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 4

msuPAR2-Tg mice present FSGS-like kidney pathology.

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msuPAR2-Tg mice present FSGS-like kidney pathology. (A) PAS staining of ...
(A) PAS staining of kidney sections from spontaneous non–HFD treated mice. Segmental glomerular sclerosis was shown in some glomeruli of msuPAR2-Tg mice. In contrast, no abnormality was observed in littermate control WT mice. Scale bars: 20 μm. Arrow shows sclerotic area. (B) Kidney histology of HFD-treated mice. Left panel, PAS staining; right panels, H&E staining. Histological features of advanced FSGS were observed in HFD-treated msuPAR2-Tg mouse kidneys. Scale bars: 20 μm. Arrows show sclerotic area. TEM examination (C) and analysis (D) indicate that foot-process (FP) effacement significantly increased with msuPAR2-Tg mice. Data were represented by the FP counts per μm of glomerular basement membrane (GBM). n = 17 WT; n = 14 msuPAR2-Tg. ***P < 0.001, Student’s t test. Scale bars: 1 μm. (E) Localization of msuPAR2 in the glomeruli. Kidney cryosections were performed with double-immunofluorescent stainings with anti-msuPAR2 antibody and anti-synaptopodin antibody. Syno, synaptopodin (used as a podocyte marker). Colocalization of msuPAR2 (green) with synapopodin (red) is shown in brown. (F) Localization of msuPAR1 in the glomeruli by msuPAR1 antibody. Compared with WT and msuPAR2-Tg mice, an abundance of msuPAR1 was clearly observed in the msuPAR1-Tg mice. Scale bars: 20 μm. Negative staining of both msuPAR1 and msuPAR2 in uPAR-KO mice indicates the specificities of the suPAR antibodies employed.