Protein localization of SLC26A2 (DTDST) in rat kidney

The SLC26 family represents a group of integral membrane anion transport proteins. Mutations in one member of this protein family, SLC26A2 (DTDST or diastrophic dysplasia sulfate transporter), result in various chondrodysplasias due to undersulfation of proteoglycans in chondrocytes, a major site of DTDST protein expression. DTDST mRNA has been detected in the kidney, but protein expression has not been characterized. Our objective for this study was to determine the protein localization of this sulfate transporter in the kidney. We used immunofluorescence (IMF) techniques with an anti-DTDST monoclonal antibody to examine kidneys harvested from adult rats. Double labeling was performed with antibodies directed against megalin, which is found in the microvillus membrane and coated pits of the proximal tubule. IMF analysis indicated that DTDST protein expression was limited to the microvillus membrane of proximal tubule cells in the renal cortex but absent in glomeruli and other nephron segments. DTDST was also detected in isolated rat kidney proximal tubule microvillus membranes by Western blot analysis, confirming the immunofluorescent localization of the DTDST transporter to this nephron segment. The functional role of the DTDST protein in the kidney is unknown, but it may play a role in proximal tubule sulfate transport.