Kidney Week

Abstract: FR-PO746

Protective Effect of GIT2 against Podocyte Injury in Mice

Session Information

• Glomerular Diseases: Mechanisms and Podocyte Biology
  October 25, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology

Authors

• Matsuda, Jun, Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan

Jun Matsuda, MD, PhD

• Shimada, Naoyuki, Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan

Naoyuki Shimada, MD

• Asano-Matsuda, Kana, Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan

Kana Asano-Matsuda, MD

• Tokuchi, Maho, Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan

Maho Tokuchi, MD

• Masztalerz, Agnieszka, Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada

Agnieszka Masztalerz, PhD

• Lemay, Serge, Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada

Serge Lemay, MD

• Takano, Tomoko, Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada

Tomoko Takano, MD, PhD

• Isaka, Yoshitaka, Department of Nephrology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan

Yoshitaka Isaka, MD, PhD

Background

Podocytes have an intricate structure featured by numerous actin-based projections called foot processes (FP). Rho GTPases, including Rac1, play important roles in actin cytoskeletal remodeling required for cell morphology and adhesion. We previously showed that Rac1 activation in podocytes causes FP effacement and proteinuria, but the upstream regulatory mechanism directing Rac1 is largely unknown. Recently, we identified focal adhesion protein GIT2 as one of the Rac1-interacting proteins in immortalized human podocytes, and showed that GIT2 knockdown elicited Rac1 activation.

Methods

The protein and mRNA expression of GIT2 in mice kidney were studied by immunoblotting and in situ hybridization, respectively. Git2-floxed mice were established using CLICK (CRISPR with long single-stranded DNA inducing conditional knockout alleles). They were then crossed with NPHS2-Cre mice to generate podocyte-specific Git2 knockout (KO) mice. KO mice and age-matched controls were subjected to the minimal change disease model by lipopolysaccharide (LPS) or the salt-sensitive hypertension model by uninephrectomy (UNx) with deoxycorticosterone acetate (DOCA)/salt.

Results

GIT2 was relatively enriched in glomeruli including podocytes in the kidney. In KO mice, glomerular expression of GIT2 protein was significantly reduced compared with controls. When challenged with LPS, KO mice showed sustained high levels of proteinuria, resulting in a significantly higher urine albumin to creatinine ratio (ACR) at 48hours compared with controls. When treated with UNx-DOCA/salt, systolic blood pressure was increased similarly at day14 in both KO and control mice. While UNx-DOCA/salt induced a significant increase of ACR in both mouse groups, KO mice tended to have more severe proteinuria. Rac1 inhibitor NSC23766 significantly decreased ACR in UNx-DOCA/salt-treated KO mice. Serum UN was significantly increased in UNx-DOCA/salt-treated KO mice compared with controls. In both LPS and UNx-DOCA/salt models, FP effacement was exacerbated in KO mice compared with controls.

Conclusion

In the current study, we demonstrated that GIT2 protects podocytes and glomerular function against injury. GIT2 may become a new therapeutic target on the Rac1 pathway in podocytopathy.