iTRAQ-Based Proteomic Analysis of APP Transgenic Mouse Urine Exosomes

Area of Science:

• Neuroscience
• Biochemistry
• Gerontology

Background:

• Alzheimer's disease (AD) is a prevalent neurodegenerative disorder causing dementia in older adults.
• Understanding the early pathological mechanisms of AD is crucial for developing effective interventions.
• Exosomes, particularly neuron-derived exosomes (N-exo), are increasingly recognized as key players in intercellular communication and disease progression.

Purpose of the Study:

• To investigate the proteomic differences in urine exosomes (U-exo) and neuron-derived exosomes (N-exo) from an early-stage Alzheimer's disease mouse model.
• To identify proteins associated with lipid and amyloid-beta (Aβ) metabolism and clearance in early AD.
• To gain insights into the underlying pathological mechanisms of early-onset AD.

Main Methods:

• Isolation of U-exo from urine of J20 (AD model) and wild-type (WT) mice using polymer precipitation.
• Isolation of N-exo from U-exo via immunoprecipitation.
• Proteomic analysis using iTRAQ-based MALDI TOF MS/MS to compare protein expression profiles.

Main Results:

• Significant increases in protein levels were observed in J20 U-exo (61 proteins) and N-exo (92 proteins) compared to WT.
• Gene ontology analysis highlighted enrichment in pathways related to sphingolipid and ceramide catabolism, membrane lipid metabolism, and Aβ clearance and metabolism.
• Key proteins identified include Asah1 (lipid metabolism) and clusterin, ApoE, neprilysin, and ACE (Aβ metabolism/clearance).
• Protein-protein interaction analysis revealed protein complexes involving clusterin and ApoE.

Conclusions:

• Early-stage AD mouse models exhibit distinct proteomic signatures in urine and neuron-derived exosomes.
• These exosomes contain proteins crucial for lipid and Aβ metabolism, suggesting their involvement in early AD pathogenesis.
• Urine exosomes represent a promising non-invasive source for understanding early AD pathophysiology.