Journal Article

Angiotensin II signaling via protein kinase C phosphorylates Kelch-like 3, preventing WNK4 degradation

Lam, TuKiet T., Shibata, Shigeru, Puthumana, Jeremy, Uchida, Shunya, Zhang, Junhui, Castañeda-Bueno, María, Stone, Kathryn L., Arroyo, Juan Pablo, Lifton, Richard P.

2014

Overview

Hypertension contributes to the global burden of cardiovascular disease. Increased dietary K ⁺ reduces blood pressure; however, the mechanism has been obscure. Human genetic studies have suggested that the mechanism is an obligatory inverse relationship between renal salt reabsorption and K ⁺ secretion. Mutations in the kinases with-no-lysine 4 (WNK4) or WNK1, or in either Cullin 3 (CUL3) or Kelch-like 3 (KLHL3)—components of an E3 ubiquitin ligase complex that targets WNKs for degradation—cause constitutively increased renal salt reabsorption and impaired K ⁺ secretion, resulting in hypertension and hyperkalemia. The normal mechanisms that regulate the activity of this ubiquitin ligase and levels of WNKs have been unknown. We posited that missense mutations in KLHL3 that impair binding of WNK4 might represent a phenocopy of the normal physiologic response to volume depletion in which salt reabsorption is maximized. We show that KLHL3 is phosphorylated at serine 433 in the Kelch domain (a site frequently mutated in hypertension with hyperkalemia) by protein kinase C in cultured cells and that this phosphorylation prevents WNK4 binding and degradation. This phosphorylation can be induced by angiotensin II (AII) signaling. Consistent with these in vitro observations, AII administration to mice, even in the absence of volume depletion, induces renal KLHL3 S⁴³³ phosphorylation and increased levels of both WNK4 and the NaCl cotransporter. Thus, AII, which is selectively induced in volume depletion, provides the signal that prevents CUL3/KLHL3-mediated degradation of WNK4, directing the kidney to maximize renal salt reabsorption while inhibiting K ⁺ secretion in the setting of volume depletion. Significance Aldosterone produces distinct adaptive responses in volume depletion and hyperkalemia. Mutations in with-no-lysine (WNK) kinases or ubiquitin ligases containing Cullin 3 (CUL3) and Kelch-like 3 (KLHL3) cause a Mendelian disease featuring hypertension and hyperkalemia due to constitutive renal salt reabsorption and inhibited K ⁺ secretion. WNKs modulate activities of aldosterone-regulated electrolyte flux pathways, and WNK levels are regulated by CUL3/KLHL3; disease-causing mutations prevent WNK degradation. This manuscript shows that angiotensin II (AII), a hormone produced only in volume depletion, induces PKC-mediated phosphorylation of KLHL3, preventing WNK degradation and phenocopying KLHL3 mutations. These findings provide a mechanism by which AII signaling alters WNK4, promoting increased renal salt reabsorption and reduced K ⁺ secretion.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: absorption / aldosterone / Amino Acid Sequence / angiotensin II / Angiotensin II - metabolism / Animals / Antibodies / Biological Sciences / Blood pressure / Cardiovascular diseases / Carrier Proteins - chemistry / Carrier Proteins - metabolism / Cell Line / COS cells / electrolytes / Gene expression regulation / Humans / Hyperkalemia / Hypertension / Kidney - metabolism / Kidneys / Kinases / Mice, Inbred C57BL / Molecular Sequence Data / Mutation / Phosphorylation / Phosphoserine - metabolism / Physiological regulation / Protein Binding / protein kinase C / Protein Kinase C - metabolism / Protein-Serine-Threonine Kinases - metabolism / Proteolysis / Salts / Secretion / Signal Transduction / Sodium chloride / ubiquitin-protein ligase / Western blotting