Biology subjects

Miller-Fleming, L.

Publications and source records attributed to Miller-Fleming, L..

5 recordsLinked to original sources

bioRxiv2024

Clu1/Clu form mitochondria-associated granules upon metabolic transitions and regulate mitochondrial protein translation via ribosome interactions

Mitochondria perform essential metabolic functions and respond rapidly to changes in metabolic and stress conditions. As the majority of mitochondrial proteins are nuclear-encoded, intricate post-transcriptional regulation is crucial to enable mitochondria to adapt to changing cellular demands. The eukaryotic Clustered mitochondria protein family has emerged as an important regulator of mitochondrial function during metabolic shifts. Here, we show that the Drosophila melanogaster and Saccharomyces cerevisiae Clu/Clu1 proteins form dynamic, membraneless granules adjacent to mitochondria in response to metabolic changes. Yeast Clu1 regulates the translation of a subset of nuclear-encoded mitochondrial protein by interacting with their mRNAs while these are engaged in translation. We further show that Clu1 regulates translation by interacting with polysomes, independently of whether it is in a diffuse or granular state. Our results demonstrate remarkable functional conservation with other members of the Clustered mitochondria protein family and suggests that Clu/Clu1 granules isolate and concentrate ribosomes engaged in translating their mRNA targets, thus, integrating metabolic signals with the regulation of mitochondrial protein synthesis.

molecular biology↗

bioRxiv2023

Activation of the Keap1/Nrf2 pathway suppresses mitochondrial dysfunction in C9orf72 ALS/FTD in vivo models and patient iNeurons

Mitochondrial dysfunction such as excess production of reactive oxygen species (ROS) and defective mitochondrial dynamics are common features of C9orf72 Amyotrophic Lateral Sclerosis/Frontotemporal Dementia (ALS/FTD), but it remains unclear whether these are causative or a consequence of the pathogenic process. To address this, we have performed a comprehensive characterisation of mitochondrial dysfunction in vivo model, analysing multiple transgenic Drosophila models of C9orf72-related pathology, which can be correlated to disease-relevant locomotor deficits. Genetic manipulations to reverse different aspects of mitochondrial disruption revealed that only genetic upregulation of antioxidants such as mitochondrial Sod2 and catalase were able to rescue C9orf72 locomotor deficits, suggesting a causative link between mitochondrial dysfunction, ROS and behavioural phenotypes. By analysing the Keap1/Nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, a central antioxidant response pathway, we observed a blunted response in the C9orf72 models. However, both genetic reduction of Keap1 and its pharmacological targeting by dimethyl fumarate (DMF), was able to rescue C9orf72-related motor deficits. In addition, analysis of C9orf72 patient-derived iNeurons showed increased ROS that was suppressed by DMF treatment. These results indicate that mitochondrial oxidative stress is an upstream pathogenic mechanism leading to downstream mitochondrial dysfunction such as alterations in mitochondrial function and turnover. Consequently, our data support targeting the Keap1/Nrf2 signalling pathway as a viable therapeutic strategy for C9orf72-related ALS/FTD.

neuroscience↗

bioRxiv2021

A late-stage assembly checkpoint of the human mitochondrial ribosome large subunit

The epitranscriptome plays a key regulatory role in cellular processes in health and disease, including ribosome biogenesis. Here, analysis of the human mitochondrial transcriptome shows that 2-O-methylation is limited to residues of the mitoribosomal large subunit (mtLSU) 16S mt-rRNA, modified by MRM1, MRM2, and MRM3. Ablation of MRM2 leads to a severe impairment of the oxidative phosphorylation system, caused by defective mitochondrial translation and accumulation of mtLSU assembly intermediates. Structures of these particles (2.58 [A]) present disordered RNA domains, partial occupancy of bL36m and bound MALSU1:L0R8F8:mtACP anti-association module. Additionally, we present five mtLSU assembly states with different intersubunit interface configurations. Complementation studies demonstrate that the methyltransferase activity of MRM2 is dispensable for mitoribosome biogenesis. The Drosophila melanogaster orthologue, DmMRM2, is an essential gene, with its knock-down leading to developmental arrest. This work identifies a key late-stage quality control step during mtLSU assembly, ultimately contributing to the maintenance of mitochondrial homeostasis.

molecular biology↗

bioRxiv2020

Decreasing pdzd8-mediated mitochondrial-ER contacts in neurons improves fitness by increasing mitophagy

The complex cellular architecture of neurons combined with their longevity makes maintaining a healthy mitochondrial network particularly important and challenging. One of the many roles of mitochondrial-ER contact sites (MERCs) is to mediate mitochondrial quality control through regulating mitochondrial turn over. Pdzd8 is a newly discovered MERC protein, the organismal functions of which have not yet been explored. Here we identify and provide the first functional characterization of the Drosophila melanogaster ortholog of Pdzd8. We find that reducing pdzd8-mediated MERCs in neurons slows age-associated decline in locomotor activity and increases lifespan in Drosophila. The protective effects of pdzd8 knockdown in neurons correlate with an increase in mitophagy, suggesting that increased mitochondrial turnover may support healthy aging of neurons. In contrast, increasing MERCs by expressing a constitutive, synthetic ER-mitochondria tether disrupts mitochondrial transport and synapse formation, accelerates age-related decline in locomotion and reduces lifespan. We also show that depletion of pdzd8 rescues the locomotor defects characterizing an Alzheimers disease (AD) fly model over-expressing Amyloid{beta}1-42 (A{beta}42) and prolongs the survival of flies fed with mitochondrial toxins. Together, our results provide the first in vivo evidence that MERCs mediated by the tethering protein pdzd8 play a critical role in the regulation of mitochondrial quality control and neuronal homeostasis.

cell biology↗

bioRxiv2017

A Yeast Global Genetic Screen Reveals that Metformin Induces an Iron Deficiency-Like State

We report here a simple and global strategy to map out gene functions and target pathways of drugs, toxins or other small molecules based on \"homomer dynamics\" Protein-fragment Complementation Assays (hdPCA). hdPCA measures changes in self-association (homomerization) of over 3,500 yeast proteins in yeast grown under different conditions. hdPCA complements genetic interaction measurements while eliminating confounding effects of gene ablation. We demonstrate that hdPCA accurately predicts the effects of two longevity and health-span-affecting drugs, immunosuppressant rapamycin and type II diabetes drug metformin, on cellular pathways. We also discovered an unsuspected global cellular response to metformin that resembles iron deficiency. This discovery opens a new avenue to investigate molecular mechanisms for the prevention or treatments of diabetes, cancers and other chronic diseases of aging.

systems biology↗