Bax-PGAM5L-Drp1 complex is required for intrinsic apoptosis execution.

Wenjuan Xu,Linlin Jing,Chung-Chih Lin,Xiaoting Chen,Jianxin Diao,Quanshi Wang,Xuegang Sun,Yuanliang Liu

doi:10.18632/oncotarget.5013

Abstract

Intrinsic apoptosis eliminates cells with damaged DNA and cells with dysregulated expression of oncogene. PGAM5, a member of the phosphoglycerate mutase family, has two splicing variants: PGAM5L (the long form) and PGAM5S (the short form). It has been well established that PGAM5 is at the convergent point of multiple necrosis pathways. However, the role of PGAM5 in intrinsic apoptosis is still controversial. Here we report that the PGAM5L, but not PGAM5S is a prerequisite for the activation of Bax and dephosphorylation of Drp1 in arenobufagin and staurosporine induced intrinsic apoptosis. Knockdown of PGAM5L inhibits the translocation of Bax to the mitochondria and reduces mitochondrial fission. The interaction between PGAM5L and Drp1 was observed in both arenobufagin and staurosporine treated HCT116 cells, but not in HCT116 Bax(-/-) cells. Bax transfection rescues the formation of the triplex in both arenobufagin and staurosporine stimulated HCT116 Bax(-/-) cells. Arenobufagin shows remarkable anti-cancer effects both in orthotropic and heterotropic CRC models and demonstrates less toxic effects as compared with that of cisplatin. Bax-PGAM5L-Drp1 complex is detected in arenobufagin and staurosporine treated CRC cells in vitro and in arenobufagin and cisplatin treated tumor in vivo as well. In summary, our results demonstrate that Bax-PGAM5L-Drp1 complex is required for intrinsic apoptosis execution.

Highlights

Cancer is a major public health problem which accounts for 1/4 deaths in the United States [1]
Electron microscope images showed that the increased small fragmented mitochondria were significantly reduced by PGAM5L short hairpin RNA (shRNA) (Figure 5E). These results suggested that interaction between PGAM5L and Drp1 is linked to mitochondria fission
Our experimental data indicated that PGAM5L, one of the two splice variants of the mitochondrial protein phosphatase PGAM5, is indispensable for the execution of intrinsic apoptosis

Summary

Introduction

Cancer is a major public health problem which accounts for 1/4 deaths in the United States [1]. Apoptosis resistance is a strategy of choice for cancer cells that employ multiple mechanisms to override apoptosis for survival [2]. Understanding and tweaking the mechanisms of apoptosis are pivotal to eliminate potentially malignant cells. PGAM5 has two splicing forms, the shorter form (PGAM5S) and the longer isoform (PGAM5L). Both isoforms of PGAM5 function in the intrinsic necrosis pathway, based on the evidence that PGAM5 knockdown attenuates ROS- and calcium ionophore induced necrotic death [3]. The role of PGAM5 in apoptosis is still controversial. Staurosporine-induced apoptotic death is not affected by PGAM5 knockdown

Methods

Results

Conclusion