Biology subjects

Fernandez, O.

Publications and source records attributed to Fernandez, O..

4 recordsLinked to original sources

bioRxiv2026

A single Omicron mutation reshapes ORF3a-driven host-cell remodelling

SARS-CoV-2 ORF3a remodels host membranes, but the structural basis and metabolic consequences of this process remain unclear. Here, we combine complementary imaging approaches to define ORF3a function at nanometric scale, identifying underlying mechanisms, and determining how Omicron variant rewire this activity. ORF3a from the ancestral Wuhan strain disrupts Golgi cisternae, drives the formation of ORF3a dense vesicles, remodels mitochondrial architecture, and promotes lipid droplet expansion. Multi-omics analyses further reveal selective triacylglycerol accumulation linked to DGAT1 upregulation, which we validate pharmacologically through DGAT1 inhibition. In contrast, Omicron ORF3a variant, despite carrying only the Thr223Ile substitution within the {beta}7-{beta}8 loop at the bottom of the cytosolic domain, induced a dramatic phenotypic shift: ORF3a localizes to multivesicular bodies, preserves Golgi architecture, and fails to induce lipid accumulation. All together, these results identify ORF3a as a regulator of membrane organization and lipid homeostasis, showing how minimal sequence variation rewires host-cell remodelling. Graphical TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/742305v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@135032borg.highwire.dtl.DTLVardef@1633d4borg.highwire.dtl.DTLVardef@4d4115org.highwire.dtl.DTLVardef@1ebdf65_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

An atlas of microtubule lattice parameters regulated through ligand binding to the microtubule stabilizing sites.

Microtubules (MTs) are dynamic cytoskeletal polymers whose lattice architecture regulates force generation, nucleotide hydrolysis, and recognition by motor proteins and microtubule-associated proteins (MAPs). Microtubule-stabilizing agents (MSAs), including taxanes and laulimalide/peloruside-site ligands, suppress depolymerization by binding to defined lattice sites, yet stabilization is not structurally neutral. How ligand chemistry reshapes lattice organization and function remains unresolved. Here, we address three mechanistic questions. First, do distinct ligand classes induce defined lattice states? Using X-ray fiber diffraction, we show that MSAs selectively stabilize two preferred longitudinal conformations, a compact state ([~]4.06 nm monomer rise) and an expanded state ([~]4.17 nm), while modulating lateral organization reflected in shifts in mean MT radius. These axial spacings cluster around discrete values across chemotypes, indicating stabilization of pre-existing conformational minima rather than continuous distortion. Second, are these states interconvertible upon changes in ligand occupancy? Time-resolved diffraction reveals that longitudinal transitions occur within seconds of ligand addition even at substoichiometric occupancy; whereas, lateral equilibration proceeds slower, consistent with redistribution within heterogeneous protofilament organizations. Third, do such structural states alter nucleotide hydrolysis and motor/MAP behavior? Expanded lattices are associated with reduced apparent GTP hydrolysis rates under steady-state assembly conditions and altered kinesin motility, whereas compact lattices preferentially promote tau binding and distinct motor interaction profiles. Together, these findings establish longitudinal lattice conformation as a regulatory parameter and position microtubule-stabilizing agents as chemical tools that bias a dynamic structural landscape with predictable catalytic and transport consequences. Significance statementMicrotubules generate force and support intracellular transport through lattice geometries selectively recognized by motor proteins and microtubule-associated proteins. Microtubule-stabilizing drugs such as taxanes and epothilones are widely used in chemotherapy but can cause neurotoxicity, likely because stabilization alters lattice architecture rather than simply preventing depolymerization. Here, we show that stabilizing ligands bias microtubules between two preferred longitudinal conformations, compact and expanded, that can switch within seconds of binding, while lateral organization adjusts slower. These structural states differentially regulate GTP hydrolysis and recognition by tau and kinesin, linking lattice geometry to catalytic and transport functions. By establishing lattice conformation as a tunable regulatory parameter, this work provides a framework for interpreting drug effects and designing structure-selective stabilizers with improved therapeutic profiles.

biophysics↗

bioRxiv2020

Metabolic profile discriminates and predicts Arabidopsis susceptibility to virus under field conditions

As obligatory parasites, plant viruses alter host cellular metabolism. There is a lack of information on the variability of virus-induced metabolic responses among genetically diverse plants in a natural context with daily changing conditions. To decipher the metabolic landscape of plant-virus interactions in a natural setting, one hundred and thirty-two and twenty-six accessions of Arabidopsis thaliana were inoculated with Turnip mosaic virus (TuMV), in two field experiments over 2 years. The accessions were phenotyped for viral accumulation, above-ground biomass, targeted and untargeted metabolic profiles. The accessions revealed quantitative response to the virus, from susceptibility to resistance. Susceptible accessions accumulate primary and secondary metabolites upon infection, at the cost of hindered growth. Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) revealed that the primary metabolites sucrose, glucose and glutamate discriminate susceptible and resistant accessions. Twenty-one metabolic signatures were found to significantly accumulate in resistant accessions whereas they maintained their growth at the same level as mock-inoculated plants without biomass penalty. Metabolic content was demonstrated to discriminate and to be highly predictive of the susceptibility of inoculated Arabidopsis. The PLS coefficient estimated in the training data set reveals, after cross-validation, a correlation of 0.61 between predicted and true viral accumulation. This study is the first to describe the metabolic landscape of plant-virus interactions in a natural setting and its predictive link to susceptibility. It reveals that, in this undomesticated species and in ecologically realistic conditions, growth and resistance are in a permanent conversation and provides new insights on plant-virus interactions.

plant biology↗

bioRxiv2019

Activation of macrophages by lysophosphatidic acid through the lysophosphatidic acid receptor 1 as a novel mechanism in multiple sclerosis pathogenesis.

Multiple sclerosis (MS) is a neuro-inflammatory disease for which the pathogenesis remains largely unclear. Lysophosphatidic acid (LPA) is an endogenous phospholipid that is involved in multiple immune cell functions and is dysregulated in MS. Its receptor LPA1 is expressed in macrophages and regulates their activation, which is of interest due to the role of macrophage activation in MS in both destruction and repair. In this study, we studied the viable Malaga variant of LPA1-null mutation as well as pharmaceutical inhibition of LPA1 in mice with experimental autoimmune encephalomyelitis (EAE), a model of MS. LPA1 expression was also analyzed in both wild-type EAE mice and MS patient immune cells. The effect of LPA and LPA1 on macrophage activation was studied in human monocyte-derived macrophages. We show that lack of LPA1 activity induces a milder clinical course in EAE, and that Lpar1 expression in peripheral blood mononuclear cells (PBMCs) correlates with onset of relapses and severity in wild-type EAE mice. We see the same over-expression in PBMCs from MS patients during relapse compared to progressive forms of the disease, and in monocyte-derived macrophages after exposure to pro-inflammatory stimuli. In addition, LPA induced a pro-inflammatory-like response in macrophages through LPA1, providing a plausible way in which LPA and LPA1 dysregulation can lead to the inflammation seen in MS. These data show a new mechanism of LPA signaling in the pathogenesis of MS, prompting further research into its use as a therapeutic target biomarker.

neuroscience↗