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Zweckstetter, M.

Publications and source records attributed to Zweckstetter, M..

At least 19 recordsLinked to original sources

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↗

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↗

Multivalent Tau-Fyn interactions cooperatively arrest postsynaptic density condensate dynamics

Tau-Fyn signaling at postsynaptic sites is implicated in synaptic dysfunction and neuronal hyperexcitability in Alzheimers disease and related tauopathies, yet the molecular mechanisms by which Tau-Fyn interactions influence postsynaptic signaling assemblies remain poorly understood. Here, we reconstitute biomolecular condensates and membrane-associated assemblies that mimic the postsynaptic density (PSD) to investigate how Tau and Fyn regulate PSD organization and dynamics. We show that Tau and Fyn co-partition into PSD condensates and N-methyl D-aspartate receptor subtype 2B (NR2B)-associated PSD clusters, with both proteins preferentially enriching in the condensed phase relative to core PSD scaffold proteins. Enrichment of Fyn within PSD condensates is recapitulated by an SH3-SH2 fragment lacking the kinase domain, indicating that the kinase domain is dispensable for condensate partitioning. Fluorescence recovery after photobleaching reveals that Tau markedly reduces Fyn mobility and, together with Fyn, cooperatively drives a pronounced dynamic arrest of PSD condensate components, including the central scaffold protein PSD-95. Disruption of a major Tau-Fyn interaction hotspot by P216A/P219A mutations in Tau nearly completely restores the mobility of both Fyn and PSD-95, demonstrating that cooperative Tau-Fyn interactions are required for dynamic arrest. NMR spectroscopy identifies a multivalent interaction network between the Tau proline-rich region and the Fyn SH3 domain involving multiple binding motifs, with residues P216 and P219 acting as major interaction determinants. A 1.4 [A] crystal structure of the Fyn SH3 domain bound to a Tau peptide reveals a ternary 2:1 Fyn:Tau assembly, providing structural support for multivalent Tau- Fyn engagement. Together, our findings establish a condensate-based mechanism by which multivalent Tau-Fyn interactions cooperatively regulate PSD condensate dynamics and provide a molecular framework linking Tau-Fyn signaling to synaptic dysfunction in tauopathies.

biochemistry↗

A Heart Disease-Associated TSPO Variant Alters Transmembrane Helix Dynamics

The 18-kDa translocator protein TSPO is an outer mitochondrial membrane protein involved in cholesterol transport, stress response, and cellular metabolism. Although its five-helix architecture is conserved across species, the structural and dynamic features of human TSPO remain unresolved. Using solution NMR spectroscopy, we characterize the conformational dynamics of human TSPO in complex with a third-generation diagnostic ligand. We identify a dynamic N-terminal segment of the first transmembrane helix that does not form a stably populated helix but instead defines a flexible boundary between the cytosolic region and the transmembrane core. The common disease-associated A14V variant reduces this conformational heterogeneity by introducing short-range contacts and redistributing backbone dynamics across the protein. These changes preserve the overall fold while locally stabilizing the N-terminal transmembrane helix toward the VDAC interaction interface. Our findings reveal a human-specific dynamic architecture of TSPO and link variant-induced stabilization to modulation of transmembrane helix dynamics.

biophysics↗

Decoding conformational heterogeneity across disordered proteomes

Intrinsically disordered proteins (IDPs) comprise nearly one-third of the human proteome and play key roles in regulation, signaling, and disease, yet their dynamic nature has resisted accurate structural prediction even by the state of the art deep-learning methods. Here we introduce AI-IDP, a framework combining established deep-learning structure prediction of isolated short IDP fragments with their flexible physical restrains-aware assembly to transform sequence information into experiment-consistent conformational ensembles of disordered proteins. AI-IDP reproduces experimental observables across local, medium-range, and global scales, including transient secondary structure, mutation sensitivity, and overall chain dimensions. Applied to more than 3,000 disordered regions across human and non-human proteomes, AI-IDP reveals that transient -helices and polyproline-II conformations are pervasive and evolutionarily tuned features of disorder. By uncovering how sequence encodes conformational heterogeneity, AI-IDP provides a practical framework for understanding the structural and functional logic of disordered proteomes and enables rationally targeting the dynamic protein states that underlie health and disease.

