Expression of Constitutively Active CDK1 Stabilizes APC-Cdh1 Substrates and Potentiates Premature Spindle Assembly and Checkpoint Function in G1 Cells

Mitotic progression in eukaryotic cells depends upon the activation of cyclin-dependent kinase 1 (CDK1), followed by its inactivation through the anaphase-promoting complex (APC)/cyclosome-mediated degradation of M-phase cyclins. Previous work revealed that expression of a constitutively active CDK1 (CDK1AF) in HeLa cells permitted their division, but yielded G1 daughter cells that underwent premature S-phase and early mitotic events. While CDK1AF was found to impede the sustained activity of APC-Cdh1, it was unknown if this defect improperly stabilized mitotic substrates and contributed to the occurrence of these premature M phases. Here, we show that CDK1AF expression in HeLa cells improperly stabilized APC-Cdh1 substrates in G1-phase daughter cells, including mitotic kinases and the APC adaptor, Cdc20. Division of CDK1AF-expressing cells produced G1 daughters with an accelerated S-phase onset, interrupted by the formation of premature bipolar spindles capable of spindle assembly checkpoint function. Further characterization of these phenotypes induced by CDK1AF expression revealed that this early spindle formation depended upon premature CDK1 and Aurora B activities, and their inhibition induced rapid spindle disassembly. Following its normal M-phase degradation, we found that the absence of Wee1 in these prematurely cycling daughter cells permitted the endogenous CDK1 to contribute to these premature mitotic events, since expression of a non-degradable Wee1 reduced the number of cells that exhibited premature cyclin B1oscillations. Lastly, we discovered that Cdh1-ablated cells could not be forced into a premature M phase, despite cyclin B1 overexpression and proteasome inhibition. Together, these results demonstrate that expression of constitutively active CDK1AF hampers the destruction of critical APC-Cdh1 targets, and that this type of condition could prevent newly divided cells from properly maintaining a prolonged interphase state. We propose that this more subtle type of defect in activity of the APC-driven negative-feedback loop may have implications for triggering genome instability and tumorigenesis

Probing the performances of MOFs for VOCs recovery

Ce travail est une contribution à la compréhension des performances de matériaux hybrides poreux de type MOFs pour le captage de benzène, dans le cadre de la lutte contre les émissions de Composés Organiques Volatils (COVs) à partir de procédés basés sur l'adsorption d'effluents gazeux. Dans ce but, nous avons couplé diverses techniques expérimentales (spectroscopie d'impédance complexe, diffraction des rayons X, manométrie d'adsorption, …) à des simulations moléculaires (calculs basés sur la Théorie de la Fonctionnelle de la Densité, Monte Carlo ou Dynamique Moléculaire) pour étudier ces matériaux en termes de capacité et de mécanisme d'adsorption. Différentes familles de MOFs ont été sélectionnées afin d'analyser l'impact de diverses caractéristiques de ces matériaux, comme la flexibilité du réseau, la présence de cations extra-réseau et la nature chimique des ligands organiques, sur leurs propriétés d'adsorption de benzène. Par ailleurs, l'eau étant souvent considérée comme un facteur limitant lors de l'adsorption sélective d'une espèce à partir d'effluents gazeux chargés d'humidité, nous avons également envisagé l'étude de cet adsorbat seul, avant d'explorer la co-adsorption de mélanges benzène/eau dans des proportions différentes. Une rationalisation des données nous a permis de conclure que certains des matériaux explorés présentent une sélectivité benzène/eau intéressante pour envisager leur utilisation potentielle dans le cadre du captage de traces.The Metal Organic Frameworks (MOFs), a recent class of hybrid porous solids, appears as valuable candidates for various applications related to their sorption abilities. The optimization of their performances requires a control of the parameters that govern the adsorption process, including the confined species/MOF interactions and the synergic dynamics of the system. In this context, experimental tools (Complex Impedance Spectroscopy, X Ray Diffraction, volumetric adsorption…) were combined with molecular simulations (Density Functional Theory, Monte Carlo and Molecular Dynamics calculations) to explore the benzene adsorption of MOFs in terms of capacity and microscopic mechanism. Different series of MOFs were selected to address the impact of various features, including the lattice flexibility, the presence of extra-framework cations and the ligand functionalization, on their adsorption performances. Benzene and water were considered as adsorbents separately, before exploring the co-adsorption of various benzene/water mixtures. The rationalization of the data allowed us to understand why some of the selected solids, showing interesting benzene/water selectivity, are likely to be used for the capture of benzene traces in humid conditions

A Joint Experimental/Computational Exploration of the Dynamics of Confined Water/Zr-Based MOFs Systems

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Switch from calcineurin inhibitors to belatacept in kidney transplant patients with chronic-active antibody mediated rejection results in lower decline in kidney function at three years

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Adsorption of Benzene in the Cation-Containing MOFs MIL-141

International audienceThe adsorption of benzene in the cation containing MOF MIL-141(Cs) was first explored by manometry measurements coupled with Monte Carlo simulations. This joint experimental-modeling approach demonstrates that this solid shows a high affinity for this guest molecule that does not result from a direct interaction between benzene and Cs+ cations in contrast to what is commonly observed in zeolites. This behavior was attributed to a high confinement degree of Cs+ which prevents any cation de-trapping upon adsorption as revealed by Dielectric Relaxation Spectroscopy and Molecular Dynamics simulations. This peculiar adsorption behavior is further discussed when one considers the other alkali extra-framework cations including Li+, Na+, K+ and Rb+

