Significance The four-helix bundle (4HB) domain of Mixed Lineage Kinase Domain-Like (MLKL) bears two clusters of residues that are required for cell death by necroptosis. Mutations within a cluster ...centered on the α4 helix of the 4HB domain of MLKL prevented its membrane translocation, oligomerization, and ability to induce necroptosis. This cluster is composed principally of acidic residues and therefore challenges the idea that the 4HB domain engages negatively charged phospholipid membranes via a conventional positively charged interaction surface. The importance of membrane translocation to MLKL-mediated death is supported by our identification of a small molecule that binds the MLKL pseudokinase domain and retards membrane translocation to inhibit necroptotic signaling.
Necroptosis is considered to be complementary to the classical caspase-dependent programmed cell death pathway, apoptosis. The pseudokinase Mixed Lineage Kinase Domain-Like (MLKL) is an essential effector protein in the necroptotic cell death pathway downstream of the protein kinase Receptor Interacting Protein Kinase-3 (RIPK3). How MLKL causes cell death is unclear, however RIPK3–mediated phosphorylation of the activation loop in MLKL trips a molecular switch to induce necroptotic cell death. Here, we show that the MLKL pseudokinase domain acts as a latch to restrain the N-terminal four-helix bundle (4HB) domain and that unleashing this domain results in formation of a high-molecular-weight, membrane-localized complex and cell death. Using alanine-scanning mutagenesis, we identified two clusters of residues on opposing faces of the 4HB domain that were required for the 4HB domain to kill cells. The integrity of one cluster was essential for membrane localization, whereas MLKL mutations in the other cluster did not prevent membrane translocation but prevented killing; this demonstrates that membrane localization is necessary, but insufficient, to induce cell death. Finally, we identified a small molecule that binds the nucleotide binding site within the MLKL pseudokinase domain and retards MLKL translocation to membranes, thereby preventing necroptosis. This inhibitor provides a novel tool to investigate necroptosis and demonstrates the feasibility of using small molecules to target the nucleotide binding site of pseudokinases to modulate signal transduction.
Human papillomavirus (HPV)-positive oropharyngeal cancer (OPSCC) is associated with improved survival compared with HPV-negative disease. However, a minority of HPV-positive patients have poor ...prognosis. Currently, there is no generally accepted strategy for identifying these patients.
We retrospectively analysed 270 consecutively treated OPSCC patients from three centres for effects of clinical, pathological, immunological, and molecular features on disease mortality. We used Cox regression to examine associations between factors and OPSCC death, and developed a prognostic model for 3-year mortality using logistic regression analysis.
Patients with HPV-positive tumours showed improved survival (hazard ratio (HR), 0.33 (0.21-0.53)). High levels of tumour-infiltrating lymphocytes (TILs) stratified HPV-positive patients into high-risk and low-risk groups (3-year survival; HPV-positive/TIL(high)=96%, HPV-positive/TIL(low)=59%). Survival of HPV-positive/TIL(low) patients did not differ from HPV-negative patients (HR, 1.01; P=0.98). We developed a prognostic model for HPV-positive tumours using a 'training' cohort from one centre; the combination of TIL levels, heavy smoking, and T-stage were significant (AUROC=0·87). This model was validated on patients from the other centres (detection rate 67%; false-positive rate 5.6%; AUROC=0·82).
Our data suggest that an immune response, reflected by TIL levels in the primary tumour, has an important role in the improved survival seen in most HPV-positive patients, and is relevant for the clinical evaluation of HPV-positive OPSCC.
Abstract
The gravitational potential φ = GM/Rc2 at the surface of the white dwarf G191-B2B is 10,000 times stronger than that at the Earth’s surface. Numerous photospheric absorption features are ...detected, making this a suitable environment to test theories in which the fundamental constants depend on gravity. We have measured the fine structure constant, α, at the white dwarf surface, used a newly calibrated Hubble Space Telescope STIS spectrum of G191-B2B, two new independent sets of laboratory Fe V wavelengths, and new atomic calculations of the sensitivity parameters that quantify Fe V wavelength dependency on α. The two results obtained are: Δα/α0 = (6.36 ± 0.35stat ± 1.84sys) × 10−5 and Δα/α0 = (4.21 ± 0.48stat ± 2.25sys) × 10−5. The measurements hint that the fine structure constant increases slightly in the presence of strong gravitational fields. A comprehensive search for systematic errors is summarised, including possible effects from line misidentifications, line blending, stratification of the white dwarf atmosphere, the quadratic Zeeman effect and electric field effects, photospheric velocity flows, long-range wavelength distortions in the HST spectrum, and variations in the relative Fe isotopic abundances. None fully account for the observed deviation but the systematic uncertainties are heavily dominated by laboratory wavelength measurement precision.
The Large Underground Xenon (LUX) experiment is a dual-phase xenon time-projection chamber operating at the Sanford Underground Research Facility (Lead, South Dakota). The LUX cryostat was filled for ...the first time in the underground laboratory in February 2013. We report results of the first WIMP search data set, taken during the period from April to August 2013, presenting the analysis of 85.3 live days of data with a fiducial volume of 118 kg. A profile-likelihood analysis technique shows our data to be consistent with the background-only hypothesis, allowing 90% confidence limits to be set on spin-independent WIMP-nucleon elastic scattering with a minimum upper limit on the cross section of 7.6 × 10(-46) cm(2) at a WIMP mass of 33 GeV/c(2). We find that the LUX data are in disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.
The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical ...infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5-10 kiloelectronvolt energy band range from 10(39) to 10(41) ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 10(40) ergs per second), which require black hole masses of 50-100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3-30 kiloelectronvolt range of 4.9 × 10(39) ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3-10 kiloelectronvolt range of 1.8 × 10(40) ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.
