Bim and VDAC1 are hierarchically essential for mitochondrial ATF2 mediated cell death.

Zhaoyun Liu,Qianfu Luo,Chunbao Guo

doi:10.1186/s12935-015-0188-y

Abstract

BackgroundATF2 mediated cytochrome c release is the formation of a channel with some unknown factors larger than that of the individual proteins. BHS-only proteins (BH3s), such as Bim, could induce BAX and VDAC, forming a new channel. According to this facts, we can speculated that there is possible signal relationship with BH3s and ATF2, which is associated with mitochondrial-based death programs.MethodsThe growth inhibitory effects of mitochondrial ATF2 were tested in cancer cell lines B16F10, A549, EG7, and LL2. Apoptosis was measured by flow cytometry. The effects of ATF2 and levels of apoptosis regulatory proteins were measured by Western blotting. The interaction of proteins were evaluated by immunoprecipitation analysis. The in vivo antitumor activity of mitochondrial ATF2 were tested in xenograft B16F10 models.ResultsGenotoxic stress enabled mitochondrial ATF2 accumulation, perturbing the HK1-VDAC1 complex, increasing mitochondrial permeability, and promoting apoptosis. ATF2 inhibition strongly reduced the conformational activation of Bim, suggesting that Bim acts downstream of ATF2. Although Bim downregulation had no effect on ATF2 activation, Bim knockdown abolished VDAC1 activation; the failure of VDAC1 activation in Bim-depleted cells could be reversed by the BH3-only protein mimic ABT-737. We also demonstrate that silencing of ATF2 in B16F10 cells increases both the incidence and prevalence of tumor xenografts in vivo, whereas stably mitochondrial ATF2 transfection inhibited B16F10 tumor xenografts growth.ConclusionsAltogether, these results show that ATF2 is a component of the apoptosis machinery that involves a hierarchical contribution of ATF2, Bim, and VDAC1. Our data offer new insight into the mechanism of mitochondrial ATF2 in mitochondrial apoptosis.

Highlights

As one member of activator protein-1 (AP-1) transcription factor, a growing number of transcription dependent and independent functions have been described, while attesting to its capacity to regulate diverse and often opposing functions, which implicated some of the most challenging therapeutic targets [1,2]
activating transcription factor 2 (ATF2) mitochondrial localization is critical for genotoxic-induced apoptosis To test the contribution of mitochondrial ATF2 to apoptosis, we measured the cytotoxic effect of genotoxic insults on several cancer cell lines by a cell viability analysis while measuring the ATF2 mitochondria accumulation within these cells
To assess the effect of elevated mitochondrial ATF2 expression in B16F10 cells, cells were transfected with the ATF2T52A expression vector, which preferentially localizes to the mitochondria [3]

Summary

Introduction

As one member of activator protein-1 (AP-1) transcription factor, a growing number of transcription dependent and independent functions have been described, while attesting to its capacity to regulate diverse and often opposing functions, which implicated some of the most challenging therapeutic targets [1,2]. Evidence involved in activator BHS-only proteins (BH3s), such as Bim, has been presented, which could induce BAX and VDAC reconstituted into liposomes, forming a new channel at the MOM [12,13,14]. According to this facts, we can speculated that there is possible signal relationship with BH3s and ATF2, which is related to mitochondrial involved apoptosis. BHS-only proteins (BH3s), such as Bim, could induce BAX and VDAC, forming a new channel According to this facts, we can speculated that there is possible signal relationship with BH3s and ATF2, which is associated with mitochondrial-based death programs

Methods

Results

Discussion

Conclusion