Biology subjects

Barnea, E.

Publications and source records attributed to Barnea, E..

6 recordsLinked to original sources

bioRxiv2026

Structural and Functional Plasticity of the Staphylococcus aureus Virulence-Associated Amyloid Peptide PSMα1

Phenol-soluble modulin 1 (PSM1) is a cytolytic peptide secreted by Staphylococcus aureus that contributes to host-cell damage and biofilm stability, yet the relationship between its assembly behavior and function remains incompletely understood. Here, we combine cellular assays, molecular spectroscopy, and high-resolution structural approaches to elucidate how environmental conditions govern PSM1 activity and supramolecular organization. Live-cell imaging and cytotoxicity assays show that PSM1 accumulates at the plasma membrane of human cells prior to membrane permeabilization, linking membrane association to cytotoxic outcomes. This process is strongly attenuated by epigallocatechin gallate (EGCG). Cryogenic electron microscopy (cryo-EM) reveals two polymorphic canonical amyloid fibril architectures that share a conserved hydrophobic core and protofilament interface. In parallel, we identify pH as a key determinant of PSM1 assembly pathways, driving a bifurcation between cross-{beta} amyloid fibrils at extreme acidic and alkaline conditions and heterogeneous, long-lived, thermally stable -helical nanotubular assemblies at acidic, near-neutral, and slightly alkaline conditions, which act as transient intermediates under highly acidic conditions. Together, these findings demonstrate that PSM1 is not a single amyloid structure but a condition-dependent structural system in which environmental cues dictate assembly, membrane interaction, and cytotoxic function. This work provides a framework for understanding how polymorphic assembly of bacterial virulence peptides interfaces with host-cell interactions and suggests new avenues for targeting PSM-mediated pathogenicity. Statement of significanceStaphylococcus aureus causes severe infections and uses the peptide PSM1 to damage host cells and strengthen protective biofilms. Like many disease-associated proteins, PSM1 self-assembles into amyloid fibrils, though their role in virulence remains unclear. We show that PSM1 does not adopt a single architecture. Instead, environmental changes, such as those at infection sites, drive the peptide into distinct assemblies, including cross-{beta} amyloid fibrils and unexpectedly stable nanotubes with -helical features. Live-cell imaging shows PSM1 accumulates at the plasma membrane before cell death, and that epigallocatechin gallate reduces membrane association and toxicity. These findings show that bacterial virulence can be regulated through environmentally controlled transitions between protein assemblies, identifying membrane accumulation as a promising anti-virulence target.

biophysics↗

bioRxiv2026

Preimplantation factor (PIF) is an endogenous inhibitor of potassium channel KV1.3 regulating neutrophil function during pregnancy

Pregnancy is a unique period regarding immune cell regulation. Within the placenta, maternal immune cells play a central role in immune surveillance and tissue remodeling. However, regulatory mechanisms of systemic immunity during pregnancy are less clear. Here, we show that neutrophil function is altered in pregnant mice (E13.5), indicated by increased slow rolling velocity and reduced adhesion. Mechanistically, PreImplantation factor (PIF), a 15 amino acid peptide which is produced by human and murine trophoblast cells of the placenta, is continuously secreted into the maternal circulation and plays a key role in modulating neutrophil function via blocking the voltage-gated potassium channel KV1.3. This resulted in impaired intracellular Ca2+ signaling and subsequently disturbance of neutrophil post-arrest modifications and a higher susceptibility to physiological shear forces in vivo and in vitro. Furthermore, PIF-mediated KV1.3 blockade impaired E-selectin-mediated release of S100A8/A9 and phagocytosis. Taken together, we have identified PIF as an important modulator of neutrophil function during pregnancy suggesting a critical role in regulating innate immune responses throughout gestation.

immunology↗

bioRxiv2025

RNA Selectively Modulates Activity of Virulent Amyloid PSMα3 and Host Defense LL-37 via Phase Separation and Aggregation Dynamics

Amyloid-forming peptides are increasingly recognized as dynamic regulators at the host-pathogen interface, yet how environmental factors control their assembly and activity remains poorly understood. Here, RNA acts as a concentration-dependent regulator of two sequence-related -helical peptides with fundamentally different assembly behaviors: the cross- amyloid-forming Staphylococcus aureus virulence factor PSM3 and the non-amyloidogenic human host-defense peptide LL-37. RNA drives PSM3 through distinct assembly states, from liquid-like condensates to fibrillar polymorphs, while preserving cytotoxic and antimicrobial activity over time. In contrast, RNA attenuates LL-37 cytotoxicity toward host cells while maintaining antibacterial activity, consistent with a host-protective immunomodulatory effect. Together with the opposing effects of EGCG, which redirects both peptides into amorphous assemblies, these findings support a mechanistic model in which biological activity is governed by supramolecular architecture, assembly trajectory, and dynamics rather than by monomer abundance or mature fibrils alone. More broadly, our findings identify RNA as an environmental regulator of -helical peptide assemblies and establish assembly-state control as a tunable determinant of virulence and host defense.

