Bestrophin 1 and 2 are components of the Ca(2+) activated Cl(-) conductance in mouse airways.
Ca(2+) activated Cl(-) transport is found in airways and other organs and is abnormal in cystic fibrosis, polycystic kidney disease and infectious diarrhea. The molecular identity of Ca(2+) activated Cl(-) channels (CaCC) in the airways is still obscure. Bestrophin proteins were described to form CaCC and to regulate voltage gated Ca(2+) channels. The present Ussing chamber recordings on tracheas of bestrophin 1 knockout (vmd2(-/-)) mice indicate a reduced Cl(-) secretion when activated by the purinergic agonist ATP (0.1-1 muM). As two paralogs, best1 and best2, are present in mouse tracheal epithelium, we examined the contribution of each paralog to Ca(2+) activated Cl(-) secretion. In whole cell patch-clamp measurements on primary airway epithelial cells from vmd2(-/-) tracheas, ATP activated Cl(-) currents were reduced by 50%. Additional knockdown of mbest2 in vmd2(-/-) cells by short interfering RNA further suppressed ATP-induced Cl(-) currents down to 20% of that observed in cells from vmd2(+/+) animals. Moreover, RNAi-suppression of both mbest1 and mbest2 reduced CaCC in vmd2(+/+) cells. Direct activation of CaCC by increase of intracellular Ca(2+) was also reduced in whole cell recordings of vmd2(-/-) cells. These results clearly suggest a role of bestrophin 1 and 2 for Ca(2+) dependent Cl(-) secretion in mouse airways.
Barro-Soria
René
R
Institut für Physiologie, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany.
Schreiber
Rainer
R
Kunzelmann
Karl
K
D000818:Animals; D000075002:Bestrophins; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002713:Chlorine / Q000378:metabolism*; D004594:Electrophysiology; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D007473:Ion Channels; D051379:Mice; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D014132:Trachea / Q000378:metabolism*
C491856:Best1 protein, mouse; C497463:Best2 protein, mouse; D000075002:Bestrophins; D018118:Chloride Channels; D005136:Eye Proteins; D007473:Ion Channels; D002713:Chlorine; D002118:Calcium