Combined antisense and pharmacological approaches implicate hTASK as an airway O2 sensing K+ channel

Neuroepithelial bodies act as airway oxygen sensors. The lung carcinoma line H146 is an established model for neuroepithelial body cells. Although O-2 sensing in both cells is via NADPH oxidase H2O2/free radical production and acute hypoxia promotes K+ channel closure and cell depolarization, the identity of the K+ channel is still controversial. However, recent data point toward the involvement of a member of the tandem P domain family of K+ channels. Reverse transcription-polymerase chain reaction screening indicates that all known channels other than hTWIK1 and hTRAAK are expressed in H146 cells. Our detailed pharmacological characterization of the O-2-sensitive K+ current described herein is compatible with the involvement of hTASK1 or hTASK3 (pH dependence, tetraethylammonium and dithiothreitol insensitivity, blockade by arachidonic acid, and halothane activation). Furthermore, we have used antisense oligodeoxynucleotides directed against hTASK1 and hTASK3 to suppress almost completely the hTASK1 protein and show that these cells no longer respond to acute hypoxia; this behavior was not mirrored in liposome-only or missense-treated cells. Finally, we have used Zn2+ treatment as a maneuver able to discriminate between these two homologues of hTASK and show that the most likely candidate channel for O-2 sensing in these cells is hTASK3.