Protein localization of SLC26A2 (DTDST) in rat kidneys

Abstract

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 a range of chondrodysplasias due to undersulfation of proteoglycans in chondrocytes, a major site of DTDST protein expression. DTDST mRNA had previously been detected in the kidney, but protein expression had 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 also performed with antibodies directed against megalin, which is found in the brush border membrane and coated pits of the proximal tubule. IMF analysis indicates that DTDST protein expression is limited to the brush border membrane of proximal tubule cells in the renal cortex. DTDST expression was not detected in glomeruli or 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.