The Substrate-Driven Transition to an Inward-Facing Conformation in the Functional Mechanism of the Dopamine Transporter

The dopamine transporter (DAT), a member of the neurotransmitter:Na(+) symporter (NSS) family, terminates dopaminergic neurotransmission and is a major molecular target for psychostimulants such as cocaine and amphetamine, and for the treatment of attention deficit disorder and depression. The crystal structures of the prokaryotic NSS homolog of DAT, the leucine transporter LeuT, have provided critical structural insights about the occluded and outward-facing conformations visited during the substrate transport, but only limited clues regarding mechanism. To understand the transport mechanism in DAT we have used a homology model based on the LeuT structure in a computational protocol validated previously for LeuT, in which steered molecular dynamics (SMD) simulations guide the substrate along a pathway leading from the extracellular end to the intracellular (cytoplasmic) end.Key findings are (1) a second substrate binding site in the extracellular vestibule, and (2) models of the conformational states identified as occluded, doubly occupied, and inward-facing. The transition between these states involve a spatially ordered sequence of interactions between the two substrate-binding sites, followed by rearrangements in structural elements located between the primary binding site and the cytoplasmic end. These rearrangements are facilitated by identified conserved hinge regions and a reorganization of interaction networks that had been identified as gates.Computational simulations supported by information available from experiments in DAT and other NSS transporters have produced a detailed mechanistic proposal for the dynamic changes associated with substrate transport in DAT. This allosteric mechanism is triggered by the binding of substrate in the S2 site in the presence of the substrate in the S1 site. Specific structural elements involved in this mechanism, and their roles in the conformational transitions illuminated here describe, a specific substrate-driven allosteric mechanism that is directly amenable to experiment as shown previously for LeuT

Quantitative Analysis of Membrane Deformation by Multi-Helical Transmembrane Proteins

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Diversity of bacterial communities in acid mine drainage from the Shen-bu copper mine, Gansu province, China

This study presents bacterial population analyses of microbial communities inhabiting three sites of acid mine drainage (AMD) in the Shen-bu copper mine, Gansu Province, China. These sites were located next to acid-leached chalcopyrite slagheaps that had been abandoned since 1995. The pH values of these samples with high concentrations of metals ranged from 2.0 to 3.5. Amplified ribosomal DNA restriction analysis (ARDRA) was used to characterize the bacterial population by amplifying the 16S rRNA gene of microorganisms. A total of 39 operational taxonomic units (OTUs) were obtained from the three samples and sequenced from 384 clones. Sequence data and phylogenetic analyses showed that two dominant clones (JYC-1B, JYC-1D) in sample JYC-1 represented 69.5% of the total clones affiliated with Acidithiobacillus ferrooxidans (\u3b3-Proteobacteria), and the most dominant clones of JYC-2 and JYC-3 were affiliated with Caulobacter crescentus (\u3b1-Protebacteria). At the level of bacterial divisions, differences in the relative incidence of particular phylogenetic groups among the three samples and discrepancies in physicochemical characteristics suggested that the physico-chemical characteristics had an influence on phylogenetic diversity. Furthermore, the relationships between the discrepancies of physicochemical characteristics and the diversity of the bacteria communities in the three samples suggested that the biogeochemical properties, pH and concentration of soluble metal, could be key factors in controlling the structure of the bacterial population

Global incidence trends of early-onset colorectal cancer and related exposures in early-life: an ecological analysis based on the GBD 2019

BackgroundThe incidence of early-onset colorectal cancer (EOCRC) is increasing globally. This study aims to describe the temporal trends of incidence and explore related risk exposures in early-life at the country level based on the GBD 2019.MethodsData on the incidence and attributable risk factors of EOCRC were obtained from the GBD 2019. Temporal trends of age-standardized incidence were evaluated by average annual percentage change (AAPC). Early-life exposures were indicated as summary exposure values (SEV) of selected factors, SDI and GDP per capita in previous decades and at ages 0–4, 5–9, 10–14 and 15–19 years. Weighted linear or non-linear regressions were applied to evaluate the ecological aggregate associations of the exposures with incidences of EOCRC.ResultsThe global age-standardized incidence of EOCRC increased from 3.05 (3.03, 3.07) to 3.85 (3.83, 3.86) per 100,000 during 1990 and 2019. The incidence was higher in countries with high socioeconomic levels, and increased drastically in countries in East Asia and Caribbean, particularly Jamaica, Saudi Arabia and Vietnam. The GDP per capita, SDI, and SEVs of iron deficiency, alcohol use, high body-mass index, and child growth failure in earlier years were more closely related with the incidences of EOCRC in 2019. Exposures at ages 0–4, 5–9, 10–14 and 15–19 years were also associated with the incidences, particularly for the exposures at ages 15–19 years.ConclusionThe global incidence of EOCRC increased during past three decades. The large variations at regional and national level may be related with the distribution of risk exposures in early life

Generation of integration-free neural progenitor cells from cells in human urine

Human neural stem cells hold great promise for research and therapy in neural disease. We describe the generation of integration-free and expandable human neural progenitor cells (NPCs). We combined an episomal system to deliver reprogramming factors with a chemically defined culture medium to reprogram epithelial-like cells from human urine into NPCs (hUiNPCs). These transgene-free hUiNPCs can self-renew and can differentiate into multiple functional neuronal subtypes and glial cells in vitro. Although functional in vivo analysis is still needed, we report that the cells survive and differentiate upon transplant into newborn rat brain.postprin

