Impact of PINK1 knockout on expression and phosphorylation of mitochondrial proteins and dopamine regulation: insight into early-stage Parkinson’s Disease in the rat model.
Joshia John1, Michael F. Salvatore, PhD2
1UNTHSC Texas College of Osteopathic Medicine, 2Pharmacology & Neuroscience, University of North Texas Health Sciences Center
Objective:

A nonsense mutation in PINK1, a mitochondrial protein, causes recessively inherited young-onset Parkinson’s Disease (PD). To model the impact of the PINK1 mutation, a rat model has been developed, but ambiguous results on dopamine regulation and motor function have been reported early in the lifespan. The objective of this study is to evaluate the impact of the PINK1 mutation on subsequent mitochondrial proteins, coinciding in changes in dopamine regulation.

Background:

Dopaminergic neurons are vulnerable to mitochondrial dysfunction due to high metabolic demands placed on them by their intricate axonal system and signaling pathways. Sustained stimulation of these pathways can cause oxidant stress and increased mitochondrial turnover. It is unclear whether the loss of mitochondrial protein expression is what leads to PD or whether dysfunction is the driver of early-stage pathogenesis.

Design/Methods:
In five-month-old PINK1 knock-out (KO) and age-matched wild-type (WT) rats, we confirmed the genotype by PCR, indicating the 26-base pair deletion as shown in the human mutation. Protein expression of PINK1, Parkin, phosphorylated Parkin, and TOM-20 were evaluated in comparison with dopamine tissue content, dopamine turnover, and tyrosine hydroxylase expression using quantitative Western Blotting
Results:
In the PINK1 KO, dopamine tissue content decreased 43% in the striatum and 26% in the substantia nigra as compared to wild-type rats, commensurate with increased dopamine turnover in both regions. Parkin, phosphorylated Parkin, and TOM-20 protein expression were not significantly different in the PINK1 KO rat.
Conclusions:

This study suggests that compensatory changes in Parkin expression or phosphorylation are not modified in the PINK1 KO rat, though there is increased dopamine turnover and loss in both regions. Individuals with the PINK1 knockout mutation begin seeing motor impairments around 34 years of age so targeting mitochondrial dysfunction prior to when symptoms arise could diminish nigrostriatal dopamine loss and be a promising approach to the development of future treatment.

10.1212/WNL.0000000000202996