Biology subjects

Landau, M.

Publications and source records attributed to Landau, M..

At least 19 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

Kinase-specific phosphorylation of tau outside the amyloid core encodes fibril fold selection

Tauopathies are defined by the accumulation of filamentous tau assemblies that adopt disease-specific molecular conformations, or tau strains. Although tau is extensively hyperphosphorylated in Alzheimers disease, how phosphorylation patterns influence tau folding and strain selection remains unclear. Here, we show that site-specific phosphorylation of 0N3R tau by extracellular signal-regulated kinase 2 (ERK2), occurring predominantly within the proline-rich region and largely excluding the microtubule-binding domain, is sufficient to direct tau assembly into a structurally homogeneous fibril conformation. Residue-resolved NMR spectroscopy identifies a defined and quantifiable ERK2 phosphorylation pattern in the proline-rich region of tau. Cryo-electron microscopy at 3.0 [A] resolution reveals that ERK2-phosphorylated 3R tau assembles into filaments with an ordered cross-{beta} fold adopting an Alzheimers disease PHF fold, despite the absence of phospho-sites within the fibril core. These filaments exhibit robust seeding activity in tau biosensor cells. Together, these results demonstrate that kinase-specific phosphorylation outside the amyloid core can be sufficient to bias tau toward a defined fibril structure, establishing a direct mechanistic link between kinase specificity, post-translational modification, and tau strain formation.

molecular biology↗

bioRxiv2025

Enhancer-directed gene delivery for digit regeneration based on conserved epidermal factors

Limb loss remains a significant clinical challenge, but regenerative medicine approaches such as gene therapy offer a promising strategy to trigger endogenous regeneration programs. Optimal vector configurations and molecular targets for appendicular skeletal repair are not well defined. Here, we leveraged insights from species with a high endogenous capacity for appendage regeneration to design an enhancer-directed gene delivery platform that functions during mouse digit regeneration, a well characterized model for partial limb regeneration in mammals. Single-cell RNA sequencing of zebrafish caudal fin regeneration, combined with expression data in regenerating salamander limbs and mouse digit tips, implicated the SP family of transcription factors as conserved, epidermally-expressed mediators of appendage regrowth. Null mutants of Sp8 demonstrated impaired limb regeneration in salamanders, while conditional knockout of Sp6 and/or Sp8 in the mouse basal epidermis resulted in defective bony digit tip regeneration, involving an IL-17 mediated osteoclastogenic program. Spatiotemporally focused expression of FGF8, a known target of SP factors, using a zebrafish-derived tissue regeneration enhancer element via adeno-associated viral vectors, could partially rescue digit tip regeneration in SP knockout mice and accelerate digit regeneration in wildtype mice. Our results demonstrate a contextual gene therapy approach to address limb loss based on genes like SP transcription factors conserved across multiple contexts of appendage regeneration. Significance StatementInstructing regeneration of complex structures in mammals remains an unsolved problem. Gene therapy offers a compelling approach to foster endogenous regeneration by delivering therapeutic gene products to specific cells post injury. We identified a conserved regeneration-linked epidermal transcriptional program in mouse digit regeneration centered on the SP6 and SP8 transcription factors, involving inflammatory responses from osteoclasts. We engineered AAVs harboring a zebrafish tissue regeneration enhancer to direct FGF8 expression in the epidermis after amputation. This enhancer directed delivery partially rescued impaired digit regeneration in Sp6 and Sp8 conditional knockout mice and accelerated regrowth in wildtype digits. Our work links developmental signaling to adult regeneration and establishes a modular, injury site specific gene therapy framework that enables new interventions for limb healing.

genetics↗

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↗

bioRxiv2025

Structural and Functional Versatility of the Amyloidogenic Antimicrobial Peptide Citropin 1.3

Citropin 1.3 is an antimicrobial peptide produced by the amphibian Litoria citropa (Southern bell frog), which self-aggregates into distinct fibrillar structures, however, the function of the fibrils remains unclear and largely unexplored. In this study, the structural and functional properties of citropin 1.3 were investigated using cryogenic electron microscopy and fluorescence microscopy in the presence of membrane and cell models, and with X-ray crystallography. Canonical amyloids, multilayered nanotubes, and a novel mixed fibril were observed. Experiments with negatively charged giant unilamellar vesicles revealed that the peptide facilitates membrane fusion while simultaneously undergoing phase separation in the presence of phospholipids. In presence of mammalian cells, citropin 1.3 permeabilizes membranes, leading to cell death, and over time, colocalizes with genetic material. Overall, this work provides new insights into the structural dynamics of the amyloidogenic antimicrobial peptide citropin 1.3 and its interactions with different systems.

