Structural and kinetic analysis of protein-aggregate strains in vivo using binary epitope mapping

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Protein aggregation in vitro is well-studied, but the in vivo mechanisms of protein-aggregation diseases remain unclear.
• Pathological protein aggregates in neural tissue are often present in low quantities, hindering conventional analysis.
• Understanding aggregate structure and quantity is crucial for elucidating disease pathogenesis.

Purpose of the Study:

• To develop a novel method for determining the structure and quantity of protein aggregates in small neural tissue samples.
• To apply this method to investigate aggregates in a mouse model of amyotrophic lateral sclerosis (ALS).
• To characterize the properties and disease association of identified aggregate strains.

Main Methods:

• Binary epitope mapping using anti-peptide antibodies to analyze aggregate structure and quantity.
• Application of the method to neural tissue from mice modeling ALS with superoxide dismutase-1 (SOD1) aggregation.
• Comparison of in vivo aggregates with in vitro generated SOD1 aggregates.

Main Results:

• Identification of two distinct strains of intracellular SOD1 aggregates in ALS mouse models.
• These strains exhibited different structural architectures, molecular properties, and growth kinetics.
• The identified in vivo strains differed significantly from SOD1 aggregates produced in vitro.
• Different aggregate strains were associated with varying disease progressions.

Conclusions:

• The developed binary epitope mapping method enables the study of low-abundance protein aggregates in small tissue samples.
• Two distinct SOD1 aggregate strains exist in vivo, differing from in vitro models.
• These findings support the principles of seeding, infectivity, and strain dependence in neurodegenerative diseases like ALS.