Proteasome Inhibitor MG132 is Toxic and Inhibits the Proliferation of Rat Neural Stem Cells but Increases BDNF Expression to Protect Neurons.

Young Min Kim,Hyun-Jung Kim

doi:10.3390/biom10111507

Abstract

Regulation of protein expression is essential for maintaining normal cell function. Proteasomes play important roles in protein degradation and dysregulation of proteasomes is implicated in neurodegenerative disorders. In this study, using a proteasome inhibitor MG132, we showed that proteasome inhibition reduces neural stem cell (NSC) proliferation and is toxic to NSCs. Interestingly, MG132 treatment increased the percentage of neurons in both proliferation and differentiation culture conditions of NSCs. Proteasome inhibition reduced B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X protein ratio. In addition, MG132 treatment induced cAMP response element-binding protein phosphorylation and increased the expression of brain-derived neurotrophic factor transcripts and proteins. These data suggest that proteasome function is important for NSC survival and differentiation. Moreover, although MG132 is toxic to NSCs, it may increase neurogenesis. Therefore, by modifying MG132 chemical structure and developing none toxic proteasome inhibitors, neurogenic chemicals can be developed to control NSC cell fate.

Highlights

Neural stem cells (NSCs) possess the capacity to self-renew and can differentiate into neurons, astrocytes, and oligodendrocytes [1,2,3]
The ICC data revealed that 100 nM MG132 significantly reduced cell proliferation and induced the percentage of neurons in NSCs, even in the presence of epidermal growth factor (EGF) and fibroblast growth factor 2 (FGF2) (Figure 1A,D)
Astrocytes were determined by the antibody that detects glial fibrillary acidic protein (GFAP) (Figure 1A,B); quantitation results showed that MG132 does not significantly enhance astrocytogenesis (Figure 1E)

Summary

Introduction

Neural stem cells (NSCs) possess the capacity to self-renew and can differentiate into neurons, astrocytes, and oligodendrocytes [1,2,3]. It is critical to understand the regulation mechanism of NSC fate. Different types of cells have cell-type-specific protein profile expression; gene transcription, translation, and protein degradation regulate the distinct proteome expression [2,8,9,10]. Protein breakdown occurs in the lysosomes by acid hydrolases and in the proteasomes by an ATP-dependent mechanism [11]. The eukaryotic 26S proteasome is a 2.5 MDa multi-catalytic proteinase complex composed of a 19S regulatory unit and a 20S core unit [11,12]. The 19S regulatory particle caps one or both sides of the 20S core unit and controls the entrance of degradable proteins to the 20S particle, which has proteolytic activities [13]. Proteins prone to degradation are modified by ubiquitin and recognized by proteasomes [14]

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Results

Discussion

Conclusion