The Neurotoxicity of Vesicles Secreted by ALS Patient Myotubes Is Specific to Exosome-Like and Not Larger Subtypes.

Ekene Anakor,Cecile Martinat,Julie Dumonceaux,William Duddy,Owen Connolly,Pierre Francois Pradat,Stephanie Duguez,Vanessa Milla

doi:10.3390/cells11050845

Abstract

Extracellular vesicles can mediate communication between tissues, affecting the physiological conditions of recipient cells. They are increasingly investigated in Amyotrophic Lateral Sclerosis, the most common form of Motor Neurone Disease, as transporters of misfolded proteins including SOD1, FUS, TDP43, or other neurotoxic elements, such as the dipeptide repeats resulting from C9orf72 expansions. EVs are classified based on their biogenesis and size and can be separated by differential centrifugation. They include exosomes, released by the fusion of multivesicular bodies with the plasma membrane, and ectosomes, also known as microvesicles or microparticles, resulting from budding or pinching of the plasma membrane. In the current study, EVs were obtained from the myotube cell culture medium of ALS patients or healthy controls. EVs of two different sizes, separating at 20,000 or 100,000 g, were then compared in terms of their effects on recipient motor neurons, astrocytes, and myotubes. Compared to untreated cells, the smaller, exosome-like vesicles of ALS patients reduced the survival of motor neurons by 31% and of myotubes by 18%, decreased neurite length and branching, and increased the proportion of stellate astrocytes, whereas neither those of healthy subjects, nor larger EVs of ALS or healthy subjects, had such effects.

Highlights

Cell–cell communication occurs via a variety of mechanisms including secretion of soluble factors, direct contact via tunnelling nanotubes and cytonemes, as well as extracellular vesicles [1]
Several markers were used to distinguish exosomal from non-exosomal properties of Extracellular vesicles (EVs): tetraspanins CD63, CD81, and CD82, are typical of exosomes [9], while Annexin A1 is a specific marker of microvesicles that are shed from the plasma membrane, and ADPribosylation factor 6 (ARF6) regulates abscission and shedding of microvesicles [50,51]
EVs participate in cell-to-cell communication that takes place between and within similar or different cell types, and they are implicated in neurodegenerative diseases where they mediate the transport and spread of misfolded proteins, lipids, and nucleic acids [53]

Summary

Introduction

Cell–cell communication occurs via a variety of mechanisms including secretion of soluble factors, direct contact via tunnelling nanotubes and cytonemes, as well as extracellular vesicles [1]. Extracellular vesicles (EVs) have garnered great interest owing to their ability to mediate near as well as distant communication within and between different cell types and tissues, impacting the pathological and physiological conditions of the targeted cells, as observed in metastatic cancer and in neurodegenerative diseases [2–4]. EVs are constitutively secreted [5,6] and can be classified based on their biogenesis and size as: exosomes, ectosomes, or apoptotic bodies. Exosomes are formed when multivesicular bodies (MVBs) containing intraluminal vesicles fuse with the plasma membrane, releasing vesicles that typically measure between 50 and 200 nm [7–9]. Apoptotic bodies are released from apoptotic or dying cells, containing fragments with a wide variety of cellular components, and measuring between 500 nm and 2 μm [12]. Exosomes and ectosomes are known to carry functional proteins and RNAs to recipient cells [9,13–15]

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