SLC26A2 function in the kidney

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Sulfate is essential for normal cellular function. For example, it is required for the sulfation of proteoglycans, molecules that contribute to the structure of normal cartilage. Loss-of-function mutations in a cartilage sulfate transporter (SLC26A2) are the cause of a group of autosomal recessive chondrodysplasias. In these disorders, impaired sulfate uptake into chondrocytes leads to reduced proteoglycan sulfation. However, SLC26A2 is not only expressed in cartilage, but also in other tissues, such as the kidney. There, it specifically localizes to the apical (luminal) brush border membrane of proximal tubular cells. Sulfate is known to be freely filtered and extensively reabsorbed in the kidney, in particular the proximal tubule, but the exact function of SLC26A2 for renal sulfate transport has not been explored.We here propose to explore the renal function and regulation of SLC26A2. In preliminary studies, using the CRISPR/Cas9 system, we knocked out SLC26A2 in a cellular model of the proximal tubule, OK (opossum kidney) cells. We established a radioactive assay and demonstrated reduced cellular uptake of sulfate in SLC26A2 knockout cells.In the first part of this project, we aim to further characterize sulfate transport in OK cells regarding the transporters involved, their localization and interplay, as well as effects of various other ions on sulfate transport, with a focus on SLC26A2.Global Slc26a2 knockout is lethal in mice. We thus propose to generate a proximal tubule-specific knockout of Slc26a2 to define the role of Slc26a2 in renal sulfate transport. We will perform transport assays and compare sulfate levels in blood and urine between knockout mice and controls.Finally, we aim to study protein domains that determine SLC26A2 trafficking and apical membrane insertion. We will study the effect of dietary sulfate on Slc26a2 expression in the mouse model.We hope that these studies will form a basis for future translational studies on SLC26A2.