Brain glyceraldehyde-3-phosphate dehydrogenase activity in human trinucleotide repeat disorders

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Abnormal gene products in hereditary neurodegenerative disorders are linked to expanded CAG trinucleotide repeats.
• The mechanism of cell death caused by expanded polyglutamine proteins remains unclear.
• Mutant proteins interacting with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) may damage brain neurons.

Purpose of the Study:

• To quantify GAPDH activity in postmortem brain tissue from patients with CAG repeat disorders.
• To investigate the potential link between polyglutamine proteins and neuronal damage via GAPDH.

Main Methods:

• GAPDH activity was measured in affected and unaffected brain regions.
• Analysis included patients with Huntington disease, spinocerebellar ataxias (SCA1, SCA2, SCA3), Friedreich ataxia, and Alzheimer disease.
• Matched control subjects were used for comparison.

Main Results:

• Overall, brain GAPDH activity was normal across most patient groups.
• A slight, statistically significant reduction in GAPDH activity was noted in the caudate nucleus of Huntington disease patients (-12%).
• A similar region-specific reduction was observed in the temporal cortex of Alzheimer disease patients (-19%).

Conclusions:

• Expanded polyglutamine proteins in CAG repeat disorders do not cause substantial irreversible inactivation of GAPDH in the human brain.
• The observed minor reductions in specific regions suggest a complex, localized interaction rather than widespread enzyme dysfunction.
• These findings help elucidate the molecular mechanisms underlying neurodegeneration in these disorders.