Biology subjects

Zweckstetter, M.

Publications and source records attributed to Zweckstetter, M..

28 records · Page 2Linked to original sources

bioRxiv2021

Common molecular mechanisms underlie the transfer of alpha-synuclein, Tau and huntingtin and modulate spontaneous activity in neuronal cells

The misfolding and accumulation of disease-related proteins are common hallmarks among several neurodegenerative diseases. Alpha-synuclein (aSyn), Tau and huntingtin (wild-type and mutant, 25QHtt and 103QHtt, respectively) were recently shown to be transferred from cell-to-cell through different cellular pathways, thereby contributing to disease progression and neurodegeneration. However, the relative contribution of each of these mechanisms towards the spreading of these different proteins and the overall effect on neuronal function is still unclear. To address this, we exploited different cell-based systems to conduct a systematic comparison of the mechanisms of release of aSyn, Tau and Htt, and evaluated the effects of each protein upon internalization in microglial, astrocytic, and neuronal cells. In the models used, we demonstrate that 25QHtt, aSyn and Tau are released to the extracellular space at higher levels than 103QHtt, and their release can be further augmented with the co-expression of USP19. Furthermore, cortical neurons treated with recombinant monomeric 43QHtt exhibited alterations in neuronal activity that correlated with the toxicity of the polyglutamine expansion. Tau internalization resulted in an increase in neuronal activity, in contrast to slight effects observed with aSyn. Interestingly, all these disease-associated proteins were present at higher levels in ectosomes than in exosomes. The internalization of both types of extracellular vesicles (EVs) by microglial or astrocytic cells elicited the production of pro-inflammatory cytokines and promoted an increase in autophagy markers. Additionally, the uptake of the EVs modulated neuronal activity in cortical neurons. Overall, our systematic study demonstrates the release of neurodegenerative disease-associated proteins through similar cellular pathways. Furthermore, it emphasizes that protein release, both in a free form or in EVs, might contribute to a variety of detrimental effects in receiving cells and to progression of pathology, suggesting they may be exploited as valid targets for therapeutic intervention in different neurodegenerative diseases. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=153 SRC="FIGDIR/small/452825v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1400e8org.highwire.dtl.DTLVardef@1478fccorg.highwire.dtl.DTLVardef@1319abcorg.highwire.dtl.DTLVardef@1a5ad40_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

α-Synuclein polymorphism determines oligodendroglial dysfunction

Synucleinopathies, such as Parkinsons disease (PD) and Multiple System Atrophy (MSA) are progressive and unremitting neurological diseases. For both PD and MSA, -synuclein fibril inclusions inside brain cells are neuropathological hallmarks. In addition, amplification of -synuclein fibrils from body fluids is a potential biomarker distinguishing PD from MSA. However, little is known about the structure of -synuclein fibrils amplified from human samples and its connection to -synuclein fibril structure in the human brain. Here we amplified -synuclein fibrils from PD and MSA brain tissue, characterized its seeding potential in oligodendroglia, and determined the 3D structures by cryo-electron microscopy. We show that the -synuclein fibrils from a MSA patient are more potent in recruiting the endogenous -synuclein and evoking a redistribution of TPPP/p25 protein in mouse primary oligoden-droglial cultures compared to those amplified from a PD patient. Cryo-electron microscopy shows that the PD- and MSA-amplified -synuclein fibrils share a similar protofilament fold but differ in their inter-protofilament interface. The structures of the brain-tissue amplified -synuclein fibrils are also similar to other in vitro and ex vivo -synuclein fibrils. Together with published data, our results suggest that Syn fibrils differ between PD and MSA in their quaternary arrangement and could further vary between different forms of PD and MSA.

