Characterization of single nucleotide polymorphism in human steroid conjugate transporters in Korean osteoporosis patients

초록

Estrogen is the key steroid hormone for maintenance of bone mass and its deficiency is the major cause of age-related bone loss in humans. Estrogen deficiency also induces an imbalance in bone remodeling, which accelerates loss of bone mass and increases the risk of fracture. It is well known that estrogen conjugates were transported by several membrane integrated transporters such as ABC, SLC21 and SLC22 families. In SLC22 family, SLC22A8, A9 and A11 are well characterized as steroid sulfate conjugate (estrone sulfate and dehydroepiandrosterone sulfate) transporter. Therefore we screen single nucleotide polymorphism of steroid sulfate conjugate transporters (SLC22A8, A9 and A11) in 50 female osteoporosis patients and 50 control subject in the Korean women using denaturing gradient gel electrophoresis (DGGE). Using GC-clamp PCR and DGGE assay, we found a SNP in SLC22A8, six SNPs in SLC22A9 and five SNPs in SLC22A11. Among them, two and one non-synonymous SNPs were found in SLC22A9 (Q256R and F426S) and SLC22A11 (E278K), respectively. We prepare E2 78K mutant of SLC22A11 and investigated its transport properties. The uptake of [<SUP>3</SUP>H] estrone sulfate via mutant E278K was reduced when compared with wild-type SLC22A11. The Km value for wild type and E278K was 0.7 and 1.2 &mu;M, and the Vmax for wild-type and E278K was 1.8 and 0.47 pmol/oocyte/h, respectively. The present study demonstrates that SLC22A11 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 and functional analysis of SLC22A9 should be necessary.