Biology subjects

Perocchi, F.

Publications and source records attributed to Perocchi, F..

7 recordsLinked to original sources

bioRxiv2025

MCUR1-CCDC90B complex is a conserved regulator of metabolic homeostasis

The mitochondrial calcium uniporter regulator 1 (MCUR1) is an evolutionarily conserved protein of the inner mitochondrial membrane1, yet its physiological role has remained elusive. Although initially proposed to function as a subunit of the mitochondrial calcium uniporter complex (MCUC)2-4, emerging evidence suggests that MCUR1 has a broader functional spectrum5-7. Here, we identify a biallelic loss-of-function MCUR1 variant (c.802C>T; p.R268X) in a patient with a progressive neurological phenotype. This mutation leads to loss of MCUR1 protein and exerts a dominant-negative effect on its paralog, CCDC90B. We show that MCUR1 and CCDC90B form a hetero-oligomeric complex whose stability depends on MCUR1. Deletion of MCUR1 and CCDC90B in the fission yeast Schizosaccharomyces pombe, which lacks the MCUC, impairs lipid and amino acid metabolism and causes nitrogen source-dependent growth defects that are rescued by expression of human MCUR1. Patient serum metabolomics confirms an imbalance in the amino acid pool, while MCUR1 deficiency in patient-derived skin fibroblasts upregulates autophagy, perturbs non-essential amino acid metabolism, and limits biosynthetic capacity, resulting in delayed proliferation and migration. These findings redefine the MCUR1-CCDC90B coiled-coil complex as a transmembrane scaffold critical for the integrity of mitochondrial protein complexes and the maintenance of metabolic homeostasis, suggesting a potential link between MCUR1 deficiency and human neurometabolic disease.

cell biology↗

bioRxiv2024

Systematic mapping of MCU-mediated mitochondrial calcium signaling networks

The Mitochondrial Ca2+ Uniporter Channel (MCUC) allows calcium entry into the mitochondrial matrix to regulate energy metabolism but also cell death. Although, several MCUC components have been identified, the molecular basis of mitochondrial Ca2+ signaling networks and their remodeling upon changes in uniporter activity have not been systematically assessed. Using an unbiased and quantitative proteomic approach, we map the MCUC interactome in HEK293 cells under physiological conditions and upon chronic loss or gain of mitochondrial Ca2+ uptake. Besides all previously known subunits of the uniporter, we identify 89 high-confidence interactors linking MCUC to several mitochondrial complexes and pathways, half of which are currently linked to metabolic, neurological, and immunological diseases. As a proof-of-concept, we validate EFHD1 as a binding partner of MCU, EMRE and MCUB with a MICU1-dependent inhibitory effect on Ca2+ uptake. To investigate compensatory mechanisms and functional consequences of mitochondrial Ca2+ dyshomeostasis, we systematically survey the MCU interactome upon silencing of EMRE, MCUB, MICU1 or MICU2. We observe profound changes in the MCU interconnectivity, whereby downregulation of EMRE reduces the number of MCU interactors of over 10-fold, while silencing of MCUB leads to a wider functional network linking MCU to mitochondrial stress response pathways and cell death. Altogether our study provides a comprehensive map of MCUC protein-protein interactions and a rich, high-confidence resource that can be explored to gain insights into the players and mechanisms involved in calcium signal transduction cascades and their relevance in human diseases.

cell biology↗

bioRxiv2020

Adaptive mitochondrial regulation of the proteasome

The proteasome is the main proteolytic system for targeted protein degradation in the cell. Its function is fine-tuned according to cellular needs. Regulation of proteasome function by mitochondrial metabolism, however, is unknown. Here, we demonstrate that mitochondrial dysfunction reduces the assembly and activity of the 26S proteasome in the absence of oxidative stress. Impaired respiratory complex I function leads to metabolic reprogramming of the Krebs cycle and deficiency in aspartate. Aspartate supplementation activates assembly and activity of 26S proteasomes via transcriptional activation of the proteasome assembly factors p28 and Rpn6. This metabolic adaptation of 26S proteasome function involves sensing of aspartate via the mTORC1 pathway. Metformin treatment of primary human cells similarly reduced assembly and activity of 26S proteasome complexes, which was fully reversible and rescued by supplementation of aspartate or pyruvate. Of note, respiratory dysfunction conferred resistance towards the proteasome inhibitor Bortezomib. Our study uncovers a fundamental novel mechanism of how mitochondrial metabolism adaptively adjusts protein degradation by the proteasome. It thus unravels unexpected consequences of defective mitochondrial metabolism in disease or drug-targeted mitochondrial reprogramming for proteasomal protein degradation in the cell. As metabolic inhibition of proteasome function can be alleviated by treatment with aspartate or pyruvate, our results also have therapeutic implications.

cell biology↗

bioRxiv2020

Discovery of EMRE in fungi resolves the true evolutionary history of the mitochondrial calciumuniporter