neuroscience↗

bioRxiv2021

Molecular basis of small-molecule binding to α-synuclein

Intrinsically disordered proteins (IDPs) are implicated in many human diseases. They have generally not been amenable to conventional structure-based drug design, however, because their intrinsic conformational variability has precluded an atomic-level understanding of their binding to small molecules. Here we present long-timescale, atomic-level molecular dynamics (MD) simulations of monomeric -synuclein (an IDP whose aggregation is associated with Parkinsons disease) binding the small-molecule drug fasudil in which the observed protein-ligand interactions were found to be in good agreement with previously reported NMR chemical shift data. In our simulations, fasudil, when bound, favored certain charge-charge and {pi}-stacking interactions near the C terminus of -synuclein, but tended not to form these interactions simultaneously, rather breaking one of these interactions and forming another nearby (a mechanism we term dynamic shuttling). Further simulations with small molecules chosen to modify these interactions yielded binding affinities and key structural features of binding consistent with subsequent NMR experiments, suggesting the potential for MD-based strategies to facilitate the rational design of small molecules that bind with disordered proteins.

biophysics↗

bioRxiv2020

Doxycycline interferes with tau amyloid aggregation abolishing its associated neuronal toxicity

Tauopathies are neurodegenerative disorders with increasing incidence and still without cure. The extensive time required for development and approval of novel therapeutics highlights the need for testing and repurposing known safe molecules. Since doxycycline impacts -synuclein aggregation and toxicity, herein we tested its effect on tau. We found that doxycycline reduces amyloid aggregation of the different isoforms of tau protein in a dose-dependent manner, remodeling the resultant species. Furthermore, doxycycline interacts with tau microtubule-binding domain preventing its aggregation. In a cell free system doxycycline also prevents tau seeding and in cell culture reduces toxicity of tau aggregates. Overall, our results expand the spectrum of action of doxycycline against aggregation-prone proteins, opening novel perspectives for its repurposing as a disease-modifying drug for tauopathies.

biophysics↗

bioRxiv2020

Nucleocapsid protein of SARS-CoV-2 phase separates into RNA-rich polymerase-containing condensates

The etiologic agent of the Covid-19 pandemic is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The viral membrane of SARS-CoV-2 surrounds a helical nucleocapsid in which the viral genome is encapsulated by the nucleocapsid protein. The nucleocapsid protein of SARS-CoV-2 is produced at high levels within infected cells, enhances the efficiency of viral RNA transcription and is essential for viral replication. Here we show that RNA induces cooperative liquid-liquid phase separation of the SARS-CoV-2 nucleocapsid protein. In agreement with its ability to phase separate in vitro, we show that the protein associates in cells with stress granules, cytoplasmic RNA/protein granules that form through liquid-liquid phase separation and are modulated by viruses to maximize replication efficiency. Liquid-liquid phase separation generates high-density protein/RNA condensates that recruit the RNA-dependent RNA polymerase complex of SARS-CoV-2 providing a mechanism for efficient transcription of viral RNA. Inhibition of RNA-induced phase separation of the nucleocapsid protein by small molecules or biologics thus can interfere with a key step in the SARS-CoV-2 replication cycle.

biophysics↗

bioRxiv2020

Effects of pharmacological modulators of α-synuclein and tau aggregation and internalization

Parkinsons disease (PD) and Alzheimers disease (AD) are common neurodegenerative disorders of the elderly and, therefore, affect a growing number of patients worldwide. Both diseases share, as a common hallmark, the accumulation of characteristic protein aggregates, known as Lewy bodies (LB) in PD, and neurofibrillary tangles in AD. LBs are primarily composed of misfolded -synuclein (aSyn), and neurofibrillary tangles are primarily composed of tau protein. Importantly, upon pathological evaluation, most AD and PD/Lewy body dementia cases exhibit mixed pathology, with the co-occurrence of both Lewy bodies and neurofibrillary tangles, among other protein inclusions. Recent studies suggest that both aSyn and tau pathology can spread and propagate through neuronal connections. Therefore, it is important to investigate the mechanisms underlying aggregation and propagation of these proteins for the development of novel therapeutic strategies. Here, we assessed the effects of different pharmacological interventions on the aggregation and internalization of tau and aSyn. We found that anle138b and epigallocatechin gallate decrease aSyn aggregation, that fulvic acid attenuates aggregation of the repeat domain of tau, and that dynasore reduces tau internalization. Establishing the effects of small molecules with different chemical properties on the aggregation and spreading of aSyn and tau will be important for the development of future therapeutic interventions.

neuroscience↗

bioRxiv2020

Cooperativity of membrane-protein and protein-protein interactions control membrane remodeling by epsin 1 and regulate clathrin-mediated endocytosis