bioinformatics↗

Direct binding of TDP-43 and Tau drives their co-condensation, but suppresses Tau fibril formation and seeding

Neuronal Tau aggregates are a hallmark of Alzheimers disease (AD), but more than half of the patients exhibit additional TDP-43 inclusions and some have co-aggregates of both proteins. The presence of Tau/TDP-43 co-pathology is associated with increased disease severity, although the causal relationship remains unclear. Here we demonstrate that Tau and TDP-43 mutually promote each others condensation through direct interaction in vitro, forming irregularly shaped or multiphasic co-condensates with lower TDP-43 mobility, but higher Tau dynamics. While Tau promotes TDP-43 aggregation in vitro, TDP-43 suppresses formation of Tau fibrils and instead causes formation of oligomeric Tau and Tau/TDP-43 species. These co-assemblies hinder Tau seeding in a biosensor assay specific for proteopathic Tau seeds. Consistent with this data, SarkoSpin extracts from AD brains with Tau/TDP-43 co-pathology exhibit reduced Tau seeding compared to Tau-only AD brains. In contrast, patient-derived extracts from AD brains with Tau/TDP-43 co-pathology are highly potent in seeding TDP-43 neoaggregates in a TDP-43 reporter cell line. Our results suggest that direct interaction of TDP-43 and Tau may suppress Tau pathology, while promoting TDP-43 pathology. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/662960v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1ed5dfaorg.highwire.dtl.DTLVardef@b4ef07org.highwire.dtl.DTLVardef@b8dbe8org.highwire.dtl.DTLVardef@6d9b49_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

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↗

Human- and Rodent-derived Extracellular Vesicles Mediate the Spread of Pathology in MSA-like Models

Multiple system atrophy (MSA) is characterized by the presence of protein-rich inclusions mainly within oligodendrocytes, comprised primarily by the neuronal protein Synuclein and the oligodendroglial-specific phosphoprotein TPPP/p25. Mature oligodendrocytes do not normally express detectable Synuclein levels, suggesting that its oligodendroglial accumulation may arise from intercellular transfer, potentially via extracellular vesicles (EVs); however the precise role of oligodendroglial-derived EVs in MSA progression remains relatively understudied. Herein, we characterized the cargo/features and pathogenic potential of EVs released by oligodendrocytes treated with human Synuclein fibrils amplified from MSA or Parkinsons disease patient brains (or human recombinant Synuclein fibrils) and EVs isolated from murine and human MSA (or respective control) brains. Our findings reveal that both oligodendroglial cell- and brain-derived EVs harbor pathological Synuclein and TPPP/p25 conformations, similar to those accumulating in human MSA brains. These EVs are readily taken up by both neurons and oligodendrocytes, driving Synuclein propagation in vitro. Importantly, inoculation of these MSA-like EVs in animal models induce robust pSer129-Synuclein accumulation along the nigrostriatal axis, colocalizing with markers of mature oligodendrocytes and dopaminergic neurons. These findings underscore the pivotal role of oligodendroglial-derived EVs in pathology progression and neuronal-oligodendroglial communication, positioning them as promising targets for therapeutic strategies aimed at combating alpha-Synucleinopathies.

neuroscience↗

Knockout of the LRRK2-counteracting RAB phosphatase PPM1H disrupts axonal autophagy and exacerbates alpha-synuclein aggregation

Parkinson disease-causing mutations in the LRRK2 gene hyperactivate LRRK2 kinase activity, leading to increased phosphorylation of a subset of RAB GTPases, which are master regulators of intracellular trafficking. In neurons, processive retrograde transport of autophagosomes is essential for autophagosome maturation and effective degradation of autophagosomal cargo in the axon. We found that knockout of the LRRK2-counteracting RAB phosphatase PPM1H resulted in a gene dose-dependent disruption of the axonal transport of autophagosomes, leading to impaired degradation of axonal alpha-synuclein (aSyn), a key protein in Parkinson disease pathophysiology. Defective autophagosome transport and impaired aSyn degradation also correlated with increased aSyn aggregation in primary PPM1H knockout neurons exposed to preformed fibrils of aSyn, an effect that was dependent on LRRK2 kinase activity. Thus, our results link LRRK2-mediated RAB hyperphosphorylation to aSyn pathology in Parkinson disease and further establish a role for impaired autophagy in Parkinson disease pathophysiology.

