Klotho Stabilizes the Podocyte Actin Cytoskeleton in Idiopathic Membranous Nephropathy through Regulating the TRPC6/CatL Pathway

Am J Nephrol. 2024;55(3):345-360. doi: 10.1159/000537732. Epub 2024 Feb 8.

Abstract

Introduction: The aim of this study was to explore the renoprotective effects of Klotho on podocyte injury mediated by complement activation and autoantibodies in idiopathic membranous nephropathy (IMN).

Methods: Rat passive Heymann nephritis (PHN) was induced as an IMN model. Urine protein levels, serum biochemistry, kidney histology, and podocyte marker levels were assessed. In vitro, sublytic podocyte injury was induced by C5b-9. The expression of Klotho, transient receptor potential channel 6 (TRPC6), and cathepsin L (CatL); its substrate synaptopodin; and the intracellular Ca2+ concentration were detected via immunofluorescence. RhoA/ROCK pathway activity was measured by an activity quantitative detection kit, and the protein expression of phosphorylated-LIMK1 (p-LIMK1) and p-cofilin in podocytes was detected via Western blotting. Klotho knockdown and overexpression were performed to evaluate its role in regulating the TRPC6/CatL pathway.

Results: PHN rats exhibited proteinuria, podocyte foot process effacement, decreased Klotho and Synaptopodin levels, and increased TRPC6 and CatL expression. The RhoA/ROCK pathway was activated by the increased phosphorylation of LIMK1 and cofilin. Similar changes were observed in C5b-9-injured podocytes. Klotho knockdown exacerbated podocyte injury, while Klotho overexpression partially ameliorated podocyte injury.

Conclusion: Klotho may protect against podocyte injury in IMN patients by inhibiting the TRPC6/CatL pathway. Klotho is a potential target for reducing proteinuria in IMN patients.

Keywords: Idiopathic membranous nephropathy; Podocyte; Ras homolog gene family member A; Rho-associated coiled-coil protein kinase; Transient receptor potential channel 6.

MeSH terms

  • Actin Cytoskeleton* / metabolism
  • Animals
  • Cathepsin L* / metabolism
  • Complement Membrane Attack Complex / metabolism
  • Disease Models, Animal
  • Glomerulonephritis, Membranous* / metabolism
  • Glomerulonephritis, Membranous* / pathology
  • Glucuronidase* / metabolism
  • Humans
  • Klotho Proteins*
  • Male
  • Microfilament Proteins / metabolism
  • Podocytes* / metabolism
  • Podocytes* / pathology
  • Proteinuria / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction*
  • TRPC Cation Channels / metabolism
  • TRPC6 Cation Channel* / metabolism
  • rho-Associated Kinases / metabolism
  • rhoA GTP-Binding Protein / metabolism

Substances

  • Klotho Proteins
  • Glucuronidase
  • Trpc6 protein, rat
  • TRPC6 Cation Channel
  • Cathepsin L
  • rhoA GTP-Binding Protein
  • Microfilament Proteins
  • rho-Associated Kinases
  • TRPC Cation Channels
  • Complement Membrane Attack Complex

Grants and funding

This study was supported by the National Natural Science Foundation of China (No. 82074364), the Health Commission of Hubei Province of China (No. WJ2021M180), and the Wuhan Science and Technology Bureau of China (No. 2022020801020506). The funder had no role in the study design, experimental process, interpretation of the results, or writing of the manuscript.