Biology subjects

Brischigliaro, M.

Publications and source records attributed to Brischigliaro, M..

6 recordsLinked to original sources

bioRxiv2025

Structural Basis of TACO1-Mediated Efficient Mitochondrial Translation

Translation elongation is a universally conserved step in protein synthesis, relying on elongation factors that engage the ribosomal L7/L12 stalk to mediate aminoacyl-tRNA delivery, accommodation, and ribosomal translocation. Using in organello cryo-electron microscopy, we reveal how the mitochondrial translation accelerator TACO1 promotes efficient elongation on human mitoribosomes. TACO1 binds the mitoribosomal region typically bound by elongation factor Tu (mtEF-Tu), bridging the large and small subunits via contacts with 16S rRNA, bL12m, A-site tRNA, and uS12m. While active throughout elongation, TACO1 is especially critical when translating polyproline motifs. Its absence prolongs mtEF-Tu residence in A/T states, causes persistent mitoribosomal stalling and premature subunit dissociation. Structural analyses indicate that TACO1 competes with mtEF-Tu for mitoribosome binding, stabilizes A-site tRNA, and enhances peptidyl transfer through a mechanism distinct from EF-P and eIF5A. These findings suggest that bacterial TACO1 orthologs may serve analogous roles, highlighting an evolutionarily conserved strategy for maintaining elongation efficiency during challenging translation events.

biophysics↗

bioRxiv2024

Sprint interval exercise disrupts mitochondrial ultrastructure driving a unique mitochondrial stress response and remodelling in humans

Exercise remains the most effective lifestyle intervention to remodel the mitochondrial network and to prevent most non-communicable diseases. Despite this, the molecular mechanisms by which different exercise prescriptions dictate mitochondrial remodelling are poorly understood in humans. Here, we show that, compared to moderate-intensity continuous exercise (MICE), sprint-interval exercise (SIE) - a known time-efficient high-intensity exercise - leads to mitochondrial stress and activates the mitochondrial unfolded protein response (UPRmt). The SIE-specific signature is characterized by a morphological and ultrastructural mitochondrial disturbance, concurrent with the activation of the integrated stress response (ISR) and mitochondrial quality control (MQC) pathways. When the respective exercises are repeated over time (8 weeks), our results demonstrate that moderate-intensity continuous training (MICT) and sprint-interval training (SIT) lead to a divergent mitochondrial remodelling. MICT elicits a mitochondrial adaptation characterized by an increase in markers of mitochondrial content, complex I activity, and enrichment of proteins involved in tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) system. On the other hand, SIT leads to proteomic enrichment of pathways involved in mitochondrial 1-Carbon metabolism and protein quality control, concurrently with improvements in mitochondrial respiratory function. Lastly, we have identified COX7A2L as a divergently regulated protein across groups, significantly accumulating in III2+IV1 respiratory supercomplexes only following SIT. In conclusion, our study provides mechanistic insights on how SIE and MICE divergently impact the post-exercise mitochondrial signalling, and subsequent long-term mitochondrial remodelling following training. These findings provide a strong basis for targeted exercise prescription to modulate specific mitochondrial adaptations in human skeletal muscle.

molecular biology↗

bioRxiv2024

Mitochondrial complex I deficiency occurs in skeletal muscle of a subgroup of individuals with Parkinson's disease

Widespread neuronal complex I (CI) deficiency was recently reported to be a characteristic in a subgroup of individuals with idiopathic Parkinsons disease (PD). Here, we sought to determine whether a CI deficient subgroup could be discerned using clinically accessible muscle biopsy. Vastus lateralis needle biopsies were collected from 83 individuals with PD and 29 neurologically healthy controls and analyzed by immunohistochemistry for complexes I and IV, cytochrome c oxidase/succinate dehydrogenase (COX/SDH) histochemistry, and spectrophotometric activity assays of complexes I-IV. Mitochondrial DNA (mtDNA) copy number, deletions, and point variation were analyzed in single muscle fibers and bulk biopsy samples. PD muscle exhibited reduced CI activity at the group level, with 9% of cases falling below two standard deviations of the control group. This deficiency was not associated with mtDNA abnormalities. Our findings support the existence of a PD subpopulation characterized by CI pathology and suggest that stratification by extra-neural mitochondrial dysfunction may be informative for selecting individuals for clinical trials.

neuroscience↗

bioRxiv2024

COA8 is a COX10-binding protein involved in the early biogenesis of cytochrome c oxidase

Human cytochrome c oxidase (COX) is composed of fourteen subunits, only two of which are catalytic. The functions of a myriad of accessory factors are needed to put together the structural subunits, as well as for the formation of the active centers. The molecular roles of most of these factors are still unknown, even if they are essential for COX function since their defects cause severe mitochondrial disease. COA8 is exclusively found in metazoa and loss-of-function genetic variants cause mitochondrial encephalopathy and COX deficiency in humans. In this work, we have resolved the function of COA8, as a factor that specifically binds to COX10, the heme O synthase. This interaction is necessary not only for the stabilization of human COX10, but also to guarantee its catalytic activity as the first step for the synthesis of the heme A cofactor, which is a crucial component of the COX catalytic center.

biochemistry↗

bioRxiv2023

The human mitochondrial mRNA structurome reveals mechanisms of gene expression

The mammalian mitochondrial genome encodes thirteen oxidative phosphorylation system proteins, crucial in aerobic energy transduction. These proteins are translated from 9 monocistronic and 2 bicistronic transcripts, whose native structures remain unexplored, leaving fundamental molecular determinants of mitochondrial gene expression unknown. To address this gap, we developed a mitoDMS-MaPseq approach and used DREEM clustering to resolve the native human mitochondrial mt-mRNA structurome. We gained insights into mt-mRNA biology and translation regulatory mechanisms, including a unique programmed ribosomal frameshifting for the ATP8/ATP6 transcript. Furthermore, absence of the mt-mRNA maintenance factor LRPPRC led to a mitochondrial transcriptome structured differently, with specific mRNA regions exhibiting increased or decreased structuredness. This highlights the role of LRPPRC in maintaining mRNA folding to promote mt-mRNA stabilization and efficient translation. In conclusion, our mt-mRNA folding maps reveal novel mitochondrial gene expression mechanisms, serving as a detailed reference and tool for studying them in different physiological and pathological contexts.

molecular biology↗

bioRxiv2023

Structural rather than catalytic role for mitochondrial respiratory chain supercomplexes

Mammalian mitochondrial respiratory chain (MRC) complexes are able to associate into quaternary structures named supercomplexes (SCs), which normally coexist with non bound individual complexes. The functional significance of SCs has not been fully clarified and the debate has been centered on whether or not they confer catalytic advantages to the non-bound individual complexes. Mitochondrial respiratory chain organization does not seem to be conserved in all organisms. In fact, and differently from mammalian species, mitochondria from Drosophila melanogaster tissues are characterized by low amounts of SCs, despite the high metabolic demands and MRC activity shown by these mitochondria. Here, we show that attenuating the biogenesis of individual respiratory chain complexes was accompanied by increased formation of stable SCs, which are missing in Drosophila melanogaster in physiological conditions. This phenomenon was not accompanied by an increase in mitochondrial respiratory activity. Therefore, we conclude that SC formation is necessary to stabilize the complexes in suboptimal biogenetic conditions, but not for the enhancement of respiratory chain catalysis.

biochemistry↗