PARK2 Mutation Causes Metabolic Disturbances and Impaired Survival of Human iPSC-Derived Neurons

Abstract

The protein parkin, encoded by the PARK2 gene, is vital for mitochondrial homeostasis, and although it has been implicated in Parkinson’s disease (PD), the disease mechanisms remain unclear. We have applied mass spectrometry-based proteomics to investigate the effects of parkin dysfunction on the mitochondrial proteome in human isogenic induced pluripotent stem cell-derived neurons with and without PARK2 knockout (KO). The proteomic analysis quantified nearly 60% of all mitochondrial proteins, 119 of which were dysregulated in neurons with PARK2 KO. The protein changes indicated disturbances in oxidative stress defense, mitochondrial respiration and morphology, cell cycle control, and cell viability. Structural and functional analyses revealed an increase in mitochondrial area and the presence of elongated mitochondria as well as impaired glycolysis and lactate-supported respiration, leading to an impaired cell survival in PARK2 KO neurons. This adds valuable insight into the effect of parkin dysfunction in human neurons and provides knowledge of disease-related pathways that can potentially be targeted for therapeutic intervention.

Lysosomal perturbations in dopaminergic neurons derived from induced pluripotent stem cells with PARK2 mutation

“…One of the consequences of mitochondrial deficits caused by parkin dysfunction in this cellular model of PD was an increased lysosomal number and size. This altered phenotype appeared at differentiation day 25, when the cells also exhibit aberrant mitochondria, indicating increased vulnerability of mature neurons (29). Similar lysosomal alterations to those observed in our study were detected in mitochondrial mutants exhibiting disrupted mitochondrial fission-fusion processes and cristae structure and mitochondrial impairment (27,(39)(40)(41).…”

“…As earlier reported we have subjected PARK2 KO and isogenic control neuronal cultures to a mass spectrometry-based proteomic analysis, which enabled the identification and quantification of a large number of proteins (29). Based on this recently published dataset (29) we detected significant changes in levels of 22 lysosomal proteins in PARK2 KO neurons ( Table 1). A number of these proteins were of importance for vesicle-mediated protein trafficking through the endosomal-lysosomal system and for the ALP pathway ( Table 1).…”

“…In our recent report we demonstrated prominent mitochondrial-related defects and the mitochondrial proteome perturbations (29) in response to parkin deficiency. Therefore, to explore the reciprocal relationship between mitochondrial and lysosomal pathways in PD, in the present study we investigated the impact of parkin dysfunction on lysosome structure and function by applying human iPSC-derived neurons with PARK2 mutations and isogenic healthy control.…”

“…To study the disease mechanism underlining PARK2-mediated PD, we analyzed two isogenic iPSC lines created from a healthy control iPSC line, where KO of the PARK2 gene was created by zinc finger nuclease gene editing technology (30). Detailed cell line information is reported in our recent study (29).…”

“…By studying the lysosomal compartment and function in the context of parkin deficiency, we sought to address whether chronic mitochondrial dysfunction causes lysosomal impairment, contributing to PD pathogenesis. For this purpose, we studied isogenic iPSC-derived neuronal cultures with and without PARK2 mutation, which we have recently demonstrated lead to several mitochondrial defects (29). Parkin deficiency resulted in a number of perturbations including altered lysosomal content, morphology and function as well as impaired autophagic flux, indicating a connection between parkin deficiency and lysosomal disturbances.…”