Zinc induces temperature-dependent reversible self-assembly of Tau

Tau is an intrinsically disordered microtubule-associated protein that is implicated in several neurodegenerative disorders called tauopathies. In these diseases, Tau is found in the form of intracellular inclusions that consist of aggregated paired helical filaments (PHFs) in neurons. Given the importance of this irreversible PHF formation in neurodegenerative disease, Tau aggregation has been extensively studied. Several different factors, such as mutations or post translational modifications, have been shown to influence the formation of late-stage non-reversible Tau aggregates. It was recently shown that zinc ions accelerated heparin-induced oligomerization of Tau constructs. Indeed, in vitro studies of PHFs have usually been performed in the presence of additional co-factors, such as heparin, in order to accelerate their formation. Using turbidimetry, we investigated the impact of zinc ions on Tau in the absence of heparin and found that zinc is able to induce a temperature-dependent reversible oligomerization of Tau. The obtained oligomers were not amyloid-like and dissociated instantly following zinc chelation or a temperature decrease. Finally, a combination of isothermal titration calorimetry and dynamic light scattering experiments showed zinc binding to a high-affinity binding site and three low-affinity sites on Tau, accompanied by a change in Tau folding. Altogether, our findings stress the importance of zinc in Tau oligomerization. This newly identified Zn-induced oligomerization mechanism may be a part of a pathway different of and concurrent to Tau aggregation cascade leading to PHF formation

Biophysical study of the tau - zinc interaction

La protéine tau est un acteur important de la physiopathologie des neurones, de par son rôle dans la régulation de la dynamique des microtubules, mais aussi par son agrégation pathologique dans les maladies neurodégénératives. Depuis de nombreuses années, les agrégats de tau sont les objets d'études in vivo et in vitro qui visent à comprendre pourquoi et comment la protéine s'agrège, en essayant d'identifier des facteurs qui déclenchent cette agrégation. Durant ces dernières années, le zinc est apparu comme un acteur important pouvant contribuer à cette agrégation pathologique dans la cellule. Cependant, le mécanisme moléculaire à l'origine de cette agrégation en présence de zinc n'a pas été décrit. Par des approches biophysiques (turbidimétrie, ITC, DLS, microscopie électronique), nous nous sommes intéressés à ce mécanisme en montrant dans un premier temps que le zinc induit la formation d'agrégats de tau réversibles en se liant directement à la protéine, et que ces agrégats possèdent une structure différente de celle des agrégats pathologiques de tau. Dans un second temps, nous avons identifié les sites de fixation du zinc par RMN et proposé un schéma de liaison entre la protéine tau et le zinc par ITC. Ce travail décrit pour la première fois le mécanisme d'agrégation de la protéine tau induit par le zinc, qui pourrait être à l'origine de l'agrégation pathologique observée dans les pathologies neurodégénératives. En parallèle, nous avons développé l'utilisation d'une méthode biophysique permettant d'étudier à la fois l'agrégation et les interactions protéiques : la nanoDSF.The tau protein is an important actor of physiopathology in neurons, mainly because of its regulation role of microtubules dynamics and its pathological aggregation in neurodegenerative disorders. For many years, tau aggregates are studied in vivo and in vitro in order to understand why and how this aggregation can occur. In the last few years, several factors were identified as enhancers or inducers of aggregation in neurons, including zinc. However, the molecular mechanism behind this aggregation was not described yet. With biophysical approaches (turbidimetry, ITC, DLS, TEM), we focused on this mechanism and showed in a first instance that zinc induces the formation of reversible aggregates of tau by binding directly to tau, and that these aggregates have a different morphology in comparison to the pathological ones. In a second time, we identified the zinc binding sites on tau by NMR experiments and proposed a binding scheme of the tau-zinc interaction with ITC while highlighting the importance of the C-terminal part of tau in the aggregation process with turbidimetry and DLS experiments. This work describes for the first time the zinc-induced aggregation of tau, which may be the first step leading to the pathological aggregation largely described in neurodegenerative diseases. In parallel, we derived the classical utilization of a biophysical technique called nanoDSF in order to study protein aggregation and interaction with one unique experiment

