Cells maintain healthy mitochondria by degrading damaged mitochondria through mitophagy; defective mitophagy is linked to Parkinson's disease. Here we report that USP30, a deubiquitinase localized to mitochondria, antagonizes mitophagy driven by the ubiquitin ligase parkin (also known as PARK2) and protein kinase PINK1, which are encoded by two genes associated with Parkinson's disease. Parkin ubiquitinates and tags damaged mitochondria for clearance. Overexpression of USP30 removes ubiquitin attached by parkin onto damaged mitochondria and blocks parkin's ability to drive mitophagy, whereas reducing USP30 activity enhances mitochondrial degradation in neurons. Global ubiquitination site profiling identified multiple mitochondrial substrates oppositely regulated by parkin and USP30. Knockdown of USP30 rescues the defective mitophagy caused by pathogenic mutations in parkin and improves mitochondrial integrity in parkin- or PINK1-deficient flies. Knockdown of USP30 in dopaminergic neurons protects flies against paraquat toxicity in vivo, ameliorating defects in dopamine levels, motor function and organismal survival. Thus USP30 inhibition is potentially beneficial for Parkinson's disease by promoting mitochondrial clearance and quality control.

The mitochondrial deubiquitinase USP30 opposes parkin-mediated mitophagy

Owing to their ability to efficiently generate ATP required to sustain normal cell function, mitochondria are often considered the ‘powerhouses of the cell’. However, our understanding of the role of mitochondria in cell biology recently expanded when we recognized that they are key platforms for a plethora of cell signalling cascades. This functional versatility is tightly coupled to constant reshaping of the cellular mitochondrial network in a series of processes, collectively referred to as mitochondrial membrane dynamics and involving organelle fusion and fission (division) as well as ultrastructural remodelling of the membrane. Accordingly, mitochondrial dynamics influence and often orchestrate not only metabolism but also complex cell signalling events, such as those involved in regulating cell pluripotency, division, differentiation, senescence and death. Reciprocally, mitochondrial membrane dynamics are extensively regulated by post-translational modifications of its machinery and by the formation of membrane contact sites between mitochondria and other organelles, both of which have the capacity to integrate inputs from various pathways. Here, we discuss mitochondrial membrane dynamics and their regulation and describe how bioenergetics and cellular signalling are linked to these dynamic changes of mitochondrial morphology. Mitochondrial networks are dynamically remodelled via fusion, fission and ultrastructural changes to mitochondrial membranes. These mitochondrial membrane dynamics are tightly coupled to cell function, with morphological changes to mitochondria accompanying a multitude of processes as diverse as cell pluripotency, division, differentiation, senescence and death. Accordingly, disturbed dynamics of mitochondrial membranes are linked to severe human disorders.

The cell biology of mitochondrial membrane dynamics

https://febs.onlinelibrary.wiley.com/doi/epdf/10.1002/1873-3468.12964

Role of mitochondrial ROS in the brain: from physiology to neurodegeneration

PINK1/Parkin-mediated mitophagy in mammalian cells.

Parkinson's disease is a common, progressive neurodegenerative disorder, affecting 3% of those older than 75 years of age. Clinically, Parkinson's disease (PD) is associated with resting tremor, postural instability, rigidity, bradykinesia, and a good response to levodopa therapy. Over the last 15 years, numerous studies have confirmed that genetic factors contribute to the complex pathogenesis of PD. Highly penetrant mutations producing rare, monogenic forms of the disease have been discovered in singular genes such as SNCA, Parkin, DJ-1, PINK 1, LRRK2, and VPS35. Unique variants with incomplete penetrance in LRRK2 and GBA have been shown to be strong risk factors for PD in certain populations. Additionally, over 20 common variants with small effect sizes are now recognized to modulate the risk for PD. Investigating Mendelian forms of PD has provided precious insight into the pathophysiology that underlies the more common idiopathic form of disease; however, no treatment methodologies have developed. Furthermore, for identified common risk alleles, the functional basis underlying risk principally remains unknown. The challenge over the next decade will be to strengthen the findings delivered through genetic discovery by assessing the direct, biological consequences of risk variants in tandem with additional high-content, integrated datasets. This review discusses monogenic risk factors and mechanisms of Mendelian inheritance of Parkinson disease. Highly penetrant mutations in SNCA, Parkin, DJ-1, PINK 1, LRRK2 and VPS35 produce rare, monogenic forms of the disease, while unique variants within LRRK2 and GBA show incomplete penetrance and are strong risk factors for PD. Additionally, over 20 common variants with small effect sizes modulate disease risk. The challenge over the next decade is to strengthen genetic findings by assessing direct, biological consequences of risk variants in tandem with high-content, integrated datasets. This article is part of a special issue on Parkinson disease.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/jnc.13593

Genetics in Parkinson disease: Mendelian versus non-Mendelian inheritance.

Compelling evidence indicates that two autosomal recessive Parkinson's disease genes, PINK1 (PARK6) and Parkin (PARK2), cooperate to mediate the autophagic clearance of damaged mitochondria (mitophagy) Mutations in the F-box domain-containing protein Fbxo7 (encoded by PARK15) also cause early-onset autosomal recessive Parkinson's disease, by an unknown mechanism Here we show that Fbxo7 participates in mitochondrial maintenance through direct interaction with PINK1 and Parkin and acts in Parkin-mediated mitophagy Cells with reduced Fbxo7 expression showed deficiencies in translocation of Parkin to mitochondria, ubiquitination of mitofusin 1 and mitophagy In Drosophila, ectopic overexpression of Fbxo7 rescued loss of Parkin, supporting a functional relationship between the two proteins Parkinson's disease-causing mutations in Fbxo7 interfered with this process, emphasizing the importance of mitochondrial dysfunction in Parkinson's disease pathogenesis © 2013 Nature America, Inc All rights reserved

The Parkinson's disease–linked proteins Fbxo7 and Parkin interact to mediate mitophagy

The Parkinson's disease (PD)-related protein F-box only protein 7 (Fbxo7) is the substrate-recognition component of the Skp1-Cullin-F-box protein E3 ubiquitin ligase complex. We have recently shown that PD-associated mutations in Fbxo7 disrupt mitochondrial autophagy (mitophagy), suggesting a role for Fbxo7 in modulating mitochondrial homeostasis. Here we report that Fbxo7 deficiency is associated with reduced cellular NAD+ levels, which results in increased mitochondrial NADH redox index and impaired activity of complex I in the electron transport chain. Under these conditions of compromised respiration, mitochondrial membrane potential and ATP contents are reduced, and cytosolic reactive oxygen species (ROS) production is increased. ROS activates poly (ADP-ribose) polymerase (PARP) activity in Fbxo7-deficient cells. PARP inhibitor restores cellular NAD+ content and redox index and ATP pool, suggesting that PARP overactivation is cause of decreased complex I-driven respiration. These findings bring new insight into the mechanism of Fbxo7 deficiency, emphasising the importance of mitochondrial dysfunction in PD.

/pdf/deficiency-of-parkinson-s-disease-related-gene-fbxo7-is-4qe548xyvl.pdf

Marta Delgado-Camprubi

Papers

The Parkinson's disease–linked proteins Fbxo7 and Parkin interact to mediate mitophagy

Deficiency of Parkinson's Disease-Related Gene Fbxo7 Is Associated With Impaired Mitochondrial Metabolism by PARP Activation