Parkin drives pS65-Ub turnover independently of canonical autophagy in Drosophila

Parkinson's disease-related proteins, PINK1 and parkin, act in a common pathway to maintain mitochondrial quality control. While the PINK1-parkin pathway can promote autophagic mitochondrial turnover (mitophagy) in cell culture, recent studies have questioned whether they contribute to mitophagy in vivo, and alternative PINK1- and parkin-dependent mitochondrial quality control pathways have been proposed. To determine the mechanisms by which the Pink1-parkin pathway operates in vivo, we developed methods to detect Ser65-phosphorylated ubiquitin (pS65-Ub) in Drosophila. Exposure to the oxidant paraquat led to robust, Pink1-dependent pS65-Ub production. Surprisingly, parkin-null flies displayed strikingly elevated basal levels of pS65-Ub, suggestive of disrupted flux through the Pink1-parkin pathway. Depletion of the core autophagy proteins Atg1, Atg5 and Atg8a did not cause pS65-Ub accumulation to the same extent as loss of parkin, and overexpression of parkin was able to reduce both basal and paraquat-induced pS65-Ub levels in an Atg5-null background. Taken together, these results suggest that the Pink1-parkin pathway is able to promote mitochondrial turnover independently of canonical autophagy in vivo.

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Characterization of a Cul9–Parkin double knockout mouse model for Parkinson’s disease

Scientific Reports ◽

10.1038/s41598-020-73854-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Emilie Hollville ◽

Valerie Joers ◽

Ayumi Nakamura ◽

Vijay Swahari ◽

Malú G. Tansey ◽

...

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Quality Control ◽

Double Knockout ◽

Mitochondrial Quality Control ◽

Term Survival ◽

Long Term Survival ◽

Knockout Mouse Model

Abstract Mitochondrial quality control is essential for the long-term survival of postmitotic neurons. The E3 ubiquitin ligase Parkin promotes the degradation of damaged mitochondria via mitophagy and mutations in Parkin are a major cause of early-onset Parkinson’s disease (PD). Surprisingly however, mice deleted for Parkin alone are rather asymptomatic for PD-related pathology, suggesting that other complementary or redundant mitochondrial quality control pathways may exist in neurons. Mitochondrial damage is often accompanied by the release of toxic proteins such as cytochrome c. We have reported that once in the cytosol, cytochrome c is targeted for degradation by the E3 ligase CUL9 in neurons. Here we examined whether CUL9 and Parkin cooperate to promote optimal neuronal survival in vivo. We generated mice deficient for both Cul9 and Parkin and examined them for PD-related phenotypes. Specifically, we conducted assays to examine behavioural deficits (locomotor, sensory, memory and learning) and loss of dopaminergic neurons in both males and females. Our results show that the loss of Cul9 and Parkin together did not enhance the effect of Parkin deficiency alone. These results indicate that while both Parkin and CUL9 participate in mitochondrial quality control, neurons likely have multiple redundant mechanisms to ensure their long-term survival.

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Targeting mitophagy in Parkinson's disease

Journal of Biological Chemistry ◽

10.1074/jbc.rev120.014294 ◽

2020 ◽

pp. jbc.REV120.014294

Author(s):

Emily H Clark ◽

Aurelio Vázquez de la Torre ◽

Tamaki Hoshikawa ◽

Thomas Briston

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Quality Control ◽

High Throughput Screening ◽

Drug Targets ◽

Therapeutic Potential ◽

Biological Properties ◽

Loss Of Function ◽

Mitochondrial Quality Control

The genetics and pathophysiology of Parkinson’s disease (PD) strongly implicate mitochondria in disease aetiology. Elegant studies over the last two decades have elucidated complex molecular signalling governing the identification and removal of dysfunctional mitochondria from the cell, a process of mitochondrial quality control known as mitophagy. Mitochondrial deficits and specifically reduced mitophagy are evident in both sporadic and familial PD. Mendelian genetics attributes loss-of-function mutations in key mitophagy regulators PINK1 and Parkin to early-onset PD. Pharmacologically enhancing mitophagy and accelerating the removal of damaged mitochondria are of interest for developing a disease-modifying PD therapeutic. However, despite significant understanding of both PINK1/Parkin-dependent and -independent mitochondrial quality control pathways, the therapeutic potential of targeting mitophagy remains to be fully explored. Here, we provide a summary of the genetic evidence supporting the role for mitophagy-failure as a pathogenic mechanism in PD. We assess the tractability of mitophagy pathways and prospects for drug discovery and consider intervention points for mitophagy enhancement. We explore the numerous hit molecules beginning to emerge from high-content/high-throughput screening as well as the biochemical and phenotypic assays that enabled these screens. The chemical and biological properties of these reference compounds suggest many could be used to interrogate and perturb mitochondrial biology to validate promising drug targets. Finally, we address key considerations and challenges in achieving pre-clinical proof-of-concept, including in vivo mitophagy reporter methodologies and disease models, as well as patient stratification and biomarker development for mitochondrial forms of the disease.

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PINK1: A Bridge between Mitochondria and Parkinson’s Disease

Life ◽

10.3390/life11050371 ◽

2021 ◽

Vol 11 (5) ◽

pp. 371

Author(s):

Filipa Barroso Gonçalves ◽

Vanessa Alexandra Morais

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Quality Control ◽

High Energy ◽

Common Denominator ◽

Mitochondrial Quality Control ◽

Mitochondrial Homeostasis ◽

Cellular Environment ◽

Familial Form ◽

Mitochondrial Functions

Mitochondria are known as highly dynamic organelles essential for energy production. Intriguingly, in the recent years, mitochondria have revealed the ability to maintain cell homeostasis and ultimately regulate cell fate. This regulation is achieved by evoking mitochondrial quality control pathways that are capable of sensing the overall status of the cellular environment. In a first instance, actions to maintain a robust pool of mitochondria take place; however, if unsuccessful, measures that lead to overall cell death occur. One of the central key players of these mitochondrial quality control pathways is PINK1 (PTEN-induce putative kinase), a mitochondrial targeted kinase. PINK1 is known to interact with several substrates to regulate mitochondrial functions, and not only is responsible for triggering mitochondrial clearance via mitophagy, but also participates in maintenance of mitochondrial functions and homeostasis, under healthy conditions. Moreover, PINK1 has been associated with the familial form of Parkinson’s disease (PD). Growing evidence has strongly linked mitochondrial homeostasis to the central nervous system (CNS), a system that is replenished with high energy demanding long-lasting neuronal cells. Moreover, sporadic cases of PD have also revealed mitochondrial impairments. Thus, one could speculate that mitochondrial homeostasis is the common denominator in these two forms of the disease, and PINK1 may play a central role in maintaining mitochondrial homeostasis. In this review, we will discuss the role of PINK1 in the mitochondrial physiology and scrutinize its role in the cascade of PD pathology.

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