The human renal sodium sulfate cotransporter (SLC13A1; hNaSi-1) cDNA and gene: organization, chromosomal localization, and functional characterization

Sulfate plays an essential role during growth, development, bone/cartilage formation, and cellular metabolism. In this study, we have determined the structure of the human Na+-sulfate cotransporter (hNaSi-1) cDNA (Human Genome Nomenclature Committee-approved symbol SLC13A1) and gene (NAS1). hNaSi-1 encodes a protein of 595 Amino acids with 13 putative transmembrane domains. hNaSi-1 mRNA expression was exclusive to the human kidney. Expression of hNaSi-1 protein in Xenopus oocytes demonstrated a high-affinity Na+-sulfate cotransporter that was inhibited by selenate, thiosulfate, molybdate, tungstate, citrate, and succinate. Antisense inhibition experiments suggest hNaSi-1 to represent the major Na+-sulfate cotransporter in the human kidney. NAS1 was localized on human chromosome 7, mapped to 7q31-q32, near the sulfate transporter genes, DRA and SUT-1. The NAS1 gene contains 15 exons, spanning over 83 kb in length. Knowledge of the structure, function, and chromosomal localization of hNaSi-1 will permit the screening of NAS1 mutations in humans with disorders in renal sulfate reabsorption and homeostasis.