Modulation of Myelopoiesis Progenitors Is an Integral Component of Trained Immunity

Trained innate immunity fosters a sustained favorable response of myeloid cells to a secondary challenge, despite their short lifespan in circulation. We thus hypothesized that trained immunity acts via modulation of hematopoietic stem and progenitor cells (HSPCs). Administration of β-glucan (prototypical trained-immunity-inducing agonist) to mice induced expansion of progenitors of the myeloid lineage, which was associated with elevated signaling by innate immune mediators, such as IL-1β and granulocyte-macrophage colony-stimulating factor (GM-CSF), and with adaptations in glucose metabolism and cholesterol biosynthesis. The trained-immunity-related increase in myelopoiesis resulted in a beneficial response to secondary LPS challenge and protection from chemotherapy-induced myelosuppression in mice. Therefore, modulation of myeloid progenitors in the bone marrow is an integral component of trained immunity, which to date, was considered to involve functional changes of mature myeloid cells in the periphery

Cryo-EM structure of the complete and ligand-saturated insulin receptor ectodomain

Glucose homeostasis and growth essentially depend on the hormone insulin engaging its receptor. Despite biochemical and structural advances, a fundamental contradiction has persisted in the current understanding of insulin ligand-receptor interactions. While biochemistry predicts two distinct insulin binding sites, 1 and 2, recent structural analyses have resolved only site 1. Using a combined approach of cryo-EM and atomistic molecular dynamics simulation, we present the structure of the entire dimeric insulin receptor ectodomain saturated with four insulin molecules. Complementing the previously described insulin-site 1 interaction, we present the first view of insulin bound to the discrete insulin receptor site 2. Insulin binding stabilizes the receptor ectodomain in a T-shaped conformation wherein the membrane-proximal domains converge and contact each other. These findings expand the current models of insulin binding to its receptor and of its regulation. In summary, we provide the structural basis for a comprehensive description of ligand-receptor interactions that ultimately will inform new approaches to structure-based drug design.Peer reviewe

The RNA binding protein HuR is a gatekeeper of liver homeostasis

BACKGROUND AND AIMS: Non-alcoholic fatty liver disease (NAFLD) is initiated by steatosis and can progress via fibrosis and cirrhosis to hepatocellular carcinoma (HCC). The RNA binding protein HuR controls RNAs at the posttranscriptional level; hepatocyte HuR has been implicated in the regulation of diet-induced hepatic steatosis. The present study aimed to understand the role of hepatocyte-HuR in NAFLD development and progression to fibrosis and HCC. APPROACH AND RESULTS: Hepatocyte-specific HuR-deficient mice and control HuR-sufficient mice were fed either a normal diet or a NAFLD-inducing diet. Hepatic lipid accumulation, inflammation, fibrosis and HCC development were studied by histology, flow cytometry, quantitative PCR and RNA sequencing. The liver lipidome was characterized by lipidomics analysis and the HuR-RNA interactions in the liver were mapped by RNA immunoprecipitation-sequencing. Hepatocyte-specific HuR-deficient mice displayed spontaneous hepatic steatosis and fibrosis predisposition, compared to control HuR-sufficient mice. On a NAFLD-inducing diet, hepatocyte-specific HuR-deficiency resulted in exacerbated inflammation, fibrosis and HCC-like tumor development. A multi-omic approach, including lipidomics, transcriptomics and RNA-immunoprecipitation sequencing revealed that HuR orchestrates a protective network of hepatic-metabolic and lipid homeostasis-maintaining pathways. Consistently, HuR-deficient livers accumulated, already at steady-state, a triglyceride signature resembling that of NAFLD livers. Moreover, upregulation of Spp1 and its product osteopontin mediated, at least partially, the fibrosis development in hepatocyte-specific HuR deficiency on a NAFLD-inducing diet, as shown by experiments utilizing antibody blockade of osteopontin. CONCLUSIONS: HuR is a gatekeeper of liver homeostasis preventing NAFLD-related fibrosis and HCC, suggesting that the HuR-dependent network could be exploited therapeutically

Does Credit Composition have Asymmetric Effects on Income Inequality? New Evidence from Panel Data

