Kidney Week

Abstract: TH-PO0044

Kidney-Specific (KS)-WNK1 Is Required for K+-Dependent Regulation of Protein Phosphatase 1 (PP1) and Na-Cl Cotransporter (NCC) Dephosphorylation

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Basic Research
  October 22, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolytes, and Acid-Base Disorders

• 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

• Vergara Radillo, Laura Fernanda, Unidad de investigación UNAM-INCICH-IIB, Laboratorio de Fisiología Experimental, Tlalpan, Mexico City, Mexico

Laura Fernanda Vergara Radillo, MD

• Bahena-López, Jessica Paola, Oregon Health & Science University, Portland, Oregon, United States

Jessica Paola Bahena-López, MD, PhD

• Vázquez, Norma Hilda, Universidad Nacional Autonoma de Mexico Instituto de Investigaciones Biomedicas, Mexico City, Mexico

Norma Hilda Vázquez

• Gamba, Gerardo, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Mexico City, Mexico

Gerardo Gamba, MD, PhD

• Chavez-Canales, Maria, Unidad de investigación UNAM-INCICH-IIB, Laboratorio de Fisiología Experimental, Tlalpan, Mexico

Maria Chavez-Canales, MD, PhD

• Cabrales Alcaraz, José Andrés, Unidad de investigación UNAM-INCICH-IIB, Laboratorio de Fisiología Experimental, Tlalpan, Mexico City, Mexico

José Andrés Cabrales Alcaraz

Background

The WNK-SPAK/OSR1-NCC pathway regulates salt reabsorption in the DCT in response to plasma K⁺ levels. KS-WNK1, a kinase-deficient isoform enriched in the DCT, promotes WNK body formation during low K⁺ conditions. Previous work from our group showed that KS-WNK1 is required for both NCC activation during hypokalemia and NCC dephosphorylation during hyperkalemia. In KS-WNK1^KO mice, NCC remains phosphorylated under high K⁺ diet (HKD), suggesting impaired phosphatase regulation. Here, we investigated whether dietary K⁺ modulates PP1 expression, localization, or colocalization with WNK bodies in the DCT, and whether these responses are altered in KS-WNK1^KO mice.

Methods

WT and KS-WNK1^KO mice were maintained on a K⁺-free diet (0KD) for 10 days followed by 12 hours of HKD (5% KCl). Plasma electrolytes were measured, and pNCC, NCC, and PP1 abundance were analyzed by Western blot. PP1 distribution in NCC-positive DCTs was quantified by immunofluorescence, and cellular localization was evaluated using WNK1 and SPAK staining. Correlations between PP1 expression and plasma K⁺ were also assessed.

Results

WT mice appropriately dephosphorylated NCC following HKD, whereas KS-WNK1^KO mice failed to do so, resulting in persistently elevated pNCC/NCC ratios and higher plasma K⁺ levels. Regression analysis revealed a reduced inverse relationship between plasma K⁺ and NCC phosphorylation in KS-WNK1^KO mice, indicating impaired NCC responsiveness to K⁺ changes. PP1 abundance increased after HKD in WT mice but remained unchanged in KS-WNK1^KO animals. Although PP1 did not colocalize with WNK bodies, WT mice showed K⁺ sensitive regulation of PP1 expression, absent in KO mice. PP1 expression strongly correlated with plasma K⁺ in WT mice (R² = 0.68) but not in KS-WNK1^KO mice (R² = 0.005). Spatial distribution analysis further revealed genotype-dependent differences in PP1 redistribution after HKD, with altered apical–basolateral profiles in KS-WNK1^KO tubules during K⁺ loading.

Conclusion

These findings identify KS-WNK1 as a key regulator of DCT adaptation to K⁺ challenges. Loss of KS-WNK1 impairs dynamic NCC regulation, disrupts K⁺ sensitive PP1 regulation and redistribution, and reduces NCC responsiveness to plasma K+ changes, supporting a role for KS-WNK1 in coordinating kinase and phosphatase-dependent mechanisms during K⁺ adaptation in the distal nephron.

Acknowledgment

LV is supported by a SECIHTI fellowship (CVU 1271820). This work was funded by SECIHTI grants CBF-2025-G-704, and PAPIIT-UNAM grants IN223324 to MCC.