Amyloid precursor protein 𝛽CTF accumulates in synapses in sporadic and genetic forms of Alzheimer's disease

Amyloid precursor protein (APP) 훽-C-terminal fragment (훽CTF) may have a neurotoxic role in Alzheimer's disease (AD). 훽CTF accumulates in the brains of patients with sporadic (SAD) and genetic forms of AD. Synapses degenerate early during the pathogenesis of AD. We studied whether the 훽CTF accumulates in synapses in SAD, autosomal dominant AD (ADAD) and Down syndrome (DS).We used array tomography to determine APP at synapses in human AD tissue. We measured 훽CTF, A훽40, A훽42 and phosphorylated tau181 (p-tau181) concentrations in brain homogenates and synaptosomes of frontal and temporal cortex of SAD, ADAD, DS and controls.APP colocalised with pre- and post-synaptic markers in human AD brains. APP 훽CTF was enriched in AD synaptosomes.We demonstrate that 훽CTF accumulates in synapses in SAD, ADAD and DS. This finding might suggest a role for 훽CTF in synapse degeneration. Therapies aimed at mitigating 훽CTF accumulation could be potentially beneficial in AD.