Abstract: TH-PO0887
MDM2-ARRB2 Axis Regulates Membranous AT1R Endocytosis of Glomerular Endothelium During Renal Ischemia-Reperfusion Injury
Session Information
- Transplantation: Basic Research
November 06, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Transplantation
- 2101 Transplantation: Basic
Authors
- Jiang, Shan, Huazhong University of Science and Technology, Wuhan, China
- Su, Hua, Huazhong University of Science and Technology, Wuhan, China
Background
The exposure of endothelial non-human leukocyte antigen (HLA) is closely associated with the occurrence of antibody mediated rejection (ABMR), especially under ischemia-reperfusion (I/R). Angiotensin II type 1 receptor (AT1R) is one of the most important non-HLA in renal transplantation. Currently, the clinical practice for antihypertensive drugs targeting AT1R cannot effectively block the ectodomain of AT1R, which is critically attributes to the immunogenicity. As membranous protein, the endocytosis of AT1R is crucial for the exposure of its epitope, therefore, exploring the mechanisms involved in AT1R endocytosis of glomerular endothelial cell (GEC) is prospective for preventing I/R associated ABMR.
Methods
A bilateral kidney I/R model of mice was constructed by clamping renal arteries for 25 min and removing for reperfusion 1 day. Knockdown of MDM2 by renal cortical injection of AAV. In vitro, rat GEC (RGEC) were treated with hypoxia for 12 h and reoxygenation for 3 h (H/R). Moreover, the expression of the molecules was detected by WB and IF. Co-IP was carried out to verify the interaction between molecules.
Results
The expression of MDM2 and membranous AT1R were increased in GEC in vivo and in vitro during renal I/R. In vivo, knockdown of MDM2 resulted in increased AT1R expression on GEC membranes. In vitro, overexpression of MDM2 followed by H/R of RGEC resulted in decreased membrane AT1R level, however, upregulation of MDM2 may impair endothelial function and promoted inflammation. Thus, to further explore how MDM2 regulates AT1R is essential. It is known that MDM2 modulates the β-arrestin 2 (ARRB2)-associated endocytosis. Accordingly, our study found that MDM2 directly interacts with ARRB2 via Co-IP. Reportedly, MDM2 mediates ARRB2 ubiquitination, but this modification didn’t induce ARRB2 degradation but to promote its anchoring to membrane. Furthermore, knockdown of ARRB2 led to an enhanced membranous AT1R, whereas ARRB2 agonist resulted in membrane AT1R reduction in RGEC. By Co-IP, it was shown that ARRB2 directly bound with Clathrin, and the Clathrin inhibitor increased the expression of membrane AT1R in RGEC under H/R.
Conclusion
This study demonstrates that increased level of MDM2 in GEC in renal I/R promotes ARRB2 ubiquitination, which in turn targets the clathrin-dependent endocytosis pathway to promote AT1R endocytosis on GEC membranes.