Étude biophysique de l'interaction protéine tau - zinc

The tau protein is an important actor of physiopathology in neurons, mainly because of its regulation role of microtubules dynamics and its pathological aggregation in neurodegenerative disorders. For many years, tau aggregates are studied in vivo and in vitro in order to understand why and how this aggregation can occur. In the last few years, several factors were identified as enhancers or inducers of aggregation in neurons, including zinc. However, the molecular mechanism behind this aggregation was not described yet. With biophysical approaches (turbidimetry, DLS, ITC, TEM), we focused on this mechanism and showed in a first instance that zinc induces the formation of reversible aggregates of tau by binding directly to tau, and that these aggregates have a different morphology in comparison to the pathological ones. In a second time, we identified the zinc binding sites on tau by NMR and proposed a binding scheme of the tau-zinc interaction with ITC while highlighting the importance of the C-terminal part of tau in the aggregation process with turbidity and DLS experiments. This work describes for the first time the zinc-induced aggregation of tau, which may be the first step leading to the pathological aggregation largely described in neurodegenerative diseases. In parallel, we derived the classical utilization of a biophysical device called nanoDSF Prometheus NT.Plex in order to study protein aggregation and interaction with one unique experiment.La protéine tau est un acteur important de la physiopathologie des neurones, de par son rôle dans la régulation de la dynamique des microtubules, mais aussi par son agrégation pathologique dans les maladies neurodégénératives. Depuis de nombreuses années, les agrégats de tau sont les objets d’études in vivo et in vitro qui visent à comprendre pourquoi et comment la protéine s’agrège, en essayant d’identifier des facteurs qui déclenchent cette agrégation. Durant ces dernières années, le zinc est apparu comme un acteur important pouvant contribuer à cette agrégation pathologique dans la cellule. Cependant, le mécanisme moléculaire à l’origine de cette agrégation en présence de zinc n’a pas été décrit. Par des approches biophysiques (turbidimétrie, DLS, ITC, microscopie électronique), nous nous sommes intéressés à ce mécanisme en montrant dans un premier temps que le zinc induit la formation d’agrégats de tau réversibles en se liant directement à la protéine, et que ces agrégats possèdent une structure différente de celle des agrégats pathologiques de tau. Dans un second temps, nous avons identifié les sites de fixation du zinc par RMN et proposé un schéma de liaison entre la protéine tau et le zinc par ITC, en mettant en évidence l’importance de la partie C-terminale de tau dans le processus d’agrégation avec des expériences de turbidimétrie et de DLS. Ce travail décrit pour la première fois le mécanisme d’agrégation de la protéine tau induit par le zinc, qui pourrait être à l’origine de l’agrégation pathologique observée dans les pathologies neurodégénératives. En parallèle, nous avons développé l’utilisation d’un appareil biophysique permettant d’étudier à la fois l’agrégation et les interactions protéiques : le nanoDSF Prometheus NT.Plex

Zinc Induces Temperature-Dependent Reversible Self-Assembly of Tau

International audienceTau is an intrinsically disordered microtubule associated protein that is implicated in several neurodegenerative disorders called Tau opathies. In these diseases, Tau is found in the form of intracellular inclusions that consist of aggregated paired helical filaments (PHFs) in neurons. Given the importance of this irreversible PHF formation in neurodegenerative disease, Tau aggregation has been extensively studied. Several different factors, such as mutations or post translational modifications, have been shown to influence the formation of late stage non-reversible Tau aggregates. It was recently shown that zinc ions accelerated heparin induced oligomerization of Tau constructs. Indeed, in vitro studies of PHFs have usually been performed in the presence of additional co-factors, such as heparin, in order to accelerate their formation. Using turbidimetry, we investigated the impact of zinc ions on Tau in the absence of heparin and found that zinc is able to induce a temperature dependent reversible oligomerization of Tau. The obtained oligomers were not amyloid like, and dissociated instantly following zinc chelation or a temperature decrease. Finally, a combination of isothermal titration calorimetry and dynamic light scattering experiments showed zinc binding to a high affinity binding site and three low affinity sites on Tau, accompanied by a change in Tau folding. Altogether, our findings stress the importance of zinc in Tau oligomerization. This newly identified Zn-induced oligomerization mechanism may be a part of a pathway different of and concurrent to Tau aggregation cascade leading to PHF formation

