Solid state NMR characterization of wild-type and mutant GFAP intermediate filament assemblies

Area of Science:

• Biochemistry
• Neuroscience
• Structural Biology

Background:

• Glial fibrillary acidic protein (GFAP) is a type III intermediate filament crucial for astrocyte structure and mechanical strength.
• GFAP mutations are linked to Alexander disease, a neurodegenerative disorder.
• The atomic-level mechanism of GFAP filament assembly remains poorly understood.

Purpose of the Study:

• To characterize the structure of wild-type GFAP tetrameric and filamentous assemblies.
• To investigate the impact of a specific GFAP mutation (C294S) on filament assembly.
• To establish a foundation for using solid-state NMR to study intermediate filament assembly and disease mutations.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• Characterization of both wild-type GFAP and an assembly-deficient mutant (C294S).

Main Results:

• Wild-type GFAP filaments exhibit uniform rigid alpha-helical structures with mobile intrinsically disordered regions.
• Wild-type tetramers show increased mobility, particularly in head and tail domains.
• The C294S mutation prevents full-length filament assembly, showing structural consistency with tetramers but increased mobile regions compared to wild-type filaments.

Conclusions:

• Solid-state NMR can effectively characterize intermediate filament assembly mechanisms.
• The C294S mutation disrupts GFAP filament formation by altering structural dynamics.
• These findings provide insights into Alexander disease pathogenesis and potential therapeutic targets.