Abstract: FR-PO1191
LRP2 Donnai-Barrow Syndrome Variant p.C1400R Impairs Proximal Tubule Endocytosis but Not LRP2 Biosynthesis
Session Information
- CKD: Mechanisms, AKI, and Beyond - 2
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2303 CKD (Non-Dialysis): Mechanisms
Authors
- Beenken, Andrew Samuel, Columbia University, New York, New York, United States
- Ghotra, Aryan S., Columbia University, New York, New York, United States
- Shen, Tian, Columbia University, New York, New York, United States
- Sturley, Rachel, Columbia University, New York, New York, United States
- Erdjument-Bromage, Hediye, New York University, New York, New York, United States
- Neubert, Thomas A, New York University, New York, New York, United States
- High, Frances, Massachusetts General Hospital, Boston, Massachusetts, United States
- Weisz, Ora A., University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Barasch, Jonathan M., Columbia University, New York, New York, United States
Background
LRP2 and cubilin cooperate in the proximal tubule (PT) to capture low molecular weight proteins that escape the glomerular filtration barriers. Variants causing LRP2 loss of function (LoF) lead to Donnai-Barrow Syndrome (DBS), characterized by neurologic developmental abnormalities and proteinuria. LRP2 variants causing DBS are thought to induce LoF primarily through impaired LRP2 expression. Here, we investigated the LRP2 p.C1400R variant (p.C1401R in mouse), demonstrating that it preserves LRP2 biosynthesis but impairs PT endocytosis.
Methods
Urine samples from nine DBS-affected children and eight parental controls were analyzed with liquid chromatography mass spectrometry (LC-MS/MS). One patient harbored LRP2 p.C1400R, and this variant was characterized with a CRISPR mouse model. Immunofluorescence (IF) experiments probed localization of LRP2 and endosomal compartment markers. LRP2 was purified from mutant mice using anion exchange and size exclusion chromatography. LC-MS/MS analyzed purified LRP2 p.C1401R to confirm the presence of the peptide carrying the missense variant. APEX-V5-tagged receptor-associated protein (RAP) was perfused in vivo to LRP2 p.C1401R mice.
Results
LC-MS/MS analysis revealed 186 significant proteins present in the urine of DBS patients relative to parental controls (BH-FDR, q<0.01). Proteinuria due to LRP2 p.C1400R was indistinguishable from that due to LRP2 frame shifts or truncations. In the mouse model, LRP2 was expressed, but endocytosis of Alexa-labeled myoglobin was attenuated. Recycling and late endosomal compartments had reduced abundance in both IF and quantitative Western blotting. RAP-APEX-V5 had robust uptake to the PT in WT mice that was attenuated in LRP2 p.C1401R mice.
Conclusion
A missense variant of LRP2 spares its biosynthesis but perturbs PT endocytosis. This study demonstrates that mouse models of DBS variants have the potential to serve as tools for dissecting PT cell biology. A range of variant-specific mechanisms may underlie the common phenotype of proteinuria in DBS, and understanding the pathophysiology of these specific disease states will shed new light on protein uptake by the PT.
Funding
- NIDDK Support