SIRT3, PP2A and TTP protein stability in the presence of TNF-α on vincristine-induced apoptosis of leukaemia cells.

Liang‐Jun Wang,Chia‐Hui Huang,Jing‐Ting Chiou,Yi‐Jun Shi,Yuan‐Chin Lee,Long‐Sen Chang

doi:10.1111/jcmm.14949

Abstract

The contribution of vincristine (VCR)‐induced microtubule destabilization to evoke apoptosis in cancer cells remains to be resolved. Thus, we investigated the cytotoxic mechanism of VCR on U937 and HL‐60 human leukaemia cell lines. We discovered that VCR treatment resulted in the up‐regulation of TNF‐α expression and activation of the death receptor pathway, which evoked apoptosis of U937 cells. Moreover, VCR induced microtubule destabilization and mitotic arrest. VCR treatment down‐regulated SIRT3, and such down‐regulation caused mitochondrial ROS to initiate phosphorylation of p38 MAPK. p38 MAPK suppressed MID1‐modulated degradation of the protein phosphatase 2A (PP2A) catalytic subunit. The SIRT3‐ROS‐p38 MAPK‐PP2A axis inhibited tristetraprolin (TTP)‐controlled TNF‐α mRNA degradation, consequently, up‐regulating TNF‐α expression. Restoration of SIRT3 and TTP expression, or inhibition of the ROS‐p38 MAPK axis increased the survival of VCR‐treated cells and repressed TNF‐α up‐regulation. In contrast to suppression of the ROS‐p38 MAPK axis, overexpression of SIRT3 modestly inhibited the effect of VCR on microtubule destabilization and mitotic arrest in U937 cells. Apoptosis of HL‐60 cells, similarly, went through the same pathway. Collectively, our data indicate that the SIRT3‐ROS‐p38 MAPK‐PP2A‐TTP axis modulates TNF‐α expression, which triggers apoptosis of VCR‐treated U937 and HL‐60 cells. We also demonstrate that the apoptotic signalling is not affected by VCR‐elicited microtubule destabilization.

Highlights

Microtubule dynamics and stability affect intracellular trafficking, cell division, cellular motility and cell shape maintenance.[1]
The plasmids pCMV3-His-SIRT3 and pCMV3-MID1-HA were the products of Sino Biological Inc (Wayne, PA)
The down-regulation of FADD increased the survival of VCR-treated cells (Figure S2E). These results revealed the association of the death receptor-mediated pathway with VCR-induced apoptosis in U937 cells

Summary

Introduction

Microtubule dynamics and stability affect intracellular trafficking, cell division, cellular motility and cell shape maintenance.[1]. Pre-treatment with NAC, GLX351322 and Mito-TEMPO inhibited p38 MAPK phosphorylation (Figure 2B, 2C and 2D), suggesting that VCRinduced ROS production induces p38 MAPK activation in U937 cells. Prior studies have consistently shown that activated p38 MAPK causes dephosphorylation of ERK in U937 cells.[24] SB202190 pre-treatment reduced the cell death (Figure 2E) and sub-G1 population (Figure 2F) induced by VCR, indicating that VCR cytotoxicity is mediated through mitochondrial ROS-triggered p38 MAPK activation.

Results

Conclusion