molecular biology↗

bioRxiv2024

Sla2 is a core interaction hub for Clathrin Light Chain and the Pan1/End3/Sla1Complex

The interaction network of Sla2, a vital adaptor protein in the endocytic mid-coat, undergoes constant rearrangement incorporating or replacing interacting proteins over time. Sla2 serves as a scaffold linking the membrane to the actin cytoskeleton, with this role modulated by Clathrin Light Chain (CLC), which inhibits Sla2s function under certain conditions. We show that Sla2 has two independent binding sites for CLC: one previously described in homologs of Fungi (Sla2) and Metazoa (Hip1R), and a second found only in Fungi. We present the structural model of the Sla2 actin-binding domains in the context of regulatory structural domains by electron cryo-microscopy. We provide an interaction map of Sla2 and the regulatory proteins Sla1 and Pan1, predicted by AI modelling and confirmed by molecular biophysics techniques. Pan1 competes with CLC for the conserved binding site on Sla2. These results enhance the mapping of crucial interactions at endocytic checkpoints and highlight the divergence between Metazoa and Fungi in this vital process. TeaserSla2 forms complexes with three regulatory proteins in the endocytic pit, two of which compete for the same site

molecular biology↗

bioRxiv2024

A new class of receptors: Lipids regulate mammalian Gsalpha-stimulated adenylyl cyclase activities via their membrane anchors

The biosynthesis of cAMP by mammalian membrane-bound adenylyl cyclases (mACs) is predominantly regulated by G-protein-coupled-receptors (GPCRs). Up to now the two hexahelical transmembrane domains of mACs were considered to fix the enzyme to membranes. Here we show that the transmembrane domains serve in addition as signal receptors and transmitters of lipid signals that control Gs-stimulated mAC activities. We identify aliphatic fatty acids and anandamide as receptor ligands of mAC isoforms 1 to 7 and 9. The ligands enhance (mAC isoforms 2, 3, 7, and 9) or attenuate (isoforms 1, 4, 5, and 6) Gs-stimulated mAC activities in vitro and in vivo. Substitution of the stimulatory membrane receptor of mAC3 by the inhibitory receptor of mAC5 results in a ligand inhibited mAC5-mAC3 chimera. Thus, we discovered a new class of membrane receptors in which two signaling modalities are at a crossing, direct tonic lipid and indirect phasic GPCR-Gs signaling regulating the biosynthesis of cAMP.

biochemistry↗

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↗

bioRxiv2023

Sea anemone MACPF proteins demonstrate an evolutionary transitional state between venomous and developmental functions

Gene duplication is a major force driving evolutionary innovation. A classic example is generating new animal toxins via duplication of physiological protein-encoding genes and recruitment into venom. While this process drives the innovation of many animal venoms, reverse-recruitment of toxins into non-venomous cells remains unresolved. Using comparative genomics, we find members of the Membrane Attack Complex and Perforin Family (MACPF) have been recruited into venom-injecting cells (cnidocytes), in soft and stony corals and sea anemones, suggesting that the ancestral MACPF was a cnidocyte expressed toxin. Further investigation into the model sea anemone Nematostella vectensis, reveals that three members have undergone Nematostella-specific duplications leading to their reverse-recruitment into mesoendodermal cells. Furthermore, simultaneous knock-down of all three mesoendodermally-expressed MACPFs leads to mis-development, supporting that these paralogs have non-venomous function. By resolving the evolutionary history and function of MACPFs in Nematostella, we provide the first proof for reverse-recruitment from venom to organismal development. Significance statementIn this study, we reveal how a gene can gain a new function, even from a most unexpected origin. Specifically, we report that in the last common ancestor of corals and sea anemones a member of the Membrane Attack Complex and Perforin Family (MACPF), which is commonly associated with the immune system, was recruited into venom-injecting cells called cnidocytes. Using the sea anemone Nematostella vectensis we find repeated gene duplication has occurred leading to the new copies adopting divergent functions including being retained in cnidocytes but also recruited into non-venomous mesoendodermal cells. Furthermore, when we deplete Nematostella of mesoendodermally-expressed MACPFs we disrupt normal embryonic development, supporting that these copies have indeed been recruited from venom into the developmental plan.

