Exogenous polyserine and polyleucine are toxic to recipient cells

Ryuji Owada,Kazuhiro Nakamura,Shinichi Mitsui

doi:10.1038/s41598-022-05720-y

Abstract

Repeat-associated non-AUG (RAN) translation of mRNAs/transcripts responsible for polyglutamine (polyQ) diseases may generate peptides containing different mono amino acid tracts such as polyserine (polyS) and polyleucine (polyL). The propagation of aggregated polyQ from one cell to another is also an intriguing feature of polyQ proteins. However, whether the RAN translation-related polyS and polyL have the ability to propagate remains unclear, and if they do, whether the exogenous polyS and polyL exert toxicity on the recipient cells is also not known yet. In the present study, we found that aggregated polyS and polyL peptides spontaneously enter neuron-like cells and astrocytes in vitro. Aggregated polyS led to the degeneration of the differentiated neuron-like cultured cells. Likewise, the two types of aggregates taken up by astrocytes induced aberrant differentiation and cell death in vitro. Furthermore, injection of each of the two types of aggregates into the ventricles of adult mice resulted in their behavioral changes. The polyS-injected mice showed extensive vacuolar degeneration in the brain. Thus, the RAN translation-related proteins containing polyS and polyL have the potential to propagate and the proteins generated by all polyQ diseases might exert universal toxicity in the recipient cells.

Highlights

repeat-associated non-AUG (RAN) proteins with polyQ and polyA were reported to be generated from the ataxin 3 gene, a gene responsible for spinocerebellar ataxia (SCA) type 3, and the RAN proteins induced apoptosis[18]
Among RAN translation-generated amino acid repeats from CAG repeat-containing genes, we focused on polyL because polyL encoded by mixed DNA repeats displayed higher toxicity than polyQ in mammalian c ells[21]
We addressed whether RAN translationrelated 13 serine repeats (13S) and 13 leucine repeats (13L) led to cell degeneration

Summary

Introduction

RAN proteins with polyQ and polyA were reported to be generated from the ataxin 3 gene, a gene responsible for spinocerebellar ataxia (SCA) type 3, and the RAN proteins induced apoptosis[18]. Transfer between cells has been reported in other misfolded proteins that are responsible for neurodegenerative disorders[20] Whether this is the case for RAN proteins generated from genes for polyQ diseases has not been determined yet. Electron microscopic analysis revealed the entry of the two types of aggregates into neuron-like cells and astrocytes. Functional analyses such as cell death, degeneration and differentiation were performed using the recipient cells. We introduced the two types of aggregates into the ventricles of adult mice and conducted behavioral analyses such as tests for anxiety and depression

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