Hyperosmolarity stimulates transporter-mediated insertion of estrone sulfate into the plasma membrane, but inhibits the uptake by SLC10A1 (NTCP)

Many drugs are largely hydrophobic molecules; a transporter might conceivably insert these into the plasma membrane. At least 18 transporters from diverse families have been reported to transport model compound estrone sulfate alias estrone-3-sulfate (E3S). Out of these, we recently examined SLC22A11 (OAT4). We concluded comparison E3S and uric acid that does not translocate cytosol, but Here present hyperosmolarity hypertonicity assay differentiate mechanisms. Human were expressed heterologously in 293 cells. Solute uptake intact cells was measured by LC-MS. Addition mannitol or sucrose led rapid cell shrinkage, viability after 60 min hyperosmolar buffer impaired. A decrease substrate accumulation with increasing osmolarity as observed here for several substrates SLC22A11, ETT (SLC22A4), OCT2 (SLC22A2), OAT3 (SLC22A8), MATE1 (SLC47A1) suggests regular translocation cytosol. An increase OAT3, MATE1, SLC22A9, SLC10A6 implies insertion In marked contrast other transporters, bile SLC10A1 (NTCP, Na+ taurocholate co-transporting polypeptide) showed buffer; same taurocholic acid. Indeed, our data functional assays strongly suggest mechanism is identical both substrates. Apparently, unique has established evolution ensures amphipathic, detergent-like molecules