From K+ sensing to NCC on/off switching: KS-WNK1 as a spatial organizer of WNK signaling.

PURPOSE OF REVIEW: In the distal convoluted tubule (DCT), the NaCl cotransporter (NCC) regulates renal K+ homeostasis by controlling distal Na+ delivery. Although the kidney-specific WNK1 isoform kidney-specific with no lysine (k) kinase (KS-WNK1) is a key determinant of K+-dependent NCC responsiveness, divergent baseline phenotypes across murine alleles have obscured its core function. Here, we integrate evidence from heterologous systems and multiple mouse models to resolve these discrepancies and define a state-dependent role for KS-WNK1.

RECENT FINDINGS: Across K+ stress paradigms, KS-WNK1 promotes NCC activation during K+ depletion through assembly and apical positioning of WNK body condensates and enables efficient NCC shutdown during K+ repletion/excess, thereby expanding the dynamic range of K+-dependent NCC regulation.

SUMMARY: KS-WNK1 expands the dynamic range of K+-dependent NCC control by coupling spatial organization to signaling output in the distal nephron. Key open questions include how condensate positioning interfaces with apical NCC-regulatory microdomains and which phosphatase modules terminate signaling during refeeding, with implications for disordered Na+/K+ handling in hyperkalemia and hypertension.