neuroscience↗

Synthetic chaperone based on Hsp90-Tau interaction inhibits pathological Tau aggregation and rescues physiological Tau-Microtubule interaction

The accumulation of intracellular aggregates of Tau protein is one main hallmark of Alzheimers disease (AD) and is the consequence of Tau conformational changes, increased phosphorylation, and self-association to form fibrillar aggregates. This pathological process prevents the physiological interaction of Tau with microtubules to the detriment of the structural integrity of neurons. In healthy cells, aberrant protein misfolding and aggregation are counteracted by chaperone proteins whose protective capacity decreases with age. The role of the chaperone Hsp90 and the mechanism by which it can prevent Tau aggregation toxicity are controversial. The innovative strategy of mimicking Hsp90 through the design of the {beta}-hairpin like peptidomimetic {beta}-Hsp90, inspired by two Hsp90/Tau interaction sequences, is presented here. {beta}-Hsp90 inhibits Tau aggregation both in vitro and in cells, restoring Taus physiological interaction with microtubules. {beta}-Hsp90, which interacts with the P1 region of Tau, is more effective than individual peptide sequences from the chaperone HSP90 and another {beta}-hairpin mimic based on Tau sequences. Moreover, {beta}-Hsp90 dramatically reduces AD-associated A{beta}1-42 aggregation, offering the development of a dual inhibitor. This work paves the way for the design of new drugs targeting devastating untreated amyloid diseases, by mimicking physiological chaperones with small synthetic peptide drugs.

pharmacology and toxicology↗

Polyamines promote disordered protein phase separation

AbstactMembrane-less organelles are spatially heterogenous deposits of interacting macromolecules, often intrinsically disordered proteins and RNA, that form and dissolve in response to cellular stimuli. How membraneless organelles control composition while maintaining stimuli-responsiveness in an environment with competitive interactions is not well understood. Here we demonstrate that natural polyamines, which are found in all living organisms and help in many biological processes, promote protein phase separation via attractive interactions with acidic disordered domains. We show that the abundant polyamine spermine promotes phase separation of the stress-granule associated protein G3BP1 and modulates together with RNA the phase separation and amyloid formation of the Parkinsons disease-related protein -synuclein. Polyamine-promoted phase separation is controllable via polyamine acetylation and RNA-mediated competitive interactions. The results suggest that cellular polyamines may serve diverse roles in biomolecular condensation and the regulation of membraneless organelles.

biochemistry↗

p23-FKBP51 chaperone complex regulates tau aggregation

The pathological deposition of tau into insoluble amyloid fibrils is a pathological hallmark of tauopathies. Molecular chaperones are important cellular factors contributing to the regulation of tau misfolding and aggregation. Here we reveal an Hsp90-independent modulation of tau aggregation by a molecular complex of the two Hsp90 co-chaperones p23 and FKBP51. Integrating NMR spectroscopy, SAXS, molecular docking, and site-directed mutagenesis we reveal the structural basis of the p23-FKBP51 complex. We show that p23 specifically recognizes the TPR domain of FKBP51 and interacts with tau through its C-terminal disordered tail. We further show that the p23-FKBP51 complex binds tau to form a dynamic p23-FKBP51-tau trimeric complex that inhibits tau aggregation and thus may counteract Hsp90-FKBP51 mediated toxicity. Taken together, our findings reveal a co-chaperone mediated Hsp90-independent chaperoning of tau protein.

biophysics↗

GSK3β phosphorylation catalyzes the aggregation of Tau into Alzheimer's disease-like amyloid strain

