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 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 3

msuPAR2-Tg mice develop progressive proteinuria and severe kidney dysfunction.

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msuPAR2-Tg mice develop progressive proteinuria and severe kidney dysfun...
(A) Proteinuria profiling in msuPAR1-Tg mice. Proteinuria, in terms of ACR, which was absent before HFD treatment at baseline, developed in msuPAR1-Tg mice after 6 months of HFD. n = 25 WT/baseline (BS); n = 26 msuPAR1-Tg/BS; n = 27 WT/HFD6mo; n = 30 msuPAR1-Tg/HFD6mo. Two-way ANOVA; data were log-transformed to normal distribution. (B) Spontaneous proteinuria in msuPAR2-Tg mice. Without HFD treatment, proteinuria was evident in msuPAR2-Tg mice at 2 months of age and increased significantly by 12 months of age. n = 9 at 2 mo (2 month) /BS; n = 7 at 12 mo. Two-way ANOVA. (C) With HFD treatment, msuPAR2-Tg mice developed accelerated and progressive proteinuria over a period of 6 months. n = 30 WT/BS; n = 26 msuPAR2-Tg/BS; n = 9 WT/HFD2mo; n = 16 msuPAR2-Tg/HFD2mo; n = 13 WT/HFD4mo; n = 16 msuPAR2-Tg/HFD4mo; n = 31 WT/HFD6mo; n = 36 msuPAR-Tg/HFD6mo. Baseline was at 2 months old, before HFD treatment. Two-way ANOVA. Data were log-transformed to normal distribution. (D) Serum albumin decreased significantly in HFD-treated msuPAR2-Tg mice compared with WT (littermate control) mice. n = 17 WT; n = 8 msuPAR1-Tg; n = 19 msuPAR2-Tg mice. One-way ANOVA. (E) Serum creatinine increased significantly in HFD-treated msuPAR2-Tg mice. n = 10 WT; n = 6 msuPAR1-Tg; n = 16 msuPAR2-Tg mice. One-way ANOVA. (F) Serum BUN levels increased significantly in HFD-treated msuPAR2-Tg mice. n = 10 WT; n = 6 msuPAR1-Tg; n = 16 msuPAR2-Tg mice. One-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.