evolutionary biology↗

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↗

bioRxiv2022

Distinct glycerophospholipids potentiate Gsα-activated adenylyl cyclase activity

Nine mammalian adenylyl cyclases (AC) are pseudoheterodimers with two hexahelical membrane domains which are isoform-specifically conserved. Previously we proposed that these membrane domains are orphan receptors (10.7554/eLife.13098; 10.1016/j.cellsig.2020.109538). Lipids extracted from fetal bovine serum at pH 1 inhibited several mAC activities. Guided by a lipidomic analysis we tested glycerophospholipids as potential ligands. Contrary to expectations we surprisingly discovered that 1-stearoyl-2-docosahexaenoyl-phosphatidic acid (SDPA) potentiated Gs-activated activity of human AC isoform 3 seven-fold. The specificity of fatty acyl esters at glycerol positions 1 and 2 was rather stringent. 1-Stearoyl-2-docosahexaenoyl-phosphatidylserine and 1-stearoyl-2-docosahexaenoyl-phosphatidylethanolamine significantly potentiated several Gs-activated mAC isoforms to different extents. SDPA appears not interact with forskolin activation of AC isoform 3. SDPA enhanced Gs-activated AC activities in membranes from mouse brain cortex. The action of SDPA was reversible. Unexpectedly, SDPA did not affect cAMP generation in HEK293 cells stimulated by isoproterenol, PGE2 and adenosine, virtually excluding a role as an extracellular ligand and, instead, suggesting an intracellular role. In summary, we discovered a new dimension of intracellular AC regulation by chemically defined glycerophospholipids.

biochemistry↗

bioRxiv2022

The Cryo-EM Structures of two Amphibian Antimicrobial Cross-β Amyloid Fibrils

The amyloid-antimicrobial link hypothesis is based on antimicrobial properties found in human amyloids involved in neurodegenerative and systemic diseases, along with amyloidal structural properties found in antimicrobial peptides (AMPs) across kingdoms of life. Supporting this hypothesis, we here determined the fibril structure of two AMPs from amphibians, uperin 3.5 and aurein 3.3, by cryogenic electron microscopy (cryo-EM), revealing amyloid cross-{beta} fibrils of mated {beta}-sheets at atomic resolution. Uperin 3.5 displayed substantial polymorphism with a protofilament of two mated {beta}-sheets. The determined structure was a polymorph showing a 3-blade symmetrical propeller of nine peptides per fibril layer including tight {beta}-sheet interfaces. This cross-{beta} cryo-EM structure complements the cross- fibril conformation previously determined by a crystal structure, substantiating a secondary structure switch mechanism of uperin 3.5. The aurein 3.3 arrangement consisted of six peptides per fibril layer, all showing kinked {beta}-sheets allowing a rounded compactness of the fibril. The kinked {beta}-sheets are similar to LARKS (Low-complexity, Amyloid-like, Reversible, Kinked segments) found in human functional amyloids. The amyloidal properties of antimicrobial peptides shed light on a mechanism of regulation of animicrobial activity involving self-assembly and fibril morphological variations. Moreover, the known endurance of amyloid structures can provide a template for the design of sturdy antimicrobials.

molecular biology↗

bioRxiv2021

Structure and conservation of amyloid spines from the Candida albicans Als5 adhesin including similarity to human LARKS

