SPAK and OSR1 Sensitive Cell Membrane Protein Abundance and Activity of KCNQ1/E1 K+ Channels

Abstract

Background/Aims: KCNQ1/E1 channels are expressed in diverse tissues and serve a variety of functions including endolymph secretion in the inner ear, cardiac repolarization, epithelial transport and cell volume regulation. Kinases involved in regulation of epithelial transport and cell volume include SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1), which are under control of WNK (with-no-K[Lys]) kinases. The present study explored whether KCNQ1/E1 channels are regulated by SPAK and/or OSR1. Methods: cRNA encoding KCNQ1/E1 was injected into Xenopus oocytes with or without additional injection of cRNA encoding wild-type SPAK, constitutively active ^T233ESPAK, WNK insensitive ^T233ASPAK, catalytically inactive ^D212ASPAK, wild-type OSR1, constitutively active ^T185EOSR1, WNK insensitive ^T185AOSR1 and catalytically inactive ^D164AOSR1. Voltage gated K⁺ channel activity was quantified utilizing dual electrode voltage clamp and KCNQ1/E1 channel protein abundance in the cell membrane utilizing chemiluminescence of KCNQ1/E1 containing an extracellular Flag tag epitope (KCNQ1-Flag/E1). Results: KCNQ1/E1 activity and KCNQ1-Flag/E1 protein abundance were significantly enhanced by wild-type SPAK and ^T233ESPAK, but not by ^T233ASPAK and ^D212ASPAK. Similarly, KCNQ1/E1 activity and KCNQ1-Flag/E1 protein abundance were significantly increased by wild-type OSR1 and ^T185EOSR1, but not by ^T185AOSR1 and ^D164AOSR1. Conclusions: SPAK and OSR1 participate in the regulation of KCNQ1/E1 protein abundance and activity.