WNK4

BACKGROUND: The calcium-sensing receptor (CaSR) in the distal convoluted tubule (DCT) activates the NaCl cotransporter (NCC). Glucose acts as a positive allosteric modulator of the CaSR. Under physiologic conditions, no glucose is delivered to the DCT, and fructose delivery depends on consumption. We hypothesized that glucose/fructose delivery to the DCT modulates the CaSR in a positive allosteric way, activating the WNK4-SPAK-NCC pathway and thus increasing salt retention. METHODS: We evaluated the effect of glucose/fructose arrival to the distal nephron on the CaSR-WNK4-SPAK-NCC pathway using HEK-293 cells, C57BL/6 and WNK4-knockout mice, ex vivo perfused kidneys, and healthy humans...

The potassium switch refers to plasma potassium regulation of the sodium-chloride cotransporter (NCC), which controls distal sodium delivery and therefore potassium secretion. Low extracellular potassium activates NCC by relieving chloride inhibition of With-No-Lysine 4 (WNK4). A new mouse model carrying a chloride-insensitive WNK4 mutant still shows NCC activation on low potassium diet. These effects are mediated by WNK4 activation and kelch-like 3 (KLHL3) inhibition and reveal additional chloride-sensitive pathways for NCC activation...

OBJECTIVE: To explore the co-expression network of the osteoarthritis (OA) risk gene WWP2 in articular cartilage and study cartilage characteristics when mimicking the effect of OA risk allele rs1052429-A on WWP2 expression in a human 3D in vitro model of cartilage. METHOD: Co-expression behavior of WWP2 with genes expressed in lesioned OA articular cartilage (N=35 samples) was explored. By applying lentiviral particle mediated WWP2 upregulation in 3D in vitro pellet cultures of human primary chondrocytes (N=8 donors) the effects of upregulation on cartilage matrix deposition was evaluated...

Mutations in the ubiquitin ligase scaffold protein Cullin 3 (CUL3) cause the disease Familial Hyperkalemic Hypertension (FHHt). We recently reported that in the kidney, aberrant mutant CUL3 (CUL3-Δ9) activity lowers abundances of CUL3-Δ9 and Kelch-Like 3, the CUL3 substrate adaptor for WNK4, and that this is mechanistically important. However, whether CUL3-Δ9 exerts additional effects on other targets that may alter renal function is unclear. Here, we sought to determine (i) whether CUL3-Δ9 expression can rescue the phenotype of renal tubule-specific Cul3 knockout mice and (ii) whether CUL3-Δ9 expression affects other CUL3 substrates...

Regulated Na+ transport in the distal nephron is of fundamental importance to fluid and electrolyte homeostasis. Further upstream, Na+ is the principal driver of secondary active transport of numerous organic and inorganic solutes. In the distal nephron, Na+ continues to play a central role in controlling the body levels and concentrations of a more select group of ions, including K+ , Ca++ , Mg++ , Cl- , and HCO3 - , as well as water. Also, of paramount importance are transport mechanisms aimed at controlling the total level of Na+ itself in the body, as well as its concentrations in intracellular and extracellular compartments...

Low potassium intake activates the kidney sodium-chloride cotransporter (NCC) whose phosphorylation and activity depend on the With-No-Lysine kinase 4 (WNK4) that is inhibited by chloride binding to its kinase domain. Low extracellular potassium activates NCC by decreasing intracellular chloride thereby promoting chloride dissociation from WNK4 where residue L319 of WNK4 participates in chloride coordination. Since the WNK4-L319F mutant is constitutively active and chloride-insensitive in vitro, we generated mice harboring this mutation that displayed slightly increased phosphorylated NCC and mild hyperkalemia when on a 129/sv genetic background...

