bims-mitlys 2021-11-07 papers

Issue of 2021–11–07
four papers selected by
Nicoletta Plotegher, University of Padova

Curr Opin Neurobiol. 2021 Oct 27. pii: S0959-4388(21)00106-9. [Epub ahead of print]72 111-119

PTEN-induced kinase 1 (PINK1) and Parkin: Unlocking a mitochondrial quality control pathway linked to Parkinson's disease.

Shalini Agarwal, Miratul M K Muqit.

Dissection of the function of two Parkinson's disease-linked genes encoding the protein kinase, PTEN-induced kinase 1 (PINK1) and ubiquitin E3 ligase, Parkin, has illuminated a highly conserved mitochondrial quality control pathway found in nearly every cell type including neurons. Mitochondrial damage-induced activation of PINK1 stimulates phosphorylation-dependent activation of Parkin and ubiquitin-dependent elimination of mitochondria by autophagy (mitophagy). Structural, cell biological and neuronal studies are unravelling the key steps of PINK1/Parkin-dependent mitophagy and uncovering new insights into how the pathway is regulated. The emerging role for aberrant immune activation as a driver of dopaminergic neuron degeneration after loss of PINK1 and Parkin poses new exciting questions on cell-autonomous and noncell-autonomous mechanisms of PINK1/Parkin signalling in vivo.

DOI: https://doi.org/10.1016/j.conb.2021.09.005

Circ Res. 2021 Nov 02.

Alternative Mitophagy Protects the Heart Against Obesity-Associated Cardiomyopathy.

Mingming Tong, Toshiro Saito, Peiyong Zhai, Shin-Ichi Oka, Wataru Mizushima, Michinari Nakamura, Shohei Ikeda, Akihiro Shirakabe, Junichi Sadoshima.

Rationale: Obesity-associated cardiomyopathy characterized by hypertrophy and mitochondrial dysfunction. Mitochondrial quality control mechanisms, including mitophagy, are essential for the maintenance of cardiac function in obesity-associated cardiomyopathy. However, autophagic flux peaks at around 6 weeks of high fat diet (HFD) consumption and declines thereafter. Objective: We investigated whether mitophagy is activated during the chronic phase of cardiomyopathy associated with obesity (obesity cardiomyopathy) after general autophagy is downregulated and, if so, what the underlying mechanism and the functional significance are. Methods and Results: Mice were fed either a normal diet (ND) or a HFD (60 kcal % fat). Mitophagy, evaluated using Mito-Keima, was increased after 3 weeks of HFD consumption and continued to increase after conventional mechanisms of autophagy were inactivated, at least until 24 weeks. HFD consumption time-dependently up-regulated both Ser555-phosphorylated Ulk1 and Rab9 in the mitochondrial fraction. Mitochondria were sequestrated by Rab9-positive ring-like structures in cardiomyocytes isolated from mice after 20 weeks of HFD consumption, consistent with the activation of alternative mitophagy. Increases in mitophagy induced by HFD consumption for 20 weeks were abolished in cardiac-specific ulk1 knockout mouse hearts, in which both diastolic and systolic dysfunction were exacerbated. Rab9 S179A knock-in mice, in which alternative mitophagy is selectively suppressed, exhibited impaired mitophagy and more severe cardiac dysfunction than control mice following HFD consumption for 20 weeks. Overexpression of Rab9 in the heart increased mitophagy and protected against cardiac dysfunction during HFD consumption. HFD-induced activation of Rab9-dependent mitophagy was accompanied by upregulation of TFE3, which plays an essential role in transcriptional activation of mitophagy. Conclusions: Ulk1-Rab9-dependent alternative mitophagy is activated during the chronic phase of HFD consumption and serves as an essential mitochondrial quality control mechanism, thereby protecting the heart against obesity cardiomyopathy.

DOI: https://doi.org/10.1161/CIRCRESAHA.121.319377

Nat Commun. 2021 Nov 04. 12(1): 6409

Constitutive activation of the PI3K-Akt-mTORC1 pathway sustains the m.3243 A > G mtDNA mutation.

Chih-Yao Chung, Kritarth Singh, Vassilios N Kotiadis, Gabriel E Valdebenito, Jee Hwan Ahn, Emilie Topley, Joycelyn Tan, William D Andrews, Benoit Bilanges, Robert D S Pitceathly, Gyorgy Szabadkai, Mariia Yuneva, Michael R Duchen.

Mutations of the mitochondrial genome (mtDNA) cause a range of profoundly debilitating clinical conditions for which treatment options are very limited. Most mtDNA diseases show heteroplasmy - tissues express both wild-type and mutant mtDNA. While the level of heteroplasmy broadly correlates with disease severity, the relationships between specific mtDNA mutations, heteroplasmy, disease phenotype and severity are poorly understood. We have carried out extensive bioenergetic, metabolomic and RNAseq studies on heteroplasmic patient-derived cells carrying the most prevalent disease related mtDNA mutation, the m.3243 A > G. These studies reveal that the mutation promotes changes in metabolites which are associated with the upregulation of the PI3K-Akt-mTORC1 axis in patient-derived cells and tissues. Remarkably, pharmacological inhibition of PI3K, Akt, or mTORC1 reduced mtDNA mutant load and partially rescued cellular bioenergetic function. The PI3K-Akt-mTORC1 axis thus represents a potential therapeutic target that may benefit people suffering from the consequences of the m.3243 A > G mutation.

DOI: https://doi.org/10.1038/s41467-021-26746-2

Commun Biol. 2021 Nov 04. 4(1): 1262

Mitochondrial-nuclear cross-talk in the human brain is modulated by cell type and perturbed in neurodegenerative disease.

Aine Fairbrother-Browne, Aminah T Ali, Regina H Reynolds, Sonia Garcia-Ruiz, David Zhang, Zhongbo Chen, Mina Ryten, Alan Hodgkinson.

Mitochondrial dysfunction contributes to the pathogenesis of many neurodegenerative diseases. The mitochondrial genome encodes core respiratory chain proteins, but the vast majority of mitochondrial proteins are nuclear-encoded, making interactions between the two genomes vital for cell function. Here, we examine these relationships by comparing mitochondrial and nuclear gene expression across different regions of the human brain in healthy and disease cohorts. We find strong regional patterns that are modulated by cell-type and reflect functional specialisation. Nuclear genes causally implicated in sporadic Parkinson's and Alzheimer's disease (AD) show much stronger relationships with the mitochondrial genome than expected by chance, and mitochondrial-nuclear relationships are highly perturbed in AD cases, particularly through synaptic and lysosomal pathways, potentially implicating the regulation of energy balance and removal of dysfunction mitochondria in the etiology or progression of the disease. Finally, we present MitoNuclearCOEXPlorer, a tool to interrogate key mitochondria-nuclear relationships in multi-dimensional brain data.

DOI: https://doi.org/10.1038/s42003-021-02792-w