Deleterious effects of amyloid-beta peptide in the neuromuscular junction: consequences in ALS disease.

Amyotrophic lateral sclerosis (ALS) is a devastating and fatal neurodegenerative disease of adults which preferentially attacks the neuromotor system. It has been shown that Amyloid-β (Aβ) levels are elevated in spinal cords of late-stage superoxide dismutase 1 (SOD1) G93A mice (model of familial amyotrophic lateral sclerosis [ALS]) and that Aβ peptide(s) were localized predominantly within affected motor neurons (MN) and surrounding glial cells. Moreover, neuromuscular junction (NMJ) loss and MN degeneration were reduced in SOD1 mice when APP was genetically ablated, suggesting that endogenous APP actively contributes to the pathophysiology of this form of ALS. Additionally, Aβ and glutamate have been physiologically found in NMJs. Previous work done in our lab, showed the tight relationship between glutamate and Aβ in the NMJ. We showed that an interconnection between glutamate and Aβ peptide, as demonstrated in cortical and hippocampal neurons, is also operating in nerve-muscle co-cultures (Combes et al., 2015). Here, using a nerve-muscle co-culture system, we studied the toxicity of Aβ and the mechanisms involved in the process of NMJ death. The aim of this study was to investigated the role and the mechanism of Aβ on an in vitro model of functional NMJ.