Exposure to ALS-FTD-CSF generates TDP-43 aggregates in glioblastoma cells through exosomes and TNTs-like structure

Xuebing Ding,Jingzheng Yin,Junfang Teng,Erxi Wu,Mingming Ma,Jason H Huang,Shuang Zhou,Ekokobe Fonkem,Robert K.F Teng,Xuejing Wang

doi:10.18632/oncotarget.4680

Abstract

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent a continuum of devastating neurodegenerative diseases, characterized by transactive response DNA-binding protein of 43 kDa (TDP-43) aggregates accumulation throughout the nervous system. Despite rapidly emerging evidence suggesting the hypothesis of 'prion-like propagation' of TDP-43 positive inclusion in the regional spread of ALS symptoms, whether and how TDP-43 aggregates spread between cells is not clear. Herein, we established a cerebrospinal fluid (CSF)-cultured cell model to dissect mechanisms governing TDP-43 aggregates formation and propagation. Remarkably, intracellular TDP-43 mislocalization and aggregates were induced in the human glioma U251 cells following exposure to ALS-FTD-CSF but not ALS-CSF and normal control (NC) -CSF for 21 days. The exosomes derived from ALS-FTD-CSF were enriched in TDP-43 C-terminal fragments (CTFs). Incubation of ALS-FTD-CSF induced the increase of mislocated TDP-43 positive exosomes in U251 cells. We further demonstrated that exposure to ALS-FTD-CSF induced the generations of tunneling nanotubes (TNTs)-like structure and exosomes at different stages, which mediated the propagation of TDP-43 aggregates in the cultured U251 cells. Moreover, immunoblotting analyses revealed that abnormal activations of apoptosis and autophagy were induced in U251 cells, following incubation of ALS-CSF and ALS-FTD-CSF. Taken together, our data provide direct evidence that ALS-FTD-CSF has prion-like transmissible properties. TNTs-like structure and exosomes supply the routes for the transfer of TDP-43 aggregates, and selective inhibition of their over-generations may interrupt the progression of TDP-43 proteinopathy.

Highlights

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease, in which loss of motor neurons leads to progressive weakness of the voluntary muscles
transactive response DNA-binding protein of 43 kDa (TDP-43) C-terminal fragments (CTFs) are more prone to form the toxic, insoluble, and ubiquitin- and phospho-positive cytoplasmic inclusions within cells [18, 27, 35]. These findings suggest that full-length TDP-43 and TDP-43 CTFs in the exosomes from ALS-Frontotemporal dementia (FTD)-cerebrospinal fluid (CSF) act as a ‘seed’ which induces the prion-like aggregates of TDP-43 in the cultured U251 cells
Our results demonstrate that ALSFTD-CSF containing the exosomes which display enrichment of full-length TDP-43 and TDP-43 CTFs induced the generation of TDP-43 aggregates in the cultured U251 cells

Summary

Introduction

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease, in which loss of motor neurons leads to progressive weakness of the voluntary muscles. TDP-43 is found to be modified, including cleavage, ubiquitination, and phosphorylation; this leads to its misfolding and aggregation [8]. These findings have generated new insights into the pathogenesis of a spectrum of diseases called TDP-43 proteinopathies, including Perry syndrome, inclusion body myopathy, and Paget disease of the bone. TDP-43 proteinopathies likely contribute to neurodegeneration very broadly [7] It is well-known that TDP-43 aggregates are involved in pathogenesis of ALS and FTD; its formation and propagation in CNS remains largely unclear and warrants further investigation

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