ClC-K chloride channels are essential for sodium chloride resorption in the loop of Henle of the kidney and for secretion of potassium by the stria vascularis of the inner ear. Renal and inner ear chloride channels consist of pore-forming ClC-Ka and ClC-Kb subunits and the accessory subunit barttin. We studied palmitoylation of barttin and could demonstrate that barttin is palmitylated in mouse kidney as well as upon heterologous expression in HEK293T cells. Palmitoylation was nearly abolished when Cys54 and Cys56 at the carboxy-terminal end of the transmembrane core were both mutated to serine. Individual point mutations reduced palmitoylation to a lesser extent.

Whole cell patch clamp recordings of HEK293T cells co-expressing barttin and hClC-Ka or hClC-Kb channels revealed reduced current amplitudes for C54S as well as for C56S. The degree of current reduction corresponded to the percentage of palmitoylated barttin. Noise analysis demonstrated that C54S or C56S modified neither the open probability nor the unitary current amplitude, but only the number of functional ClC-K/barttin channels. C54S/C56S barttin completely abolished anion currents.

The chaperone action of barttin does not require palmitoylation since confocal images displayed co-localization of hClC-K channels and barttin within the surface membrane of transfected MDCK-cells. Moreover, we did not observe changes in subcellular distribution of the ClC-K/barttin complex into the apical or basolateral membrane. We conclude that palmitoylation of barttin is necessary for function of ClC-K/barttin channels, demonstrating a powerful post-translational regulatory pathway to adapt the sodium chloride re-absorption of the kidney on a short time scale.