Biology subjects

Scifo, E.

Publications and source records attributed to Scifo, E..

7 recordsLinked to original sources

bioRxiv2026

Msp1-dependent extraction promotes ubiquitylation of translocation-stalled mitochondrial precursor proteins

The translocase of the outer membrane (TOM complex) imports more than 1,000 proteins into mitochondria. Clogging of the TOM pore with a precursor protein causes proteotoxic stress and eventually cell death. Two quality control pathways remove translocation-stalled precursor proteins. In the mitochondrial protein translocation-associated degradation (mitoTAD), Ubx2 recruits the cytosolic AAA-ATPase Cdc48 to clear precursor proteins from the TOM complex. In the mitochondrial compromised protein import response (mitoCPR), the stress-induced Cis1 recruits the AAA-ATPase Msp1 to Tom70. The role of Msp1 for the removal of mitochondrial precursor proteins remains unknown. Here, we demonstrate that parallel loss of Msp1 and Ubx2 strongly affects removal of precursor proteins and cell viability. Msp1 and Ubx2 bind independently of import stress and Cis1 to the TOM complex to remove a large variety of precursor proteins. Msp1-dependent extraction promotes ubiquitylation of precursor proteins, which in turn allows Ubx2-recruited Cdc48 to transfer the substrates to proteasomal degradation. We conclude that two AAA-ATPases cooperate in mitochondrial precursor quality control. Msp1-dependent extraction from the TOM complex facilitates precursor ubiquitylation and Cdc48-mediated transfer to proteasomal degradation.

molecular biology↗

bioRxiv2026

Nup153 regulates neuronal responsiveness through HDAC1-mediated epigenetic modulation

Neural activity-dependent gene regulation is central to the development of neural networks and neuronal plasticity. Induction of activity-dependent gene programs is equally important as repression of these programs, and both need to be balanced carefully. However, little is known about how repressive mechanisms modulate neuronal responsiveness across the genome before stimulation. Here, we identify nucleoporin-dependent regulation of neuronal responsiveness, in which Nup153 represses neuronal genes including activity-regulated genes (ARGs), in the basal state. By characterizing the genome-wide landscape of chromatin accessibility, histone modifications and Nup153 chromatin binding, we show that Nup153 bidirectionally regulates chromatin states through both basal activity-dependent and -independent mechanisms and influences associated genes. Mechanistically, Nup153 associates with HDAC1 to modulate histone acetylation and chromatin accessibility at target regulatory regions. Our data suggests Nup153 organizes chromatin states that regulate neuronal gene programs involved in maintaining neuronal responsiveness. TeaserNup153 primes neuronal responsiveness through multi-layered epigenetic regulation.

neuroscience↗

bioRxiv2026

The multistep quality control of mitochondrial β-barrel protein import

Mitochondrial {beta}-barrel proteins fulfill essential functions for cell viability including transport of proteins, ions and metabolites across the outer membrane. The translocase of the outer membrane (TOM complex) and the sorting and assembly machinery (SAM complex) transport these proteins into the outer membrane. Although {beta}-barrel proteins are essential for cell viability, the quality control mechanisms that monitor their import into the outer membrane remain unknown. We uncovered that Msp1 and Ubx2-recruited Cdc48 cooperate to remove a SAM-arrested Tom40 variant. Prior to degradation, the {beta}-barrel protein is deposited in cytosolic protein storages, termed MitoStores, to minimize accumulation of aberrant proteins in the cell. The cytosolic AAA ATPase Hsp104 disaggregates these proteins to facilitate their proteasomal degradation. Altogether, mitochondrial and cytosolic factors cooperate to degrade translocation-arrested mitochondrial {beta}-barrel proteins.

molecular biology↗

bioRxiv2025

Manipulation of the Extracellular Vesicle Biogenesis Pathway in Paternal Somatic Cells Contributes to the Phenotypic Fate of the Next Generation

Human and animal studies have shown that risk factors for certain diseases are linked to our fathers physiological and psychological condition. So far, mainly in vitro evidence indicates extracellular vesicles (EVs) as one of the potential mediators of these paternal effects. In a full in vivo model system, we demonstrate that targeting the EV biogenesis pathway within somatic cells of the male Drosophila melanogaster reproductive tract induces sex-specific phenotypic changes in the progeny. These findings highlight the critical role of the EV pathway in paternal somatic cells in shaping the phenotypic destiny of the next generation and underscore the necessity for further investigations into the mechanisms of somatic to germline information transfer.