Candida Als family adhesins mediate adhesion to biological and abiotic substrates, as well as fungal cell aggregation and fungal-bacterial co-aggregation. The activity of at least two family members, Als5 and Als1, is dependent on amyloid-like protein aggregation that is initiated by shear force. Each Als adhesin has a [~]300-residue N-terminal Ig-like/invasin region. The following 108-residue, low complexity, threonine-rich (T) domain unfolds under shear to expose a critical amyloid-forming segment 322SNGIVIVATTRTV334 at the interface between the Ig-like/invasin domain 2 and the T domain of Candida albicans Als5. Amyloid prediction programs identified six potential amyloidogenic sequences in the Ig/invasin region and three others in the T domain of C. albicans Als5. Peptides derived from four of these sequences formed fibrils that bound thioflavin T, the amyloid indicator dye, and three of these revealed atomic-resolution structures of cross-{beta} spines. These are the first atomic-level structures for fungal adhesins. One of these segments, from the T domain, revealed kinked {beta}-sheets, similarly to LARKS (Low-complexity, Amyloid-like, Reversible, Kinked segments) found in human functional amyloids. Based on the cross-{beta} structures in Als proteins, we use evolutionary arguments to identify functional amyloidogenic sequences in other fungal adhesins. Thus, cross-{beta} structures are often involved in fungal pathogenesis and potentially in antifungal therapy. ImportanceFungal adhesins form cell-to-cell bonds in biofilms. Many of the cellular interactions are dependent on formation of amyloid-like cross-{beta} protein aggregates. Such structures are called functional amyloids because they perform physiological activities and they are dependent on the same types of protein interactions that form the more familiar amyloid deposits in neurodegenerative diseases. We have identified sequence segments that form cross-{beta} structures in the Als5 adhesin from the human pathogen Candida albicans. Such sequences are widespread among ALS family adhesins, including those from other human pathogens including Candida auris. Moreover, we revealed a structural similarity in a segment originating from Als5 threonine-rich low complexity region to human LARKS, pointing on a common structural motif coding for functional amyloids in different kingdoms of life.

microbiology↗

bioRxiv2020

The Amphibian Antimicrobial Peptide Uperin 3.5 is a Cross-α/Cross-β Chameleon Functional Amyloid

Antimicrobial activity is being increasingly linked to amyloid fibril formation, suggesting physiological roles for some human amyloids, which have historically been viewed as strictly pathological agents. This work reports on formation of functional cross- amyloid fibrils of the amphibian antimicrobial peptide uperin 3.5 at atomic-resolution, an architecture initially discovered in the bacterial PSM3 cytotoxin. The fibrils of uperin 3.5 and PSM3 were comprised of parallel and anti-parallel helical sheets, respectively, recapitulating properties of {beta}-sheets. Uperin 3.5 helical fibril formation was largely induced by, and formed on, bacterial cells or membrane mimetics, and led to membrane damage and cell death. Uperin 3.5 demonstrated chameleon properties, with a secondary structure switch to cross-{beta} fibrils with reduced antibacterial activity in the absence of lipids or after heat shock. These findings suggest a regulation mechanism, which includes storage of inactive peptides as well as environmentally induced activation of uperin 3.5, via chameleon cross-/{beta} amyloid fibrils.

biochemistry↗

bioRxiv2020

Toxin-like neuropeptides in the sea anemone Nematostella unravel recruitment from the nervous system to venom

The sea anemone Nematostella vectensis (Anthozoa, Cnidaria) is a powerful model system for characterizing the evolution of genes functioning in venom and nervous systems. Despite being an example for evolutionary novelty, the evolutionary origin of most toxins remains unknown. Here we report the first bona fide case of protein recruitment from the cnidarian nervous to venom system. The ShK-like1 peptide has ShKT cysteine motif, is lethal for fish larvae and packaged into nematocysts, the cnidarian venom-producing stinging capsules. Thus, ShK-like1 is a toxic venom component. Its paralog, ShK-like2, is a neuropeptide localized to neurons and is involved in development. Interestingly, both peptides exhibit similarities in their functional activities: both of them provoke contraction in Nematostella polyps and are toxic to fish. Because ShK-like2 but not ShK-like1 is conserved throughout sea anemone phylogeny, we conclude that the two paralogs originated due to a Nematostella-specific duplication of a ShK-like2 ancestor, a neuropeptide-encoding gene, followed by diversification and partial functional specialization. Strikingly, ShK-like2 is represented by two gene isoforms controlled by alternative promoters conferring regulatory flexibility throughout development. Additionally, we characterized the expression patterns of four other peptides with structural similarities to studied venom components, and revealed their unexpected neuronal localization. Thus, we employed genomics, transcriptomics and functional approaches to reveal one new venom component, five neuropeptides with two different cysteine motifs and an evolutionary pathway from nervous to venom system in Cnidaria.

evolutionary biology↗

bioRxiv2020

Atomic Structure of the LL-37(17-29) Human Antimicrobial Peptide Reveals Functional Helical Fibril

