Characterisation and regulation of wild type and mutant TASK-1 two pore domain potassium channels indicated in pulmonary arterial hypertension

KEY POINTS SUMMARY

The TASK-1 channel gene (KCNK3) has been identified as a possible disease-causing gene in heritable pulmonary arterial hypertension (PAH). In this study we show that novel mutated TASK-1 channels, seen in PAH patients, have a substantially reduced current compared to wild type TASK-1 channels. These mutated TASK-1 channels are located at the plasma membrane to the same degree as wild type TASK-1 channels. ONO-RS-082 and alkaline pH 8.4 both activate TASK-1 channels but do not recover current through mutant TASK-1 channels. We show that the guanylate cyclase activator, riociguat, a novel treatment for PAH, enhances current through TASK-1 channels but does not recover current through mutant TASK-1 channels.

ABSTRACT

Pulmonary arterial hypertension (PAH) affects approximately 15-50 people per million. KCNK3, the gene that encodes the two pore domain potassium channel TASK-1 (K2P3.1), has been identified as a possible disease-causing gene in heritable PAH. Recently two new mutations have been identified in KCNK3, G106R and L214R, in PAH patients. The aim of this study is to characterise the functional properties and regulation of wildtype (WT) and mutated TASK-1 channels and understand how these might contribute to PAH and its treatment. Currents through WT and mutated human TASK-1 channels transiently expressed in tsA201 cells were measured using whole-cell patch-clamp electrophysiology. Localisation of fluorescently-tagged channels was visualised using confocal microscopy and quantified with in-cell and on-cell Westerns. G106R or L214R mutated channels were located at the plasma membrane to the same degree as WT channels, however their current was markedly reduced compared to WT TASK-1 channels. Functional current through these mutated channels could not be restored using activators of WT TASK-1 channels (pH 8.4, ONO-RS-082). The guanylate cyclase activator, riociguat, enhanced current through WT TASK-1 channels, however, like the other activators investigated, riociguat did not have any effect on current through mutated TASK-1 channels. Thus, novel mutations in TASK-1 seen in PAH, substantially alter the functional properties of these channels. Current through these channels could not be restored by activators of TASK-1 channels. Riociguat enhancement of current through TASK-1 channels could contribute to its therapeutic benefit in the treatment of PAH.