Scudieri, Paolo, Caci, Emanuela, Bruno, Silvia, Ferrara, Loretta, Schiavon, Marco, Sondo, Elvira, Tomati, Valeria, Gianotti, Ambra, Zegarra-Moran, Olga, Pedemonte, Nicoletta, Rea, Federico and Galietta, Luis J V (2012) Association of TMEM16A protein expression with mucous cell metaplasia of human bronchial epithelial cells. Journal of Physiology.

Abstract

The TMEM16A membrane protein has a potential role as a Ca2+-activated Cl- channel
(CaCC) in airway epithelia. Accordingly, TMEM16A may be physiologically
important in the homeostasis of the airway surface fluid and may represent a drug
target to correct the defective Cl- secretion in cystic fibrosis. We investigated the
function and expression of TMEM16A in primary human bronchial epithelial cells
and in a bronchial cell line (CFBE41o-) using short-circuit recordings, patch-clamp
experiments, immunofluorescence, and western blots. Under resting conditions,
TMEM16A protein expression in these cells was relatively low. However,
TMEM16A silencing with specific siRNAs caused a marked inhibition of CaCC
activity thus demonstrating that a relatively low TMEM16A expression is sufficient to
support Ca2+-dependent Cl- transport. CaCC activity was also markedly inhibited
with the pharmacological inhibitor CaCCinh-A01. Following treatment for 24-72
hours with interleukin-4 (IL-4), a cytokine that induces mucous cell metaplasia, we
found that 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 decreased the percentage of ciliated cells and
increased that of cells expressing MUC5AC, a marker of goblet cells. Interestingly,
MUC5AC expression in epithelia treated for 24 hours with IL-4 was restricted to ~
15% of TMEM16A-positive cells. After 72 hours of treatment, the percentage of
cells co-expressing MUC5AC and TMEM16A increased to ~ 60%. In contrast,
ciliated cells showed expression of the CFTR 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. Furthermore,
TMEM16A upregulation appears as an early event of goblet cell differentiation
induced by IL-4. These findings may suggest that TMEM16A expression is
particularly required under conditions of mucus hypersecretion to ensure adequate
secretion of electrolytes and water.

Item Type:	Article
Additional Information:	Literature compounds T16Ainh-A01 and CaCCinh-01 synthesised and provided by Novartis.
Date Deposited:	13 Oct 2015 13:14
Last Modified:	13 Oct 2015 13:14
URI:	https://oak.novartis.com/id/eprint/8017