Nonimmune cell–derived ICOS ligand functions as a renoprotective αvβ3 integrin–selective antagonist
Kwi Hye Koh, … , Jochen Reiser, Eunsil Hahm
Kwi Hye Koh, … , Jochen Reiser, Eunsil Hahm
Published February 12, 2019
Citation Information: J Clin Invest. 2019;129(4):1713-1726. https://doi.org/10.1172/JCI123386.
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Research Article Nephrology

Nonimmune cell–derived ICOS ligand functions as a renoprotective αvβ3 integrin–selective antagonist

Abstract

Soluble urokinase receptor (suPAR) is a circulatory molecule that activates αvβ3 integrin on podocytes, causes foot process effacement, and contributes to proteinuric kidney disease. While active integrin can be targeted by antibodies and small molecules, endogenous inhibitors haven’t been discovered yet. Here we report what we believe is a novel renoprotective role for the inducible costimulator ligand (ICOSL) in early kidney disease through its selective binding to podocyte αvβ3 integrin. Contrary to ICOSL’s immune-regulatory role, ICOSL in nonhematopoietic cells limited the activation of αvβ3 integrin. Specifically, ICOSL contains the arginine-glycine-aspartate (RGD) motif, which allowed for a high-affinity and selective binding to αvβ3 and modulation of podocyte adhesion. This binding was largely inhibited either by a synthetic RGD peptide or by a disrupted RGD sequence in ICOSL. ICOSL binding favored the active αvβ3 rather than the inactive form and showed little affinity for other integrins. Consistent with the rapid induction of podocyte ICOSL by inflammatory stimuli, glomerular ICOSL expression was increased in biopsies of early-stage human proteinuric kidney diseases. Icosl deficiency in mice resulted in an increased susceptibility to proteinuria that was rescued by recombinant ICOSL. Our work identified a potentially novel role for ICOSL, which serves as an endogenous αvβ3-selective antagonist to maintain glomerular filtration.

Authors

Kwi Hye Koh, Yanxia Cao, Steve Mangos, Nicholas J. Tardi, Ranadheer R. Dande, Ha Won Lee, Beata Samelko, Mehmet M. Altintas, Vincent P. Schmitz, Hyun Lee, Kamalika Mukherjee, Vasil Peev, David J. Cimbaluk, Jochen Reiser, Eunsil Hahm

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Figure 1

Increased ICOSL expression is an early cellular response to renal injury.

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Increased ICOSL expression is an early cellular response to renal injury...
Relative mRNA expression values measured by quantitative PCR targeting ICOSL in both mouse (A–C; mPodo) and human (D; hPodo) podocyte cell lines. (A) qPCR analysis of Icosl mRNA in mouse podocyte cell lines 1, 3, or 6 hours after 50 μg/ml LPS treatment, normalized with the expression level of Gapdh and presented relative to the expression of Icosl in untreated control cells. (B) Primary podocyte isolation from BALB/c mice by Dynabead perfusion followed by 50 μg/ml LPS treatment for 3 hours. The cells were cultured and harvested, and relative expression levels of Icosl were measured by qPCR. (C) Relative mRNA expression levels of Icosl in mouse podocyte cell lines treated with 50 μg/ml LPS or 100 ng/ml TNF-α for 3 hours. (D) Relative expression levels of ICOSL in human podocyte cell lines following the same treatments as in C. Representative images (E) and quantification (F) of immunofluorescence staining of ICOSL protein in human podocytes treated with 50 μg/ml LPS (orange dots in F) or PBS (black dots in F) as control. For quantification, cells were individually defined by tracing cell borders, and the levels of ICOSL protein expression were measured by mean fluorescence intensity (MFI) using ImageJ software (n = 15 cells/group). (G–I) Human kidney biopsy samples were double-stained to detect ICOSL (green) and synaptopodin (Synpo; red) by immunofluorescence staining. As depicted, analysis groups include healthy control and kidney tissues from patients with FSGS or DN at early/late stages (n = 5/group). The confocal micrographs were analyzed for glomerular expression of ICOSL by manually selecting glomeruli, defined by synaptopodin, as the region of interest. Representative confocal microscopic images are shown in G. Scale bars, 50 μm. ICOSL MFI in FSGS (H) or DN (I) groups was normalized to that of healthy controls, and data are presented as fold changes. Data are shown as mean ± SEM; *P < 0.05, **P < 0.01, ***P < 0.001; 1-way ANOVA with Dunnett’s multiple comparison test (A, C, and D) or with Tukey’s multiple comparison test (H and I) and Student’s 2-tailed, unpaired t test (B and F).