Canine SOD1 harboring E40K or T18S mutations promotes protein aggregation without reducing the global structural...

Area of Science:

• Neurodegenerative diseases
• Protein biochemistry
• Molecular biology

Background:

• Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease.
• Protein aggregation of superoxide dismutase 1 (SOD1) is implicated in ALS pathogenesis.
• Canine degenerative myelopathy (DM) is an ALS-like disease in dogs.

Purpose of the Study:

• Investigate the impact of T18S and E40K mutations on canine SOD1 protein aggregation.
• Characterize the structural and functional consequences of these mutations.
• Elucidate the mechanism of SOD1 aggregation in canine DM.

Main Methods:

• Circular dichroism (CD) spectroscopy to assess protein structure.
• Enzymatic activity assays.
• Thioflavin-T (ThT) binding assays to detect amyloid formation.
• Transmission electron microscopy (TEM) to visualize aggregates.
• Analysis of Cu²⁺/Zn²⁺-bound and unbound states.

Main Results:

• T18S and E40K mutations did not affect global structure, enzymatic activity, or stability of canine SOD1.
• These mutations significantly promoted the formation of fibrous SOD1 aggregates.
• Aggregation was particularly pronounced in the metal ion-unbound state.
• Evidence suggests aggregation may involve local structural destabilization or altered charge.

Conclusions:

• T18S and E40K mutations in canine SOD1 induce protein aggregation without altering global stability.
• The findings provide insights into the molecular mechanisms underlying canine degenerative myelopathy.
• This study highlights a unique aggregation pathway for SOD1 mutations in a canine neurodegenerative disease model.