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Kidney Week

Abstract: SA-OR94

Bub1 Is a Potential Mediator of TGFβ-Induced Renal Fibrosis

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis

Authors

  • Onishi, Yasuhiro, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Uchida, Haruhito A., Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Sakurabu, Yoshimasa, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Asakawa, Tomohiko, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Katayama, Katsuyoshi, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Hada, Yoshiko, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Takeuchi, Hidemi, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Tanaka, Keiko, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Umebayashi, Ryoko, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
  • Wada, Jun, Department of Nephrology, Rheumatology, Endocrinology and Metabolism, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan
Background

Budding Uninhibited by Benzimidazole 1 (Bub1) is a widely conserved eukaryotic kinase and Bub1 gene-deficient mice are embryonic lethal. Bub1 has long been recognized to localise to the centromere in mitosis as a component of the spindle checkpoint complex and to regulate chromosome segregation. Meanwhile, on siRNA screening targeting human kinases against cancer cell lines, it has been suggested that Bub1 may co-activate with TGFβ receptors to regulate SMAD2/3 phosphorylation. Since TGF-β/SMAD pathway is a major pathway in fibrosis, it is assumed that Bub1 may be involved in development of fibrosis as a novel mediator of the TGF-β/SMAD pathway. These findings are limited to cancer cell lines, therefore, it remais unknown whether similar events will be identified in the kidney.

Methods

The expression and localization of Bub1 was confirmed in the kidney of wild type (BL6) mice. To generate conditional Bub1 knockout mice, the Bub1fl/fl mice were crossed with gGT-Cre mice or FSP1-Cre mice. Renal fibrosis was induced in 8-10 week old male conditional Bub1 knockout mice by unilateral ureteral obstruction (UUO) model. In vitro, human renal proximal tubular epithelial cells (HK-2) were cultured, then Bub1 knockdown was performed by siRNA transfection.

Results

In wild-type mice, Bub1 was expressed in renal tubular epithelial cells by immunofluorescence staining with LTA. The Bub1 staining was diminished in conditional Bub1 renal knockout mice. Renal fibrosis and the expression of aSMA induced by UUO were attenuated in the mice with Bub1 proximal tubular cells (PTCs) knockout compared to wild type mice. On the other hand, the renal fibrosis induced by UUO in the mice with Bub1 fibroblasts knockout was not changed compared to wild type mice. Furthermore, knockdown of Bub1 in HK-2 cells attenuated the phosphorylation of SMAD3 by TGF-β stimulation.

Conclusion

These results uncovered that Bub1 deficiency of renal proximal tubular cells plays a protective role in renal fibrosis triggered by UUO via TGF-β/SMAD pathway.

Funding

  • Government Support – Non-U.S.