The transmembrane protein 16A Ca(2+)-activated Cl- channel in airway smooth muscle contributes to airway hyperresponsiveness

Am J Respir Crit Care Med. 2013 Feb 15;187(4):374-81. doi: 10.1164/rccm.201207-1303OC. Epub 2012 Dec 13.


Rationale: Asthma is a chronic inflammatory disorder with a characteristic of airway hyperresponsiveness (AHR). Ca(2+)-activated Cl(-) [Cl((Ca))] channels are inferred to be involved in AHR, yet their molecular nature and the cell type they act within to mediate this response remain unknown.

Objectives: Transmembrane protein 16A (TMEM16A) and TMEM16B are Cl((Ca)) channels, and activation of Cl((Ca)) channels in airway smooth muscle (ASM) contributes to agonist-induced airway contraction. We hypothesized that Tmem16a and/or Tmem16b encode Cl((Ca)) channels in ASM and mediate AHR.

Methods: We assessed the expression of the TMEM16 family, and the effects of niflumic acid and benzbromarone on AHR and airway contraction, in an ovalbumin-sensitized mouse model of chronic asthma. We also cloned TMEM16A from ASM and examined the Cl(-) currents it produced in HEK293 cells. We further studied the impacts of TMEM16A deletion on Ca(2+) agonist-induced cell shortening, and on Cl((Ca)) currents activated by Ca(2+) sparks (localized, short-lived Ca(2+) transients due to the opening of ryanodine receptors) in mouse ASM cells.

Measurements and main results: TMEM16A, but not TMEM16B, is expressed in ASM cells and its expression in these cells is up-regulated in ovalbumin-sensitized mice. Niflumic acid and benzbromarone prevent AHR and contraction evoked by methacholine in ovalbumin-sensitized mice. TMEM16A produces Cl((Ca)) currents with kinetics similar to native Cl((Ca)) currents. TMEM16A deletion renders Ca(2+) sparks unable to activate Cl((Ca)) currents, and weakens caffeine- and methacholine-induced cell shortening.

Conclusions: Tmem16a encodes Cl((Ca)) channels in ASM and contributes to Ca(2+) agonist-induced contraction. In addition, up-regulation of TMEM16A and its augmented activation contribute to AHR in an ovalbumin-sensitized mouse model of chronic asthma. TMEM16A may represent a potential therapeutic target for asthma.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Anoctamin-1
  • Asthma / genetics
  • Asthma / metabolism*
  • Asthma / physiopathology
  • Blotting, Western / methods
  • Bronchial Hyperreactivity / genetics
  • Bronchial Hyperreactivity / metabolism*
  • Bronchial Hyperreactivity / physiopathology
  • Chloride Channels / genetics
  • Chloride Channels / metabolism*
  • Disease Models, Animal
  • Female
  • Mice
  • Mice, Inbred C57BL
  • Myocytes, Smooth Muscle / metabolism*
  • Patch-Clamp Techniques / methods
  • Real-Time Polymerase Chain Reaction / methods
  • Up-Regulation / genetics


  • ANO1 protein, mouse
  • Anoctamin-1
  • Chloride Channels