Combined Antisense and Pharmacological Approaches Implicate hTASK as an Airway O2 Sensing K+Channel

Abstract

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 H 2 O 2 /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 Zn 2؉ 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.

Ion channels in autoimmune neurodegeneration

“…These results and other lines of evidence point to TASK1 channels as being critical modulators of T cell immunity and neurodegeneration. Hypoxia and tissue acidification, that are characteristic conditions for an inflammatory environment as it occurs in EAE brain and in spinal cord tissue [6], modulate TASK1 channel function [66][67][68][69]. Based on these results, on the unique pharmacological profile of TASK1 and on the knowledge about its extensive actions on basic cellular processes, it is assumed that TASK1 channels on neurons could push apoptotic mechanisms.…”

Molecular Background of Leak K+Currents: Two-Pore Domain Potassium Channels

“…It has been suggested that NADPH oxidase maintains oxidizing environment required for tonic K ϩ channel activity, and this is abolished during hypoxia (257). In a well-established model of neuroepithelial cells, in the human H146 carcinoma cell line, RT-PCR revealed the expression of TASK-1 (258) and TASK-3 (128). Hypoxia also reduced a TASK-like K ϩ conductance, which first appeared to be resistant to acidification (compared with the extreme sensitivity of TASK-1; Ref.…”

Expression of Tandem P Domain K+Channel, TREK-1, in the Rat Carotid Body

“…Several potassium channels show an oxygen-sensing property: TASK-1 in cerebellar granule neurons (Plant et al 2002) and in glomus cells (Buckler et al 2000); TASK1 and TASK-3 in H146 cells (Hartness et al 2001); THIK-1 in glossopharyngeal neurons (Campanucci et al 2003); Kv3.4 and Kv4.3 in rabbit glomus cells (Sanchez et al 2002). However, TREK-1 sensitivity for oxygen is argued.…”