Abstract: TH-PO0360
SERCA-Mediated Calcium Homeostasis Regulates Slit Diaphragm Integrity, Autophagy, and Nephrocyte Function
Session Information
- Glomerular Diseases: Genetics to Therapeutics
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
- Zhao, Yunpo, University of Maryland Baltimore School of Medicine, Baltimore, Maryland, United States
- Duan, Jianli, University of Maryland Baltimore School of Medicine, Baltimore, Maryland, United States
- Han, Zhe, University of Maryland Baltimore School of Medicine, Baltimore, Maryland, United States
Background
Disrupted intracellular Ca2+ homeostasis contributes to podocyte injury and proteinuric kidney disease. SERCA is an ER Ca2+ pump that maintains intracellular Ca2+ balance, but its role in renal filtration cells remains poorly defined.
Methods
Using Drosophila nephrocytes, an in vivo podocyte model, we tested SERCA function by RNAi depletion, wild-type overexpression, and expression of the disease-associated SERCA-A617T variant. Nephrocyte function was assessed by fluorescent uptake assays. Slit diaphragm structure, beta-integrin distribution, F-actin organization, cytosolic Ca2+, lysosomal activity, autophagic flux, and ultrastructure were analyzed by confocal microscopy, CaLexA reporter assays, LysoTracker staining, GFP-mCherry-Atg8a reporter analysis, Ref(2)p staining, and TEM.
Results
SERCA depletion reduced nephrocyte uptake and disrupted filtration barrier architecture, including loss of Polychaetoid and beta-integrin cortical fingerprint patterns. SERCA knockdown elevated cytosolic Ca2+, induced nephrocyte hypertrophy, disorganized cortical F-actin, and impaired autophagy, shown by reduced LysoTracker signal, accumulation of GFP-positive autophagosomes, and increased Ref(2)p aggregates. TEM revealed loss of slit diaphragms and abnormal multilayer membrane vesicles. Wild-type SERCA overexpression was well tolerated and did not alter albumin uptake, cell size, beta-integrin patterning, or F-actin organization. In contrast, SERCA-A617T reduced albumin uptake, increased cell size, elevated cytosolic Ca2+, disrupted beta-integrin organization, induced actin stress fibers, and increased Ref(2)p aggregation.
Conclusion
SERCA-mediated ER Ca2+ homeostasis is essential for nephrocyte filtration structure, integrin-actin organization, lysosomal function, and autophagy. SERCA-A617T acts as a deleterious loss-of-function variant in nephrocytes, linking Ca2+ dysregulation to cytoskeletal disruption, proteostasis failure, and renal filtration-cell injury.
SERCA loss and SERCA-A617T elevate cytosolic Ca2+ in nephrocytes. CaLexA reporter activity is increased by SERCA-RNAi and SERCA-A617T, but not wild-type SERCA, indicating disrupted Ca2+ homeostasis. Scale bar, 20 um.
Funding
- NIDDK Support