Biology subjects

Lombardi, S.

Publications and source records attributed to Lombardi, S..

3 recordsLinked to original sources

bioRxiv2026

PGM3 inhibition rewires RUVBL2-dependent DNA repair and induces a BRCAness-like state in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) exhibits profound metabolic rewiring and strong resistance to DNA-damaging therapies, yet how metabolic pathways regulate genome maintenance remains poorly understood. The hexosamine biosynthetic pathway (HBP) integrates nutrient availability with protein glycosylation through production of UDP-GlcNAc, but its role in DNA damage response (DDR) regulation is unclear. Here we show that inhibition of the HBP enzyme phosphoglucomutase-3 (PGM3) reduces DNA repair capacity in pancreatic cancer cells. Transcriptomic and functional analyses reveal that the selective PGM3 inhibitor FR054 amplifies gemcitabine-induced replication stress, disrupts ATR-CHK1 and ATM-CHK2 checkpoint signaling, and selectively impairs homologous recombination. Glycoproteomic profiling identifies the AAA+ ATPase RUVBL2 as a key metabolic-DDR node. Gemcitabine increases RUVBL2 O-GlcNAcylation, with Thr81 identified as a modified residue within the Walker A nucleotide-binding motif. Structural modelling predicts that Thr81 O-GlcNAcylation stabilizes the RUVBL1-RUVBL2 complex without compromising ATP-Mg engagement. PGM3 inhibition and Thr81 mutation similarly reduced ATR and ATM abundance and promoted persistent DNA damage, supporting a role for RUVBL2 Thr81 O-GlcNAcylation in sustaining checkpoint signalling and genome stability. Consequently, PGM3 inhibition induces a BRCAness-like state that sensitizes pancreatic cancer cells to PARP inhibition, both in vitro and in vivo, as well as to ionizing radiation. These findings reveal a nutrient-sensitive mechanism linking protein glycosylation to genome maintenance and identify HBP-dependent DNA repair as a potentially actionable vulnerability in pancreatic cancer.

cancer biology↗

bioRxiv2026

Nuclear DNA damage is a primary driver of mitochondrial dysfunction in C9ORF72 ALS/FTD

Amyotrophic lateral sclerosis (ALS) is characterized by progressive motor neuron degeneration associated with genomic instability and mitochondrial dysfunction, although the mechanistic relationship between these hallmarks remains unclear. To determine whether nuclear DNA damage alone induces mitochondrial dysfunction, we exploited the AID-DIvA system, selectively generating DNA double-strand breaks (DSBs) in nuclear DNA. DSB induction caused early impairment of mitochondrial bioenergetics, including reduced basal respiration, ATP-linked respiration, and maximal respiratory capacity, preceding more pronounced mitochondrial alterations, after prolonged damage. Resolution of DSBs restored mitochondrial function, demonstrating a direct and reversible link between nuclear genome instability and mitochondrial dysfunction. Mechanistically, persistent activation of the DNA damage response (DDR) triggered PARP1-dependent NAD{square} depletion, while PARP1 inhibition rescued mitochondrial respiration and ATP synthesis. We next investigated the consequences of DDR activation triggered by the expression of 102 (G4C2) repeats in an inducible cell model of C9ORF72-linked ALS. In these cells, DDR activation preceded mitochondrial dysfunction, recapitulating the sequence observed in AID-DIvA cells. Mitochondrial defects included impaired oxidative phosphorylation and reduced ATP production without increased mitochondrial ROS, suggesting that DNA damage signalling acts upstream of mitochondrial dysfunction. In support of this hypothesis, inhibition of ATM as well as nicotinamide riboside-mediated replenishment of cellular NAD+significantly restored mitochondrial functions. Collectively, our findings identify nuclear DNA damage as a trigger of mitochondrial dysfunction and uncover a pathogenic DDR-mitochondria crosstalk mediated by persistent DNA damage signalling. These results support a bidirectional relationship between genome instability and mitochondrial dysfunction and highlight mitochondrial and DNA damage response modulators as potential therapeutic targets for ALS and related neurodegenerative disorders.

cell biology↗

bioRxiv2025

Spatial transcriptomic profiling uncovers the molecular effects of the neurotoxicant polychlorinated biphenyls (PCBs) in the brains of adult mice

Environmental toxicants, such as polychlorinated biphenyls (PCBs), are highly stable synthetic organic compounds that are present in air, water, and soil. PCBs have been identified in post-mortem human brains of individuals with neurodegenerative diseases, indicating a possible link between environmental factors and disease risk. Research has revealed an association between PCB exposure and cognitive decline. Therefore, it is crucial to evaluate how PCB mixtures relevant to humans affect brain function and cognition. To investigate the effects of PCBs on memory and transcriptomic profiles, we exposed adult male C57BL/6J mice orally to a synthetic PCB mixture daily. After seven weeks of exposure, the mice were assessed in a spatial object recognition task (SOR) to evaluate long-term spatial memory. Our findings showed that mice exposed to PCBs exhibited deficits in long-term spatial memory. To examine the molecular effects of PCB on the brain, we used a spatial transcriptomics technique to analyze gene expression changes in five brain regions: the hippocampus, neocortex, thalamus, caudal putamen, and fiber tracts. Our analysis of spatial gene expression revealed the molecular signatures influenced by PCB in these susceptible brain regions of mice. Network analysis suggests that these changes are associated with higher chlorinated PCBs present in the brain. Additionally, we show that PCB exposure disrupts the expression of tight junction proteins, which are crucial for maintaining the integrity of the blood-brain barrier (BBB). Thus, our results offer mechanistic insights into how PCB exposure affects brain function and cognition.

neuroscience↗