This paper studied the effects of credit to private non-financial sectors on income inequality. In particular, we focused on the distinction between household and firm credits, and investigated whether these two types of credit had adverse effects on income inequality. Employing cross-section augmented cointegrating regressions and using balanced panel data for 30 developed and developing countries over the period from 1995 to 2013, we showed that firm credit reduced income inequality, whereas there was no significant impact of household credit on income inequality. We concluded that it was not the size of the private credit but its composition which mattered in reducing income inequality, due to the asymmetric effects of different types of credit

Regulation of human EGF receptor by lipids

The human epidermal growth factor receptor (EGFR) is a key representative of tyrosine kinase receptors, ubiquitous actors in cell signaling, proliferation, differentiation, and migration. Although the receptor is well-studied, a central issue remains: How does the compositional diversity and functional diversity of the surrounding membrane modulate receptor function? Reconstituting human EGFR into proteoliposomes of well-defined and controlled lipid compositions represents a minimal synthetic approach to systematically address this question. We show that lipid composition has little effect on ligand-binding properties of the EGFR but rather exerts a profound regulatory effect on kinase domain activation. Here, the ganglioside GM3 but not other related lipids strongly inhibited the autophosphorylation of the EGFR kinase domain. This inhibitory action of GM3 was only seen in liposomes compositionally poised to phase separate into coexisting liquid domains. The inhibition by GM3 was released by either removing the neuraminic acid of the GM3 headgroup or by mutating a membrane proximal lysine of EGFR (K642G). Our results demonstrate that GM3 exhibits the potential to regulate the allosteric structural transition from inactive to a signaling EGFR dimer, by preventing the autophosphorylation of the intracellular kinase domain in response to ligand binding

Structural characterization of an ATPase active F-1-/V-1-ATPase (alpha(3)beta(3)EG) hybrid complex

Co-reconstitution of subunits E and G of the yeast V-ATPase and the α and β subunits of the F1-ATPase from the thermophilic Bacillus PS3 (TF1) resulted in an α3β3EG hybrid complex showing 53% of the ATPase activity of TF1. The α3β3EG oligomer was characterized by electron microscopy. By processing 40,000 single particle projections, averaged two-dimensional projections at 1.2–2.4-nm resolution were obtained showing the hybrid complex in various positions. Difference mapping of top and side views of this complex with projections of the atomic model of the α3β3 subcomplex from TF1 demonstrates that a seventh mass is located inside the shaft of the α3β3 barrel and extends out from the hexamer. Furthermore, difference mapping of the α3β3EG oligomer with projections of the A3B3E and A3B3EC subcomplexes of the V1 from Caloramator fervidus shows that the mass inside the shaft is made up of subunit E, whereby subunit G was assigned to belong at least in part to the density of the protruding stalk. The formation of an active α3β3EG hybrid complex indicates that the coupling subunit γ inside the α3β3 oligomer of F1 can be effectively replaced by subunit E of the V-ATPase. Our results have also demonstrated that the E and γ subunits are structurally similar, despite the fact that their genes do not show significant homology

Structure and Subunit Arrangement of the A-type ATP Synthase Complex from the Archaeon Methanococcus jannaschii Visualized by Electron Microscopy

In Archaea, bacteria, and eukarya, ATP provides metabolic energy for energy-dependent processes. It is synthesized by enzymes known as A-type or F-type ATP synthase, which are the smallest rotatory engines in nature. Here, we report the first projected structure of an intact A1A0 ATP synthase from Methanococcus jannaschii as determined by electron microscopy and single particle analysis at a resolution of 1.8 nm. The enzyme with an overall length of 25.9 nm is organized in an A1 headpiece (9.4 × 11.5 nm) and a membrane domain, A0 (6.4 × 10.6 nm), which are linked by a central stalk with a length of ~8 nm. A part of the central stalk is surrounded by a horizontal-situated rod-like structure (“collar”), which interacts with a peripheral stalk extending from the A0 domain up to the top of the A1 portion, and a second structure connecting the collar structure with A1. Superposition of the three-dimensional reconstruction and the solution structure of the A1 complex from Methanosarcina mazei Gö1 have allowed the projections to be interpreted as the A1 headpiece, a central and the peripheral stalk, and the integral A0 domain. Finally, the structural organization of the A1A0 complex is discussed in terms of the structural relationship to the related motors, F1F0 ATP synthase and V1V0 ATPases.