Modulation of Homer1 EVH1 domain internal dynamics by putative autism-associated mutations

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• The Homer1 scaffold protein and its EVH1 domain are crucial for postsynaptic density (PSD) formation.
• Homer1 interacts with Shank3, a key component of the PSD, forming an essential synaptic network.
• Autism spectrum disorder (ASD) has been potentially linked to specific mutations in the Homer1 EVH1 domain.

Purpose of the Study:

• To investigate the structural and functional impact of two specific Homer1 EVH1 domain mutations (M65I and S97L).
• To determine if these mutations affect Homer1's interaction with Shank3 and its overall stability.
• To elucidate the effects of these mutations on the internal dynamics of the Homer1 EVH1 domain.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was employed to analyze protein structure and dynamics.
• Computational methods were integrated with NMR data for a comprehensive analysis.
• Thermal stability assays were performed to assess the impact of mutations on protein stability.

Main Results:

• Neither the M65I nor the S97L mutation significantly altered the overall structure or partner binding of Homer1.
• The M65I mutation induced greater chemical shift perturbations and thermal destabilization compared to S97L.
• Both mutations were found to perturb the microsecond- to millisecond-timescale internal motions of the EVH1 domain.

Conclusions:

• The studied Homer1 EVH1 domain mutations do not substantially disrupt its structure or interaction with Shank3.
• The M65I mutation shows a more pronounced effect on protein stability and dynamics compared to S97L.
• These findings suggest that the impact of these specific Homer1 mutations on synaptic function may be more subtle than previously hypothesized, potentially influencing protein dynamics rather than direct binding or overall structure.