CFTR is a mechanosensitive anion channel: a real stretch?

The cystic fibrosis transmembrane conductance regulator (CFTR) anion channel represents the rate-limiting step for chloride and fluid secretion in most epithelial tissues in the body. More recently, CFTR activity has also been shown to regulate muscle contraction, neuroendocrine function, and cartilage formation, implicating the channel in many important physiological activities from diverse systems. A major interest in the channel stems from the fact that loss of function mutations in the gene encoding CFTR result in the inherited disease cystic fibrosis, one of the most common, life threatening, diseases found in the Caucasian population. At the other end of the spectrum, and affecting far more people globally, over active CFTR causes clinically important secretory diarrhoea induced by toxins from pathogenic bacteria like cholera. Therefore, it is not surprising that much research has focussed on understanding how CFTR channel activity is regulated and what goes wrong in disease states. For the channel to open, it must be first phosphorylated by PKA, and then ATP must also bind to CFTR's cytoplasmic domains. Now a recent Nature Cell Biology paper has shown that CFTR can also be activated by increases in membrane tension (or stretch), through a phosphorylation and ATP- independent mechanism. This unexpected and novel finding identifies CFTR as a mechanosensitive ion channel. This work could have major implications for our understanding of the biological control of CFTR as well identifying new roles for this channel in mechanosensitive tissues and processes such as regulatory volume decrease and muscle contraction.