Characterization of the L683P mutation of SLC26A9 in Xenopus oocytes

In the present study, we characterized a STAS-domain amino acid mutation of SLC26A9 having a significant impact on ion transport. We focused on the sole conserved L- leucine residue of the STAS domain identified among SLC26 members. We therefore characterized the L683P mutation of SLC26A9 in Xenopus oocytes by monitoring the protein functional expression (two-electrode technique for voltage-clamp analysis) and its presence at the cell membrane (surface protein biotinylation technique). This mutation was found to reduce Cl⁻ transport through SLC26A9 as well as the positive interaction exerted by SLC26A9 on CFTR ion transport activity. The origin of this effect is discussed in the light of the presence of the SLC26A9–L683P mutant at the plasma membrane.