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Abstract: FR-PO1011

ER Stress Induced by Dysregulated PI3K/AKT/mTOR Signaling Drives Increased Apoptosis in Podocytes Expressing the Human FSGS-Causing ANLN R431C Mutation

Session Information

Category: Genetic Diseases of the Kidney

  • 1002 Genetic Diseases of the Kidney: Non-Cystic

Authors

  • Lane, Brandon M., Duke University School of Medicine, Durham, North Carolina, United States
  • Hall, Gentzon, Duke University School of Medicine, Durham, North Carolina, United States
  • Wu, Guanghong, Duke University School of Medicine, Durham, North Carolina, United States
  • Wang, Liming, Duke University School of Medicine, Durham, North Carolina, United States
  • Chryst-Stangl, Megan, Duke Molecular Physiology Institute, Durham, North Carolina, United States
  • Spurney, Robert F., Duke University School of Medicine, Durham, North Carolina, United States
  • Gbadegesin, Rasheed A., Duke University School of Medicine, Durham, North Carolina, United States
Background

We previously reported that mutations in ANLN cause familial forms of focal segmental glomerulosclerosis (FSGS). Anillin is a F-actin binding protein that modulates podocyte cell motility and interacts with the phosphoinositide 3-kinase (PI-3K) pathway through the slit diaphragm adaptor protein CD2A-associated Protein (CD2AP). However, it is unclear how ANLNR431C causes the FSGS phenotype. We hypothesized that the R431C mutation exerts its pathogenic effects by uncoupling ANLN from CD2AP and inducing aberrant PI3K/AKT signaling.

Methods

To understand the cellular effects of ANLNR431C, we performed in vitro functional assays using human podocyte cell lines stably expressing ANLNWT or ANLNR431C.

Results

We found that ANLNR431C increased cell migration (p=0.001), enhanced cellular proliferation (p=0.001), and apoptosis (p=0.029) relative to ANLNWT cells. Biochemical characterization of these dysregulated phenotypes revealed hyperactivation of the PI-3K/AKT/mTOR/Rac1 signaling axis and activation of mTOR-driven ER stress in ANLNR431C podocytes. Podocyte hypermotility, hyperproliferation, and ER stress-induced apoptosis were ameliorated by inhibition of mTOR, GSK-3b, Rac1, or calcineurin (Cn). Additionally, we found that endogenous ANLN and mTOR expression are regulated by the Cn/NFAT pathway suggesting that the benefits derived from calcineurin inhibition in FSGS may be due, in part, to the suppression of endogenous anillin and mTOR protein levels.

Conclusion

The ANLNR431C mutation causes multiple derangements in podocyte function through hyperactivation of PI-3K/AKT/mTOR/p70S6K/Rac1 signaling. These studies illustrate that rational therapeutic targets for familial FSGS can be identified through biochemical characterization of dysregulated podocyte phenotypes.

Funding

  • NIDDK Support