Zinc induced structural changes in the intrinsically disordered BDNF Met prodomain confer synaptic elimination

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Brain-derived neurotrophic factor (BDNF) is crucial for neuronal function, with a common polymorphism affecting its prodomain.
• The BDNF Met66 prodomain variant is linked to neurological and psychiatric disorders and promotes neuronal structural remodeling.
• Previous studies indicated minimal structural differences between Met66 and Val66 prodomains in their unbound state.

Purpose of the Study:

• To investigate the differential effects of zinc (Zn) binding on the Met66 and Val66 BDNF prodomains.
• To determine the role of Zn2+-mediated conformational changes in the Met66 prodomain's bioactivity.
• To elucidate the molecular mechanisms underlying Met66 prodomain-mediated neuronal remodeling.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy to assess protein structure and dynamics.
• Isothermal Titration Calorimetry (ITC) to quantify binding affinities.
• Dynamic Light Scattering and Cryo-Electron Microscopy (cryo-EM) for structural analysis.
• Site-directed mutagenesis of a key zinc-binding residue (His40).

Main Results:

• Val66 and Met66 prodomains exhibit differential zinc binding affinities and patterns.
• Zn2+ binding induces distinct conformational and macroscopic changes in Met66 compared to Val66 prodomain.
• Mutation of the His40 zinc-binding site abolished Met66 prodomain bioactivity, suggesting a role in multimerization.

Conclusions:

• Zinc binding is essential for the Met66 BDNF prodomain's ability to promote neuronal remodeling.
• The Met66 prodomain's bioactivity relies on Zn2+-induced higher-order molecular assembly, likely involving His40.
• These findings highlight a novel mechanism for BDNF's role in neuronal plasticity and its dysregulation in disorders.