ARF6-dependent interaction of the TWIK1 K+ channel with EFA6, a GDP/GTP exchange factor for ARF6.

TWIK1 belongs to a family of K(+) channels involved in neuronal excitability and cell volume regulation. Its tissue distribution suggests a role in epithelial potassium transport. Here we show that TWIK1 is expressed in a subapical compartment in renal proximal tubules and in polarized MDCK cells. In nonpolarized cells, this compartment corresponds to pericentriolar recycling endosomes. We identified EFA6, an exchange factor for the small G protein ADP-ribosylation factor 6 (ARF6), as a protein binding to TWIK1. EFA6 interacts with TWIK1 only when it is bound to ARF6. Because ARF6 modulates endocytosis at the apical surface of epithelial cells, the ARF6/EFA6/TWIK1 association is probably important for channel internalization and recycling.