TMEM16A, A Membrane Protein Associated with Calcium-Dependent Chloride Channel Activity

TLDR

Calcium‑dependent chloride channels are essential for electrolyte and fluid secretion, olfactory perception, and neuronal and smooth muscle excitability, yet their molecular identity remains unclear. The study sought to identify IL‑4‑regulated membrane proteins that constitute calcium‑dependent chloride channels, aiming to enhance understanding of chloride transport physiology and facilitate drug‑development tools. By combining global gene‑expression profiling with siRNA knockdown in epithelial cells, the authors showed that TMEM16A is linked to calcium‑dependent chloride currents, as confirmed by halide‑sensitive fluorescence, short‑circuit current, and patch‑clamp recordings. IL‑4 treatment increased calcium‑dependent chloride channel activity, and the results demonstrate that TMEM16A is an intrinsic component of this channel.

Abstract

Calcium-dependent chloride channels are required for normal electrolyte and fluid secretion, olfactory perception, and neuronal and smooth muscle excitability. The molecular identity of these membrane proteins is still unclear. Treatment of bronchial epithelial cells with interleukin-4 (IL-4) causes increased calcium-dependent chloride channel activity, presumably by regulating expression of the corresponding genes. We performed a global gene expression analysis to identify membrane proteins that are regulated by IL-4. Transfection of epithelial cells with specific small interfering RNA against each of these proteins shows that TMEM16A, a member of a family of putative plasma membrane proteins with unknown function, is associated with calcium-dependent chloride current, as measured with halide-sensitive fluorescent proteins, short-circuit current, and patch-clamp techniques. Our results indicate that TMEM16A is an intrinsic constituent of the calcium-dependent chloride channel. Identification of a previously unknown family of membrane proteins associated with chloride channel function will improve our understanding of chloride transport physiopathology and allow for the development of pharmacological tools useful for basic research and drug development.