Tilman Breiderhoff1, Nina Himmerkus2, Luca Meoli3, Anja Fromm3, Sebastian Sewerin4, Natalia Kriuchkova5, Oliver Nagel3, Yury Ladilov3, Susanne M Krug3, Catarina Quintanova2, Meike Stumpp6, Dieter Garbe-Schönberg7, Ulrike Westernströer7, Cosima Merkel2, Merle Annette Brinkhus2, Janine Altmüller8,9,10, Michal R Schweiger8,11,12, Dominik Müller1, Kerim Mutig13,14, Markus Morawski15,16, Jan Halbritter4,17, Susanne Milatz2, Markus Bleich2, Dorothee Günzel18. 1. Department of Pediatrics, Division of Gastroenterology, Nephrology and Metabolic Diseases, Charité-Universitätsmedizin Berlin, Berlin, Germany. 2. Institute of Physiology, Kiel University, Kiel, Germany. 3. Clinical Physiology/Division of Nutritional Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany. 4. Division of Nephrology, University of Leipzig Medical Center, Leipzig, Germany. 5. Institute for Functional Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany. 6. Zoological Institute, Comparative Immunobiology, Kiel University, Kiel, Germany. 7. Institute of Geosciences, Kiel University, Kiel, Germany. 8. Cologne Center for Genomics, University of Cologne, Köln, Germany. 9. Berlin Institute of Health at Charité, Berlin, Germany. 10. Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany. 11. Institute for Translational Epigenetics, University Hospital Cologne, University of Cologne, Köln, Germany. 12. Center for Molecular Medicine Cologne, Köln, Germany. 13. Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany. 14. Department of Pharmacology, I.M. Sechenov First Moscow State Medical University of the Ministry of Healthcare of the Russian Federation (Sechenov University), Moscow, Russia. 15. Paul Flechsig Institute of Brain Research, Leipzig, Germany. 16. Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany. 17. Department of Nephrology and Medical Intensive Care, Charité-Universitätsmedizin Berlin, Berlin, Germany. 18. Clinical Physiology/Division of Nutritional Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany dorothee.guenzel@charite.de.
Abstract
BACKGROUND: The tight junction proteins claudin-2 and claudin-10a form paracellular cation and anion channels, respectively, and are expressed in the proximal tubule. However, the physiologic role of claudin-10a in the kidney has been unclear. METHODS: To investigate the physiologic role of claudin-10a, we generated claudin-10a-deficient mice, confirmed successful knockout by Southern blot, Western blot, and immunofluorescence staining, and analyzed urine and serum of knockout and wild-type animals. We also used electrophysiologic studies to investigate the functionality of isolated proximal tubules, and studied compensatory regulation by pharmacologic intervention, RNA sequencing analysis, Western blot, immunofluorescence staining, and respirometry. RESULTS: Mice deficient in claudin-10a were fertile and without overt phenotypes. On knockout, claudin-10a was replaced by claudin-2 in all proximal tubule segments. Electrophysiology showed conversion from paracellular anion preference to cation preference and a loss of paracellular Cl- over HCO3 - preference. As a result, there was tubular retention of calcium and magnesium, higher urine pH, and mild hypermagnesemia. A comparison with other urine and serum parameters under control conditions and sequential pharmacologic transport inhibition, and unchanged fractional lithium excretion, suggested compensative measures in proximal and distal tubular segments. Changes in proximal tubular oxygen handling and differential expression of genes regulating fatty acid metabolism indicated proximal tubular adaptation. Western blot and immunofluorescence revealed alterations in distal tubular transport. CONCLUSIONS: Claudin-10a is the major paracellular anion channel in the proximal tubule and its deletion causes calcium and magnesium hyper-reabsorption by claudin-2 redistribution. Transcellular transport in proximal and distal segments and proximal tubular metabolic adaptation compensate for loss of paracellular anion permeability.
BACKGROUND: The tight junction proteins claudin-2 and claudin-10a form paracellular cation and anion channels, respectively, and are expressed in the proximal tubule. However, the physiologic role of claudin-10a in the kidney has been unclear. METHODS: To investigate the physiologic role of claudin-10a, we generated claudin-10a-deficient mice, confirmed successful knockout by Southern blot, Western blot, and immunofluorescence staining, and analyzed urine and serum of knockout and wild-type animals. We also used electrophysiologic studies to investigate the functionality of isolated proximal tubules, and studied compensatory regulation by pharmacologic intervention, RNA sequencing analysis, Western blot, immunofluorescence staining, and respirometry. RESULTS: Mice deficient in claudin-10a were fertile and without overt phenotypes. On knockout, claudin-10a was replaced by claudin-2 in all proximal tubule segments. Electrophysiology showed conversion from paracellular anion preference to cation preference and a loss of paracellular Cl- over HCO3 - preference. As a result, there was tubular retention of calcium and magnesium, higher urine pH, and mild hypermagnesemia. A comparison with other urine and serum parameters under control conditions and sequential pharmacologic transport inhibition, and unchanged fractional lithium excretion, suggested compensative measures in proximal and distal tubular segments. Changes in proximal tubular oxygen handling and differential expression of genes regulating fatty acid metabolism indicated proximal tubular adaptation. Western blot and immunofluorescence revealed alterations in distal tubular transport. CONCLUSIONS: Claudin-10a is the major paracellular anion channel in the proximal tubule and its deletion causes calcium and magnesium hyper-reabsorption by claudin-2 redistribution. Transcellular transport in proximal and distal segments and proximal tubular metabolic adaptation compensate for loss of paracellular anion permeability.
Authors: Nicole Meyers; Carol Nelson-Williams; Laura Malaga-Dieguez; Horacio Kaufmann; Erin Loring; James Knight; Richard P Lifton; Howard Trachtman Journal: Am J Kidney Dis Date: 2018-10-25 Impact factor: 8.860
Authors: Michael Lawrence; Wolfgang Huber; Hervé Pagès; Patrick Aboyoun; Marc Carlson; Robert Gentleman; Martin T Morgan; Vincent J Carey Journal: PLoS Comput Biol Date: 2013-08-08 Impact factor: 4.475
Authors: Hannes Gonschior; Christopher Schmied; Rozemarijn Eva Van der Veen; Jenny Eichhorst; Nina Himmerkus; Jörg Piontek; Dorothee Günzel; Markus Bleich; Mikio Furuse; Volker Haucke; Martin Lehmann Journal: Nat Commun Date: 2022-08-25 Impact factor: 17.694