An enhanced one-dimensional model has been developed for an alkaline electrolyser cell for hydrogen production, based on linked modular mathematical models in Simulink®. Where possible, the model ...parameters were derived on a physical basis and related to the materials of construction and the configuration of its components. This means that the model can be applied to many alkaline electrolyser cells, whereas existing semi-empirical models were generally developed for a specific cell. In addition to predicting the overall equilibrium electrolyser cell performance, the model is a powerful tool for understanding the contributions to cell voltage from the various internal components. It is thus useful as a guide to researchers aiming for improved performance through modified geometry and enhanced electrode materials. The model performed very well when compared to published models tested against the same sets of experimental data.
•The model is based on physical parameters with minimum empiricism.•Electrode and electrolyte bubble effects are carefully modelled.•Although 1D, the model fits experimental data better than published models.•The model is useful for exploring electrolyser performance and diagnosing problems.
The magnitude and quality of the germinal center (GC) response decline with age, resulting in poor vaccine-induced immunity in older individuals. A functional GC requires the co-ordination of ...multiple cell types across time and space, in particular across its two functionally distinct compartments: the light and dark zones. In aged mice, there is CXCR4-mediated mislocalization of T follicular helper (T
) cells to the dark zone and a compressed network of follicular dendritic cells (FDCs) in the light zone. Here we show that T
cell localization is critical for the quality of the antibody response and for the expansion of the FDC network upon immunization. The smaller GC and compressed FDC network in aged mice were corrected by provision of T
cells that colocalize with FDCs using CXCR5. This demonstrates that the age-dependent defects in the GC response are reversible and shows that T
cells support stromal cell responses to vaccines.
The analysis of the phylogenetic structure of communities can help reveal contemporary ecological interactions, as well as link community ecology with biogeography and the study of character ...evolution. The number of studies employing this broad approach has increased to the point where comparison of their results can now be used to highlight successes and deficiencies in the approach, and to detect emerging patterns in community organization. We review studies of the phylogenetic structure of communities of different major taxa and trophic levels, across different spatial and phylogenetic scales, and using different metrics and null models. Twenty‐three of 39 studies (59%) find evidence for phylogenetic clustering in contemporary communities, but terrestrial and/or plant systems are heavily over‐represented among published studies. Experimental investigations, although uncommon at present, hold promise for unravelling mechanisms underlying the phylogenetic community structure patterns observed in community surveys. We discuss the relationship between metrics of phylogenetic clustering and tree balance and explore the various emerging biases in taxonomy and pitfalls of scale. Finally, we look beyond one‐dimensional metrics of phylogenetic structure towards multivariate descriptors that better capture the variety of ecological behaviours likely to be exhibited in communities of species with hundreds of millions of years of independent evolution.
Synchronization of circadian clocks to the day-night cycle ensures the correct timing of biological events. This entrainment process is essential to ensure that the phase of the circadian oscillator ...is synchronized with daily events within the environment 1, to permit accurate anticipation of environmental changes 2, 3. Entrainment in plants requires phase changes in the circadian oscillator, through unidentified pathways, which alter circadian oscillator gene expression in response to light, temperature, and sugars 4–6. To determine how circadian clocks respond to metabolic rhythms, we investigated the mechanisms by which sugars adjust the circadian phase in Arabidopsis 5. We focused upon metabolic regulation because interactions occur between circadian oscillators and metabolism in several experimental systems 5, 7–9, but the molecular mechanisms are unidentified. Here, we demonstrate that the transcription factor BASIC LEUCINE ZIPPER63 (bZIP63) regulates the circadian oscillator gene PSEUDO RESPONSE REGULATOR7 (PRR7) to change the circadian phase in response to sugars. We find that SnRK1, a sugar-sensing kinase that regulates bZIP63 activity and circadian period 10–14 is required for sucrose-induced changes in circadian phase. Furthermore, TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1), which synthesizes the signaling sugar trehalose-6-phosphate, is required for circadian phase adjustment in response to sucrose. We demonstrate that daily rhythms of energy availability can entrain the circadian oscillator through the function of bZIP63, TPS1, and the KIN10 subunit of the SnRK1 energy sensor. This identifies a molecular mechanism that adjusts the circadian phase in response to sugars.
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•The transcription factor bZIP63 binds and regulates the circadian clock gene PRR7•bZIP63 is required for adjustment of circadian period by sugars•Trehalose-6-phosphate metabolism and KIN10 signaling regulate circadian period•Sugar signals establish the correct circadian phase in light and dark cycles
Frank et al. identify mechanisms by which the Arabidopsis circadian clock entrains to sugars. Metabolic adjustment of circadian phase involves trehalose-6-phosphate, SnRK1 subunit KIN10 and the transcription factor bZIP63. bZIP63 regulates the circadian clock gene PSEUDORESPONSE REGULATOR7. This sets the circadian phase in light and dark cycles.
Methods of storing hydrogen for energy applications have been widely discussed, both across time and by people from various organisations and backgrounds. Recently, interest in hydrogen storage has ...developed for space exploration, for both terrestrial and extra-terrestrial applications, and more recently by politicians and business leaders for displacing carbon-intensive fuels. Hydrogen storage options range from solid to gas phases, with several detailed reviews focussing on metal hydrides such as alkali-earth alloys, chemical hydrides such as ammonia, and liquid organic carriers available. An overlooked part of the literature has been hydrogen storage in slurries, where each method of storage has unique advantages, challenges, and stages of research and development. Here, we focus on reviewing the literature on slush hydrogen and slurries of metal and chemical hydrides.
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•Review of progress in hydrogen storage in slurries.•Slush hydrogen, metal hydride and ammonia borane slurries are reviewed.•Advantages of slurries include higher hydrogen storage and easier handling.•More work is needed to address the challenges of each method.
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