Biology subjects

Vial, A.

Publications and source records attributed to Vial, A..

3 recordsLinked to original sources

bioRxiv2026

Serum modulates the aggregation - toxicity landscape of the staphylococcal toxin PSMα3

The pathogenicity of Staphylococcus aureus relies on the secretion of various toxins, including phenol-soluble modulins 3 (PSM3), which play key roles in invasion and infection through its cytolytic activities. Recent controversies have focused on whether PSM3 propensity to self-assemble into unique amyloid-like cross- structures would underlie its high cytotoxicity. Here, by integrating Thioflavin T fluorescence, electron microscopy, and cell-based assays, we demonstrate that early soluble entities formed upon fibrillation - rather than mature fibrils - drive PSM3 cytotoxicity under near-physiological conditions. This mirrors the behavior of neurodegenerative disease related peptides, thus pointing towards a general mechanism of toxicity by amyloid forming peptides. Importantly, we elucidate the critical role of serum in this process: lipoproteins inhibit the formation of oligomeric and fibrillar entities, both in a time- and concentration-dependent manner, thereby drastically reducing cytotoxicity. We further reveal the uptake of such soluble entities in cells, where membrane interactions likely initiate and trigger cell death. These findings reconcile conflicting interpretations of PSM3 toxicity, highlighting the importance of the cellular environment in shaping peptide aggregation and biological function. By targeting such key virulence determinants, e.g. though the rational design of aggregation inhibitors, this study could open novel avenues in the quest for novel drugs against S. aureus infections.

biophysics↗

bioRxiv2024

N-formylation modifies membrane damage associated to PSMα3 interfacial fibrillation

The virulence of Staphylococcus aureus, a multi-drug resistant pathogen, notably depends on the expression of the phenol soluble modulins 3 (PSM3) peptides, able to self-assemble into amyloid-like cross- fibrils. Despite remarkable advances evidencing the crucial, yet insufficient, role of fibrils in PSM3 cytotoxic activities towards host cells, the relationship between its molecular structures, assembly propensities, and modes of action remains an open intriguing problem. In this study, combining Atomic Force Microscopy (AFM) imaging and infrared spectroscopy, we first demonstrated in vitro that the charge provided by the N-terminal capping of PSM3 alters its interactions with model membranes of controlled lipid composition, without compromising its fibrillation kinetics or morphology. N-formylation eventually dictates PSM3 - membrane binding via electrostatic interactions with the lipid head groups. Furthermore, PSM3 insertion within the lipid bilayer is favoured by hydrophobic interactions with the lipid acyl chains, only in the fluid-phase of membranes, and not in the gel-like ordered domains. Strikingly, our real-time AFM imaging emphasizes how intermediate protofibrillar entities, formed along PSM3 self-assembly and promoted at the membrane interface, likely disrupt membrane integrity via peptide accumulation, and subsequent membrane thinning in a peptide concentration and lipid-dependent manner. Overall, our multiscale and multimodal approach sheds new light on the key roles of N-formylation and intermediate self-assembling entities, rather than mature fibrils, in dictating deleterious interactions of PSM3 with specific membrane lipids, likely underscoring its ultimate cellular toxicity in vivo, and in turn S. aureus pathogenesis.

biophysics↗

bioRxiv2022

Structure and mechanics of the human Nuclear Pore Complex basket

Nuclear pore complexes (NPCs) are the only gateways between the nucleus and cytoplasm in eukaryotic cells. They restrict free diffusion to molecules below 5 nm while facilitating the active transport of selected cargoes, sometimes as large as the pore itself. This versatility implies an important pore plasticity. Recently, cryo-EM and AI-based protein modeling revealed with acute precision how most NPC constituents are arranged. But the basket, a fish trap-like structure capping the nucleoplasmic side of the pore, remains the missing piece in this puzzle. Here by Atomic Force Microscopy (AFM) coupled to Single Molecule Localization Microscopy (SMLM) we revealed that the basket is very soft and explores a large conformational landscape: apart from its canonical shape, it dives into the central pore channel or opens, with filaments reaching to the pore sides. Our observations enlighten how this structure can adapt and let morphologically diverse cargoes shuttling through NPCs.

biophysics↗