Kir5.1-Modulated Potassium Flux Stimulates an Anabolic Kidney Phenotype

Background: Maintaining potassium (K) homeostasis imposes a significant metabolic burden on the kidney, requiring constant energy to support electrolyte transport and prevent K imbalance. Reduced dietary K triggers nephron remodeling and enhanced proximal tubule sodium (Na) reabsorption—adaptations requiring metabolic reprogramming. The proximal tubule inwardly rectifying K channel Kir4.2 and its partner Kir5.1 mediate this response but the metabolic pathways supporting these processes are poorly understood Methods: We generated a mouse expressing a dominant-negative Kir5.1 channel (Kir5.1C496del) and studied it under normal and K-free diets. Thallium flux assays confirmed dominant-negative function. Blood and urine electrolytes were measured by ion-specific electrodes. Protein and metabolite levels were quantified using Western blot and GC-MS, respectively. Deuterium-labeled water with GC-MS assessed de novo palmitate synthesis. Kidney proteomics was performed after 4 days of 0 per cent vs. 1 per cent K diet. Glycolytic flux was measured in ex vivo cortical kidney punches using Seahorse analysis. Immunofluorescence was performed to measure Ki67. Results: Kir5.1DN mice displayed a K-wasting phenotype, worsened by K restriction, with reduced Na transporter expression and metabolic acidosis. Low K diet increased kidney size and epithelial proliferation in Kir5.1WT mice—responses blunted in Kir5.1DN animals. Proteomics identified 559 differentially expressed proteins, including upregulation of carbohydrate, glutamine, and fatty acid metabolism pathways. Pyruvate kinase was most upregulated. Low K increased glycolytic flux and metabolites (PEP, G3P) in Kir5.1WT but not Kir5.1DN mice. Glycolytic enzyme expression and amino acid levels were similarly reduced in Kir5.1DN animals. De novo lipogenesis was also impaired, with reduced palmitate synthesis in mutant mice. Conclusion: Results uncover metabolic details of a low K-stimulated anabolic kidney program, including stimulation of glycolytic and de novo lipogenic pathways. These changes require intact Kir5.1 channel function and highlight a therapeutic role for targeting Kir channels to modulate cell physiology and metabolism. Funding: Other NIH Support - NIH Director's Early Independence Award