Sinđić, Aleksandra

Many diseases are caused by altered epithelial Cl − or HCO 3 − transport. Mutations in the SLC26A3 transporter are causative for congenital chloride‐losing diarrhea; however, no other SLC26 transporter plays such a direct genetic role in disorders of epithelial Cl − transport. SLC26A9 is expressed in the lung, stomach, intestine and kidney (lesser extent) but its physiological function in these epithelia is not clear. Thus far, no diseases result from SLC26A9 mutations. However, database analysis reveals three single nucleotide polymorphisms (SNPs). We reasoned that the human SLC26A9‐SNPs would provide insight into what a disease phenotype might be functionally manifest. Here we analyzed the ion transport characteristics of human SLC26A9 and its SNPs: V622L, V744M and H748R. Human SLC26A9 and its three SNPs were expressed in Xenopus laevis oocytes. Effects on ion transport were evaluated using ion selective electrodes and voltage clamping. Measuring Cl − and HCO 3 − flux, our results show that SLC26A9 is a Cl − /HCO 3 − exchanger. One SNP, V622L, is located in the C‐terminus just before the STAS domain of SLC26A9. V622L has ~50% function (current and Cl − transport). These results suggest that the possession of V622L allele in humans would decrease SLC26A9 function and modulate the risk for lung disease (cystic fibrosis), gut disease (gastric ulcer) or hypertension, due to reduced Cl − transport across epithelial cells.