bims-tofagi 2024-04-14 papers

Mol Neurobiol. 2024 Apr 06.

Mitophagy Upregulation Occurs Early in the Neurodegenerative Process Mediated by α-Synuclein.

Sarah Hui, Jimmy George, Minesh Kapadia, Hien Chau, Zahn Bariring, Rebecca Earnshaw, Kashfia Shafiq, Lorraine V Kalia, Suneil K Kalia.

Parkinson's disease (PD) is a progressive neurogenerative movement disorder characterized by dopaminergic cell death within the substantia nigra pars compacta (SNpc) due to the aggregation-prone protein α-synuclein. Accumulation of α-synuclein is implicated in mitochondrial dysfunction and disruption of the autophagic turnover of mitochondria, or mitophagy, which is an essential quality control mechanism proposed to preserve mitochondrial fidelity in response to aging and stress. Yet, the precise relationship between α-synuclein accumulation, mitochondrial autophagy, and dopaminergic cell loss remains unresolved. Here, we determine the kinetics of α-synuclein overexpression and mitophagy using the pH-sensitive fluorescent mito-QC reporter. We find that overexpression of mutant A53T α-synuclein in either human SH-SY5Y cells or rat primary cortical neurons induces mitophagy. Moreover, the accumulation of mutant A53T α-synuclein in the SNpc of rats results in mitophagy dysregulation that precedes the onset of dopaminergic neurodegeneration. This study reveals a role for mutant A53T α-synuclein in inducing mitochondrial dysfunction, which may be an early event contributing to neurodegeneration.

Keywords: Alpha-synuclein; Lysosomes; Mitochondria dysfunction; Mitophagy; Neurodegeneration; Parkinson’s disease; Substantia nigra pars compacta

DOI: https://doi.org/10.1007/s12035-024-04131-6

NPJ Parkinsons Dis. 2024 Apr 09. 10(1): 80

Elevated α-synuclein levels inhibit mitophagic flux.

Inge Kinnart, Liselot Manders, Thibaut Heyninck, Dorien Imberechts, Roman Praschberger, Nils Schoovaerts, Catherine Verfaillie, Patrik Verstreken, Wim Vandenberghe.

The pathogenic effect of SNCA gene multiplications indicates that elevation of wild-type α-synuclein levels is sufficient to cause Parkinson's disease (PD). Mitochondria have been proposed to be a major target of α-synuclein-induced damage. PINK1/parkin/DJ-1-mediated mitophagy is a defense strategy that allows cells to selectively eliminate severely damaged mitochondria. Here, we quantified mitophagic flux and non-mitochondrial autophagic flux in three models of increased α-synuclein expression: 1/Drosophila melanogaster that transgenically express human wild-type and mutant α-synuclein in flight muscle; 2/human skin fibroblasts transfected with α-synuclein or β-synuclein; and 3/human induced pluripotent stem cell (iPSC)-derived neurons carrying an extra copy of wild-type SNCA under control of a doxycycline-inducible promoter, allowing titratable α-synuclein upregulation. In each model, elevated α-synuclein levels potently suppressed mitophagic flux, while non-mitochondrial autophagy was preserved. In human neurons, a twofold increase in wild-type α-synuclein was already sufficient to induce this effect. PINK1 and parkin activation and mitochondrial translocation of DJ-1 after mitochondrial depolarization were not affected by α-synuclein upregulation. Overexpression of the actin-severing protein cofilin or treatment with CK666, an inhibitor of the actin-related protein 2/3 (Arp2/3) complex, rescued mitophagy in neurons with increased α-synuclein, suggesting that excessive actin network stabilization mediated the mitophagy defect. In conclusion, elevated α-synuclein levels inhibit mitophagic flux. Disruption of actin dynamics may play a key role in this effect.

DOI: https://doi.org/10.1038/s41531-024-00696-0

Autophagy. 2024 Apr 10.

MITOCHONDRIAL IMPORT STRESS and PINK1-MEDIATED MITOPHAGY: THE ROLE of the PINK1-TOMM-TIMM23 SUPERCOMPLEX.

Mohamed A Eldeeb, Armaan Fallahi, Andrea Soumbasis, Andrew N Bayne, Jean-François Trempe, Edward A Fon.

Mutations in the PINK1 kinase cause Parkinson disease (PD) through physiological processes that are not yet fully elucidated. PINK1 kinase accumulates selectively on damaged mitochondria, where it recruits the E3 ubiquitin ligase PRKN/Parkin to mediate mitophagy. Upon mitochondrial import failure, PINK1 accumulates in association with the translocase of outer mitochondrial membrane (TOMM). However, the molecular basis of this PINK1 accumulation on the TOMM complex remain elusive. We recently demonstrated that TIMM23 (translocase of the inner mitochondrial membrane 23) is a component of the PINK1-supercomplex formed in response to mitochondrial stress. We also uncovered that PINK1 is required for the formation of this supercomplex and highlighted the biochemical regulation and significance of this supercomplex; expanding our understanding of mitochondrial quality control and PD pathogenesis.

