Deregulation of AP-1 Proteins in Collagen Gel-induced Epithelial Cell Apoptosis Mediated by Low Substratum Rigidity

Yao-Hsien Wang,Wen-Tai Chiu,Yang-Kao Wang,Ching-Chou Wu,Tsu-Ling Chen,Chiao-Feng Teng,Wen-Tsan Chang,Hsien-Chang Chang,Ming-Jer Tang

doi:10.1074/jbc.m604801200

Yao-Hsien Wang, Wen-Tai Chiu + Show 7 more

Open Access

https://doi.org/10.1074/jbc.m604801200

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Abstract

In this study, we established that collagen gel, but not collagen gel coating, induced apoptosis exclusively in epithelial cell lines, which indicated that low substratum rigidity might trigger cell apoptosis. To confirm this, we used collagen gels with different rigidities due to cross-linking or physical disruption of collagen fibrils caused by sonication. We found that collagen gel-induced apoptosis was inversely correlated with substratum rigidity. Low substratum rigidity collagen gel-induced apoptosis was neither prevented by Bcl-2 overexpression nor preceded by mitochondrial release of cytochrome c. This suggested that the mitochondrial pathway was not involved in low substratum rigidity-induced apoptosis. Low substratum rigidity activated c-Jun N-terminal kinase (JNK) within 4 h, but it also rapidly down-regulated c-Jun within 1 h and triggered persistent aberrant expression of c-Fos for at least 24 h. Either reduced c-Jun expression or c-Fos overexpression induced apoptosis in several epithelial cells. Inhibiting low substratum rigidity-induced JNK activation prevented aberrant c-Fos expression but only partially blocked low substratum rigidity-induced apoptosis. Taking these results together, we conclude that low substratum rigidity collagen gel induced apoptosis in epithelial cells and that deregulated AP-1 proteins mediated that apoptosis, at least in part.

Highlights

The physical properties of extracellular matrix influenced the locomotion [1, 2], survival [3], gene expression, and proliferation [4] of cells
Characterization of LLC-PK1 Cell Death Induced by Fibril Collagen Gel—LLC-PK1 and HEK 293 cells were cultured for 24 h on normal culture dishes or 0.3% type I collagen gel prepared from the tail tendons of 1-month-old rats
We demonstrated that low substratum rigidity, the physical property of fibril collagen, induced apoptosis in epithelial cells but not in fibroblasts or transformed cells

Summary

Introduction

The physical properties of extracellular matrix influenced the locomotion [1, 2], survival [3], gene expression, and proliferation [4] of cells. We established that collagen gel, but not collagen gel coating, induced apoptosis exclusively in epithelial cell lines, which indicated that low substratum rigidity might trigger cell apoptosis. An analysis of the DNA extracted from LLC-PK1 cells cultured on collagen gel showed a DNA ladder pattern, indicating that collagen gel-induced cell death was apoptosis (Fig. 1B).

Results

Conclusion