SLC21A3 Protein, Human (sf9, His, MBP, FLAG)

SLC21A3, a Na(+)-independent transporter, facilitates the cellular uptake of a diverse array of organic anions, including unconjugated and conjugated bile salts such as cholate, deoxycholate, taurocholate, and glycocholate, at the plasma membrane. This transporter is crucial for the intestinal absorption of bile acids and is responsible for the uptake of dehydroepiandrosterone 3-sulfate (DHEAS), estrone 3-sulfate, 17beta-estradiol 17-O-(beta-D-glucuronate), and all-trans-retinol (atROL) across the human retinal pigment epithelium, essential for maintaining visual cycle integrity and vision. Additionally, SLC21A3 mediates the transport of clinically used drugs, thyroid hormones (T3 and T4), prostaglandin E2, and neuropeptides such as substance P/TAC1 and vasoactive intestinal peptide/VIP. It is implicated in blood-brain and -cerebrospinal fluid barrier transport of organic anions and signal mediators, hormone uptake by neural cells, and potentially contributes to the regulation of organic compound transport in the testis across the blood-testis barrier. Furthermore, SLC21A3 exhibits a pH-sensitive substrate specificity, with hydrogencarbonate/HCO3(-) acting as the probable counteranion in the exchange for organic anions, suggesting a role in substrate transport in acidic microenvironments. The protein may also play a role in the plasma and tissue distribution of chemotherapeutic drugs such as methotrexate and paclitaxel.