion transporters as steroid sulfate conjugate transporter in Korean women with osteoporosis

초록

Single nucleotide polymorphisms (SNPs) are the most common form of human genetic variation. The non-synonymous SNPs (nsSNPs) cause changes in certain amino acid sequence that are likely to be failed to show the functional diversity of encoded proteins. The organic anion transporters (OATs) play an important role for elimination or reabsorption of endogenous or exogenous organic anionic compounds. Among OATs, hOAT3, 4 and 5 mediated the high affinity transport of estrone sulfate and dehydroepiandrosterone sulfate. The rapid bone loss that occurs in post-menopausal women is mainly due to the net decrease of estrogen. From 50 healthy subjects and 50 subjects with osteoporosis we screened for genetic polymorphism in coding region of hOAT3, 4 and 5 by denaturing gradient gel electrophoresis (DGGE). Using GC-clamp PCR and DGGE assay, we were able to find one SNP in hOAT3, three SNPs in hOAT4 and six SNPs in hOAT5 in Korean osteoporosis and normal subjects. Among them three non-synonymous SNPs were found in osteoporosis group (E278K of hOAT4 and Q256R and F426S of hOAT5). Among them we prepare E278K mutant of hOAT4 and investigated its transport properties. The uptake of [3H] estrone sulfate via hOAT4 mutant E278K was reduced when compared with wild-type hOAT4. The Km value for wild type and E278K was 0.7 M and 1.2 M, and the Vmax for wild-type and E278K was 1.8 and 0.47 pmol/oocyte/h, respectively. The present study demonstrates that hOAT4 variants are causing to inter-individual variations that is leading to the differences in anionic drug disposition and perhaps used as a marker to certain disease including osteoporosis. In addition, the comparative investigation of transport properties on the other hOAT5 mutant will be necessary.