With-No lysine kinases (WNKs) have been newly implicated in alveolar fluid clearance (AFC). Epithelial sodium channels (ENaC) serve a vital role in AFC. The potential protective effect of WNK4 in acute respiratory distress syndrome (ARDS), mediated by ENaC-associated AFC was investigated in the study. A model of lipopolysaccharide-induced ARDS was established in C57BL/6 mice. WNK4, Sterile 20-related proline-alanine-rich kinase (SPAK), small interfering RNA (siRNA)-WNK4 or siRNA-SPAK were transfected into mouse lung or primary alveolar epithelial type II (ATII) cells...

HYPOTHESIS: KS-WNK1 a shorter isoform of WNK1 that is exclusively expressed in the kidney, with abundance in the distal convoluted tubule (DCT), but its physiological role remains elusive. KS-WNK1 stimulates NCC activity via WNK4-SPAK pathway. Under low potassium diet, a known stimuli for NCC activity, WNK bodies are formed in DCT cells, and this requires the presence of KS-WNK1. We recently shown that KS-WNNK1 is highly sensitive to the CUL3-KLHL3 complex (JCI 2020) and its expression under control conditions is negligible, but it is increased under low potassium diet (AJP Renal 2021)...

INTRODUCTION: Hypertension is caused by multi-factors, and the pathogenesis is linked to, generally, the increases in the protein expressions and functions of renal sodium transport proteins along the nephron. One of the major side effects of clozapine (common antipsychotic drug) is hypertension. The mechanism is unknown. HYPOTHESIS: the pathogenesis of the clozapine-induced hypertension is associated with increases of renal sodium transport proteins. METHODS: we examined the blood pressures (BP) and protein expressions of major sodium transport proteins profiled along the renal tubules in the C57Bl6/J male mice (9 weeks old, n=4-5/group) treated with clozapine at three doses of 5,10 and 20 mg/ kg for 1 week via intraperitoneal injection...

ROMK channels in the aldosterone-sensitive distal nephron are tightly regulated to maintain potassium balance. In response to potassium restriction, ROMK channels are internalized from the apical membrane, safeguarding against extensive potassium loss. Previously, we found the clathrin adaptor protein, ARH, directly binds to ROMK to stimulate endocytosis (Fang et al, JCI '09). WNK signaling pathway has been implicated in activating ROMK endocytosis, but the mechanism is not clear, and physiological significance of ARH-mediated ROMK regulation remains uncertain...

With-no-lysine kinase 4 (WNK4) activates the NaCl cotransporter (NCC) which is the main pathway for sodium reabsorption in the distal convoluted tubule (DCT) of the kidney. The cullin-RING ubiquitin ligase cullin 3 (CUL3) regulates WNK4 abundance via interaction through the substrate adaptor KLHL3. The monogenic disease familial hyperkalemic hypertension (FHHt) is caused by mutations in this pathway. Mutations in KLHL3 and WNK4 mainly disrupt formation of this complex, whereas, the CUL3 mutations impair binding to the COP9 signalosome (CSN), a deneddylase and upstream regulator of cullin-RING ligases...

Cullin-RING ligases are a family of E3 ubiquitin ligases that control cellular processes through regulated degradation. Cullin 3 targets with-no-lysine kinase 4 (WNK4), a kinase that activates the Na+ -Cl- cotransporter (NCC), the main pathway for Na+ reabsorption in the distal convoluted tubule (DCT). Mutations in the cullin 3 gene lead to familial hyperkalemic hypertension by increasing WNK4 abundance. The constitutive photomorphogenesis 9 (COP9) signalosome (CSN) regulates the activity of cullin-RING ligases by removing the ubiquitin-like protein neural precursor cell expressed developmentally downregulated protein 8...

INTRODUCTION: Pseudohypoaldosteronism type II (PHA II) is a Mendelian disorder, featuring hyperkalemic acidosis and low plasma renin levels, typically associated with hypertension. Mutations in WNK1, WNK4, CUL3, and KLHL3 cause PHA II, with dominant mutations in WNK1, WNK4, and CUL3 and either dominant or recessive mutations in KLHL3. Fourteen families with recessive KLHL3 mutations have been reported, with diagnosis at the age of 3 months to 56 years, typically in individuals with normal kidney function...