Membrane remodeling is a critical process for many membrane trafficking events, including clathrin-mediated endocytosis. Several molecular mechanisms for protein induced membrane curvature have been described in some detail. Contrary, the effect that the physico-chemical properties of the membrane has on these processes is far less well understood. Here, we show that the membrane binding and curvature-inducing ENTH domain of epsin1 is regulated by phosphatidylserine (PS). ENTH binds to membranes in a PI(4,5)P2-dependent manner but only induces curvature in the presence of PS. On PS-containing membranes, the ENTH domain forms rigid homo-oligomers and assembles into clusters. Membrane binding and membrane remodeling can be separated by structure-to-function mutants. Such oligomerization mutants bind to membranes but do not show membrane remodeling activity. In vivo they are not able to rescue defects in epidermal growth factor receptor (EGFR) endocytosis in epsin knock-down cells. Together, these data show that the membrane lipid composition is important for the regulation of protein-dependent membrane deformation during clathrin-mediated endocytosis.

biophysics↗

bioRxiv2019

A nanobody-based fluorescent reporter reveals human α-synuclein in the cell cytosol

Aggregation and spreading of -Synuclein (Syn) are hallmarks of several neurodegenerative diseases, thus monitoring human Syn (hSyn) in animal models or cell cultures is vital for the field. However, the detection of native hSyn in such systems is challenging. We found that the nanobody NbSyn87, previously-described to bind hSyn, also shows cross-reactivity for the proteasomal subunit Rpn10. As such, when the NbSyn87 is expressed in the absence of hSyn, it is continuously degraded by the proteasome, while it is stabilized when it binds to hSyn. Here, we exploited this feature to design a new Fluorescent Reporter for hSyn (FluoReSyn) by coupling NbSyn87 to fluorescent proteins, which results in fluorescence signal fluctuations depending on the presence and amounts of intracellular hSyn. We characterized this biosensor in cells and tissues, and finally, revealed the presence of transmittable Syn in human cerebrospinal fluid demonstrating the potential of FluoReSyn for clinical research and diagnostics.

neuroscience↗

bioRxiv2019

Dynamic Aha1 Co-Chaperone Binding to Human Hsp90

Hsp90 is an essential chaperone that requires large allosteric changes to determine its ATPase activity and client binding. Because of the inherent low ATPase activity of human Hsp90, the co-chaperone Aha1, which is the only known ATPase stimulator in eukaryotes, is important for regulation of Hsp90s allosteric timing. Little is known, however, about the structure of the Hsp90/Aha1 full-length complex. Here, we characterize the solution structure of unmodified human Hsp90 in complex with Aha1 using NMR spectroscopy. We show that the 214 kDa complex adopts multiple conformations in the absence of nucleotide. Interaction with Aha1 induces structural changes near the nucleotide-binding site in Hsp90s N-terminal domain, providing a basis for its ATPase-enhancing activity. Moreover, the E67K mutation in Aha1 strongly diminishes the interaction, supporting a two-step binding mechanism. Our data reveal important aspects of this pivotal chaperone/co-chaperone interaction and emphasize the relevance of characterizing dynamic chaperone structures in solution.

biophysics↗

bioRxiv2018

RNA polymerase II clustering through CTD phase separation

The carboxy-terminal domain (CTD) of RNA polymerase (Pol) II is an intrinsically disordered low-complexity region that is critical for pre-mRNA transcription and processing. The CTD consists of hepta-amino acid repeats varying in number from 52 in humans to 26 in yeast. Here we report that human and yeast CTDs undergo cooperative liquid phase separation at increasing protein concentration, with the shorter yeast CTD forming less stable droplets. In human cells, truncation of the CTD to the length of the yeast CTD decreases Pol II clustering and chromatin association whereas CTD extension has the opposite effect. CTD droplets can incorporate intact Pol II and are dissolved by CTD phosphorylation with the transcription initiation factor IIH kinase CDK7. Together with published data, our results suggest that Pol II forms clusters/hubs at active genes through interactions between CTDs and with activators, and that CTD phosphorylation liberates Pol II enzymes from hubs for promoter escape and transcription elongation.

molecular biology↗