Multiplexed fractionated proteomics reveals synaptic factors associated with cognitive resilience in Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disease defined by the presence of amyloid-beta (Aβ) plaques and tau neurofibrillary tangles, and driven by dysproteostatis, inflammation, metabolic dysfunction, and oxidative injury, eventually leading to synapse loss and cell death. Synapse loss correlates with cognitive impairment and may occur independently of the extent of AD pathology. To understand how synaptic composition is changed in relation to AD neuropathology and cognition, highly sensitive multiplexed liquid chromatography mass-spectrometry was used to quantify biochemically enriched synaptic proteins from the parietal association cortex of 100 subjects with contrasting AD pathology and cognitive performance. Functional analysis showed preservation of synaptic signaling, ion transport, and mitochondrial proteins in normal aged and "resilient" (cognitively unimpaired with AD pathology) individuals. Compared to these individuals, those with cognitive impairment showed significant metabolic differences and increased immune- and inflammatory-related proteins, establishing the synapse as a potential integration point for multiple AD pathophysiologies.