Keywords: Mitochondrial import; PINK1; Parkinson’s disease; mitochondrial quality control; mitophagy

DOI: https://doi.org/10.1080/15548627.2024.2340399

Mov Disord. 2024 Apr 08.

A Novel PINK1 p.F385S Loss-of-Function Mutation in an Indian Family with Parkinson's Disease.

Karan Sharma, Asha Kishore, Anna Lechado-Terradas, Raffaele Passannanti, Francesco Raimondi, Marc Sturm, Ashwin Ashok Kumar Sreelatha, Divya Kalikavila Puthenveedu, Gangadhara Sarma, Nicolas Casadei, Rejko Krüger, Thomas Gasser, Philipp Kahle, Olaf Riess, Julia C Fitzgerald, Manu Sharma.

BACKGROUND: Most Parkinson's disease (PD) loci have shown low prevalence in the Indian population, highlighting the need for further research.
OBJECTIVE: The aim of this study was to characterize a novel phosphatase tensin homolog-induced serine/threonine kinase 1 (PINK1) mutation causing PD in an Indian family.
METHODS: Exome sequencing of a well-characterized Indian family with PD. A novel PINK1 mutation was studied by in silico modeling using AlphaFold2, expression of mutant PINK1 in human cells depleted of functional endogenous PINK1, followed by quantitative image analysis and biochemical assessment.
RESULTS: We identified a homozygous chr1:20648535-20648535 T>C on GRCh38 (p.F385S) mutation in exon 6 of PINK1, which was absent in 1029 genomes from India and in other known databases. PINK1 F385S lies within the highly conserved Deutsche Forschungsgemeinschaft (DFG) motif, destabilizes its active state, and impairs phosphorylation of ubiquitin at serine 65 and proper engagement of parkin upon mitochondrial depolarization.
CONCLUSIONS: We characterized a novel nonconservative mutation in the DFG motif of PINK1, which causes loss of its ubiquitin kinase activity and inhibition of mitophagy. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Keywords: PINK1; Parkinson's disease; genome sequencing; mitophagy; phosphorylation; ubiquitin

DOI: https://doi.org/10.1002/mds.29792

Ren Fail. 2024 Dec;46(1): 2332492

Mitophagy mediated by HIF-1α/FUNDC1 signaling in tubular cells protects against renal ischemia/reperfusion injury.

Wenjun Zhang, Chao Guo, Yi Li, Hao Wang, Huabing Wang, Yingying Wang, Tingting Wu, Huinan Wang, Gang Cheng, Jiangwei Man, Siyu Chen, Shengjun Fu, Li Yang.

Acute kidney injury (AKI) is associated with a high mortality rate. Pathologically, renal ischemia/reperfusion injury (RIRI) is one of the primary causes of AKI, and hypoxia-inducible factor (HIF)-1α may play a defensive role in RIRI. This study assessed the role of hypoxia-inducible factor 1α (HIF-1α)-mediated mitophagy in protection against RIRI in vitro and in vivo. The human tubular cell line HK-2 was used to assess hypoxia/reoxygenation (H/R)-induced mitophagy through different in vitro assays, including western blotting, immunofluorescence staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and reactive oxygen species (ROS) measurement. Additionally, a rat RIRI model was established for evaluation by renal histopathology, renal Doppler ultrasound, and transmission electron microscopy to confirm the in vitro data. The selective HIF-1α inhibitor LW6 reduced H/R-induced mitophagy but increased H/R-induced apoptosis and ROS production. Moreover, H/R treatment enhanced expression of the FUN14 domain-containing 1 (FUNDC1) protein. Additionally, FUNDC1 overexpression reversed the effects of LW6 on the altered expression of light chain 3 (LC3) BII and voltage-dependent anion channels as well as blocked the effects of HIF-1α inhibition in cells. Pretreatment of the rat RIRI model with roxadustat, a novel oral HIF-1α inhibitor, led to decreased renal injury and apoptosis in vivo. In conclusion, the HIF-1α/FUNDC1 signaling pathway mediates H/R-promoted renal tubular cell mitophagy, whereas inhibition of this signaling pathway protects cells from mitophagy, thus aggravating apoptosis, and ROS production. Accordingly, roxadustat may protect against RIRI-related AKI.

Keywords: Acute kidney injury; FUNDC1; HIF-1; roxadustat; α mitophagy

DOI: https://doi.org/10.1080/0886022X.2024.2332492