uPAR isoform 2 forms a dimer and induces severe kidney disease in mice
Changli Wei, … , M. Amin Arnaout, Jochen Reiser
Changli Wei, … , M. Amin Arnaout, Jochen Reiser
Published August 30, 2019; First published February 7, 2019
Citation Information: J Clin Invest. 2019;129(5):1946-1959. https://doi.org/10.1172/JCI124793.
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Research Article Nephrology

uPAR isoform 2 forms a dimer and induces severe kidney disease in mice

Abstract

Soluble urokinase plasminogen activator receptor (suPAR) is an immune-derived circulating signaling molecule that has been implicated in chronic kidney disease, such as focal segmental glomerulosclerosis (FSGS). Typically, native uPAR (isoform 1) translates to a 3-domain protein capable of binding and activating integrins, yet the function of additional isoforms generated by alternative splicing is unknown. Here, we characterized mouse uPAR isoform 2 (msuPAR2), encoding domain I and nearly one-half of domain II, as a dimer in solution, as revealed by 3D electron microscopy structural analysis. In vivo, msuPAR2 transgenic mice exhibited signs of severe renal disease characteristic of FSGS with proteinuria, loss of kidney function, and glomerulosclerosis. Sequencing of the glomerular RNAs from msuPAR2-Tg mice revealed a differentially expressed gene signature that includes upregulation of the suPAR receptor Itgb3, encoding β3 integrin. Crossing msuPAR2-transgenic mice with 3 different integrin β3 deficiency models rescued msuPAR2-mediated kidney function. Further analyses indicated a central role for β3 integrin and c-Src in msuPAR2 signaling and in human FSGS kidney biopsies. Administration of Src inhibitors reduced proteinuria in msuPAR2-transgenic mice. In conclusion, msuPAR2 may play an important role in certain forms of scarring kidney disease.

Authors

Changli Wei, Jing Li, Brian D. Adair, Ke Zhu, Jian Cai, Michael Merchant, Beata Samelko, Zhongji Liao, Kwi Hye Koh, Nicholas J. Tardi, Ranadheer R. Dande, Shuangxin Liu, Jianchao Ma, Salvatore Dibartolo, Stefan Hägele, Vasil Peev, Salim S. Hayek, David J. Cimbaluk, Melissa Tracy, Jon Klein, Sanja Sever, Sanford J. Shattil, M. Amin Arnaout, Jochen Reiser

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Figure 7

Blocking Src activity reduces proteinuria in msuPAR2-Tg mice.

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Blocking Src activity reduces proteinuria in msuPAR2-Tg mice. (A) Glomer...
(A) Glomerular Src activity was determined by immunofluorescent staining of the kidney cryosections with p-Src monoclonal antibody (green). Podocin was used as a podocyte marker (red). Shown are the representative glomeruli with p-Src immunofluorescent staining. As indicated by the p-Src staining intensity, glomerular Src phosphorylation was readily observed in the kidney sections from msuPAR2-Tg, but not from other investigated mice. Scale bars: 20 μm. (B) Treatment with Src inhibitors lowered proteinuria in msuPAR2-Tg mice. Both PP1 and Src inhibitor 1 (5 mg/kg) were administered into the randomly grouped msuPAR2-Tg mice intraperitoneally, with vehicle controls receiving the same amount of DMSO. n = 8 Src inhibitor group; n = 7 vehicle control group. At 72 hours after treatment, proteinuria was significantly reduced by Src inhibitor treatment. Two-way ANOVA; data were log-transformed to normal distribution. **P < 0.01.