physiology↗

bioRxiv2023

TMEM65-dependent Ca2+ extrusion safeguards mitochondrial homeostasis

The bidirectional transport of Ca2+ into and out of mitochondria is a conserved biological process controlling multiple events, including metabolism, signaling, and cell fate. In the presence of membrane potential driving mitochondrial Ca2+ accumulation, transient changes of [Ca2+]mt in response to cytosolic [Ca2+] variations are ensured by a molecular machinery for Ca2+ influx and efflux embedded in the inner mitochondrial membrane (IMM). While it is well established that influx relies on the Mitochondrial Calcium Uniporter (MCU), efflux was expected to be molecularly diversified, given the occurrence of functionally different exchange pathways with either Na+ or H+1. Accordingly, dedicated transporters ensure proper Ca2+ homeostasis and tightly regulated mitochondrial bioenergetics, but the process is not yet fully elucidated. We here demonstrate that TMEM65, a protein with an unknown biological function, is a fundamental component of the Ca2+ efflux machinery of mitochondria. As the MCU, TMEM65 has a broad tissue expression and localizes to the IMM. Its overexpression dramatically enhances Na+- and Li+-dependent mitochondrial Ca2+ extrusion, which is abrogated by the pharmacological inhibitor CGP-37157. Conversely, its downregulation chronically elevates resting mitochondrial Ca2+ levels and inhibits efficient Ca2+ efflux upon cellular activation, culminating in mitochondrial calcium overload and causing organelle dysfunction. Since TMEM65 has been associated with a severe human mitochondrial disease2, we deleted the TMEM65 homologues in Caenorhabditis elegans (CeTMEM65). While the two CeTMEM65 orthologs are dispensable for the survival at permissive growing conditions, their loss undermines embryonic developments when eggs are exposed to mild temperature-stress. In this regard, we find that CeTMEM65 (null) alleles cause necrotic lesions that are suppressed by inhibiting the mitochondrial calcium uniporter MCU-1. Overall, these results unambiguously assign a primary role in mitochondrial Ca2+ homeostasis to the orphan protein TMEM65. More importantly, our findings describe a novel molecular component that may be relevant in pathological settings in which excessive mitochondrial Ca2+ accumulation critically contribute to degenerative pathways.

biochemistry↗

bioRxiv2022

Deep Phenotyping and Lifetime Trajectories Reveal Limited Effects of Longevity Regulators on the Aging Process in C57BL/6J Mice

Current concepts regarding the biology of aging are based on studies aimed at identifying factors regulating natural lifespan. However, lifespan as a sole proxy measure for aging can be of limited value because it may be restricted by specific sets of pathologies, rather than by general physiological decline. Here, we employed large-scale phenotyping to analyze hundreds of phenotypes and thousands of molecular markers across tissues and organ systems in a single study of aging male C57BL/6J mice. For each phenotype, we established lifetime profiles to determine when age-dependent phenotypic change is first detectable relative to the young adult baseline. We examined central genetic and environmental lifespan regulators (putative anti-aging interventions, PAAIs; the following PAAIs were examined: mTOR loss-of-function, loss-of-function in growth hormone signaling, dietary restriction) for a possible countering of the signs and symptoms of aging. Importantly, in our study design, we included young treated groups of animals, subjected to PAAIs prior to the onset of detectable age-dependent phenotypic change. In parallel to our studies in mice, we assessed genetic variants for their effects on age-sensitive phenotypes in humans. We observed that, surprisingly, many PAAI effects influenced phenotypes long before the onset of detectable age-dependent changes, rather than altering the rate at which these phenotypes developed with age. Accordingly, this subset of PAAI effects does not reflect a targeting of age-dependent phenotypic change. Overall, our findings suggest that comprehensive phenotyping, including the controls built in our study, is critical for the investigation of PAAIs as it facilitates the proper interpretation of the mechanistic mode by which PAAIs influence biological aging. HighlightsO_LIPhenotyping at scale defines lifetime trajectories of age-dependent changes in C57BL/6J mice C_LIO_LICentral genetic and environmental lifespan regulators (putative anti-aging interventions; PAAIs) influence age-sensitive phenotypes (ASPs) often long before the appearance of age-dependent changes in these ASPs C_LIO_LICorresponding genetic variants in humans also have age-independent effects C_LIO_LIMany PAAI effects shift the baseline of ASPs rather than slowing their rate of change C_LI

physiology↗

bioRxiv2020

Comparative profiling of N-respirasomes predicts aberrant mitochondrial bioenergetics at single-cell resolution

AO_SCPLOWBSTRACTC_SCPLOWMitochondria sustain the energy demand of the cell. The composition and functional state of the mitochondrial oxidative phosphorylation system are informative indicators of organelle homeostasis and bioenergetic capacity. Here we describe a highly sensitive and reproducible method for single-cell visualization and quantification of mitochondrial respiratory supercomplexes as a novel means of measuring mitochondrial respiratory chain integrity. We apply a proximity ligation assay (PLA) and perform comparative studies of mitochondrial CI, CIII and CIV-containing supercomplexes (or N-respirasomes) in fixed human and mouse brain tissues, tumorigenic cells, iPSCs and iPSC-derived NPCs and neurons. Our optimized approach enables a quantitative in-situ assessment of even subtle mitochondrial lesions associated with aberrant respiration. By combining quantitative proteomics with single cell imaging analysis, we also report the mechanistic contribution of the MICOS complex subunit CHCHD3 in regulating N-respirasomes. Overall, our PLA-based profiling of N-respirasomes establishes a sensitive and complementary technique for detecting cell-type specific mitochondrial perturbations in fixed materials.

cell biology↗