Biology subjects

Destefanis, F.

Publications and source records attributed to Destefanis, F..

3 recordsLinked to original sources

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↗

bioRxiv2023

NOC1 is a Direct MYC Target, and Its Protein Interactome Dissects Its Activity in Controlling Nucleolar Function

The nucleolus is a subnuclear compartment critical in ribosome biogenesis and cellular stress responses. These mechanisms are governed by a complex interplay of proteins, including NOC1, a member of the NOC family of nucleolar proteins responsible for controlling rRNA processing and ribosomal maturation. This study reveals a novel relationship between NOC1 and MYC transcription factor, known for its crucial role in controlling ribosomal biogenesis, cell growth, and proliferation. Here, we demonstrate that NOC1 functions as a direct target of MYC, as it is transcriptionally induced through a functional MYC-binding E-box sequence in the NOC1 promoter region. Furthermore, protein interactome analysis reveals that NOC1-complex includes the nucleolar proteins NOC2 and NOC3 and other nucleolar components such as Nucleostemin1 Ns1 transporters of ribosomal subunits and components involved in rRNA processing and maturation. In response to MYC, NOC1 expression and localization within the nucleolus significantly increase, suggesting a direct functional link between MYC activity and NOC1 function. Notably, NOC1 over-expression leads to the formation of large nuclear granules and enlarged nucleoli, which co-localize with nucleolar fibrillarin and Ns1. Additionally, we demonstrate that NOC1 expression is necessary for Ns1 nucleolar localization, suggesting a role for NOC1 in maintaining nucleolar structure. Finally, the co-expression of NOC1 and MYC enhances the formation of abnormal structures formed by NOC1 within the nucleolus, outlining another aspect of NOC1 and MYC cooperation in nucleolar dynamics. This study also reveals an enrichment with NOC1 with few proteins involved in RNA processing, modification, and splicing. Moreover, proteins such as Ythdc1, Flacc, and splenito are known to mediate N6-methyladenosine (m6A) methylation of mRNAs in nuclear export, revealing NOC1s potential involvement in coordinating RNA splicing and nuclear mRNA export. In summary, we uncovered novel roles for NOC1 in nucleolar homeostasis and established its direct connection with MYC in the network governing nucleolar structure and function. These findings also highlight NOC1s interaction with proteins relevant to specific RNA functions, suggesting a broader role in addition to its control of nucleolar homeostasis and providing new insight that can be further investigated.

cell biology↗

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↗