SLC26A9 is a multifunctional anion transporter that operates as both an ion channel and anion exchanger 1. Its primary function is chloride channel activity, mediating anion transport through an alternate-access mechanism with a saturable binding site 23. SLC26A9 also functions as a chloride/bicarbonate antiporter in a DIDS- and thiosulfate-sensitive manner 41. In airway epithelia, SLC26A9 is constitutively active and localizes to the apical membrane of ciliated cells, contributing to basal chloride secretion alongside CFTR 56. SLC26A9 physically interacts with and enhances CFTR activity and expression in bronchial epithelial cells 7. Genome-wide association studies identify SLC26A9 as a significant genetic modifier of cystic fibrosis disease severity, making it a potential therapeutic target for CF lung disease 8. In renal systems, SLC26A9 participates in bicarbonate secretion synergistically with CFTR and pendrin 9. Beyond ion transport, SLC26A9 upregulation is associated with breast cancer progression through PI3K/AKT pathway activation 10. Expression patterns and functional contributions remain incompletely characterized, particularly regarding tissue-specific localization and optimal pharmacological targeting strategies.