Ligand-Dependent Conformations and Dynamics of the Serotonin 5-HT2A Receptor Determine Its Activation and Membrane-Driven Oligomerization Properties

From computational simulations of a serotonin 2A receptor (5-HT2AR) model complexed with pharmacologically and structurally diverse ligands we identify different conformational states and dynamics adopted by the receptor bound to the full agonist 5-HT, the partial agonist LSD, and the inverse agonist Ketanserin. The results from the unbiased all-atom molecular dynamics (MD) simulations show that the three ligands affect differently the known GPCR activation elements including the toggle switch at W6.48, the changes in the ionic lock between E6.30 and R3.50 of the DRY motif in TM3, and the dynamics of the NPxxY motif in TM7. The computational results uncover a sequence of steps connecting these experimentally-identified elements of GPCR activation. The differences among the properties of the receptor molecule interacting with the ligands correlate with their distinct pharmacological properties. Combining these results with quantitative analysis of membrane deformation obtained with our new method (Mondal et al, Biophysical Journal 2011), we show that distinct conformational rearrangements produced by the three ligands also elicit different responses in the surrounding membrane. The differential reorganization of the receptor environment is reflected in (i)-the involvement of cholesterol in the activation of the 5-HT2AR, and (ii)-different extents and patterns of membrane deformations. These findings are discussed in the context of their likely functional consequences and a predicted mechanism of ligand-specific GPCR oligomerization

Robust Stability Criteria for Uncertain Stochastic Cellular Neural Networks with Time Delays

In this paper, the global robust asymptotic stability problem is considered for stochastic cellular neural networks with time delays and parameter uncertainties. The aim of this paper is to establish easily verifiable conditions under which the stochastic cellular neural networks is globally robustly asymptotically stable in the mean square for all admissible parameter uncertainties. Base on Lyapunov- Krasovskii functional and stochastic analysis approaches, a linear matrix inequality (LMI) approach is developed to derive the stability criteria. A numerical example is provided to illustrate the effectiveness and applicability of the proposed criteria

Health insurance and inequalities in catastrophic health spending in cancer patients. A cross-sectional study in China

Objective: To determine the role of social health insurance programs in reducing inequality in the incidence and intensity of catastrophic health expenditure (CHE) of cancer patients in China. Method: A convenient sample of 2534 cancer patients treated in nine hospitals in 2015 and 2016 were followed up through face-to-face interviews in March-December 2018. The incidence and intensity (mean positive overshoot) of CHE (≥ 40% household consumption) were calculated. Results: About 72% of cancer patients experienced CHE events after insurance compensation, with the catastrophic mean positive overshoot amounting to 28.27% (SD: 15.83%) of the household consumption. Overall, social insurance contributed to a small percentage of drop in CHE events. Income-related inequality in CHE persisted before and after insurance compensation. Richer patients benefit more than poorer ones. Conclusions: Cancer treatment is associated with high incidence of CHE events in China. The alleviating effect of social health insurance on CHE events is limited. Resumen: Objetivo: Determinar la función de programas del seguro social de salud en reducir las desigualdades en incidencia e intensidad del gasto catastrófico en salud (GCS) en pacientes con cáncer en China. Método: Se realizó seguimiento de una muestra de conveniencia de 2534 pacientes con cáncer atendidos en nueve hospitales en 2015 y 2016, mediante entrevistas cara a cara de marzo a diciembre de 2018. Se calcularon la incidencia y la intensidad (reacción positiva promedio) de GCS (≥40% consumo del hogar). Resultados: Alrededor del 72% de los pacientes con cáncer experimentaron eventos de GCS después de la compensación del seguro; reacción positiva promedio acumulado del 28.27% (DE: 15.83%) del consumo del hogar. En general, el seguro social contribuyó al descenso de un pequeño porcentaje de eventos de GCS. La desigualdad relacionada con ingresos de GCS persistió antes y después de la compensación del seguro. Los pacientes más ricos se benefician más que los pobres. Conclusiones: El tratamiento para el cáncer está asociado con una mayor incidencia de eventos de GCS en China. El efecto mitigante del seguro social de salud es limitado en los eventos de GCS

Diversity of bacterial communities in acid mine drainage from the Shen-bu copper mine, Gansu province, China

This study presents bacterial population analyses of microbial communities inhabiting three sites of acid mine drainage (AMD) in the Shen-bu copper mine, Gansu Province, China. These sites were located next to acid-leached chalcopyrite slagheaps that had been abandoned since 1995. The pH values of these samples with high concentrations of metals ranged from 2.0 to 3.5. Amplified ribosomal DNA restriction analysis (ARDRA) was used to characterize the bacterial population by amplifying the 16S rRNA gene of microorganisms. A total of 39 operational taxonomic units (OTUs) were obtained from the three samples and sequenced from 384 clones. Sequence data and phylogenetic analyses showed that two dominant clones (JYC-1B, JYC-1D) in sample JYC-1 represented 69.5% of the total clones affiliated with Acidithiobacillus ferrooxidans (γ-Proteobacteria), and the most dominant clones of JYC-2 and JYC-3 were affiliated with Caulobacter crescentus (α-Protebacteria). At the level of bacterial divisions, differences in the relative incidence of particular phylogenetic groups among the three samples and discrepancies in physicochemical characteristics suggested that the physico-chemical characteristics had an influence on phylogenetic diversity. Furthermore, the relationships between the discrepancies of physicochemical characteristics and the diversity of the bacteria communities in the three samples suggested that the biogeochemical properties, pH and concentration of soluble metal, could be key factors in controlling the structure of the bacterial population