Binding of two zinc ions promotes liquid-liquid phase separation of Tau

International audienceTau is a naturally disordered microtubule associated protein which forms intraneuronal aggregates in several neurodegenerative diseases including Alzheimer disease (AD). It was reported that zinc interaction with tau protein can trigger its aggregation. Recently we identified three zinc binding sites located in the N-terminal part, repeat region and the C-terminal part of tau. Here we characterized zinc binding to each of three sites using isothermal titration calorimetry (ITC) and determined the impact of each site on aggregation using dynamic light scattering (DLS) assays. First, we confirmed the presence of three zinc binding sites on tau and determined the thermodynamic parameters of binding of zinc to these sites. We found a high-affinity zinc binding site located in the repeat region of tau and two N-and C-terminus binding sites with a lower binding constant for zinc. Second, we showed that tau aggregation necessitates zinc binding to the high affinity site in the R2R3 region, while LLPS necessitates zinc binding to any two binding sites. Regarding the role of zinc ions in the aggregation of proteins in neurodegenerative diseases, these findings bring new insights to the understanding of the aggregation mechanism of tau protein induced by zinc

Pulse Wave Transit Time Measurements of Cardiac Output in Septic Shock Patients: A Comparison of the Estimated Continuous Cardiac Output System with Transthoracic Echocardiography.

We determined reliability of cardiac output (CO) measured by pulse wave transit time cardiac output system (esCCO system; COesCCO) vs transthoracic echocardiography (COTTE) in mechanically ventilated patients in the early phase of septic shock. A secondary objective was to assess ability of esCCO to detect change in CO after fluid infusion.Mechanically ventilated patients admitted to the ICU, aged >18 years, in sinus rhythm, in the early phase of septic shock were prospectively included. We performed fluid infusion of 500 ml of crystalloid solution over 20 minutes and recorded CO by EsCCO and TTE immediately before (T0) and 5 minutes after (T1) fluid administration. Patients were divided into 2 groups (responders and non-responders) according to a threshold of 15% increase in COTTE in response to volume expansion.In total, 25 patients were included, average 64±15 years, 15 (60%) were men. Average SAPSII and SOFA scores were 55±21.3 and 13±2, respectively. ICU mortality was 36%. Mean cardiac output at T0 was 5.8±1.35 L/min by esCCO and 5.27±1.17 L/min by COTTE. At T1, respective values were 6.63 ± 1.57 L/min for esCCO and 6.10±1.29 L/min for COTTE. Overall, 12 patients were classified as responders, 13 as non-responders by the reference method. A threshold of 11% increase in COesCCO was found to discriminate responders from non-responders with a sensitivity of 83% (95% CI, 0.52-0.98) and a specificity of 77% (95% CI, 0.46-0.95).We show strong correlation esCCO and echocardiography for measuring CO, and change in CO after fluid infusion in ICU patients

Personal protection against biting insects and ticks.

International audienceRecent events with the first cases of local transmission of chikungunya and dengue fever virus in southern France by Aedes albopictus, adding to the nuisance and potential vectors that can be encountered when traveling in tropical or sub-tropical countries, has shown the value of a reflection on the Personal protection against vectors (PPAV). It is seen during an outbreak of vector-borne disease, or simply because of nuisance arthropods, that our fellow citizens try to protect themselves individually by using an arsenal of resources available on the market. Yet most of these means have been neither checked for effectiveness or safety tests, however, essential. Travellers, staff on mission or assignment, are looking for specific information on how to protect themselves or their families. Health workers had at their disposal so far indications that vary widely from one source to another. Therefore it seemed important to the Society of Travel Medicine (SMV) and the French Society of Parasitology (SFP) to initiate a reflection on this theme. This reflection took the form of recommendations for good practice, following the outline established by the French High Health Authority (HAS). The aim was to gather all relevant information, verified and validated and the format to be used not only by health personnel (doctors, pharmacists, nurses), but also by travel agents and individuals. This document highlights the need to take into account the risk of vector-borne diseases, some deadly, and the benefit of various methods of personal protection. The choice of methods is clearly oriented towards those whose effectiveness has been proven and potential risks assessed. The paper finally proposes two decision trees based on the transmission type (day or night) and kind of stay (short or roaming, long and steady). It concerns travellers, but also expatriates, residents and nomads

Actes de la conférence CAID 2021 (Conference on Artificial Intelligence for Defense)

6th European Cyber Week (6ème semaine européenne de la cybersécurité et de la cyberdéfense