Biology subjects

Bellosta, P.

Publications and source records attributed to Bellosta, P..

7 recordsLinked to original sources

bioRxiv2026

POSH (Plenty of SH3): a novel genetic modifier of Myc function in Drosophila

Abstract: MYC is a conserved transcriptional regulator that coordinates cellular growth, metabolism, and tissue homeostasis through a broad network of downstream effectors. However, the signaling components that translate MYC activity into specific cellular responses remain incompletely defined. Here, using Drosophila melanogaster, we identify Plenty of SH3s (POSH), a conserved RING-domain scaffold protein and regulator of JNK signaling, as a novel genetic interactor of Myc. POSH was identified in a genetic screen for modifiers of a Myc-dependent phenotype in the developing eye. The interaction was independently confirmed using a UAS-Posh transgene. Quantitative analysis showed that reduced Myc primarily decreased ommatidial size, whereas POSH expression predominantly reduced ommatidial number, with this effect becoming more pronounced in Myc-sensitized backgrounds. Myc overexpression also increased Posh transcript levels, and the Posh regulatory region contains a canonical E-box motif, supporting a functional relationship between the two genes while leaving open the question of whether Posh is a direct Myc transcriptional target. Co-expression experiments further revealed a strong morphological interaction between Myc and POSH in the adult eye. Together, these findings identify POSH as a previously unrecognized genetic modifier of Myc function in Drosophila and provide a framework for investigating how Myc interfaces with stress-responsive signaling pathways during tissue development.

genetics↗

bioRxiv2026

Glutaminase contributes to MYC-induced cell-autonomous autophagy and to RasV12-dependent non-autonomous autophagy in the Drosophila wing disc epithelium

MYC-driven metabolic reprogramming supports rapid cell growth but also creates metabolic demands that require adaptive mechanisms to maintain cellular homeostasis. Here, combining clonal analysis in Drosophila wing imaginal discs with studies in Schneider S2 cells, we identify glutamine metabolism as a component of Myc-induced autophagy. Myc increased the expression of genes involved in glutamine utilization, including glutaminase (GLS), and enhanced ammonia production, a metabolic by-product of glutaminolysis. Genetic depletion of GLS in clones suppressed the accumulation of Myc-induced Atg8a-positive structures and reduced autophagic flux, demonstrating that glutaminase contributes to the autophagic response elicited by Myc. Exogenous NHCl was sufficient to induce Atg8a-positive structures and partially restored their accumulation following GLS depletion, supporting ammonia as a downstream contributor to this response. Mechanistically, Myc-induced autophagy in clones required the core autophagy factor Atg5 but was not suppressed by depletion of Rheb or Atg1, consistent with an autophagic program that can operate independently of canonical TOR-Atg1 signaling. We further found that Myc activity is required for RasV12-driven epithelial overgrowth and that RasV12 cells induce a pronounced non-cell-autonomous accumulation of Atg8a-positive structures in wild-type cells surrounding RasV12 clones. Depletion of either Myc or GLS in RasV12 cells strongly reduced this neighboring autophagic response, linking Myc-dependent glutamine metabolism in transformed cells to autophagy in the surrounding tissue. Together, our findings identify GLS-dependent glutamine metabolism as a previously unrecognized component of Myc-induced autophagy and extend this relationship to Ras-transformed epithelia, where Myc and Gls contribute to non-cell-autonomous autophagic responses in neighboring cells.

cell biology↗

bioRxiv2025

Isoform-Specific Activation of p53B and p53C in Response to Nucleolar Stress in Drosophila wing imaginal discs

Disruption of ribosome biogenesis triggers nucleolar stress, a conserved cellular response that activates p53. We previously demonstrated that depletion of Nucleolar Complex Protein 1 (Noc1) in Drosophila wing imaginal discs impairs rRNA maturation and ribosome assembly, resulting in elevated p53 levels and apoptosis, hallmarks of nucleolar stress. The Drosophila p53 gene produces four mRNA isoforms, yet their individual contributions to nucleolar stress responses remain poorly understood. Using newly designed isoform-specific qPCR primers, we found that although all p53 isoforms exhibit moderate transcriptional changes following Noc1 reduction, the truncated isoform p53E is robustly and preferentially upregulated. Notably, p53E lacks the N-terminal transactivation domain and has been reported to negatively regulate p53-induced apoptosis in specific tissues. Furthermore, our analyses indicate that {gamma}-H2AV accumulation arises from caspase-dependent apoptosis rather than primary genomic lesions, suggesting the activation of a p53-dependent stress pathway distinct from canonical genotoxic pathways. Together, these findings suggest that p53E may be part of a novel mechanism activated during nucleolar stress, providing insight into how cells adapt to defects in ribosome biogenesis.

genetics↗

bioRxiv2023

A Novel Drosophila Model to Investigates Adipose Tissue Macrophage Infiltration (ATM) and Obesity highlights the Therapeutic Potential of Attenuating Eiger/TNF Signaling to Ameliorate Insulin Resistance and ATM.

