Effects of Apoptin-Induced Endoplasmic Reticulum Stress on Lipid Metabolism, Migration, and Invasion of HepG-2 Cells.

Ningyi Jin,Jin Zhao,Shanzhi Li,Guangze Zhu,Zirui Liu,Jianan Cong,Xiao Li,Gaojie Song,Jinbo Fang,Chao Shang,Bing Bai,Wenjie Li,Yilong Zhu,Yiquan Li

doi:10.3389/fonc.2021.614082

Abstract

In this study, we investigated the effects of Apoptin-induced endoplasmic reticulum (ER) stress on lipid metabolism, migration and invasion of HepG-2 cells, and preliminarily explored the relationship between endoplasmic reticulum stress, lipid metabolism, migration, and invasion. The effects of Apoptin on ER function and structure in HepG-2 cells were determined by flow cytometry, fluorescence staining and western blotting by assessing the expression levels of ER stress related proteins. The effects of Apoptin on HepG-2 cells’ lipid metabolism were determined by western blot analysis of the expression levels of triglyceride, cholesterol, and lipid metabolism related enzymes. The effects of Apoptin on HepG-2 cells’ migration and invasion were studied using migration and invasion assays and by Western-blot analysis of the expression of proteins involved in migration and invasion. The in vivo effects of endoplasmic reticulum stress on lipid metabolism, migration and invasion of HepG-2 cells were also investigated by immunohistochemistry analysis of tumor tissues from HepG2 cells xenografted nude mice models. Both in vitro and in vivo experiments showed that Apoptin can cause a strong and lasting ER stress response, damage ER functional structure, significantly change the expression levels of lipid metabolism related enzymes and reduce the migration and invasion abilities of HepG-2 cells. Apoptin can also affect HepG-2 cells’ lipid metabolism through endoplasmic reticulum stress and the abnormal expression of enzymes closely related to tumor migration and invasion. These results also showed that lipid metabolism may be one of the main inducements that reduce HepG-2 cells’ migration and invasion abilities.

Highlights

Apoptin is derived from chicken anemia virus [1], which has two nuclear localization signals
Process, the body can upregulate the expression of ER chaperones, inhibit protein translation, start the degradation of ER related proteins, improve the physiological state of cells and strengthen the self-repair function of endoplasmic reticulum through increasing the expression of the stress related proteins Protein Kinase like Endoplasmic Reticulum Kinase (PERK), Calnexin, Endoplasmic Reticulum Oxidoreduclin 1-La (Ero1-La), Protein Disulfide Isomerase (PDI), IRE1a, and BIP
PERK [12,13,14] is a transmembrane protein of the eIF2a kinase that is located in ER, and that couples the ER stress signal and inhibit translation

Summary

Introduction

Apoptin is derived from chicken anemia virus [1], which has two nuclear localization signals. These signals can help Apoptin to enter tumor cells’ nuclei and interact with the APC1 subunit of APC/C [2, 3], causing a C2/M cell cycle arrest and tumor cell apoptosis [4, 5]. The endoplasmic reticulum (ER) is the main site of protein, lipid and carbohydrate synthesis. It is essential for the maintenance of intracellular homeostasis and imbalance of the endoplasmic reticulum homeostasis can seriously affect its function [9]. It is of great significance to study the effect of Apoptin on the expression of ER and ER stress related proteins to explore the regulatory function of ER metabolism

Methods

Results

Conclusion