Molecular Dynamics Simulations of 4 GALC Variants Causing Krabbe Disease

Area of Science:

• Biochemistry
• Genetics
• Neuroscience

Background:

• Krabbe disease, or globoid cell leukodystrophy, is a rare, fatal lysosomal storage disorder impacting the nervous system.
• Infantile-onset Krabbe disease, the most common form, presents within the first year of life, characterized by severe neurodegeneration.
• The disease results from mutations in the GALC gene, encoding the lysosomal enzyme beta-galactocerebrosidase (GALC).

Purpose of the Study:

• To investigate the structural consequences of four specific GALC variants (Gly59Arg, Ser68Phe, Thr278Ile, Ser303Phe) associated with Krabbe disease.
• To analyze the impact of these mutations on the stability and flexibility of the human GALC enzyme.
• To understand how GALC variants affect substrate-binding residues and overall enzyme function at the lysosomal pH.

Main Methods:

• Construction of structural models for wild-type and mutated human GALC.
• All-atom molecular dynamics (MD) simulations performed at lysosomal pH (4.5) to assess enzyme stability.
• Analysis of changes in protein flexibility, intramolecular interactions, and proximity to substrate-binding sites.

Main Results:

• Observed differences in protein flexibility and intramolecular interactions between wild-type GALC and the studied variants.
• Identified effects of mutations on residues near the substrate-binding site, despite mutations not being in the active site.
• MD simulations provided insights into structural destabilization and altered interactions caused by GALC mutations.

Conclusions:

• The study elucidates how specific GALC mutations structurally alter the enzyme within the lysosomal environment.
• Findings offer potential molecular explanations for the functional deficits observed in Krabbe disease patients with these variants.
• This research contributes to understanding the structure-function relationship of GALC in lysosomal storage disorders.