NaSi-1 and Sat-1: structure, function and transcriptional regulation of two genes encoding renal proximal tubular sulfate transporters

Sulfate (SO42−) is an important anion regulating many metabolic and cellular processes. Maintenance of SO42− homeostasis occurs in the renal proximal tubule via membrane transport proteins. Two SO42− transporters that have been characterized and implicated in regulating serum SO42− levels are: NaSi-1, a Na+-SO42− cotransporter located at the brush border membrane and Sat-1, a SO42−-anion exchanger located on the basolateral membranes of proximal tubular cells. Unlike Sat-1, for which very few studies have looked at regulation of its expression, NaSi-1 has been shown to be regulated by various hormones and dietary conditions in vivo. To study this further, NaSi-1 (SLC13A1) and Sat-1 (SLC26A1) gene structures were determined and recent studies have characterized their respective gene promoters. This review presents the current understanding of the transcriptional regulation of NaSi-1 and Sat-1, and describes possible pathogenetic implications which arise as a consequence of altered SO42− homeostasis.