Ubiquitin‐proteasome system dysfunction induced by Alzheimer's disease‐linked Ab oligomers

Abstract

BackgroundBrain accumulation of the amyloid‐β peptide (Aβ) is a pathological hallmark of Alzheimer’s disease (AD). Considerable evidence indicates that soluble Ab oligomers (AβOs) cause synapse failure/loss and cognitive decline in AD. Evidence further indicates that the ubiquitin‐proteasome system (UPS) is inhibited in AD brains, likely leading to impaired synaptic plasticity and memory. However, the mechanisms underlying UPS dysfunction in AD remain to be elucidatedMethodHere, we investigated proteasome activity in primary hippocampal cultures and in isolated hippocampal synaptosomes from mice that received an intracerebroventricular (i.c.v.) infusion of AβOs. We further investigated the possible protective actions of UCH‐L1, an enzyme that enhances proteasome‐mediated degradation of target proteins, against the impact of AβOs on hippocampal neurons and memory.ResultExposure to AβOs resulted in decreased proteasome activity in primary hippocampal cultures and in isolated hippocampal synaptosomes. Synaptosomes isolated from the hippocampi of AβO‐infused mice were also inhibited compared to hippocampal synaptosomes from control, vehicle‐infused mice. Treatment with exogenous recombinant UCH‐L1 prevented oxidative stress in AβO‐exposed hippocampal neurons and memory deficit in AβO‐infused mice.ConclusionThese results indicate that AβOs inhibit the proteasome, notably at synapses, and suggest that boosting proteasomal proteolysis prevents AβO‐induced neuronal damage and memory deficit.