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 1

Characterization of msuPAR recombinant proteins.

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Characterization of msuPAR recombinant proteins. (A) SDS gel analysis of...
(A) SDS gel analysis of purified msuPAR1 and msuPAR2 before (S2 and S1) and after (S2/P and S1/P) deglycosylation with PNGase F. S1, msuPAR1; S2, msuPAR2; P, PNGase F. (B) LC-MS verification of recombinant msuPAR1 and msuPAR2 proteins. Shown are representative mass spectra of identified peptides from the deglycosylated msuPAR proteins. (C) EM structure modeling of msuPAR2. The isosurface has been set to enclose 100% of the expected protein mass. The image that is second from the left shows the same map as the first, but displays the fit of domains D1 and the expressed portion of domain D2 in the map. The additional sequences following the splice junction have not been modeled. The third image shows the same map as the first, but rotated 90°. The fourth image shows the ribbon diagram of the msuPAR1 structure (pdb id 3LAQ) for comparison. The region included in msuPAR2 is indicated in blue. Locations of the 3 domains of msuPAR1 are indicated with black lines.