Biology subjects

Moschonas, G. D.

Publications and source records attributed to Moschonas, G. D..

6 recordsLinked to original sources

bioRxiv2025

Proximity map for p53 unveils a strong link with PML Nuclear Bodies in HEK293 cells

The tumor suppressor p53 is among the most studied proteins in cancer, with mutations in nearly half of all tumors. Even when TP53 is intact, its regulatory pathways are often disrupted, underscoring its central role in tumorigenesis. To explore how cellular context shapes the subcellular environment of p53, we used BioID proximity labeling in HEK293 cells. These experiments revealed a striking enrichment of proteins involved in SUMOylation and proteins that reside in PML nuclear bodies. A strong enrichment of the adenoviral E1B protein, originally used for transformation of this cell line, may explain this striking observation, and can shed light on the remarkable difference with the proximity map of p53 in the HCT116 colon carcinoma cell line. Strong enrichment of the mediator complex in HCT116, related to active p53-dependent transcription, is missing in 293 cells and can explain the lack of p53 transcriptional activity in these cells. This study emphasizes how cellular transformation can affect the proximal proteome of a key protein in cell cycle control, DNA repair, apoptosis, senescence and metabolism, and confirms previously reported inhibition of p53-dependent transcription by sequestering the protein in PML nuclear bodies.

systems biology↗

bioRxiv2025

TurboID proximity interactome mapping reveals NR2E3 association with AP-1 and retinal developmental complexes

The photoreceptor-specific nuclear receptor NR2E3 is a key transcription factor in the retinal transcriptional network, essential in photoreceptor cell fate and maintenance. Various biallelic loss-of-function variants lead to autosomal recessive inherited retinal disease (IRD), while a single missense variant G56R has been identified to cause autosomal dominant retinitis pigmentosa (adRP). However, a comprehensive understanding of the interactome of NR2E3 remains elusive. Here, we aimed to map the interactome of this nuclear receptor and the G56R pathogenic variant through proximity labelling followed by mass spectrometry. We used the TurboID "T2A split/link design" to identify the proximity interactome of wild-type NR2E3 and mutant G56R-NR2E3 in ARPE-19 cells. Several protein complexes involved in retinal development, including the AP-1 complex, were enriched. The results suggest similar interactomes for NR2E3 and G56R-NR2E3 in ARPE-19. However, BCOR was exclusively enriched in the G56R-NR2E3 network, strengthening the connection with the IRD phenotype. In conclusion, our approach has mapped the proximity interactome of NR2E3 and G56R-NR2E3, revealing interaction with protein complexes involved in (retinal) development.

systems biology↗

bioRxiv2023

Leveraging a self-cleaving peptide for tailored control in proximity labeling proteomics

Protein-protein interactions play an important biological role in every aspect of cellular homeostasis and functioning. Proximity labeling mass spectrometry-based proteomics overcomes challenges typically associated with other methods, and has quickly become the current state-of-the-art in the field. Nevertheless, tight control of proximity labeling enzymatic activity and expression levels is crucial to accurately identify protein interactors. Here, we leverage a T2A self-cleaving peptide and a non-cleaving mutant to accommodate the protein-of-interest in the experimental and control TurboID setup. To allow easy and streamlined plasmid assembly, we built a Golden Gate modular cloning system to generate plasmids for transient expression and stable integration. To highlight our T2A Split-link design, we applied it to identify protein interactions of the glucocorticoid receptor and SARS-CoV-2 nucleocapsid and NSP7 proteins by TurboID proximity labeling. Our results demonstrate that our T2A split-link provides an opportune control that builds upon previously established control requirements in the field. MotivationIn proximity labeling proteomics protein-protein interactions are identified by in vivo biotinylation. However, the current lack of a universally applicable negative control for differential analysis affects accurate mapping of the interactome. To bridge this gap, we conceptualized a system based on the T2A self-cleaving peptide to match expression levels between control and bait protein setups while using the same bait protein. In addition, we implemented a versatile modular cloning system to build mammalian expression vectors for, but not limited to, proximity labeling assays.

biochemistry↗

bioRxiv2023

MX2 restricts HIV-1 and herpes simplex virus-1 by forming cytoplasmic biomolecular condensates that mimic nuclear pore complexes

