Association of TMEM16A chloride channel overexpression with airway goblet cell metaplasia

Abstract

Key Points• Chloride channels are important for proper hydration of the airway surface.• TMEM16A protein is an important component of calcium-activated chloride channels.• Interleukin-4, a cytokine that induces mucous cell metaplasia, also upregulates calcium-dependent chloride secretion in human bronchial epithelial cells.• In bronchial epithelial cells treated with interleukin-4, we found that TMEM16A protein becomes highly expressed in goblet but not in ciliated cells.• Upregulation of TMEM16A by interleukin-4 may be important for secretion and proper expansion of mucins. AbstractThe TMEM16A protein has a potential role as a Ca 2+ -activated Cl − channel (CaCC) in airway epithelia where it may be important in the homeostasis of the airway surface fluid. We investigated the function and expression of TMEM16A in primary human bronchial epithelial cells and in a bronchial cell line (CFBE41o-). Under resting conditions, TMEM16A protein expression was relatively low. However, TMEM16A silencing with short-interfering RNAs caused a marked inhibition of CaCC activity, thus demonstrating that a low TMEM16A expression is sufficient to support Ca 2+ -dependent Cl − transport. Following treatment for 24-72 h with interleukin-4 (IL-4), a cytokine that induces mucous cell metaplasia, TMEM16A protein expression was strongly increased in approximately 50% of primary bronchial epithelial cells, with a specific localization in the apical membrane. IL-4 treatment also increased the percentage of cells expressing MUC5AC, a marker of goblet cells. Interestingly, MUC5AC was detected specifically in cells expressing TMEM16A. In particular, MUC5AC was found in 15 and 60% of TMEM16A-positive cells when epithelia were treated with IL-4 for 24 or 72 h, respectively. In contrast, ciliated cells showed expression of the cystic fibrosis transmembrane conductance regulator Cl − channel but not of TMEM16A. Our results indicate that TMEM16A protein is responsible for CaCC activity in airway epithelial cells, particularly in cells treated with IL-4, and that TMEM16A upregulation by IL-4 appears as an early event of goblet cell differentiation. These findings suggest that TMEM16A expression is particularly required under conditions of mucus hypersecretion to ensure adequate secretion of electrolytes and water.

Targeting ion channels in cystic fibrosis

“…Interestingly, TMEM16A expression is controlled by pro-inflammatory stimuli. In particular, treatment of cultured airway epithelial cells with the Th2 cytokines IL-4 and IL-13 or induction of asthma-like conditions in mice strongly increased TMEM16A expression [66,67]. Such results were further supported by finding TMEM16A hyperexpression in the airway epithelium of asthmatic patients [67].…”

“…Such results were further supported by finding TMEM16A hyperexpression in the airway epithelium of asthmatic patients [67]. Importantly, TMEM16A was particularly found in the membrane of mucus-producing goblet cells [66] (Fig. 1).…”

Thymosin α-1 does not correct F508del-CFTR in cystic fibrosis airway epithelia

“…30; for the laboratory at the Istituto Giannina Gaslini). Briefly, epithelial cells were obtained from mainstem human bronchi, derived from CF individuals undergoing lung transplant.…”

“…These cells also have endogenous expression of CaCCs, i.e., TME-M16A (30). We incubated the cells for 24 hours with VX-809 (3 μM), Tα-1 (100 ng/ml), or scrambled peptide (100 ng/ml).…”

Correctors of mutant CFTR enhance subcortical cAMP–PKA signaling through modulating ezrin phosphorylation and cytoskeleton organization

“…All primary cells were maintained at an air-liquid interface (ALI) according to the manufacturer's instruction. Primary cell differentiation was verified by immunostaining with a monoclonal anti-acetylated tubulin antibody (Sigma-Aldrich) for ciliated cells (Scudieri et al, 2012).…”