Isolation of synaptic terminals from Alzheimer's disease cortex

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Amyloid beta (Aβ) oligomers and phosphorylated tau (p-tau) are implicated in Alzheimer's disease (AD) pathogenesis.
• The precise Aβ and p-tau species causing synaptic dysfunction in AD remain incompletely understood.
• Understanding pathology within synapses is crucial for developing effective AD therapies.

Purpose of the Study:

• To develop and validate a method for isolating synaptosomes based on size and Aβ positivity.
• To characterize the Aβ and p-tau species within isolated AD synaptosomes.
• To confirm the co-localization of Aβ and p-tau within individual synaptic terminals.

Main Methods:

• Utilized high-speed cell sorting to purify synaptosomes based on size (0.5–1.5 microns).
• Employed fluorescence-activated sorting to isolate Aβ-positive synaptosomes.
• Analyzed sorted synaptosomes using electron microscopy and immunoblotting techniques.

Main Results:

• Size-gated synaptosomes exhibited homogenous morphology consistent with synaptic vesicles.
• Sorted Aβ-positive synaptosomes showed enrichment of amyloid precursor protein (APP) and Aβ oligomers/aggregates.
• A striking accumulation of p-tau aggregates was observed in Aβ-positive synaptosomes compared to controls.

Conclusions:

• Co-localization of Aβ and p-tau within individual synaptic terminals is confirmed.
• Flow sorting of synaptosomes is a viable method for studying synaptic pathology in AD.
• This technique provides a novel approach to investigate the molecular mechanisms of synaptic failure in neurodegenerative diseases.