BACKGROUND: Mutations in the ubiquitin ligase scaffold protein Cullin 3 ( CUL3 ) gene cause the disease familial hyperkalemic hypertension (FHHt). In the kidney, mutant CUL3 ( CUL3-Δ9 ) increases abundance of With-No-Lysine (K) Kinase 4 (WNK4), inappropriately activating sterile 20/SPS-1-related proline/alanine-rich kinase (SPAK), which then phosphorylates and hyperactivates the Na+ Cl- cotransporter (NCC). The precise mechanism by which CUL3-Δ9 causes FHHt is unclear. We tested the hypothesis that reduced abundance of CUL3 and of Kelch-like 3 (KLHL3), the CUL3 substrate adaptor for WNK4, is mechanistically important...

The thiazide-sensitive sodium chloride cotransporter (NCC) plays a vital role in maintaining sodium (Na+ ) and potassium (K+ ) homeostasis. NCC activity is modulated by with-no-lysine kinases 1 and 4 (WNK1 and WNK4), the abundance of which is controlled by the RING-type E3 ligase Cullin 3 (Cul3) and its substrate adapter Kelch-like protein 3. Dietary K+ intake has an inverse correlation with NCC activity, but the mechanism underlying this phenomenon remains to be fully elucidated. Here, we investigated the involvement of other members of the cullin family in mediating K+ effects on NCC phosphorylation (active form) and abundance...

Familial hyperkalemic hypertension is caused by pathogenic variants in genes of the CUL3 (cullin-3)-KLHL3 (kelch-like-family-member-3)-WNK (with no-lysine [K] kinase) pathway, manifesting clinically as hyperkalemia, metabolic acidosis, and high systolic blood pressure. The ubiquitin E3 ligase CUL3-KLHL3 targets WNK kinases for degradation to limit activation of the thiazide-sensitive NCC (Na-Cl cotransporter). All known variants in CUL3 lead to exon 9 skipping (CUL3Δ9) and typically result in severe familial hyperkalemic hypertension and growth disturbances in patients...

STE20/SPS1-related proline/alanine-rich kinase (SPAK) and Oxidative Stress Responsive 1 (OSR1) kinase are two serine/threonine protein kinases that regulate the function of ion co-transporters through phosphorylation. The highly conserved  C -terminal (CCT) domains of SPAK and OSR1 bind to RFx[V/I] peptide sequences from their upstream With No Lysine Kinases (WNKs), facilitating their activation via phosphorylation. Thus, the inhibition of SPAK and OSR1 binding, via their CCT domains, to WNK kinases is a plausible strategy for inhibiting SPAK and OSR1 kinases...

Introduction: Familial hyperkalemic hypertension is a rare inherited form of arterial hypertension. Four genes are responsible for this disease, the variants of these genes cause disruption in the regulation of ion transport in the distal renal tubule. Whether the genotype explains the large phenotypic heterogeneity has not been fully explored. Methods: We retrospectively analyzed clinical and genetic data of 153 cases (84 probands, 69 relatives) with familial hyperkalemic hypertension...

Background: Ventilator-induced lung injury (VILI) is characterized by vascular barrier dysfunction and suppression of alveolar fluid clearance (AFC). Obesity itself leads to chronic inflammation, which may initiate an injurious cascade to the lungs and simultaneously induce a protective feedback. In this study, we investigated the protective mechanism of obesity on VILI in a mouse model. Methods: The VILI model was set up via 6-h mechanical ventilation with a high tidal volume...

Case summary: An 8-month-old female spayed Burmese cat was referred for investigation of reduced appetite, reluctance to walk and jump and amaurosis. On serum biochemistry there was severe hypokalaemia and marked elevation of creatine kinase, suggestive of hypokalaemic polymyopathy. The neurological signs were consistent with thiamine deficiency. The cat was negative for the periodic hypokalaemic polymyopathy (PHP) of Burmese cats, and was ultimately diagnosed with a previously undescribed potassium wasting nephropathy requiring ongoing oral potassium supplementation...