R. Vennekens et al., Inhibition of volume-regulated anion channels by expression of the cystic fibrosis transmembrane conductance regulator, J PHYSL LON, 515(1), 1999, pp. 75-85
1. To investigate whether the cystic fibrosis transmembrane conductance reg
ulator (CFTR) interacts with volume regulated anion channels (VRACs), we me
asured the volume-activated chloride current (I-Cl,I-swell) using the whole
-cell patch-clamp technique in calf pulmonary artery endothelial (CPAE) cel
ls and in COS cells transiently transfected with wild-type (WT) CFTR and th
e 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). T
his 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 th
ese 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 significant
ly different from the control value (112.4 +/- 13.7 %, n = 11; 21 control c
ells).
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 = 1
2) without any changes in the kinetics of the current. Non-stationary noise
analysis suggested that there is no significant difference in the single c
hannel conductance of VRAC between CFTR expressing and nonexpressing COS ce
lls.
5. We conclude that expression of WT CFTR down-regulates I-Cl,I-swell in CP
AE and COS cells, suggesting an interaction between CFTR and VRAC independe
nt of activation of CFTR.