Kidney Week

Abstract: SA-PO985

APOL1 G1-Mediated Cation Transport Inhibits Amino Acid Transport and Increases Endoplasmic Reticulum Calcium Release, Causing Podocytopathy

Session Information

• Glomerular Diseases: Podocyte Biology - II
  November 04, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1403 Podocyte Biology

Authors

• Olabisi, Opeyemi A., Duke University, Durham, North Carolina, United States

Opeyemi A. Olabisi,

• Datta, Somenath, Duke University, Durham, North Carolina, United States

Somenath Datta,

• Antonio, Brett M., Ligand Pharmaceuticals Incorporated Icagen Ion Channel Technology Center, Durham, North Carolina, United States

Brett M. Antonio,

• Zahler, Nathan, Ligand Pharmaceuticals Incorporated Icagen Ion Channel Technology Center, Durham, North Carolina, United States

Nathan Zahler,

• Krafte, Douglas, Ligand Pharmaceuticals Incorporated Icagen Ion Channel Technology Center, Durham, North Carolina, United States

Douglas Krafte,

• Hohmeier, Hans-Ewald, Duke University, Durham, North Carolina, United States

Hans-Ewald Hohmeier,

• Chaves, Alec, Duke University, Durham, North Carolina, United States

Alec Chaves,

• Nystrom, Sarah, Duke University, Durham, North Carolina, United States

Sarah Nystrom,

• Zhang, Guofang, Duke University, Durham, North Carolina, United States

Guofang Zhang,

• Ilkayeva, Olga, Duke University, Durham, North Carolina, United States

Olga Ilkayeva,

• Silas, Daniel Philip, Duke University, Durham, North Carolina, United States

Daniel Philip Silas,

• Theile, Jonathan W., Ligand Pharmaceuticals Incorporated Icagen Ion Channel Technology Center, Durham, North Carolina, United States

Jonathan W. Theile,

• Muehlbauer, Michael, Duke University, Durham, North Carolina, United States

Michael Muehlbauer,

• Becker, Thomas C., Duke University, Durham, North Carolina, United States

Thomas C. Becker,

• Li, Guojie, Duke University, Durham, North Carolina, United States

Guojie Li,

• Bain, James R., Duke University, Durham, North Carolina, United States

James R. Bain,

• Soldano, Karen, Duke University, Durham, North Carolina, United States

Karen Soldano,

• Newgard, Christopher B., Duke University, Durham, North Carolina, United States

Christopher B. Newgard,

Background

How two coding variants of APOL1 gene (G1 and G2) cause kidney disease is poorly understood. While experimental models have shown that these APOL1 renal risk variants induce cytotoxicity, the causal mechanism underlying these effects is unknown. Previously, we reported that RRVs form cation pores that transport Na⁺ and K⁺ across the plasma membrane of mammalian cells.

Methods

We blocked APOL1 G1-cation channel function with a new small molecule inhibitor, VX-147 in inducible HEK293 cells and human-derived podocytes and measured cytotoxic phenotypes. We used Real-time cation sensors including genetically-encoded Ca²⁺ sensor to measure levels of cations in the cytoplasm and the endoplasmic reticulum (ER). We used inhibitor of IP3R and CRISPR-Cas9-mediated IP3R knockout to determine the impact of IP3R on APOL1-G1-induced increases in cytoplasmic Ca²⁺ and cell viability. Finally, using metabolomics and related methods, we measured APOL1-GI-mediated changes in amino acid transport, protein synthesis and ATP production, in the presence and absence of VX-147 treatment.

Results

We demonstrate for the first time that APOL1 G1-mediated transport of Na⁺ and K⁺ induces Ca²⁺ release from the ER via IP3R and ryanodine receptor (RyR), and that the liberated Ca²⁺ triggers a sequence of downstream cytotoxic events including mitochondrial dysfunction and inhibition of protein synthesis via AMPK-TSC2-mTORC1 and eIF2a signaling. We also discovered for the first time that APOL1 G1 cation function impedes amino acid uptake in kidney cells. All observed cytotoxic phenotypes are reversed by VX-147.

Conclusion

These findings established APOL1-mediated Na⁺/K⁺ transport as the proximal driver of podocyte injury, and that Ca²⁺ signaling and protein synthesis are potential therapeutic targets for APOL1 nephropathy.

Funding

• Other NIH Support