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Kidney Week

Abstract: SA-PO324

Inhibiting Podocyte Endoplasmic Reticulum Stress-Mediated Apoptosis to Treat Genetic Nephrotic Syndrome

Session Information

Category: Glomerular Diseases

  • 1201 Glomerular Diseases: Fibrosis and Extracellular Matrix

Authors

  • Park, Sun-Ji, Washington university in St. Louis, St. Louis, Missouri, United States
  • Chen, Ying Maggie, Washington university in St. Louis, St. Louis, Missouri, United States
Background

Pierson syndrome (OMIM 609049) characterized by congenital nephrotic syndrome (NS) and diffuse mesangial sclerosis, is caused by mutations in LAMB2 encoding laminin β2. The major laminin heterotrimer in the mature glomerular basement membrane is laminin α5β2γ1, and laminin trimerization occurs in the endoplasmic reticulum (ER). There is no effective treatment for Pierson syndrome and most cases of genetic forms of NS. Here for the first time, we have shown that targeting podocyte ER stress-specific apoptosis may provide a new therapeutic approach to treat Pierson syndrome and other genetic nephrotic syndromes.

Methods

To recapitulate human Pierson syndrome, Lamb2 null mice were generated. We isolated mouse glomeruli and cultured primary podocytes before the onset of significant proteinuria to investigate ER stress signaling cascades. Western blot was utilized to determine ER stress-induced pro-apoptotic pathway. Furthermore, Lamb2-/- mice were crossed with Chop-/- mice to investigate the functional consequence of CHOP (C/EBP homologous protein) deletion in the disease development.

Results

At the early stage of NS, LAMB2 deficiency induced podocyte ER stress and selectively activated ATF6 (activating transcription factor 6) pathway without involvement of IRE1α and PERK pathways. Moreover, LAMB2 depletion differentially triggered ER stress-specific CHOP pro-apoptotic pathway, but not caspase 12 and JNK pathways, in mutant podocytes. Most importantly, CHOP ablation in Lamb2-/- mice significantly prolonged the lifespan of Lamb2 null mice.

Conclusion

Despite the importance of podocyte ER dysfunction in the pathogenesis of NS, there is no treatment that targets the podocyte ER. Our promising results indicate that antagonizing the pro-apoptotic CHOP pathway in ER-stressed podocytes may lead to paradigm-shifting innovative therapeutic strategies to combat genetic or acquired NS.

Funding

  • Other NIH Support