WNK4 regulates the balance between renal NaCl reabsorption and K+ secretion.
A key question in systems biology is how diverse physiologic processes are integrated to produce global homeostasis. Genetic analysis can contribute by identifying genes that perturb this integration. One system orchestrates renal NaCl and K+ flux to achieve homeostasis of blood pressure and serum K+ concentration. Positional cloning implicated the serine-threonine kinase WNK4 in this process; clustered mutations in PRKWNK4, encoding WNK4, cause hypertension and hyperkalemia (pseudohypoaldosteronism type II, PHAII) by altering renal NaCl and K+ handling. Wild-type WNK4 inhibits the renal Na-Cl cotransporter (NCCT); mutations that cause PHAII relieve this inhibition. This explains the hypertension of PHAII but does not account for the hyperkalemia. By expression in Xenopus laevis oocytes, we show that WNK4 also inhibits the renal K+ channel ROMK. This inhibition is independent of WNK4 kinase activity and is mediated by clathrin-dependent endocytosis of ROMK, mechanisms distinct from those that characterize WNK4 inhibition of NCCT. Most notably, the same mutations in PRKWNK4 that relieve NCCT inhibition markedly increase inhibition of ROMK. These findings establish WNK4 as a multifunctional regulator of diverse ion transporters; moreover, they explain the pathophysiology of PHAII. They also identify WNK4 as a molecular switch that can vary the balance between NaCl reabsorption and K+ secretion to maintain integrated homeostasis.
Kahle
Kristopher T
KT
Howard Hughes Medical Institute, 300 Cedar Street, TAC S-341D, and Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Wilson
Frederick H
FH
Leng
Qiang
Q
Lalioti
Maria D
MD
O'Connell
Anthony D
AD
Dong
Ke
K
Rapson
Alicia K
AK
MacGregor
Gordon G
GG
Giebisch
Gerhard
G
Hebert
Steven C
SC
Lifton
Richard P
RP
D000818:Animals; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D004705:Endocytosis; D049452:Green Fluorescent Proteins; D017136:Ion Transport; D007668:Kidney / Q000502:physiology*; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011546:Pseudohypoaldosteronism / Q000378:metabolism; D051381:Rats; D011955:Receptors, Drug; D012965:Sodium Chloride / Q000378:metabolism*; D049992:Sodium Chloride Symporters; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters; D014982:Xenopus laevis / Q000378:metabolism
D002352:Carrier Proteins; D002966:Clathrin; C510693:Kcnj1 protein, mouse; C510692:Kcnj1 protein, rat; D008164:Luminescent Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; C578875:Slc12a3 protein, mouse; C578876:Slc12a3 protein, rat; D049992:Sodium Chloride Symporters; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters; C064415:thiazide receptor; D049452:Green Fluorescent Proteins; D012965:Sodium Chloride; C499024:Prkwnk4 protein, mouse; C499025:Wnk4 protein, rat; D017346:Protein Serine-Threonine Kinases; D011188:Potassium