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WNK1 activates large-conductance Ca2+-activated K+ channels through modulation of ERK1/2 signaling.

ABSTRACT: 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 ? subunit of BK (HEK-BK? cells), siRNA-mediated knockdown of WNK1 expression significantly inhibited both BK? channel activity and open probability. Knockdown of WNK1 expression also significantly inhibited BK? protein expression and increased ERK1/2 phosphorylation, whereas overexpression of WNK1 significantly enhanced BK? expression and decreased ERK1/2 phosphorylation in a dose-dependent manner in HEK293 cells. Knockdown of ERK1/2 prevented WNK1 siRNA-mediated inhibition of BK? expression. Similarly, pretreatment of HEK-BK? cells with the lysosomal inhibitor bafilomycin A1 reversed the inhibitory effects of WNK1 siRNA on BK? expression in a dose-dependent manner. Knockdown of WNK1 expression also increased the ubiquitination of BK? channels. Notably, mice fed a high-K(+) diet for 10 days had significantly higher renal protein expression levels of BK? 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.

SUBMITTER: Liu Y

PROVIDER: S-EPMC4378107 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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WNK1 activates large-conductance Ca2+-activated K+ channels through modulation of ERK1/2 signaling.

Liu Yingli Y Song Xiang X Shi Yanling Y Shi Zhen Z Niu Weihui W Feng Xiuyan X Gu Dingying D Bao Hui-Fang HF Ma He-Ping HP Eaton Douglas C DC Zhuang Jieqiu J Cai Hui H

Journal of the American Society of Nephrology : JASN 20140821 4

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 probab ...[more]

PMID: 25145935

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Project description:The Ca2+-dependent gating mechanism of large-conductance calcium-activated K+ (BK) channels from cultured rat skeletal muscle was examined from low (4 microM) to high (1,024 microM) intracellular concentrations of calcium (Ca2+i) using single-channel recording. Open probability (Po) increased with increasing Ca2+i (K0. 5 11.2 +/- 0.3 microM at +30 mV, Hill coefficient of 3.5 +/- 0.3), reaching a maximum of approximately 0.97 for Ca2+i approximately 100 microM. Increasing Ca2+i further to 1,024 microM had little additional effect on either Po or the single-channel kinetics. The channels gated among at least three to four open and four to five closed states at high levels of Ca2+i (>100 microM), compared with three to four open and five to seven closed states at lower Ca2+i. The ability of kinetic schemes to account for the single-channel kinetics was examined with simultaneous maximum likelihood fitting of two-dimensional (2-D) dwell-time distributions obtained from low to high Ca2+i. Kinetic schemes drawn from the 10-state Monod-Wyman-Changeux model could not describe the dwell-time distributions from low to high Ca2+i. Kinetic schemes drawn from Eigen's general model for a ligand-activated tetrameric protein could approximate the dwell-time distributions but not the dependency (correlations) between adjacent intervals at high Ca2+i. However, models drawn from a general 50 state two-tiered scheme, in which there were 25 closed states on the upper tier and 25 open states on the lower tier, could approximate both the dwell-time distributions and the dependency from low to high Ca2+i. In the two-tiered model, the BK channel can open directly from each closed state, and a minimum of five open and five closed states are available for gating at any given Ca2+i. A model that assumed that the apparent Ca2+-binding steps can reach a maximum rate at high Ca2+i could also approximate the gating from low to high Ca2+i. The considered models can serve as working hypotheses for the gating of BK channels.

Dataset Information

WNK1 activates large-conductance Ca2+-activated K+ channels through modulation of ERK1/2 signaling.

Publications

WNK1 activates large-conductance Ca2+-activated K+ channels through modulation of ERK1/2 signaling.

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