Calcium-activated chloride secretion in epithelial tissues described for many years. However, the molecular identity of the channel responsible for the Ca2+-activated Cl− secretion in epithelial tissues has remained a mystery. More recently, TMEM16A has been identified as a new putative Ca2 -activated Cl- channel (CaCC),. The primary goal of this article will be to review the characterization of TMEM16A, as it relates to the physical structure of the channel, as well as, important residues that confer voltage and Ca2+-sensitivity of the channel. This review will also discuss the role of TMEM16A in epithelial physiology and potential associated-pathophysiology. This will include discussion of developed knockout models that have provided much needed insight on the functional localization of TMEM16A in several epithelial tissues. Finally, this review will examine the implications of the identification of TMEM16A as it pertains to potential novel therapies in several pathologies.

The Cl- transporting proteins CFTR, SLC26A9, and anoctamin (ANO1; ANO6) appear to have more in common than anticipated initially. They all participate in the pathogenic process and clinical outcome of renal and airway diseases. In the present review we will therefore concentrate on recent findings concerning electrolyte transport in airways and kidney, and the role of CFTR, SLC26A9, and anoctamins (ANO1 and ANO6). A particular focus will be on the airway diseases cystic fibrosis and asthma, as well as renal alkalosis and polycystic kidney disease. In essence, latest findings are summarized that demonstrate CFTR as the only relevant secretory Cl- channel in airways under basal (non-stimulated) conditions and after stimulation by secretagogues. For proper CFTR function, expression of ANO1 and ANO6 appears to be a prerequisite. Evidence is summarized suggesting that the Cl- transporter SLC26A9 may have a reabsorptive rather than a Cl- secretory function in the airways. In renal collecting ducts bicarbonate secretion takes place due to synergistic tasks of CFTR and the Cl-/HCO3- transporter SLC26A4 (pendrin), which is likely to be supported by ANO1. Finally, in autosomal dominant polycystic kidney disease (ADPKD), the secretory function of CFTR in renal cyst formation might have been overestimated, while ANO1 as well as ANO6 turned out to be crucial in ADPKD, and therefore represent novel pharmacological targets for the treatment of polycystic kidney disease.

TMEM16A is a Ca2+-activated Cl- channel expressed in various species and tissues. In mammalian skeletal muscle precursors, the activity of these channels is still poorly investigated. Here, we characterized TMEM16A channels and investigated if the pharmacological activation of Piezo1 channels could modulate the TMEM16A currents in mouse myogenic precursors. Whole-cell patch-clamp recordings combined with the pharmacological agents Ani9, T16inh-A01 and Yoda1 were used to characterize TMEM16A-mediated currents and the possible modulatory effect of Piezo1 activity on TMEM16A channels. Western blot analysis was also carried out to confirm the expression of TMEM16A and Piezo1 channel proteins. We found that TMEM16A channels were functionally expressed in fusion-competent mouse myogenic precursors. The pharmacological blockage of TMEM16A inhibited myocyte fusion into myotubes. Moreover, the specific Piezo1 antagonist Yoda1 positively regulated TMEM16A currents. The findings demonstrate, for the first time, a sarcolemmal TMEM16A channel activity and its involvement at the early stage of mammalian skeletal muscle differentiation. In addition, the results suggest a possible role of mechanosensitive Piezo1 channels in the modulation of TMEM16A currents.