Abstract: TH-PO0283
Cathepsin S-Dependent Processing of APOL1-G1 Generates Toxic Fragments Resistant to Membrane-Targeted APOL1 Inhibition
Session Information
- Glomerular Diseases: Cell Biology
October 22, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Li, Jinliang, Children's National Hospital, Washington, District of Columbia, United States
- Yu, Jing, University of Virginia, Charlottesville, Virginia, United States
- Xu, Lian, Children's National Hospital, Washington, District of Columbia, United States
- Das, Jharna R., Children's National Hospital, Washington, District of Columbia, United States
- Han, Zhe, University of Maryland Baltimore, Baltimore, Maryland, United States
- Ray, Patricio E., University of Virginia, Charlottesville, Virginia, United States
Background
APOL1-mediated kidney injury is commonly attributed to membrane-associated cytotoxicity. However, inflammatory signaling in HIV-associated nephropathy may also promote proteolytic processing of APOL1-G1 into pathogenic fragments. Whether such fragments contribute to podocyte injury through mechanisms that are distinct from APOL1 channel activity remains unclear.
Methods
Primary APOL1-G1/G1 podocytes cultured from children with HIVAN were exposed to HIV-1, TNF-α, and IFN-γ. scRNA-seq, Western blotting, proteomics, and nuclear fractionation studies were performed to evaluate APOL1 localization and cathepsin expression. Recombinant APOL1 protein was incubated with cathepsin S in the presence or absence of a cathepsin S inhibitor. Cytotoxicity assays were used to compare the effects of full-length APOL1-G1 and APOL1-G1 fragments, including their responses to the APOL1 channel inhibitor Inaxaplin.
Results
Podocyte clones exhibiting predominant nuclear localization of GFP-APOL1-G1 demonstrated markedly increased inflammatory signatures and a ~5-fold increase in cathepsin S expression compared with clones expressing APOL1-G1 mainly in the cytosol. IFN-γ induced expression of both APOL1-G1 and cathepsin S in HIVAN podocytes. In vitro cleavage assays demonstrated that cathepsin S proteolytically processed APOL1-G1 into discrete fragments, including a ~28 kDa C-terminal fragment, and this cleavage was blocked by cathepsin S inhibition. Proteomic studies identified a toxic N-terminal APOL1-G1 fragment in nuclear fractions. Notably, Inaxaplin partially reduced cytotoxicity induced by full-length APOL1-G1 but failed to rescue toxicity induced by the nuclear APOL1-G1 fragment.
Conclusion
Our findings support a novel inflammatory mechanism in which IFN-γ promotes Cathepsin S–dependent processing of APOL1-G1 into toxic fragments that contribute to podocyte injury through membrane-independent pathways potentially resistant to current APOL1 channel inhibitors. These studies identify Cathepsin S as a potential upstream therapeutic target linking inflammatory signaling to APOL1 fragmentation, altered intracellular trafficking, and nuclear toxicity. More broadly, our data suggest that proteolytic processing of APOL1-G1 may represent a central pathogenic mechanism contributing to HIVAN and other APOL1-associated kidney diseases.
Funding
- NIDDK Support