Electrophysiological Characterization of Functional and Pharmacological Effects of CLC-1 and CLC-2 Channel Activity
Introduction
The CLC family comprises of voltage-dependent cell surface chloride (Cl-) ion channels and intracellular Cl-/H+ transporters which perform an array of physiological functions. Two members of the CLC family, CLC-1 and CLC-2, are inward-rectifying ion channels with crucial roles in physiology. CLC-1 is predominantly expressed in skeletal muscle and performs a vital role in homeostasis of muscle excitability by repolarisation of skeletal muscle in response to depolarisation of an action potential. Variants of the CLCN1 gene are associated with a rare disorder of muscle membrane hyperexcitability, myotonia congenita. In contrast, the widely expressed CLC-2 is activated upon hyperpolarisation of the membrane and is involved in many physiological functions, including epithelial transport. Variants of the CLCN2 gene have been linked to rare disorders such as leukodystrophy and hyperaldosteronism.
Despite the range of channelopathies caused by CLC channel dysfunction, only a small number of selective CLC channel modulators have been reported, and the pharmacology of these channels is poorly characterized compared to other ligand-gated Cl- channels. The non-selective nature of currently defined Cl- channel modulators provides an obstacle in developing a therapeutic strategy targeting CLC channelopathies. This highlights the importance of developing novel routes to identify selective compounds in pursuit of therapeutic remedies for CLC channel dysfunction.
Advancements in 384-well automated high-throughput electrophysiology allow accelerated evaluation of large numbers of molecules against ion channel targets such as CLC-1 and CLC-2. We have developed robust, high quality recombinant cell lines expressing wild-type CLC-1 and CLC-2 ion channels. Electrophysiological characterization of these ion channels, including current-voltage relationship and assessment of known CLC inhibitors, was performed using automated voltage-clamp electrophysiology and should aid further investigation into the role of these exciting targets in physiological and pathological conditions.
