Storage of Mutant Human SOD1 in Non-Neural Cells from the Type-1 Amyotrophic Lateral Sclerosis ratG93A Model Correlated with the Lysosomes' Dysfunction.

Ilaria Bicchi,Maurizio Gelati,Carla Emiliani,Angelo L Vescovi,Chiara Argentati,Laura Rota Nodari,Francesco Morena,Sabata Martino

doi:10.3390/biomedicines9091080

Abstract

Herein, we explored the impact of the lysosome dysfunction during the progression of Amyotrophic Lateral Sclerosis type-1 (ALS1). We conducted the study in non-neural cells, primary fibroblasts (rFFFs), and bone marrow-mesenchymal stem cells (rBM-MSCs), isolated from the animal model ratG93A for ALS1 at two stages of the disease: Pre-symptomatic-stage (ALS1-PreS) and Terminal-stage (ALS1-EndS). We documented the storage of human mutant Superoxide Dismutase 1, SOD1G93A (SOD1*) in the lysosomes of ALS1-rFFFs and ALS1-rBM-MSCs and demonstrated the hallmarks of the disease in non-neural cells as in ratG93A-ALS1-tissues. We showed that the SOD1* storage is associated with the altered glycohydrolases and proteases levels in tissues and both cell types from ALS1-PreS to ALS1-EndS. Only in ALS1-rFFFs, the lysosomes lost homeostasis, enlarge drastically, and contribute to the cell metabolic damage. Contrariwise, in ALS1-rBM-MSCs, we found a negligible metabolic dysfunction, which makes these cells’ status similar to WT. We addressed this phenomenon to a safety mechanism perhaps associated with an enhanced lysosomal autophagic activity in ALS1-rBM-MSCs compared to ALS1-rFFFs, in which the lysosomal level of LC3-II/LC3I was comparable to that of WT-rFFFs. We suggested that the autophagic machinery could balance the storage of SOD1* aggregates and the lysosomal enzyme dysfunction even in ALS1-EndS-stem cells.

Highlights

Amyotrophic lateral sclerosis (ALS, OMIM#105400) is a multigenic/multifactorial progressive neurodegenerative disease with lethality occurring three years after the first symptoms in almost 60% of patients [1]
All experiments were conducted in several tissues and non-neural cells, primary fibroblasts, and bone marrow-mesenchymal stem cells, both isolated from Amyotrophic Lateral Sclerosis type-1 (ALS1)-PreS and ALS1-EndS rats and were in comparison with parallel analysis in tissues, rFFFs and rBM-MSCs isolated from Sprague-Dawley wild type (WT) rats
The ratG93A -derived tissues were used to set up the expression of SOD1* in the ALS1 model compared to Wild type (WT), and together with rFFFs and rBM-MSCs, were used to investigate the functionality of the lysosomal compartment in ALS1 (Figure 1)

Summary

Introduction

Amyotrophic lateral sclerosis (ALS, OMIM#105400) is a multigenic/multifactorial progressive neurodegenerative disease with lethality occurring three years after the first symptoms in almost 60% of patients [1]. Many aspects of the pathophysiology of the disease remain still controversial or poorly elucidated even in the most common forms of ALS, such as those caused by mutations in C9ORF72 (40%), SOD1 (20%), FUS (1–5%), and TARBDP (1–5%) genes, respectively for ALS-FTD1, ALS1, ALS6 and ALS10 [2,3,4]. Spinal Muscular Atrophy (SMA), Parkinson’s Disease (PD), Hereditary Spastic Paraplegia (HSP), Fronto-Temporal Disease (FTD), Progressive bulbar palsy (PBP) and some Lysosomal Storage Disorders (LSDs) [4]), that may be a cause of misdiagnoses, especially during the early stages of the disease [4]. Dysfunction of the autophagiclysosomal network has been documented among above mentioned neurodegenerative diseases Whether these dysregulations are a direct causative event of the ALS pathophysiology (e.g., accumulation of undegraded misfolded SOD1 aggregates), or are secondary effects of the progression of the disease, are yet an open question. During the last years, the effort has been made on elucidating ALS molecular pathways, taking advantage of different types of animal models and cell culture models for the different types of the disease [7]

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Conclusion