ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: SA-PO377

The Proteasomal Degradation System Plays a Prominent Role in Podocyte Protein Homeostasis

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Sachs, Wiebke, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
  • Sachs, Marlies, UKE , Hamburg, Germany
  • Meyer-Schwesinger, Catherine, University of Hamburg, Hamburg, Germany

Group or Team Name

  • AG Meyer-Schwesinger
Background

Protein degradation plays a major role in protein quality control and therefore in cell homeostasis. Two different degradation systems are responsible for clearance of disused or defective proteins, the ubiquitin-proteasome system (UPS) and the autophagy-lysosome system (ALS). During membranous nephropathy the UPS is upregulated. The aim of the project is to understand the significance and interplay of the proteasomal and lysosomal degradation system for podocyte proteostasis under naïve conditions and during THSD7A-associated membranous nephropathy.

Methods

For proteasomal inhibition, Balb/C mice were treated with epoxomicin over 4 days. As models of lysosomal impairment Balb/C mice were treated with the lysosomal inhibitor leupeptin A over 4 days or mice with general lysosomal dysfunction (Mucolipidosis (ML) type II) were analyzed. To investigate the effect of the degradation systems on disease progression, THSD7A-associated MN was induced and mice were treated in a preventive and a therapeutic regimen with proteasomal inhibitors and leupeptin A. Renal function was assessed by BUN and creatinine measurements, podocyte injury by proteinuria. The glomerular and tubulointerstitial integrity was assessed by PAS, confocal and electron microscopy. The effects of proteasomal or lysosomal inhibition on glomerular cell proteostasis were analyzed by Western blotting and enzyme activity assays.

Results

Mice treated with epoxomicin developed proteinuria with abnormal glomerular protein accumulations in the subepithelial space and in podocytes. Leupeptin A treatment did not affect proteasomal activity in glomeruli and the tubulointerstitium. Morphological analyses were significant for abnormal accumulations in tubular cells and the glomerular mesangium. MLII mice showed severe lysosomal dysfunction in glomeruli and tubulointerstitial cells without the development of proteinuria. Morphologically, MLII mice exhibited accumulations of large lysosomes in all resident glomerular cells. Therapeutic and preventive inhibition of both degradation systems during THSD7A-associated MN led to increased proteinuria compared to the controls.

Conclusion

Failure of the proteasomal degradation system has a great impact on podocyte cell proteostasis. Inhibition of either the proteasomal or the lysosomal degradation system enhances the progression of THSD7A-associated MN.

Funding

  • Government Support - Non-U.S.