STABLE AND FUNCTIONAL EXPRESSION OF THE CLC-3 CHLORIDE CHANNEL IN SOMATIC-CELL LINES

The CIC family is the superfamily of voltage-gated Cl(-)channels. Although the CIC channels expressed in Xenopus oocytes have been characterized, their channel properties are still poorly understood. We recently cloned a unique member of the CIC family, CIC-3, that is expressed abundantly in neurons. Its channel activity was regulated by phorbol esters. Now, we have established a stably transfected somatic cell line expressing functional CIC-3 channels and examined the CIC-3 single-channel current by patch-clamp techniques. In inside-out patches from the stably transfected cells, a rise of bath Ca2+ concentration in the physiological range of intracellular Ca2+ concentrations inhibited the CIC-3 single-channel currents. This inhibition by Ca-2+ was independent of phosphorylation and ATP. Thus, the CIC-3 channel is a Ca2+-sensitive Cl(-)channel localized in neuronal cells, and its Ca2+ sensitivity implies a physiological role in neuronal functions.