A Joint Experimental/Computational Exploration of the Dynamics of Confined Water/Zr-Based MOFs Systems

A joint modeling (molecular dynamics simulations)/​experimental (broadband dielectric spectroscopy) approach was conducted to investigate the water adsorption in the UiO-66­(Zr) MOF, and its functionalized versions bearing acidic polar groups (−COOH or 2-COOH per linker). It was first pointed out that the proton conduction measured at room temperature increases with (i) the water uptake and (ii) the concentration of the free acidic carboxylic functions. This trend was further analyzed in light of the preferential arrangements of water within the pores of each MOF as elucidated by molecular dynamics simulations. Indeed, it was revealed that the guest molecules preferentially (i) form interconnected clusters within the UiO-66­(Zr)­s cages and generate a H-bond network responsible for the proton propagation and (ii) strongly interact with the −COOH grafted functions, resulting in the creation of additional charge carriers in the case of the hydrated functionalized solids. Broadband dielectric spectroscopy shed light on how these water configurations impact the local dynamics of both the water molecules and the MOF frameworks. The dielectric relaxation investigation evidenced the existence of one or two relaxation processes, depending on the nature of the UiO-66­(Zr) framework and its hydration level. Compared to the dielectric behavior of water confined in a large variety of media, it was thus concluded that the fastest process corresponds to the dynamics of the water molecules forming clusters, while the slowest process is due to the concerted local motion of water/ligand entities

Broadly neutralizing anti-HIV-1 antibodies tether viral particles at the surface of infected cells

International audienceBroadly neutralizing antibodies (bNAbs) targeting the HIV-1 envelope glycoprotein (Env) are promising molecules for therapeutic or prophylactic interventions. Beyond neutralization, bNAbs exert Fc-dependent functions including antibody-dependent cellular cytotoxicity and activation of the complement. Here, we show that a subset of bNAbs targeting the CD4 binding site and the V1/V2 or V3 loops inhibit viral release from infected cells. We combined immunofluorescence, scanning electron microscopy, transmission electron microscopy and immunogold staining to reveal that some bNAbs form large aggregates of virions at the surface of infected cells. This activity correlates with the capacity of bNAbs to bind to Env at the cell surface and to neutralize cell-free viral particles. We further show that antibody bivalency is required for viral retention, and that aggregated virions are neutralized. We have thus identified an additional antiviral activity of bNAbs, which block HIV-1 release by tethering viral particles at the surface of infected cells

Adsorption of Benzene in the Cation-Containing MOFs MIL-141

The adsorption of benzene in the cation-containing metal–organic framework (MOF) MIL-141­(Cs) was explored by manometry measurements coupled with Monte Carlo simulations. This joint experimental/modeling approach demonstrates that this solid shows a high affinity for benzene that does not result from a direct interaction between the guest molecules and the Cs⁺ cations, in contrast to what is commonly observed in zeolites. This behavior was attributed to the high degree of confinement of Cs⁺, which prevents any cation detrapping upon adsorption, as revealed by dielectric relaxation spectroscopy and molecular dynamics simulations. This peculiar adsorption behavior is further discussed in relation to that of other alkali extraframework cations including Li⁺, Na⁺, K⁺, and Rb⁺

Asymptomatic and symptomatic SARS-CoV-2 infections elicit polyfunctional antibodies

International audienceMany SARS-CoV-2-infected individuals remain asymptomatic. Little is known about the extent and quality of their antiviral humoral response. Here, we analyze antibody functions in 52 asymptomatic infected individuals, 119 mildly symptomatic, and 21 hospitalized patients with COVID-19. We measure anti-spike immunoglobulin G (IgG), IgA, and IgM levels with the S-Flow assay and map IgG-targeted epitopes with a Luminex assay. We also evaluate neutralization, complement deposition, and antibody-dependent cellular cytotoxicity (ADCC) using replication-competent SARS-CoV-2 or reporter cell systems. We show that COVID-19 sera mediate complement deposition and kill infected cells by ADCC. Sera from asymptomatic individuals neutralize the virus, activate ADCC, and trigger complement deposition. Antibody levels and functions are lower in asymptomatic individuals than they are in symptomatic cases. Antibody functions are correlated, regardless of disease severity. Longitudinal samplings show that antibody functions follow similar kinetics of induction and contraction. Overall, asymptomatic SARS-CoV-2 infection elicits polyfunctional antibodies neutralizing the virus and targeting infected cells

Sex Differences in the Evolution of Neutralizing Antibodies to Severe Acute Respiratory Syndrome Coronavirus 2

PMCID: PMC7989436International audienceWe measured anti-spike (S), nucleoprotein (N), and neutralizing antibodies in sera from 308 healthcare workers with a positive reverse-transcription quantitative polymerase chain reaction result for severe acute respiratory syndrome coronavirus 2 and with mild disease, collected at 2 timepoints up to 6 months after symptom onset. At month 1, anti-S and -N antibody levels were higher in male participants aged >50 years and participants with a body mass index (BMI) >25 kg/m2. At months 3-6, anti-S and anti-N antibodies were detected in 99% and 59% of individuals, respectively. Anti-S antibodies and neutralizing antibodies declined faster in men than in women, independent of age and BMI, suggesting an association of sex with evolution of the humoral response