Kidney Week

Abstract: FR-PO0113

M1 Effect on APOL1 Cation Channel Function Is Modified by the Haplotype, Kidney Risk Genotype, and Cell Type

Session Information

• Hereditary Glomerular and Tubulointerstitial Kidney Diseases
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1202 Genetic Diseases of the Kidneys: Non-Cystic (Complex and Non-Cystic Monogenic)

Authors

• Bartolomeo, Korey, Cleveland Clinic, Cleveland, Ohio, United States

Korey Bartolomeo, DO

• Raheb Khelo, Joy, Cleveland Clinic, Cleveland, Ohio, United States

Joy Raheb Khelo, MD

• Onur, Omer Enes, Cleveland Clinic, Cleveland, Ohio, United States

Omer Enes Onur, MD

• Cam, Nurdan, Cleveland Clinic, Cleveland, Ohio, United States

Nurdan Cam, MSc

• Tran, Uyen, Cleveland Clinic, Cleveland, Ohio, United States

Uyen Tran

• Wessely, Oliver, Cleveland Clinic, Cleveland, Ohio, United States

Oliver Wessely, PhD

• O'Toole, John F., Cleveland Clinic, Cleveland, Ohio, United States

John F. O'Toole, MD

• Sedor, John R., Cleveland Clinic, Cleveland, Ohio, United States

John R. Sedor, MD, FASN

Background

APOL1 kidney disease (AKD) requires two copies of APOL1 risk variants (G1 or G2), but the disease is incompletely penetrant with inadequately understood mechanisms of pathogenesis. Published data shows that APOL1 mediated monovalent cation flux drives all pathogenic effector pathways, and targeted inhibitors are being evaluated in clinical trials. G2 can rarely be coinherited with p.N264K (M1), which prevents AKD risk. The mechanisms by which p.N264K mediate its protective function remain unclear. We characterized how p.N264K modifies the cation channel function of APOL1 with in vitro models.

Methods

Cell models included: (A) 293 HEK and HeLa cells with tetracycline inducible APOL1 G0 and G2 transgenes with the African haplotype; (B) podocytes differentiated from two isogenic induced pluripotent stem cell (iPSC) lines with or without gene editing to change G0 to homozygous G1 or G2 variants and (C) primary human podocytes. We performed surface biotinylation with streptavidin pulldowns, K+ conductance (thallium based) microplate assays, and cell death assays (MultiTox-Fluor and SYTOX).

Results

In both 293 and HeLa cells, the M1 haplotype reduces trafficking of APOL1 to the plasma membrane. In 293 cells, background variant and haplotype modified the tempo of APOL1 transit and abundance on the plasma membrane, the onset of K+ conductance and cellular viability. With time, all assembled channels permitted K+ conductance, including M1. M1 did significantly slow the transit of APOL1 G0 and G2 to the plasma membrane. At 6h, G2-M1 but not G0-M1 required p.150K to abrogate K+ conductance. In contrast to 293 cells, HeLa cells with APOL1 transgenes, iPSC-derived podocytes and primary human podocytes, with APOL1 expression matching 293 cells, express APOL1 on the plasma membrane that remains closed and cell viability was not impacted.

Conclusion

293 cells are uniquely sensitive to APOL1 in contrast to HeLa cells and podocytes and poorly model human kidney disease phenotypes that evolves over years or to explain the incomplete penetrance of kidney risk variants. Anchoring APOL1 in vitro models to human biology may facilitate the unraveling of phenotypic heterogeneity and mechanisms of AKD.

Funding

• NIDDK Support