Kidney Week

Abstract: TH-PO1117

Regulation of Kidney Fibroblast Functions by Palladin-MRTF Circuit in Response to TGF-β1

Session Information

• CKD: Mechanisms - 1
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2303 CKD (Non-Dialysis): Mechanisms

Authors

• Yamamoto, Naoki, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Naoki Yamamoto, MD

• Sakai, Norihiko, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Norihiko Sakai, MD, PhD

• Yamamura, Yuta, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Yuta Yamamura, MD

• Mizushima, Ichiro, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Ichiro Mizushima, MD, PhD

• Kitajima, Shinji, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Shinji Kitajima, MD, PhD

• Hara, Akinori, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Akinori Hara, MD

• Shimizu, Miho, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Miho Shimizu, MD, PhD

• Wada, Takashi, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Takashi Wada, MD, PhD

• Iwata, Yasunori, Kanazawa Daigaku, Kanazawa, Ishikawa, Japan

Yasunori Iwata, MD, PhD

Background

Kidney fibrosis is the common mechanism resulting in chronic kidney disease. We previously clarified myocardin-related transcription factor (MRTF) – serum response factor (SRF) signaling drives renal fibroblast activation and focal adhesion formation consisting of integrins through actin cytoskeleton reorganization. Thus far, it has been reported that actin-associated proteins (AAPs) regulate actin filament assembly and disassembly. However, it has yet to be understood whether AAPs relates to the pathogenesis of the fibrosis. Here, we investigated whether AAPs contributed to the renal fibroblasts (RFBs) activation and focal adhesion formation through actin cytoskeleton reorganization.

Methods

Cultured renal fibroblasts were used to examine transforming growth factor (TGF)-β₁-dependent AAPs. Of these AAPs, palladin was selected for further investigation. The effects of palladin on actin polymerization and MRTF-SRF signaling were evaluated in TGF-β₁-stimulated renal fibroblasts (RFBs) treated with paladin siRNA. In addition, palladin expression was evaluated with siRNA targeting MRTF-A/-B. Furthermore, expressions of α1 chain of type I procollagen (COLIAI), α-smooth muscle actin (αSMA), and integrin α11/β1 were explored with siRNA targeting palladin.

Results

Palladin was significantly upregulated in RFBs with TGF-β₁ stimulation. Palladin knockdown suppressed actin polymerization and MRTF-SRF signaling induced by TGF-β₁ whereas palladin expression was suppressed by siRNA targeting MRTF-A/-B. These results suggested that the amplification loop was created between palladin and MRTF-SRF signaling. In addition, the treatment of RFBs with siRNA targeting palladin attenuated COLIAI and αSMA. In addition, integrin α11/β1 expression induced by the stimulation with TGF-β₁ was also suppressed by palladin knockdown. Finally, the inhibition of integrin α11/β1 expression reduced MRTF-SRF signaling and expressions of COLIAI and αSMA.

Conclusion

TGF-β₁-induced amplification loop between palladin and MRTF-SRF signaling mediates renal fibroblast activation and focal adhesion formation, resulting in the upregulation of extracellular matrix expression.