New findings of silica nanoparticles induced ER autophagy in human colon cancer cell

Fujing Wei,Yixiang Duan,Yimin Wang,Zewei Luo,Yu Li

doi:10.1038/srep42591

Abstract

Nanoparticle-induced autophagy has been extensively studied, however, real time information about the endoplasmic reticulum involved autophagic process (ER autophagy) induced by nanomaterials remains unknown. In this work, silica nanoparticles (SNPs) were synthesized with characteristics of low toxicity, good biocompatibility and excellent water dispersibility to treat cells. Results show that either low concentration (10 μg/mL) or high concentration (200 μg/mL) of SNPs could increase the quantity of processing from microtubule-associated protein 1-light chain 3-I (LC3-I) to the other variant of LC3 (LC3-II). Interestingly, the level of autophagy induced by the SNPs is associated with the treated time but not the concentrations of SNPs. Importantly, for the first time, SNP accumulation in ER was discovered through co-localization analysis, which incurs ER autophagy. These new findings about SNPs-induced ER autophagy could open an effective way for securely designing silica-based nanoparticles and enable us to know more about ER autophagy.

Highlights

Nanoparticle-induced autophagy has been extensively studied, real time information about the endoplasmic reticulum involved autophagic process (ER autophagy) induced by nanomaterials remains unknown
A lot of research work has demonstrated that amorphous silica nanoparticles (SNPs) are relatively biocompatible[1], and the SNPs have been widely used in gene transfection, drug delivery, biosensing and bioimaging due to their unique properties of tunable pore size, high surface area, and ease of modification[2,3,4,5]
We have identified that the synthesized SNPs display special structure and physicochemical properties

Summary

Introduction

Nanoparticle-induced autophagy has been extensively studied, real time information about the endoplasmic reticulum involved autophagic process (ER autophagy) induced by nanomaterials remains unknown. Cell autophagy, a process of the degradation of intracellular materials, is a conserved catabolic process from yeast to mammals[16] It is induced by various stimuli, such as deprivation of nutrient, aggregated proteins and unwanted organelles other than SNPs11. Autophagy can be classified into two types: non-selective autophagy and selective autophagy The former is induced by starvation, and degrades cytoplasm[19,20], while the latter needs particular receptor to target specific materials, such as mitophagy for clearance of damaged mitochondria, aggrephagy for degradation of aggregating proteins, lysophagy for target of damaged lysosomes[19]. In the past few years, many research groups have proposed that ER, an integral and elaborate membrane organelle for folding and modifying secretory proteins, can itself be captured by autophagy if it is damaged[21] This process is called “ER autophagy”[22]. There will be a good reason for further exploration of the SNPs-induced ER autophagy

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Conclusion