The pathological deposition of proteins is a hallmark of several devastating neurodegenerative diseases. These pathological deposits comprise aggregates of proteins that adopt distinct structures named strains. However, the molecular factors responsible for the formation of distinct aggregate strains are unknown. Here we show that the serine/threonine kinase GSK3{beta} catalyzes the aggregation of the protein tau into an Alzheimers disease-like amyloid strain. We demonstrate that phosphorylation by GSK3{beta}, but not by several other kinases, promotes the aggregation of full-length tau through enhanced phase separation into gel-like condensate structures. Cryo-electron microscopy further reveals that the amyloid fibrils formed by GSK3{beta}-phosphorylated tau adopt a fold comparable to that of paired helical filaments isolated from the brains of AD patients. Our results elucidate the intricate relationship between post-translational modification and the formation of tau strains in neurodegenerative diseases.

biophysics↗

Contributions of the N-terminal intrinsically disordered region of the SARS-CoV-2 nucleocapsid protein to RNA-induced phase separation

SARS-CoV-2 nucleocapsid protein is an essential structural component of mature virions, encapsulating the genomic RNA and modulating RNA transcription and replication. Several of its activities might be associated with the proteins ability to undergo liquid-liquid phase separation. NSARS-CoV-2 contains an intrinsically disordered region at its N-terminus (NTE) that can be phosphorylated and is affected by disease-relevant mutations. Here we show that NTE deletion decreases the range of RNA concentrations that can induce phase separation of NSARS-CoV-2. In addition, deletion of the prion-like NTE allows NSARS-CoV-2 droplets to retain their liquid-like nature during incubation. We further demonstrate that RNA-binding engages multiple parts of the NTE and changes NTEs structural properties. The results form the foundation to characterize the impact of N-terminal mutations and post-translational modifications on the molecular properties of the SARS-CoV-2 nucleocapsid protein. StatementThe nucleocapsid protein of SARS-CoV-2 plays an important role in both genome packaging and viral replication upon host infection. Replication has been associated with RNA-induced liquid-liquid phase separation of the nucleocapsid protein. We present insights into the role of the N-terminal part of the nucleocapsid protein in the proteins RNA-mediated liquid-liquid phase separation.

biophysics↗

Hsp multichaperone complex buffers pathologically modified Tau

Alzheimers disease is a neurodegenerative disorder in which misfolding and aggregation of pathologically modified Tau is critical for neuronal dysfunction and degeneration. The two central chaperones Hsp70 and Hsp90 coordinate protein homeostasis, but the nature of the interaction of Tau with the Hsp70/Hsp90 machinery has remained enigmatic. Here we show that Tau is a high-affinity substrate of the human Hsp70/Hsp90 machinery. Complex formation involves extensive intermolecular contacts, blocks Tau aggregation and depends on Taus aggregation-prone repeat region. The Hsp90 co-chaperone p23 directly binds Tau and stabilizes the multichaperone/substrate complex, whereas the E3 ubiquitin-protein ligase CHIP efficiently disassembles the machinery targeting Tau to proteasomal degradation. Because phosphorylated Tau binds the Hsp70/Hsp90 machinery but is not recognized by Hsp90 alone, the data establish the Hsp70/Hsp90 multichaperone complex as a critical regulator of Tau in neurodegenerative diseases.

biophysics↗

Global Structure of the Intrinsically Disordered Protein Tau Emerges from its Local Structure

