Functional characterization of chloride intracellular channel 6 (CLIC6).

Abstract

Chloride intracellular channels (CLICs) are a family of proteins that can adopt soluble and transmembrane forms. The newly discovered member of the family CLIC6 is involved in several human cancers. The soluble structure of the channel has been resolved but the exact function of CLIC6 and the membrane structure remains unknown. Here we aimed to characterize the biophysical properties of this channel with a patch-clamp approach. To characterize the biophysical properties of CLIC6, we expressed CLIC6 in HEK293 cells. We established the biophysical properties of CLIC6 by using whole-cell and cell-attached configurations. By using various anion solutions, we also determined that CLIC6 is more permeable to chloride (Cl) as compared to bromide (Br), fluoride (F), and potassium (K) ions. In the whole-cell configuration, the CLIC6 currents were inhibited (48.4%) after the addition of 10 µM of IAA-94 (CLIC-specific blocker). Using qRT-PCR, we identified that CLIC6 is most abundant in lung and brain cells. High-resolution microscopy revealed that CLIC6 localizes to the plasma membrane on ectopic expression. Overall, we have determined the biophysical properties of CLIC6 and established it as a Cl channel.