Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl− channel that is essential for electrolyte and fluid homeostasis. Preliminary evidence indicates that CFTR is a mechanosensitive channel. In lung epithelia, CFTR is exposed to different mechanical forces such as shear stress (Ss) and membrane distention. The present study questioned whether Ss and/or stretch influence CFTR activity (wild type, ∆F508, G551D). Human CFTR (hCFTR) was heterologously expressed in Xenopus oocytes and the response to the mechanical stimulus and forskolin/IBMX (FI) was measured by two-electrode voltage-clamp experiments. Ss had no influence on hCFTR activity. Injection of an intracellular analogous solution to increase cell volume alone did not affect hCFTR activity. However, hCFTR activity was augmented by injection after pre-stimulation with FI. The response to injection was similar in channels carrying the common mutations ∆F508 and G551D compared to wild type hCFTR. Stretch-induced CFTR activation was further assessed in Ussing chamber measurements using Xenopus lung preparations. Under control conditions increased hydrostatic pressure (HP) decreased the measured ion current including activation of a Cl− secretion that was unmasked by the CFTR inhibitor GlyH-101. These data demonstrate activation of CFTR in vitro and in a native pulmonary epithelium in response to mechanical stress. Mechanosensitive regulation of CFTR is highly relevant for pulmonary physiology that relies on ion transport processes facilitated by pulmonary epithelial cells.
Increased cell volume induced by intracellular injection of different volumes increases the activity of human CFTR expressed in Xenopus oocytes. A) Representative recording observing activation of CFTR initiated by forskolin and IBMX application and the subsequent injection of 55nl intracellular analogous solution. B) Activation by injection was volume dependent. [Display omitted]
•CFTR is activated by increased cell volume and hydrostatic pressure.•This indicates mechanosensitive activation of CFTR.•Common mutations (∆F508, G551D) did not affect mechanical activation of CFTR.•Shear stress does not affect CFTR's activity.