TY - JOUR
T1 - WNKs are potassium-sensitive kinases
AU - Pleinis, John M.
AU - Norrell, Logan
AU - Akella, Radha
AU - Humphreys, John M.
AU - He, Haixia
AU - Sun, Qifei
AU - Zhang, Feng
AU - Sosa-Pagan, Jason
AU - Morrison, Daryl E.
AU - Schellinger, Jeffrey N.
AU - Jackson, Laurie K.
AU - Goldsmith, Elizabeth J.
AU - Rodan, Aylin R.
N1 - Publisher Copyright:
© 2021 American Physiological Society. All rights reserved.
PY - 2021/5
Y1 - 2021/5
N2 - With no lysine (K) (WNK) kinases regulate epithelial ion transport in the kidney to maintain homeostasis of electrolyte concentrations and blood pressure. Chloride ion directly binds WNK kinases to inhibit autophosphorylation and activation. Changes in extracellular potassium are thought to regulate WNKs through changes in intracellular chloride. Prior studies demonstrate that in some distal nephron epithelial cells, intracellular potassium changes with chronic low- or high-potassium diet. We, therefore, investigated whether potassium regulates WNK activity independent of chloride. We found decreased activity of Drosophila WNK and mammalian WNK3 and WNK4 in fly Malpighian (renal) tubules bathed in high extracellular potassium, even when intracellular chloride was kept constant at either ~13 mM or 26 mM. High extracellular potassium also inhibited chloride-insensitive mutants of WNK3 and WNK4. High extracellular rubidium was also inhibitory and increased tubule rubidium. The Na þ /K þ - ATPase inhibitor, ouabain, which is expected to lower intracellular potassium, increased tubule Drosophila WNK activity. In vitro, potassium increased the melting temperature of Drosophila WNK, WNK1, and WNK3 kinase domains, indicating ion binding to the kinase. Potassium inhibited in vitro autophosphorylation of Drosophila WNK and WNK3, and also inhibited WNK3 and WNK4 phosphorylation of their substrate, Ste20-related proline/alanine-rich kinase (SPAK). The greatest sensitivity of WNK4 to potassium occurred in the range of 80-180 mM, encompassing physiological intracellular potassium concentrations. Together, these data indicate chloride-independent potassium inhibition of Drosophila and mammalian WNK kinases through direct effects of potassium ion on the kinase.
AB - With no lysine (K) (WNK) kinases regulate epithelial ion transport in the kidney to maintain homeostasis of electrolyte concentrations and blood pressure. Chloride ion directly binds WNK kinases to inhibit autophosphorylation and activation. Changes in extracellular potassium are thought to regulate WNKs through changes in intracellular chloride. Prior studies demonstrate that in some distal nephron epithelial cells, intracellular potassium changes with chronic low- or high-potassium diet. We, therefore, investigated whether potassium regulates WNK activity independent of chloride. We found decreased activity of Drosophila WNK and mammalian WNK3 and WNK4 in fly Malpighian (renal) tubules bathed in high extracellular potassium, even when intracellular chloride was kept constant at either ~13 mM or 26 mM. High extracellular potassium also inhibited chloride-insensitive mutants of WNK3 and WNK4. High extracellular rubidium was also inhibitory and increased tubule rubidium. The Na þ /K þ - ATPase inhibitor, ouabain, which is expected to lower intracellular potassium, increased tubule Drosophila WNK activity. In vitro, potassium increased the melting temperature of Drosophila WNK, WNK1, and WNK3 kinase domains, indicating ion binding to the kinase. Potassium inhibited in vitro autophosphorylation of Drosophila WNK and WNK3, and also inhibited WNK3 and WNK4 phosphorylation of their substrate, Ste20-related proline/alanine-rich kinase (SPAK). The greatest sensitivity of WNK4 to potassium occurred in the range of 80-180 mM, encompassing physiological intracellular potassium concentrations. Together, these data indicate chloride-independent potassium inhibition of Drosophila and mammalian WNK kinases through direct effects of potassium ion on the kinase.
KW - Ion transport
KW - Malpighian tubule
KW - Potassium
KW - Renal physiology
KW - WNK
UR - http://www.scopus.com/inward/record.url?scp=85105520077&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85105520077&partnerID=8YFLogxK
U2 - 10.1152/ajpcell.00456.2020
DO - 10.1152/ajpcell.00456.2020
M3 - Article
C2 - 33439774
AN - SCOPUS:85105520077
SN - 0363-6143
VL - 320
SP - C703-C721
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 5
ER -