Receptor mediated endocytosis is a constitutive high capacity pathway for the reabsorption of proteins from the glomerular filtrate by the renal proximal tubule. ClC-5 is a voltage-gated chloride channel found in the proximal tubule where it has been shown to be essential for protein uptake, based on evidence from patients with Dents disease and studies in ClC-5 knockout mice. In order to further delineate the role of ClC-5 in albumin uptake, we performed a yeast 2-hybrid screen with the C-terminal tail of ClC-5 to identify any interactions of the channel with proteins involved in endocytosis. We found that the C-terminal tail of ClC-5 bound the actin depolymerising protein, cofilin, a result that was confirmed by GST-fusion pulldown assays. In cultured proximal tubule cells, cofilin was distributed in nuclear, cytoplasmic and microsomal fractions and co-localised with ClC-5. Phosphorylation of cofilin by overexpression LIMK-1 resulted in a stabilisation of the actin cytoskeleton. Phosphorylation of cofilin in two proximal tubule cell models (LLC-PK1 and OK) was also accompanied by a pronounced inhibition of albumin uptake. This study identifies a novel interaction between the C terminal tail of ClC-5 and cofilin, an actin associated protein that is crucial in the regulation of albumin uptake by the proximal tubule.