WNK1 Activates Large-Conductance Ca2+-Activated K+ Channels through Modulation of ERK1/2 Signaling

With no lysine (WNK) kinases are members of the serine/threonine kinase family. We previously showed that WNK4 inhibits renal large-conductance Ca(2+)-activated K(+) (BK) channel activity by enhancing its degradation through a lysosomal pathway. In this study, we investigated the effect of WNK1 on BK channel activity. In HEK293 cells stably expressing the α subunit of BK (HEK-BKα cells), siRNA-mediated knockdown of WNK1 expression significantly inhibited both BKα channel activity and open probability. Knockdown of WNK1 expression also significantly inhibited BKα protein expression and increased ERK1/2 phosphorylation, whereas overexpression of WNK1 significantly enhanced BKα expression and decreased ERK1/2 phosphorylation in a dose-dependent manner in HEK293 cells. Knockdown of ERK1/2 prevented WNK1 siRNA-mediated inhibition of BKα expression. Similarly, pretreatment of HEK-BKα cells with the lysosomal inhibitor bafilomycin A1 reversed the inhibitory effects of WNK1 siRNA on BKα expression in a dose-dependent manner. Knockdown of WNK1 expression also increased the ubiquitination of BKα channels. Notably, mice fed a high-K(+) diet for 10 days had significantly higher renal protein expression levels of BKα and WNK1 and lower levels of ERK1/2 phosphorylation compared with mice fed a normal-K(+) diet. These data suggest that WNK1 enhances BK channel function by reducing ERK1/2 signaling-mediated lysosomal degradation of the channel.