DDR1 contributes to kidney inflammation and fibrosis by promoting the phosphorylation of BCR and STAT3
Corina M. Borza, Gema Bolas, Fabian Bock, Xiuqi Zhang, Favour C. Akabogu, Ming-Zhi Zhang, Mark de Caestecker, Min Yang, Haichun Yang, Ethan Lee, Leslie Gewin, Agnes B. Fogo, W. Hayes McDonald, Roy Zent, Ambra Pozzi
Corina M. Borza, Gema Bolas, Fabian Bock, Xiuqi Zhang, Favour C. Akabogu, Ming-Zhi Zhang, Mark de Caestecker, Min Yang, Haichun Yang, Ethan Lee, Leslie Gewin, Agnes B. Fogo, W. Hayes McDonald, Roy Zent, Ambra Pozzi
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Research Article Cell biology Nephrology

DDR1 contributes to kidney inflammation and fibrosis by promoting the phosphorylation of BCR and STAT3

Abstract

Discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase activated by collagen, contributes to chronic kidney disease. However, its role in acute kidney injury and subsequent development of kidney fibrosis is not clear. Thus, we performed a model of severe ischemia/reperfusion-induced acute kidney injury that progressed to kidney fibrosis in WT and Ddr1-null mice. We showed that Ddr1-null mice had reduced acute tubular injury, inflammation, and tubulointerstitial fibrosis with overall decreased renal monocyte chemoattractant protein (MCP-1) levels and STAT3 activation. We identified breakpoint cluster region (BCR) protein as a phosphorylated target of DDR1 that controls MCP-1 production in renal proximal tubule epithelial cells. DDR1-induced BCR phosphorylation or BCR downregulation increased MCP-1 secretion, suggesting that BCR negatively regulates the levels of MCP-1. Mechanistically, phosphorylation or downregulation of BCR increased β-catenin activity and in turn MCP-1 production. Finally, we showed that DDR1-mediated STAT3 activation was required to stimulate the secretion of TGF-β. Thus, DDR1 contributes to acute and chronic kidney injury by regulating BCR and STAT3 phosphorylation and in turn the production of MCP-1 and TGF-β. These findings identify DDR1 an attractive therapeutic target for ameliorating both proinflammatory and profibrotic signaling in kidney disease.

Authors

Corina M. Borza, Gema Bolas, Fabian Bock, Xiuqi Zhang, Favour C. Akabogu, Ming-Zhi Zhang, Mark de Caestecker, Min Yang, Haichun Yang, Ethan Lee, Leslie Gewin, Agnes B. Fogo, W. Hayes McDonald, Roy Zent, Ambra Pozzi

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Figure 7

DDR1 activation promotes TGF-β production and STAT3 phosphorylation.

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DDR1 activation promotes TGF-β production and STAT3 phosphorylation. (A)...
(A) TGF-β was measured by ELISA in conditioned medium of RPTECs treated ± collagen I (CI) ± Cmp-1 (3 μM). Circles represent a single experiment performed in triplicate. Values are mean ± SD of 3 experiments and represent fold-changes versus vehicle-treated cells assigned as 1. Statistical analysis: 1-way ANOVA followed by Dunnett’s multiple-comparison test versus CI-treated group. (B) RPTECs were treated ± CI ± Cmp-1 (3 μM) and then analyzed by Western blot for phosphorylated (Tyr705) and total STAT3. The black vertical line separates 2 gels that were run and developed at the same time. (C) pSTAT3 and STAT3 bands were quantified by densitometry and pSTAT3 is expressed as pSTAT3/STAT3 ratio. Circles and values are as in A. Statistical analysis: 1-way ANOVA followed by Tukey’s multiple-comparison test. (D and E) Kidney cortices from uninjured (d–1), d3, and d28 injured WT and Ddr1-KO mice were analyzed by Western blot for levels of pSTAT3 and STAT3. The black vertical line separates 2 different gels. pSTAT3/STAT3 ratio was calculated as described in C. Circles represent an individual kidney (d–1 WT n = 4, d3 WT and Ddr1-KO n = 12, d28 WT and Ddr1-KO n = 5). Values are mean ± SD and represent fold-change versus d–1 assigned as 1. Statistical analysis was performed as in C. (F and G) Kidney sections from uninjured (d–1), d3, and d28 injured WT and Ddr1-KO mice were stained with anti-pSTAT3 antibody and LTL. Scale bar: 20 μm. The number of pSTAT3-positive and total number of proximal tubule cells was evaluated and expressed as described in the Methods. Circles represent a single kidney. Values represent mean ± SD (d–1 WT n = 3, d3 WT n = 5, d3 Ddr1-KO n = 3, d28 WT n = 6, d28 Ddr1-KO n = 5). Statistical analysis was performed as in C.