Mitochondrial calcium (mt-Ca2+) uptake is central for the regulation of numerous cellular processes in eukaryotes1. This occurs through a highly selective Ca2+ uniporter located at the inner mitochondrial membrane and driven by the membrane potential2-4. While the physiological role of the uniporter was extensively studied for decades, its genetic identity was only recently determined, with MCU5,6, MICU17 and EMRE8 constituting pore-forming and regulatory subunits. Preliminary evolutionary analyses suggested an ancient eukaryotic origin of mt-Ca2+ uptake, but also pinpointed inconsistent phylogenetic distributions of MCU, MICU1, and EMRE within fungi, where homologs of MCU were present in the absence of the supposedly essential regulators, MICU1 and EMRE9,10. Here, we perform the most comprehensive phylogenomic analysis of the mt-Ca2+ uptake system and trace its evolution across 1,156 fully-sequenced eukaryotes. In contrast to earlier assumptions9-11 we find compelling evidence that previously identified animal and fungal MCUs, the targets of several structural and functional efforts11-16, represent two distinct paralogous subfamilies originating from an ancestral duplication. We further uncover a complete "animal-like" uniporter complex within chytrid fungi, including bona-fide orthologs of MCU, MICU1, and EMRE. This first identification of EMRE outside Holozoa (animals and their unicellular relatives) and its strong coevolution with "animal-like" MICU1 and MCU indicates that these three components formed the core of the ancestral opisthokont uniporter. We confirm this finding experimentally, by showing that chytrid EMRE orthologs in combination with either human or "animal-like" MCUs, but not with "fungal-specific" MCUs, can reconstitute mt-Ca2+ uptake in vivo in the yeast Saccharomyces cerevisiae. Hence, we here solve a purported evolutionary paradox: the presence of MCU homologs in fungal species devoid of other uniporter components and with no detectable mt-Ca2+ uptake. Altogether, our study clarifies the evolution of the mt-Ca2+ uniporter and identifies new important targets for comparative structural and functional studies.

evolutionary biology↗

bioRxiv2019

mitoXplorer, a visual data mining platform to systematically analyze and visualize mitochondrial expression dynamics and mutations

BackgroundMitochondria produce cellular energy in the form of ATP and are involved in various metabolic and signaling processes. However, the cellular requirements for mitochondria are different depending on cell type, cell state or organism. Information on the expression dynamics of genes with mitochondrial functions (mito-genes) is embedded in publicly available transcriptomic or proteomic studies and the variety of available datasets enables us to study the expression dynamics of mito-genes in many different cell types, conditions and organisms. Yet, we lack an easy way of extracting these data for gene groups such as mito-genes.\n\nResultsHere, we introduce the web-based visual data mining platform mitoXplorer, which systematically integrates expression and mutation data of mito-genes. The central part of mitoXplorer is a manually curated mitochondrial interactome containing [~]1200 genes, which we have annotated in 35 different mitochondrial processes. This mitochondrial interactome can be integrated with publicly available transcriptomic, proteomic or mutation data in a user-centric manner. A set of analysis and visualization tools allows the mining and exploration of mitochondrial expression dynamics and mutations across various datasets from different organisms and to quantify the adaptation of mitochondrial dynamics to different conditions. We apply mitoXplorer to quantify expression changes of mito-genes of a set of aneuploid cell lines that carry an extra copy of chromosome 21. mitoXplorer uncovers remarkable differences in the regulation of the mitochondrial transcriptome and proteome due to the dysregulation of the mitochondrial ribosome in retinal pigment epithelial trisomy 21 cells which results in severe defects in oxidative phosphorylation.\n\nConclusionsWe demonstrate the power of the visual data mining platform mitoXplorer to explore expression data in a focused and detailed way to uncover underlying potential mechanisms for further experimental studies. We validate the hypothesis-creating power of mitoXplorer by testing predicted phenotypes in trisomy 21 model systems. MitoXplorer is freely available at http://mitoxplorer.ibdm.univ-mrs.fr. MitoXplorer does not require installation nor programming knowledge and is web-based. Therefore, mitoXplorer is accessible to a wide audience of experimental experts studying mitochondrial dynamics.

bioinformatics↗

bioRxiv2018

Profound functional and molecular diversity of mitochondria revealed by cell type-specific profiling in vivo

Mitochondria vary in morphology and function in different tissues, however little is known about their molecular diversity among cell types. To investigate mitochondrial diversity in vivo, we developed an efficient protocol to isolate cell type-specific mitochondria based on a new MitoTag mouse. We profiled the mitochondrial proteome of three major neural cell types in cerebellum and identified a substantial number of differential mitochondrial markers for these cell types in mice and humans. Based on predictions from these proteomes, we demonstrate that astrocytic mitochondria metabolize long-chain fatty acids more efficiently than neurons. Moreover, we identified Rmdn3 as a major determinant of ER-mitochondria proximity in Purkinje cells. Our novel approach enables exploring mitochondrial diversity on the functional and molecular level in many in vivo contexts.

cell biology↗

bioRxiv2018

MICU1 modulates MCU ion selectivity and tolerance to manganese stress

The mitochondrial calcium uniporter is a highly selective ion channel composed of species-and tissue-specific structural and regulatory subunits. However, the contribution of each component to uniporter-mediated activity still remains unclear. Here, we employ an evolutionary and synthetic biology approach to investigate the functional inter-dependence between the pore-forming subunit MCU and the EF-hand protein MICU1. Using phylogenetic profiling and genetic complementation analyses, we show that MCU and MICU1 constitute the minimal eukaryotic unit of the uniporter, pointing towards a strong selective pressure behind their co-occurrence. Heterologous reconstitution of MCU-mediated and MICU1-gated mitochondrial calcium entry in vivo in yeast cells demonstrates that MICU1 per se is essential to protect yeast from MCU-dependent manganese cytotoxicity. Accordingly, MICU1 deletion significantly sensitizes human HEK-293 cells to manganese-induced stress. Our study identifies a critical role of MICU1 in the regulation of MCU ion selectivity, with potential implications for patients with MICU1 deficiency.

cell biology↗