The paradigmatic disordered protein tau plays an important role in neuronal function and neurodegenerative diseases. To disentangle the factors controlling the balance between functional and disease-associated conformational states, we build a structural ensemble of the tau K18 fragment containing the four pseudorepeat domains involved in both microtubule binding and amyloid fibril formation. We assemble 129-residue-long tau K18 chains at atomic resolution from an extensive fragment library constructed with molecular dynamics simulations. We introduce a reweighted hierarchical chain growth (RHCG) algorithm that integrates experimental data reporting on the local structure into the assembly process in a systematic manner. By combining Bayesian ensemble refinement with importance sampling, we obtain well-defined ensembles and overcome the problem of exponentially varying weights in the integrative modeling of long-chain polymeric molecules. The resulting tau K18 ensembles capture nuclear magnetic resonance (NMR) chemical shift and J-coupling measurements. Without further fitting, we achieve excellent agreement with measurements of NMR residual dipolar couplings. The good agreement with experimental measures of global structures such as singlemolecule Forster resonance energy transfer (FRET) efficiencies is improved further by ensemble refinement. By comparing wild-type and mutant ensembles, we show that pathogenic single-point P301 mutations shift the population from the turn-like conformations of the functional microtubule-bound state to the extended conformations of disease-associated tau fibrils. RHCG thus provides us with an atomically resolved view of the population equilibrium between functional and aggregation-prone states of tau K18, and demonstrates that global structural characteristics of this intrinsically disordered protein emerge from its local structure.

biophysics↗

A novel mutation (E83Q) unlocks the pathogenicity of human alpha-synuclein fibrils and recapitulates its pathological diversity

A novel mutation (E83Q), the first in the NAC domain of alpha-synuclein (aSyn), was recently identified in a patient with dementia with Lewy bodies. We investigated the effects of this mutation on the aggregation of aSyn monomers and the structure, morphology, dynamic, and seeding activity of the aSyn fibrils in neurons. We found that it dramatically accelerates aSyn fibrillization and results in the formation of fibrils with distinct structural and dynamic properties. In cells, this mutation is associated with higher levels of aSyn, accumulation of pS129, and increased toxicity. In a neuronal seeding model of Lewy bodies (LB) formation, the E83Q mutation significantly enhances the internalization of fibrils into neurons, induce higher seeding activity and results in the formation of diverse aSyn pathologies, including the formation of LB-like inclusions that recapitulate the immunohistochemical and morphological features of brainstem LBs observed in PD patient brains. TeaserA novel mutation (E83Q) exacerbates alpha-synuclein aggregation and toxicity and reproduces PD pathological diversity.

neuroscience↗

The Pathogenic R5L Mutation Disrupts Formation of Tau Complexes on the Microtubule by Altering Local N-Terminal Structure

The microtubule-associated protein (MAP) Tau is an intrinsically disordered protein (IDP) primarily expressed in axons, where it functions to regulate microtubule dynamics, modulate motor protein motility, and participate in signaling cascades. Tau misregulation and point mutations are linked to neurodegenerative diseases, including Progressive Supranuclear Palsy (PSP), Picks Disease and Alzheimers disease. Many disease-associated mutations in Tau occur in the C-terminal microtubule-binding domain of the protein. Effects of C-terminal mutations in Tau have led to the widely accepted disease-state theory that missense mutations in Tau reduce microtubule-binding affinity or increase Tau propensity to aggregate. Here, we investigate the effect of an N-terminal disease-associated mutation in Tau, R5L, on Tau-microtubule interactions using an in vitro reconstituted system. Contrary to the canonical disease-state theory, we determine the R5L mutation does not reduce Tau affinity for the microtubule using Total Internal Reflection Fluorescence (TIRF) Microscopy. Rather, the R5L mutation decreases the ability of Tau to form larger order complexes, or Tau patches, at high concentrations of Tau. Using Nuclear Magnetic Resonance (NMR), we show that the R5L mutation results in a local structural change that reduces interactions of the projection domain in the presence of microtubules. Altogether, these results challenge both the current paradigm of how mutations in Tau lead to disease and the role of the projection domain in modulating Tau behavior on the microtubule surface. Significance StatementThe microtubule-associated protein Tau is strongly linked to a number of neurological diseases. Disease onset is typically associated with weakened interaction with the microtubule, but this widely accepted model is based on hyperphosphorylation or mutations within the C-terminal microtubule-binding domain of Tau. Here, we find an N-terminal disease-associated mutation in Tau, R5L, does not reduce Tau affinity for microtubules, but instead modifies the N-terminal structure, altering Taus behavior and ability to condense on the microtubule surface. Our findings challenge the current paradigms of both how mutations in Tau lead to disease and the functional role of the N-terminal region of Tau.

biophysics↗