Role of mitochondrial GDAP1 in Alzheimer's disease

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PROJECT SUMMARY Despite extensive research, we still do not fully understand how neurons die in Alzheimer’s disease (AD) patients' brains after withstanding decades of the accumulation of AD pathology. Oxidative damage and mitochondrial deficits are proposed to contribute to or drive neurodegeneration in AD. AD brains show an accumulation of the toxic end-product of lipid peroxidation 4-hydroxynoneal (4HNE), but it remains unclear what causes 4HNE to accumulate in AD. Moreover, a mechanistic understanding of the increased sensitivity of mitochondria and neurons in AD to oxidative damage is lacking. We determined that an atypical member of the glutathione S- transferase (GST) superfamily, GDAP1 (Ganglioside Induced Differentiation Associated Protein 1), binds 4HNE through a unique sequence motif called the α-loop, which is also essential for GDAP1 function. These data collectively indicate that 4HNE is a GDAP1 substrate and that 4HNE binding to GDAP1 is essential for the maintenance of cellular redox balance and mitochondrial function. Significantly, our preliminary RNAseq data from AD patients and analysis of four AD proteomic datasets show significantly reduced levels of GDAP1 in the prefrontal cortex of AD patients. As such, we hypothesize that GDAP1 protects mitochondria against oxidative damage by neutralizing the highly toxic 4HNE and that reduced levels of GDAP1 render AD patient brains vulnerable to 4HNE-mediated damage. We will test this hypothesis with two Aims. Aim 1 will determine the mechanism of GDAP1-mediated cryoprotection including the mechanisms of 4HNE binding and detoxification. Aim 2 will determine the impact of reduced levels of GDAP1 on mitochondrial function and accumulation of the pathological hallmarks of AD in directly converted induced neurons from control subjects and AD patients. These studies will establish the relationship between reduced GDAP1 levels, elevated 4HNE levels, and the increased vulnerability of neurons in AD patients to oxidative damage and open a potential avenue for therapeutic intervention in AD.