biophysics↗

bioRxiv2024

Resilience and Charge-Dependent Fibrillation of Functional Amyloids: Interactions of Pseudomonas Biofilm-Associated FapB and FapC

FapC and FapB are biofilm-associated amyloids involved in the virulence of Pseudomonas and other bacteria. We herein demonstrate their exceptional thermal and chemical resilience, suggesting that biofilm structures might withstand standard sterilization, thereby contributing to the persistence of P. aeruginosa infections. Our findings also underscore the impact of environmental factors on Fap proteins, suggesting that orthologs in different Pseudomonas strains adapt to specific environments and roles. Challenging previous assumptions about a simple nucleation role for FapB in promoting FapC aggregation, the study shows a significant influence of FapC on FapB aggregation. The interaction between FapB and FapC is intricate: FapB stabilizes FapC fibrils, while FapC slows down FapB fibrillation but can still serve as a cross-seeding template. This complex interplay is key to understanding their roles in bacterial biofilms. Furthermore, the study highlights distinct differences between Fap and E. colis curli CsgA amyloid, where CsgB assumes a simple unidirectional role in nucleating CsgA fibrillation, emphasizing the importance of a comprehensive understanding of various amyloid systems. This knowledge is vital for developing effective intervention strategies against bacterial infections and leveraging the unique properties of these amyloids in technological applications such as novel bio-nanomaterials or protective coatings.

biochemistry↗

bioRxiv2022

Natural Antimicrobial Peptides Self-assemble as α/β Chameleon Amyloids

Amyloid protein fibrils and some antimicrobial peptides (AMPs) share biophysical and structural properties. This observation suggests that ordered self-assembly can act as an AMP-regulating mechanism, and, vice versa, that human amyloids play a role in host defense against pathogens, as opposed to their common association with neurodegenerative and systemic diseases. Based on previous structural information on toxic amyloid peptides, we developed a sequence-based bioinformatics platform and, led by its predictions, experimentally identified 14 fibril-forming AMPs (ffAMPs) from living organisms, which demonstrated cross-{beta} and cross- amyloid properties. The results support the amyloid-antimicrobial link. The high prevalence of ffAMPs produced by amphibians and marine creatures among other species suggests that they confer unique advantageous properties in distinctive environments, potentially providing stability and adherence properties. Most of the newly identified 14 ffAMPs showed lipid-induced and/or time-dependent secondary structure transitions in the fibril form, indicating structural and functional cross-/{beta} chameleons. Specifically, ffAMP cytotoxicity against human cells correlated with inherent or lipid-induced -helical fibril structure. The findings raise hypotheses about the role of fibril secondary structure switching in regulation of processes, such as the transition between a stable storage conformation and an active state with toxicity against specific cell types.

biophysics↗

bioRxiv2021

Uncovering the modified immunopeptidome reveals insights into principles of PTM-driven antigenicity

Antigen processing and presentation are critical for modulating tumor-host interactions. While post-translational modifications (PTMs) can alter the binding and recognition of antigens, their identification remains challenging. Here we uncover the role PTMs may play in antigen presentation and recognition in human cancers by profiling 29 different PTM combinations in immunopeptidomics data from multiple clinical samples and cell lines. We established and validated an antigen discovery pipeline and showed that newly identified modified antigens from a murine cancer model are cancer-specific and can elicit T cell killing. Systematic analysis of PTMs across multiple cohorts defined new haplotype preferences and binding motifs in association with specific PTM types. By expanding the antigenic landscape with modifications, we uncover disease-specific targets, including thousands of novel cancer-specific antigens and reveal insight into PTM-driven antigenicity. Collectively, our findings highlight an immunomodulatory role for modified peptides presented on HLA I, which may have broad implications for T-cell mediated therapies in cancer and beyond. SignificanceMajor efforts are underway to identify cancer-specific antigens for personalized immunotherapy. Here, we enrich the immunopeptidome landscape by uncovering thousands of novel putative antigens that are post-translationally modified. We define unique preferences for PTM-driven alterations affecting HLA binding and TCR recognition, which in turn alter tumor-immune interactions. Conflict of interest statementAuthors declare no conflicts of interest.

cancer biology↗