pGluAβ increases accumulation of Aβ in vivo and exacerbates its toxicity

Abstract

Several species of β-amyloid peptides (Aβ) exist as a result of differential cleavage from amyloid precursor protein (APP) to yield various C-terminal Aβ peptides. Several N-terminal modified Aβ peptides have also been identified in Alzheimer’s disease (AD) brains, the most common of which is pyroglutamate-modified Aβ (AβpE3-42). AβpE3-42 peptide has an increased propensity to aggregate, appears to accumulate in the brain before the appearance of clinical symptoms of AD, and precedes Aβ1-42 deposition. Moreover, in vitro studies have shown that AβpE3-42 can act as a seed for full length Aβ1-42. In this study, we characterized the Drosophila model of AβpE3-42 toxicity by expressing the peptide in specific sets of neurons using the GAL4-UAS system, and measuring different phenotypic outcomes. We found that AβpE3-42 peptide had an increased propensity to aggregate. Expression of AβpE3-42 in the neurons of adult flies led to behavioural dysfunction and shortened lifespan. Expression of AβpE3-42 constitutively in the eyes led to disorganised ommatidia, and activation of the c-Jun N-terminal kinase (JNK) signaling pathway. The eye disruption was almost completely rescued by co-expressing a candidate Aβ degrading enzyme, neprilysin2. Furthermore, we found that neprilysin2 was capable of degrading AβpE3-42. Also, we tested the seeding hypothesis for AβpE3-42 in vivo, and measured its effect on Aβ1-42 levels. We found that Aβ1-42 levels were significantly increased when Aβ1-42 and AβpE3-42 peptides were co-expressed. Furthermore, we found that AβpE3-42 enhanced Aβ1-42 toxicity in vivo. Our findings implicate AβpE3-42 as an important source of toxicity in AD, and suggest that its specific degradation could be therapeutic.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-016-0380-x) contains supplementary material, which is available to authorized users.

Are N- and C-terminally truncated Aβ species key pathological triggers in Alzheimer's disease?

“…Aside pE-A␤ variants, A␤(4 -42) has also a propensity to form very stable aggregates (72). Fast aggregation properties of such fragments have been described in vitro (59,79) as well as in vivo in a Drosophila model (80).…”

“…Interestingly, the life span of transgenic flies was affected by pE3-42A␤. Moreover, expression of the pyroglutamylated peptide induced behavioral dysfunctions, and toxicity was observed by a disorganization of the eye structure (80). Finally, pE3-42A␤ has recently been shown to induce synaptic plasticity impairment by different mechanisms than A␤42 and independently of a co-oligomerization process (84).…”

Aβ exacerbates α‐synuclein‐induced neurotoxicity through impaired insulin signaling in α‐synuclein‐overexpressed human SK‐N‐MC neuronal cells

“…To generate a reliable conditional gene expression in vitro model, we first used the GeneSwitch System to establish an inducible expression system for αSyn overexpression in SK‐N‐MC neuronal cells . As shown in Figure A, the GeneSwitch system is based on the binding of a mifepristone (MFP)‐responsive GAL4 regulatory fusion protein to GAL4 upstream activating sequences (UAS) in the promoter controlling expression of SCNA gene.…”

“…To generate a reliable conditional gene expression in vitro model, we first used the GeneSwitch System to establish an inducible expression system for αSyn overexpression in SK-N-MC neuronal cells. 17 As shown in Figure 1A Aβ-induced cytotoxic effect was further deteriorated by the overexpression of αSyn. These results were in accordance with the findings obtained from MTT assay, which indicates overexpressed αSyn significantly enhances Aβ-induced cell viability loss from 52 ± 9.6% to 26 ± 5.7% ( Figure 2B).…”

Mulberry Fruit Cultivar ‘Chiang Mai’ Prevents Beta-Amyloid Toxicity in PC12 Neuronal Cells and in a Drosophila Model of Alzheimer’s Disease

“…Quantification of Aβ peptide was performed as reported with slight modification [53]. The heads of F1 progeny flies at day 28 were collected and homogenized in 5 M guanidine-HCl containing 2X Halt protease inhibitor cocktail (Thermo Fisher Scientific, Waltham, MA, USA).…”