Biology subjects

Viola, G.

Publications and source records attributed to Viola, G..

5 recordsLinked to original sources

bioRxiv2024

Quantitative Comparison of Monomeric StayGold Variants Using Protein Nanocages in Living Cells

To standardize comparison of fluorescent proteins and independently determine which monomeric StayGold variant is best for live microscopy, we analyzed fluorescent protein tagged I3-01 peptides that self-assemble into stable sixty subunit dodecahedrons inside live cells. We find mStayGold is 3-fold brighter and 3-fold more photostable compared with EGFP and superior to other monomeric variants in mammalian cytoplasm. In addition, analysis of intracellular nanocage diffusion confirms the monomeric nature of mStayGold.

cell biology↗

bioRxiv2024

Doublecortin reinforces microtubules to promote growth cone advance in soft environments

Doublecortin (DCX) is a microtubule-associated protein critical for brain development. Although most highly expressed in the developing central nervous system, the molecular function of DCX in neuron morphogenesis remains unknown and controversial. We demonstrate that DCX function is intimately linked to its microtubule-binding activity. By using human induced pluripotent stem cell (hiPSC)- derived cortical i3Neurons genome engineered to express mEmerald-tagged DCX from the endogenous locus, we find that DCX-MT interactions become highly polarized very early during neuron morphogenesis. DCX becomes enriched only on straight microtubules in advancing growth cones with approximately 120 DCX molecules bound per micrometer of growth cone microtubule. At a similar saturation, microtubule-bound DCX molecules begin to impede lysosome transport, and thus can potentially control growth cone organelle entry. In addition, by comparing control, DCX-mEmerald and knockout DCX -/Y i3Neurons, we find that DCX stabilizes microtubules in the growth cone peripheral domain by reducing the microtubule catastrophe frequency and the depolymerization rate. DCX -/Y i3Neuron morphogenesis was inhibited in soft microenvironments that mimic the viscoelasticity of brain tissue and DCX -/Y neurites failed to grow toward brain-derived neurotrophic factor (BDNF) gradients. Together with high resolution traction force microscopy data, we propose a model in which DCX-decorated, rigid growth cone microtubules provide intracellular mechanical resistance to actomyosin generated contractile forces in soft physiological environments in which weak and transient adhesion-mediated forces in the growth cone periphery may be insufficient for productive growth cone advance. These data provide a new mechanistic understanding of how DCX mutations cause lissencephaly-spectrum brain malformations by impacting growth cone dynamics during neuron morphogenesis in physiological environments.

cell biology↗

bioRxiv2022

A first-in-class Wiskott-Aldrich syndrome protein (WASp) activator with anti-tumor activity in hematological cancers

Hematological cancers are among the most common cancers in adults and in children. Despite significant improvements in therapies, many patients still succumb to the disease, therefore, novel therapies are needed. The Wiskott-Aldrich syndrome protein (WASp) family proteins regulate actin assembly in conjunction with the Arp2/3 complex, a ubiquitous nucleation factor. WASp is expressed exclusively in hematopoietic cells and exists in two allosteric conformations, auto-inhibited and active conformations. Here, we describe the development of EG-011, a first-in-class small molecule activator of the WASp auto-inhibited form. EG-011 possesses in vitro and in vivo anti-tumor activity as single agent in lymphoma, leukemia and multiple myeloma, including models of secondary resistance to PI3K, BTK and proteasome inhibitors. The in vitro activity was confirmed in a lymphoma xenograft. Actin polymerization induced by EG-011 was demonstrated with multiple techniques. Transcriptome analysis highlighted homology with drugs inducing actin polymerization. Key pointsO_LIEG-011 is a novel small molecule with anti-tumor activity in hematological cancers, including resistant lymphoma and multiple myeloma models C_LIO_LIEG-011 is a first-in-class small molecule activator of the auto-inhibited form of the Wiskott-Aldrich syndrome protein (WASp) C_LI

cancer 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↗

bioRxiv2018

Ask1 and Akt act synergistically to promote ROS-dependent regeneration in Drosophila

The mechanism by which apoptotic cells release signals that induce undamaged neighbor cells to proliferate and regenerate missing parts remains elusive. Oxidative stress originated by dying or damaged cells can be propagated to neighboring cells, which then promote regeneration. We investigated the nature of the stress sensing mechanism by which neighboring cells are recruited. We found that Drosophila apoptosis signal-regulating kinase 1 (Ask1) senses reactive oxygen species (ROS) differently in stressed dying cells and unstressed neighboring cells and this differential sensing is pivotal for tissue repair. In undamaged cells, this activity is attenuated, but not abolished, by Akt1 phosphorylation, which thus acts as a survival signal that results in the tolerable levels of p38 and JNK necessary for regeneration. These observations demonstrate that the non-autonomous activation of the ROS-sensing mechanism by Ask1 and Akt1 in neighboring unstressed cells. Collectively, these results provide the basis for understanding the molecular mechanism of communication between dying and living cells that triggers regeneration.\n\nAuthor summaryOne of the early events that occur after tissue damage is oxidative stress production that signals to initiate wound healing and regeneration. Several signaling pathways, such as JNK and p38, respond to oxidative stress and are necessary for regeneration. We decided to explore the mechanism that links the oxidative stress and the activation of these pathways. We used epithelia of Drosophila to genetically direct cell death in specific zones of the tissue as means of experimentally controlled cell damage. We found that the Ask1 protein, which is sensitive to oxidative stress, is a key player in this scenario. Actually it acts as an intracellular sensor that upon damage activates those signaling pathways. However, high activity of Ask1 can be toxic for the cell. This is controlled by Akt, an enzyme dowstream the insulin pathway, with attenuates the activity of Ask1 to tolerable levels. In conclusion, Ask1 and Akt act synergistically to respond to the stress generated after tissue damage and drive regeneration. In other words, we found that the link between oxidative stress and nutrition is key for tissue regeneration.

developmental biology↗