A Novel Small Compound That Promotes Nuclear Translocation of YB-1 Ameliorates Experimental Hepatic Fibrosis in Mice

Kiyoshi Higashi,Yoshitaka Tomigahara,Hiroaki Shiraki,Toshiyuki Mikami,Yutaka Inagaki,Toru Kimura,Hideo Kaneko,Tadashi Moro,Kaori Miyata

doi:10.1074/jbc.m110.151936

Abstract

Transforming growth factor-β (TGF-β) is considered to be a major factor contributing to liver fibrosis. We have previously shown that nuclear translocation of YB-1 antagonizes the TGF-β/Smad3 signaling in regulating collagen gene expression. More recently, we have demonstrated that the novel small compound HSc025 promotes nuclear translocation of YB-1, resulting in the improvement of skin and pulmonary fibrosis. Here, we presented evidence as to the mechanism by which HSc025 stimulates nuclear translocation of YB-1 and the pharmacological effects of HSc025 on a murine model of hepatic fibrosis. A proteomics approach and binding assays using HSc025-immobilized resin showed that HSc025 binds to the amino acid sequence within the C-tail region of YB-1. In addition, immunoprecipitation experiments and glutathione S-transferase pulldown assays identified poly(A)-binding protein (PABP) as one of the cytoplasmic anchor proteins of YB-1. HSc025 directly binds to YB-1 and interrupts its interaction with PABP, resulting in accelerated nuclear translocation of YB-1. Transfection of cells with PABP siRNA promoted nuclear translocation of YB-1 and subsequently inhibited basal and TGF-β-stimulated collagen gene expression. Moreover, HSc025 significantly suppressed collagen gene expression in cultured activated hepatic stellate cells. Oral administration of HSc025 to mice with carbon tetrachloride-induced hepatic fibrosis improved liver injury as well as the degree of hepatic fibrosis. Altogether, the results provide a novel insight into therapy for organ fibrosis using YB-1 modulators.

Highlights

Common response to chronic liver injury, which leads to cirrhosis and is often associated with hepatocellular carcinoma
Multiple factors play a role in fibrogenesis, it is well recognized that transforming growth factor-␤ (TGF-␤) is the key molecule accelerating hepatic fibrosis [1]
We have demonstrated that a novel small compound HSc025 inhibited collagen gene expression in hepatic stellate cells, and oral administration of HSc025 to mice with CCl4-induced hepatic fibrosis exhibited repression of extracellular matrix deposition as well as attenuation of hepatic inflammation

Summary

Introduction

Common response to chronic liver injury, which leads to cirrhosis and is often associated with hepatocellular carcinoma. We recently assessed the actions of a novel form, HSc025 (Fig. 1A), and we showed it to repress TGF-␤-induced collagen gene expression in human dermal fibroblasts [15].

Results

Conclusion