Spermine increases acetylation of tubulins and facilitates autophagic degradation of prion aggregates

Kanchan Phadwal,Abigail B Diack,Muhammad Khalid F Salamat,Vicky E Macrae,Jean C Manson,Dominic Kurian

doi:10.1038/s41598-018-28296-y

Kanchan Phadwal, Abigail B Diack + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-28296-y

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Journal: Scientific Reports	Publication Date: Jul 3, 2018
Citations: 24	License type: open-access

Affiliation: Roslin Institute, University of Edinburgh

Abstract

Autolysosomal dysfunction and unstable microtubules are hallmarks of chronic neurodegenerative diseases associated with misfolded proteins. Investigation of impaired protein quality control and clearance systems could therefore provide an important avenue for intervention. To investigate this we have used a highly controlled model for protein aggregation, an in vitro prion system. Here we report that prion aggregates traffic via autolysosomes in the cytoplasm. Treatment with the natural polyamine spermine clears aggregates by enhancing autolysosomal flux. We demonstrated this by blocking the formation of mature autophagosomes resulting in accumulation of prion aggregates in the cytoplasm. Further we investigated the mechanism of spermine’s mode of action and we demonstrate that spermine increases the acetylation of microtubules, which is known to facilitate retrograde transport of autophagosomes from the cellular periphery to lysosomes located near the nucleus. We further report that spermine facilitates selective autophagic degradation of prion aggregates by binding to microtubule protein Tubb6. This is the first report in which spermine and the pathways regulated by it are applied as a novel approach towards clearance of misfolded prion protein and we suggest that this may have important implication for the broader family of protein misfolding diseases.

Highlights

Accumulation and aggregation of misfolded proteins are hallmarks of neurodegenerative disorders, such as Alzheimer’s (AD), Parkinson’s, Huntington’s and prion diseases
We used the scrapie mouse brain (SMB) cell line infected with prion aggregates PrPSc (SMB.s15) and without prion aggregates (SMB-proteostat dye (PS))[23] for our study
In this study we have demonstrated that the natural polyamine spermine can clear the prion aggregates in prion infected cell cultures

Summary

Introduction

Accumulation and aggregation of misfolded proteins are hallmarks of neurodegenerative disorders, such as Alzheimer’s (AD), Parkinson’s, Huntington’s and prion diseases. These diseases many of which are strongly linked with age are debilitating and largely untreatable conditions. Upregulation of the bulk protein degradation process of autophagy has been shown to clear disease-associated proteins, such as mutant alpha-synuclein, ataxin-3, tau, huntingtin, TDP-43 and disease associated prion protein (PrPSc) in various in vivo and in vitro models[4,5,6,7,8,9]. In the absence of a functional UPS, the autophagosomal-lysosomal pathway is known to target insoluble protein aggregates for degradation[11]. Given the enhanced efficacy of spermine over spermidine we investigated if and how spermine can clear prion aggregates

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Results

Conclusion