Protein fibrils that perform biological activities present attractive biomaterials. Here we demonstrate, by crystal structures, the self-assembly of the antibacterial human LL-37 active core (residues 17-29) into a stable structure of densely packed helices. The surface of the fibril encompasses alternating hydrophobic and positively charged zigzagged belts, which likely underlie interactions with and subsequent disruption of negatively charged lipid bilayers, such as bacterial membranes. LL-3717-29 correspondingly formed wide, ribbon-like, thermostable fibrils in solution, which co-localized with bacterial cells, and structure-guided mutagenesis analyses supported the role of self-assembly in antibacterial activity. LL-3717-29 resembled, in sequence and in the ability to form amphipathic helical fibrils, the bacterial cytotoxic PSM3 peptide that assembles into cross- amyloid fibrils. This suggests helical, self-assembling, basic building blocks across kingdoms of life and point to potential structural mimicry mechanisms. The findings offer a scaffold for functional and durable nanostructures for a wide range of medical and technological applications.

biochemistry↗

bioRxiv2018

Structural Insights into Curli Amyloid Fibrils suggest Repurposing Anti-amyloid Compounds as Anti-biofilm Agents

Curli amyloid fibrils secreted by Enterobacteriaceae mediate host cell adhesion and contribute to biofilm formation, thereby promoting bacterial resistance to environmental stressors. Here, we present crystal structures of amyloid-forming segments from the major curlin subunit, CsgA, revealing steric zipper fibrils of tightly mated {beta}-sheets, demonstrating a structural link between curli and human pathological amyloids. We propose that these cross-{beta} segments structure the highly robust curli amyloid core. D-enantiomeric peptides, originally developed to interfere with Alzheimers disease-associated Amyloid-{beta}, inhibited CsgA fibrillation and reduced biofilm formation in Salmonella typhimurium. Moreover, CsgA fibrils cross-seeded fibrillation of Amyloid-{beta}, providing further support for the proposed structural resemblance and potential for cross-species amyloid interactions. In this study, we provide structural insights into curli formation, offer a novel strategy for disrupting amyloid-structured biofilms, and hypothesize on the formation of self-propagating prion-like species originating from a microbial source that could influence neurodegenerative diseases.\n\nSignificanceAtomic resolution structural insights into the biofilm-associated curli amyloid fibril secreted by Enterobacteriaceae revealed elements of fibrillar architecture conserved between bacterial and human amyloids. This inspired us to repurpose anti-amyloid drugs designed to target human pathological amyloids as a novel class of anti-biofilm agents. Moreover, the results provide a molecular basis for understanding interspecies cross-seeding of amyloids through the generation of prion-like agents by molecular mimicry. This raises concerns regarding human exposure to exogenous sources of amyloids, such as contaminated food and amyloid-secreting microbes. Overall, we provide a novel framework for investigating interspecies amyloid interactions at the molecular level and offer novel insights into mechanisms which may underlie the evolutionary and etiological relationships between the human and microbial amylomes.

biochemistry↗

bioRxiv2018

Toxic Determinants of Staphylococcus aureus PSMα3 Cross-α Amyloid

The phenol-soluble modulin (PSM) peptide family, secreted by Staphylococcus aureus, performs various virulence activities, some mediated by the formation of amyloid fibrils of diverse architectures. Specifically, PSM1 and PSM4 structure the S. aureus biofilm by assembling into robust cross-{beta} amyloid fibrils. PSM3, the most cytotoxic member of the family, assembles into cross- fibrils in which -helices stack into tightly mated sheets, mimicking the cross-{beta} architecture. Here we demonstrated that massive T-cell deformation and death is linked with PSM3 aggregation and co-localization with cell membranes. Our extensive mutagenesis analyses supported the role of positive charges, and especially Lys17, in interactions with the membrane, and suggested their regulation by inter- and intra-helical electrostatic interactions within the cross- fibril. We hypothesize that PSM3 cytotoxicity is governed by the ability to form cross- fibrils and involves a dynamic process of co-aggregation with cell membrane, rupturing it. HighlightsO_LIThe cytotoxic S. aureus PSM3 assembles into cross- fibrils C_LIO_LICross- fibril polymorphism and mutations-induced secondary structure switching C_LIO_LIRegulation by cross- fibril inter- and intra-helical electrostatic interactions C_LIO_LIToxicity as a putative dynamic process of PSM3 co-aggregation with membranes C_LI

biochemistry↗