Human myxovirus resistance 2 (MX2) can potently restrict HIV-1 and herpesviruses at a post-entry step by a process that requires MX2 interaction with the capsids of these viruses. The involvement of other host cell factors in this process, however, remains poorly understood. Here, we mapped the proximity interactome of MX2 revealing strong enrichment of phenylalanine-glycine (FG)-rich proteins related to the nuclear pore complex as well as proteins that are part of cytoplasmic ribonucleoprotein granules. MX2 interacted with these proteins to form multiprotein cytoplasmic biomolecular condensates that were essential for its anti-HIV-1 and -herpes simplex virus-1 (HSV-1) activity. MX2 condensate formation required the disordered N-terminal region of MX2 and its dimerization. Incoming HIV-1 and HSV-1 capsids associated with MX2 at these dynamic cytoplasmic biomolecular condensates. Our results demonstrate that MX2 forms cytoplasmic condensates that act as nuclear pore decoys, which trap capsids and induce premature viral genome release, and thereby interfere with nuclear targeting of HIV-1 and HSV-1.

microbiology↗

bioRxiv2021

Ring Finger Protein 213 Assembles into a Sensor for ISGylated Proteins with Antimicrobial Activity

ISG15 is an interferon-stimulated, ubiquitin-like protein that can conjugate to substrate proteins (ISGylation) to counteract microbial infection, but the underlying mechanisms remain elusive. Here, we used a viral-like particle trapping technology to identify ISG15-binding proteins and discovered Ring Finger Protein 213 (RNF213) as an ISG15 interactor and cellular sensor of ISGylated proteins. RNF213 is a poorly-characterized, interferon-induced megaprotein that is frequently mutated in Moyamoya disease, a rare cerebrovascular disorder. We found that interferon induces ISGylation and oligomerization of RNF213 on lipid droplets, where it acts as a sensor for ISGylated proteins. We showed that RNF213 has broad antimicrobial activity in vitro and in vivo, counteracting infection with Listeria monocytogenes, herpes simplex virus 1 (HSV-1), human respiratory syncytial virus (RSV) and coxsackievirus B3 (CVB3), and we observed a striking co-localization of RNF213 with intracellular bacteria. Together, our findings provide novel molecular insights into the ISGylation pathway and reveal RNF213 as a key antimicrobial effector.

cell biology↗

bioRxiv2021

Drug development of an affinity enhanced, broadly neutralizing heavy chain only antibody that restricts SARS-CoV-2 in hamsters

We have identified camelid single-domain antibodies (VHHs) that cross-neutralize SARS-CoV-1 and -2, such as VHH72, which binds to a unique highly conserved epitope in the viral receptor-binding domain (RBD) that is difficult to access for human antibodies. Here, we establish a protein engineering path for how a stable, long-acting drug candidate can be generated out of such a VHH building block. When fused to human IgG1-Fc, the prototype VHH72 molecule prophylactically protects hamsters from SARS-CoV-2. In addition, we demonstrate that both systemic and intranasal application protects hACE-2-transgenic mice from SARS-CoV-2 induced lethal disease progression. To boost potency of the lead, we used structure-guided molecular modeling combined with rapid yeast-based Fc-fusion prototyping, resulting in the affinity-matured VHH72_S56A-Fc, with subnanomolar SARS-CoV-1 and -2 neutralizing potency. Upon humanization, VHH72_S56A was fused to a human IgG1 Fc with optimized manufacturing homogeneity and silenced effector functions for enhanced safety, and its stability as well as lack of off-target binding was extensively characterized. Therapeutic systemic administration of a low dose of VHH72_S56A-Fc antibodies strongly restricted replication of both original and D614G mutant variants of SARS-CoV-2 virus in hamsters, and minimized the development of lung damage. This work led to the selection of XVR011 for clinical development, a highly stable anti-COVID-19 biologic with excellent manufacturability. Additionally, we show that XVR011 is unaffected in its neutralizing capacity of currently rapidly spreading SARS-CoV-2 variants, and demonstrate its unique, wide scope of binding across the Sarbecovirus clades.

molecular biology↗