Obesity is a global health concern associated with various metabolic disorders including insulin resistance and adipose tissue inflammation characterized by adipose tissue macrophage (ATM) infiltration. In this study, we present a novel Drosophila model to investigate the mechanisms underlying ATM infiltration and its association with obesity-related pathologies. Furthermore, we demonstrate the therapeutic potential of attenuating Eiger/TNF signaling to ameliorate insulin resistance and ATM. To study ATM infiltration and its consequences, we established a novel Drosophila model (OBL) that mimics key aspects of human adipose tissue and allows for investigating ATM infiltration and other related metabolic disorders in a controlled experimental system. We employed genetic manipulation to reduce ecdysone levels to prolong the larval stage. These animals are hyperphagic, and exhibit features resembling obesity in mammals, including increased lipid storage, adipocyte hypertrophy, and high levels of circulating glucose. Moreover, we observed a significant infiltration of immune cells (hemocytes) in the fat bodies accompanied by insulin resistance and systemic metabolic dysregulation. Furthermore, we found that attenuation of Eiger/TNF signaling and using metformin and anti-oxidant bio-products like anthocyanins led to a reduction in ATM infiltration and improved insulin sensitivity. Our data suggest that the key mechanisms that trigger immune cell infiltration into adipose tissue are evolutionarily conserved and may provide the opportunity to develop Drosophila models to better understand pathways critical for immune cell recruitment into adipose tissue, in relation to the development of insulin resistance in metabolic diseases such as obesity and type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD). We believe that our OBL model can also be a valuable tool and provide a platform either to perform genetic screens or to test the efficacy and safety of novel therapeutic interventions for these diseases.

physiology↗

bioRxiv2021

Nucleolar NOC1 controls protein synthesis and cell competition in Drosophila

NOC1 is a nucleolar protein necessary in yeast for both transport and maturation of ribosomal subunits. Here we show that in Drosophila NOC1 is essential for the correct animal development, and that its ubiquitous downregulation results in small larvae with reduced polysome abundance and decreased protein synthesis. NOC1 expression in multiple organs, such as the prothoracic gland and the fat body, is necessary for proper organ functioning. Reduction of NOC1 in clones from the imaginal discs results in small clones with cells that die by apoptosis, an event that is partially rescued using a M/+ background, suggesting that reduction of NOC1 causes the cells to acquire a loser state. This event was supported also by an increase in the transcription of Xrp1 and by activation of the pro-apoptotic eiger-JNK pathway, resulting in the upregulation of DILP8 as an indication of cellular damage. Here, we show that Drosophila NOC1 is important in the control of pre-rRNAs maturation and essential step in the regulation of ribosome biogenesis and its downregulation results in defects in growth and in cell competition, highlighting its novel function in this field. summary statementNOC1 is a nucleolar protein necessary for protein synthesis and ribosomal assembling. Its modulation induces cell competition and affects animal growth.

cell biology↗

bioRxiv2020

The discovery, distribution and diversity of DNA viruses associated with Drosophila melanogaster in Europe

Drosophila melanogaster is an important model for antiviral immunity in arthropods, but very few DNA viruses have been described from the family Drosophilidae. This deficiency limits our opportunity to use natural host-pathogen combinations in experimental studies, and may bias our understanding of the Drosophila virome. Here we report fourteen DNA viruses detected in a metagenomic analysis of approximately 6500 pool-sequenced Drosophila, sampled from 47 European locations between 2014 and 2016. These include three new Nudiviruses, a new and divergent Entomopox virus, a virus related to Leptopilina boulardi filamentous virus, and a virus related to Musca domestica salivary gland hypertrophy virus. We also find an endogenous genomic copy of Galbut virus, a dsRNA Partitivirus, segregating at very low frequency. Remarkably, we find that Drosophila Vesanto virus, a small DNA virus previously described as a Bidnavirus, may be composed of up to 12 segments and represent a new lineage of segmented DNA viruses. Two of the DNA viruses, Drosophila Kallithea nudivirus and Drosophila Vesanto virus are relatively common, found in 2% or more of wild flies. The others are rare, with many likely to be represented by a single infected fly. We find that virus prevalence in Europe reflects the prevalence seen in publicly-available datasets, with Drosophila Kallithea nudivirus and Drosophila Vesanto virus the only ones commonly detectable in public data from wild-caught flies and large population cages, and the other viruses being rare or absent. These analyses suggest that DNA viruses are at lower prevalence than RNA viruses in D. melanogaster, and may be less likely to persist in laboratory cultures. Our findings go some way to redressing an earlier bias toward RNA virus studies in Drosophila, and lay the foundation needed to harness the power of Drosophila as a model system for the study of DNA viruses.

microbiology↗

bioRxiv2019

Glutamine Synthetase-1 induces autophagy-lysosomal degradation of Huntingtin aggregates and ameliorates animal motility in a Drosophila model for HD

Glutamine Synthetase1 (GS1) is an enzyme that catalyzes the ATP-dependent synthesis of L-glutamine from L-glutamate and ammonia as a key element of the glutamate glutamine cycle, a complex physiological process occurring between glia and neurons, necessary to control the homeostasis of glutamate. Using a Drosophila model for Huntingtons disease, we report that expression of GS1 in neurons ameliorates the motility defects of animals expressing the mutant Httex1-Q93 form of the huntingtin gene. At the cellular level, expression of GS1 increases the basal level of autophagy and significantly reduces the size of the toxic Htt-Q93 protein aggregates. In addition, we found that expression of GS1 prevents TOR localization at the lysosomal membrane and reduction in the phosphorylation of its effector S6K. This study reveals a novel function for GS1 in neurons linking its activity to the inhibition of TOR signaling and autophagy. The identification of novel pharmacological regulators of autophagy is of particular interest considering its beneficial role in controlling neuronal health and counteracting the detrimental effects of toxic aggregates of proteinopathies including Huntingtons disease.

cell biology↗