Stimulatory Role of SPAK Signaling in the Regulation of Large Conductance Ca2+-Activated Potassium (BK) Channel Protein Expression in Kidney

Abstract

SPS1-related proline/alanine-rich kinase (SPAK) plays important roles in regulating the function of numerous ion channels and transporters. With-no-lysine (WNK) kinase phosphorylates SPAK kinase to active the SPAK signaling pathway. Our previous studies indicated that WNK kinases regulate the activity of the large-conductance Ca 2+activated K + (BK) channel and its protein expression via the ERK1/2 signaling pathway. It remains largely unknown whether SPAK kinase directly modulates the BK protein expression in kidney. In this study, we investigated the effect of SPAK on renal BK protein expression in both HEK293 cells and mouse kidney. In HEK293 cells, siRNAmediated knockdown of SPAK expression significantly reduced BK protein expression and increased ERK1/2 phosphorylation, whereas overexpression of SPAK significantly enhanced BK expression and decreased ERK1/2 phosphorylation in a dose-dependent manner. Knockdown of ERK1/2 prevented SPAK siRNA-mediated inhibition of BK expression. Similarly, pretreatment of HEK293 cells with either the lysosomal inhibitor bafilomycin A1 or the proteasomal inhibitor MG132 reversed the inhibitory effects of SPAK knockdown on BK expression. We also found that there is no BK channel activity in PCs of CCD in SPAK KO mice using the isolated split-open tubule single-cell patching. In addition, we found that BK protein abundance in the kidney of SPAK knockout mice was significantly decreased and ERK1/2 phosphorylation was significantly

Taurine depletion during fetal and postnatal development blunts firing responses of neocortical layer II/III pyramidal neurons

“…The mechanisms by which taurine depletion induces such modulation need further investigation. One possibility is the reduced signaling through the WNK kinase system under taurine-depleted conditions, because the WNK kinase and its downstream kinases of the SPS1-related proline/alanine-rich kinase (SPAK) and the oxidative stress-responsive kinase 1 (OSR1) have been reported to regulate several types of K + channels in other tissues ( Elvira et al, 2016 ; Taylor et al, 2018 ; Bi et al, 2020 ). In our recent microarray assay of signal transduction proteins in WT and TauT Homo KO brains ( Watanabe et al, 2022 ), the protein expression levels of the major WNK isoforms WNK1, WNK2 and WNK3, and the phosphorylation level of WNK1 at serine 382 were comparable between them ( Supplementary Table S1 ), although the phosphorylation levels of the other WNK isoforms were not investigated.…”