Inhibition of volume-regulated anion channels by expression of the cystic fibrosis transmembrane conductance regulator

1. To investigate whether the cystic fibrosis transmembrane conductance regulator (CFTR) interacts with volume regulated anion channels (VRACs), we measured the volume-activated chloride current (I-Cl,I-swell) using the whole-cell patch-clamp technique in calf pulmonary artery endothelial (CPAE) cells and in COS cells transiently transfected with wild-type (WT) CFTR and the deletion mutant Delta F508 CFTR. 2. I-Cl,I-swell was significantly reduced in CPAE cells expressing WT CFTR to 66.5 +/- 8.8% (n = 13; mean +/- S.E.M.) of the control value (n = 11). This reduction was independent of activation of the CFTR channel. 3. Expression of Delta F508 CFTR resulted in two groups of CP Delta E cells. In the first group IBMX and forskolin could activate a Cl- current. In these cells I-Cl,I-swell was reduced to 52.7 +/- 18.8% (n = 5) of the control value (n = 21). In the second group IBMX and forskolin could not activate a current. The amplitude of I-Cl,I-swell in these cells was not significantly different from the control value (112.4 +/- 13.7 %, n = 11; 21 control cells). 4. Using the same method we showed that expression of WT CFTR in COS cells reduced I-Cl,I-swell to 62.1 +/- 11.9% (n = 14) of the control value (n = 12) without any changes in the kinetics of the current. Non-stationary noise analysis suggested that there is no significant difference in the single channel conductance of VRAC between CFTR expressing and nonexpressing COS cells. 5. We conclude that expression of WT CFTR down-regulates I-Cl,I-swell in CPAE and COS cells, suggesting an interaction between CFTR and VRAC independent of activation of CFTR.