Abstract: FR-PO0766
G Protein-Coupled Receptor Kinase-Interacting Proteins (GIT) Cooperatively Sustain Podocyte Health and Glomerular Filtration Barrier
Session Information
- Top Trainee Posters - 2
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 01:00 PM - 01:06 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Tokuchi, Maho, The University of Osaka Suita, Osaka, Japan
- Matsuda, Jun, The University of Osaka Suita, Osaka, Japan
- Shimada, Naoyuki, The University of Osaka Suita, Osaka, Japan
- Asano-Matsuda, Kana, The University of Osaka Suita, Osaka, Japan
- Aoudjit, Lamine, McGill University Health Centre, Montreal, Quebec, Canada
- Takano, Tomoko, McGill University Health Centre, Montreal, Quebec, Canada
- Isaka, Yoshitaka, The University of Osaka Suita, Osaka, Japan
Background
The structure of podocyte foot processes is supported by the actin cytoskeleton. Rho GTPases, including Rac1, play a crucial role in regulating actin dynamics. We recently reported that the focal adhesion protein GIT2 suppresses Rac1 activity, thereby protecting podocytes against injury. However, the expression and the role of the other GIT isoform, GIT1 has not been studied in podocytes.
Methods
Subcellular localization of endogenous GIT1 in human podocytes was studied by immunocytochemistry. Podocyte-specific GIT1 deficient mice were generated by crossing GIT1 floxed mice with NPHS2-Cre mice. They were further crossed with systemic GIT2-null mice to generate mice with simultaneous deletion of GIT1 and GIT2 in podocytes (double knockout or DKO mice). Urine albumin to creatinine ratio (UACR) and renal histology were studied up to 23 weeks of age. Podocyte ultrastructure was assessed by electron microscopy. Mouse podocytes with GIT1 and/or GIT2 knockdown and their controls were established using shRNA. Cell death after Adriamycin treatment was monitored by cytotoxicity assay. Data are provided as the mean ± SE.
Results
GIT1 localized predominantly at the distal end of focal adhesions. Podocyte-specific GIT1 deficient mice showed no glomerular changes up to 23 weeks, similar to systemic GIT2-null mice. However, DKO mice presented massive proteinuria starting at around 12 weeks. Quantification of the UACR confirmed that proteinuria in DKO mice was nephrotic-range at 16 weeks and significantly increased at 23 weeks compared to controls (4175 ± 917 vs. 8.3 ± 0.76 mg/gCr). Periodic acid-Schiff staining revealed that glomeruli from DKO mice appeared intact at 7 weeks. However, segmental glomerulosclerosis and proteinaceous casts were observed in the limited area of 16-week-old DKO mice, and these became diffuse at 23 weeks. Electron microscopic analysis at 7 weeks demonstrated a significant increase in podocyte foot process width (498 ± 31 vs. 318 ± 5.1 nm) in DKO mice . Cytotoxicity assay revealed that the number of dead cells was significantly increased in double knockdown podocytes compared to controls at 48 hours (63 ± 1.9 vs. 44 ± 2.1 cells/image).
Conclusion
The results indicate that focal adhesion proteins GIT1 and GIT2 cooperatively play a critical role in podocyte health and glomerular filtration barrier.