Biology subjects

Oliva, M. A.

Publications and source records attributed to Oliva, M. A..

6 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↗

bioRxiv2026

Asgard archaeal origin of microtubules

Eukaryotic cells change their shapes, actively segregate their DNA and contain membrane networks, facilitated by a complex cytoskeleton containing actin filaments, microtubules made from tubulin, and other components. These filaments have ancient evolutionary origins since actin- and tubulin-like proteins form prokaryotic cytoskeletons in archaea and bacteria. Bona fide eukaryotic F-actin can be traced back to crenarchaea and Asgard archaea, which are the closest known relatives of eukaryotes. A possible Asgard archaeal origin of microtubules was suggested recently with the discovery of a lokiarchaeon containing AtubAB mini microtubules that share architectural features with their eukaryotic counterparts. Using phylogenetic analyses of metagenomic data, here we report the broad occurrence of tubulins in Asgard archaea. Biochemical and structural analyses showed that one of our newly discovered heimdallarchaeial AtubAB tubulin pairs forms four-protofilament mini-microtubules that show dynamic instability and are inhibited by the tubulin drug maytansine. Our work raises the possibility that microtubule architecture and dynamics evolved in Asgard archaea prior to eukaryogenesis.

cell biology↗

bioRxiv2025

Dissecting structural and functional determinants of microtubule stabilization through guided chemical modulation

Paclitaxel (PTX) is a widely used chemotherapeutic, but its efficacy is limited by peripheral neuropathy, likely due to its structural impact on neuronal microtubules (MTs). To decouple MT stabilization from adverse structural changes, we designed, synthetized and characterized several PTX analogues. Our compound 1b retains PTXs stabilizing activity in vitro and in cells, and the 1b-bound MTs preserve a native-like structure. These facts allowed us to investigate the influence of specific MT structural features on motor proteins behavior and interaction with MT-associated protein Tau. PTX-induced lattice expansion disrupted dynein-mediated retrograde transport and altered kinesin-1 motility. Additionally, PTX reduced Taus initial non-cooperative binding and envelopes growth rate while increasing dwell time and suppressing dynamic binding. In contrast, 1b preserved more physiological Tau dynamics. These findings reveal that MT stabilization and structural modulation can be separated and highlight the functional importance of MT heterogeneity in maintaining neuronal transport and MAP interactions.

molecular biology↗

bioRxiv2021

Crystal structures of taxane-tubulin complexes: Implications for the mechanism of microtubule stabilization by Taxol

Paclitaxel (Taxol(R)) is a taxane and a first-line chemotherapeutic drug that stabilizes microtubules. While the interaction of paclitaxel with microtubules is well described, the current lack of high-resolution structural information on a tubulin-taxane complex precludes a comprehensive description of the binding determinants that affect the drugs mechanism of action. Here, we solved the crystal structure of the core baccatin III moiety of paclitaxel lacking the C13 side chain in complex with tubulin at 1.9 [A] resolution. Based on this information, we engineered two tailor-made taxanes with modified C13 side chains, solved their crystal structures in complex with tubulin, and analyzed their effects along with those of paclitaxel, docetaxel, and baccatin III on the microtubule lattice by X-ray fiber diffraction. We then compared high-resolution structures of ligand-bound tubulin and microtubule complexes with apo forms and used molecular dynamics simulations to understand the consequences of taxane binding to tubulin as well as to simplified protofilament and microtubule-lattice models. Our combined approach sheds light on three mechanistic questions. Firstly, taxanes bind better to microtubules as compared to unassembled tubulin due to a dual structural mechanism: Tubulin assembly is linked to a conformational reorganization of the {beta}M loop, which otherwise occludes ligand access to the taxane site, while the bulky C13 side chains preferentially recognize the microtubule-assembled over the unassembled conformational state of tubulin. Second, the occupancy of the taxane site by a ligand has no influence on the straightness of tubulin protofilaments. Finally, binding of the taxane core to the taxane site displaces the S9-S10 loop of {beta}-tubulin resulting in microtubule expansion. Our results provide detailed new insights into the mechanism of microtubule-stabilization by taxanes.

biophysics↗

bioRxiv2020

Two antagonistic microtubule targeting drugs act synergistically to kill cancer cells

Paclitaxel is a microtubule stabilizing agent and a successful drug for cancer chemotherapy inducing, however, adverse effects. To reduce the effective dose of paclitaxel, we searched for drugs which could potentiate its therapeutic effect. We have screened a chemical library and selected Carba1, a carbazolone, which exerts synergistic cytotoxic effects on tumor cells grown in vitro, when co-administrated with a low dose of paclitaxel. Carba1 targets the colchicine binding-site of tubulin and is a microtubule-destabilizing agent. The Carba1-induced modulation of microtubule dynamics increases the accumulation of fluorescent paclitaxel inside microtubules, providing a mechanistic explanation of the observed synergy between Carba1 and paclitaxel. The synergistic effect of Carba1 with paclitaxel on tumor cell viability was also observed in vivo in xenografted mice. Thus, a new mechanism favoring paclitaxel accumulation in microtubules can be transposed to in vivo mouse cancer treatments, paving the way for new therapeutic strategies combining low doses of microtubule targeting agents with opposite mechanisms of action.

cancer biology↗

bioRxiv2016

A polymerisation-associated conformational switch in FtsZ that enables treadmilling

Bacterial cell division in many organisms involves a constricting cytokinetic ring that is orchestrated by the tubulin-like protein FtsZ. FtsZ forms dynamic filaments close to the membrane at the site of division that have recently been shown to treadmill around the division ring, guiding septal wall synthesis.\n\nHere, using X-ray crystallography of Staphylococcus aureus SaFtsZ we reveal how an FtsZ can adopt two functionally distinct conformations, open and closed. The open form is found in SaFtsZ filaments formed in crystals and also in soluble filaments of E. coli FtsZ as deduced by cryoEM. The closed form is found within several crystal forms of two non-polymerising SaFtsZ mutants and corresponds to many previous FtsZ structures from other organisms.\n\nWe argue that FtsZ undergoes a polymerisation-associated conformational switch. We show that such a switch provides explanations for both how treadmilling may occur within a single-stranded filament, and why filament assembly is cooperative.

microbiology↗