Amyloid extraction from neurodegenerative disease tissues for structural studies.

Amyloid aggregates are hallmarks of neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD). Yet structural analysis of these brain-extracted filaments requires specialized extraction protocols that minimize structural perturbation while removing tissue matrix components. This chapter focuses on amyloid-β (Aβ) filaments, the primary component of senile plaques in AD, and presents three complementary methods for isolating these filaments from human brain tissues suitable for cryo-electron microscopy analysis. These methods have enabled high-resolution structural studies reaching 2.0-3.5 Å resolution and revealed distinct conformational polymorphs in AD and other neurodegenerative diseases. Method selection depends on tissue type, target filaments, and downstream analysis requirements, with comprehensive guidance provided for optimal protocol choice and implementation. The protocols demonstrate broad applicability beyond Aβ extraction, with successful adaptations provided for tau, α-synuclein, and TDP-43 extraction. Understanding these filamentous structures extracted with minimal perturbation is essential for developing targeted therapeutics and advancing structure-based drug design approaches for AD, PD, ALS, FTD, and other neurodegenerative diseases.