Cellular endosomal potassium ion flux regulates arenavirus uncoating during virus entry

Lymphocytic choriomeningitis virus (LCMV) is an enveloped and segmented negative-sense RNA virus classified within th

MTSEA prevents ligand binding to the human melanocortin-4 receptor by modification of cysteine 130 in transmembrane helix 3

AbstractWe have investigated the effect of the sulfhydryl-reactive reagent, methyl thiosulfonate ethylammonium (MTSEA), on ligand binding to the human melanocortin-4 (MC4) receptor stably expressed in HEK-293 cells. MTSEA inhibited binding of the agonist, 125I-NDPα-MSH, and the antagonist, 125I-SHU9119, in a concentration-dependent manner. Pre-incubation of cells with either the agonist or antagonist protected from subsequent MTSEA inhibition of radioligand binding. Mutation of Cys130 in transmembrane helix 3 to alanine, whilst not affecting ligand binding, led to a complete loss of the inhibitory effect of MTSEA. Since other types of sulfhydryl-reactive reagents had no effect on ligand binding, we conclude that covalent modification of Cys130 by MTSEA disrupts ligand binding by neutralising a close-by negative charge, most likely on Asp126

Association between a rare SNP in the second intron of human Agouti related protein gene and increased BMI

<p>Abstract</p> <p>Background</p> <p>The agouti related protein (AGRP) is an endogenous antagonist of the melanocortin 4 receptor and is one of the most potent orexigenic factors. The aim of the present study was to assess the genetic variability of <it>AGRP </it>gene and investigate whether the previously reported SNP rs5030980 and the rs11575892, a SNP that so far has not been studied with respect to obesity is associated with increased body mass index (BMI).</p> <p>Methods</p> <p>We determined the complete sequence of the <it>AGRP </it>gene and upstream promoter region in 95 patients with severe obesity (BMI > 35 kg/m²). Three polymorphisms were identified: silent mutation c.123G>A (rs34123523) in the second exon, non-synonymous mutation c.199G>A (rs5030980) and c.131-42C>T (rs11575892) located in the second intron. We further screened rs11575892 in a selected group of 1135 and rs5030980 in group of 789 participants from the Genome Database of Latvian Population and Latvian State Research Program Database.</p> <p>Results</p> <p>The CT heterozygotes of rs11575892 had significantly higher mean BMI value (p = 0.027). After adjustment for age, gender and other significant non-genetic factors (presence of diseases), the BMI levels remained significantly higher in carriers of the rs11575892 T allele (p = 0.001). The adjusted mean BMI value of CC genotype was 27.92 ± 1.01 kg/m²(mean, SE) as compared to 30.97 ± 1.03 kg/m²for the CT genotype. No association was found between rs5030980 and BMI.</p> <p>Conclusion</p> <p>This study presents an association of rare allele of <it>AGRP </it>polymorphism in heterozygous state with increased BMI. The possible functional effects of this polymorphism are unclear but may relate to splicing defects.</p

Effects of Hypothalamic Neurodegeneration on Energy Balance

Normal aging in humans and rodents is accompanied by a progressive increase in adiposity. To investigate the role of hypothalamic neuronal circuits in this process, we used a Cre-lox strategy to create mice with specific and progressive degeneration of hypothalamic neurons that express agouti-related protein (Agrp) or proopiomelanocortin (Pomc), neuropeptides that promote positive or negative energy balance, respectively, through their opposing effects on melanocortin receptor signaling. In previous studies, Pomc mutant mice became obese, but Agrp mutant mice were surprisingly normal, suggesting potential compensation by neuronal circuits or genetic redundancy. Here we find that Pomc-ablation mice develop obesity similar to that described for Pomc knockout mice, but also exhibit defects in compensatory hyperphagia similar to what occurs during normal aging. Agrp-ablation female mice exhibit reduced adiposity with normal compensatory hyperphagia, while animals ablated for both Pomc and Agrp neurons exhibit an additive interaction phenotype. These findings provide new insight into the roles of hypothalamic neurons in energy balance regulation, and provide a model for understanding defects in human energy balance associated with neurodegeneration and aging

Mammalian Comparative Sequence Analysis of the Agrp Locus

Agouti-related protein encodes a neuropeptide that stimulates food intake. Agrp expression in the brain is restricted to neurons in the arcuate nucleus of the hypothalamus and is elevated by states of negative energy balance. The molecular mechanisms underlying Agrp regulation, however, remain poorly defined. Using a combination of transgenic and comparative sequence analysis, we have previously identified a 760 bp conserved region upstream of Agrp which contains STAT binding elements that participate in Agrp transcriptional regulation. In this study, we attempt to improve the specificity for detecting conserved elements in this region by comparing genomic sequences from 10 mammalian species. Our analysis reveals a symmetrical organization of conserved sequences upstream of Agrp, which cluster into two inverted repeat elements. Conserved sequences within these elements suggest a role for homeodomain proteins in the regulation of Agrp and provide additional targets for functional evaluation

Lassa Fever in Post-Conflict Sierra Leone

Background: Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease. Methodology/Principal Findings Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects. Conclusions/Significance: Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to develop more effective and/or supplemental treatments for LF

The p53 Tumor Suppressor-Like Protein nvp63 Mediates Selective Germ Cell Death in the Sea Anemone Nematostella vectensis

Here we report the identification and molecular function of the p53 tumor suppressor-like protein nvp63 in a non-bilaterian animal, the starlet sea anemone Nematostella vectensis. So far, p53-like proteins had been found in bilaterians only. The evolutionary origin of p53-like proteins is highly disputed and primordial p53-like proteins are variably thought to protect somatic cells from genotoxic stress. Here we show that ultraviolet (UV) irradiation at low levels selectively induces programmed cell death in early gametes but not somatic cells of adult N. vectensis polyps. We demonstrate with RNA interference that nvp63 mediates this cell death in vivo. Nvp63 is the most archaic member of three p53-like proteins found in N. vectensis and in congruence with all known p53-like proteins, nvp63 binds to the vertebrate p53 DNA recognition sequence and activates target gene transcription in vitro. A transactivation inhibitory domain at its C-terminus with high homology to the vertebrate p63 may regulate nvp63 on a molecular level. The genotoxic stress induced and nvp63 mediated apoptosis in N. vectensis gametes reveals an evolutionary ancient germ cell protective pathway which relies on p63-like proteins and is conserved from cnidarians to vertebrates

The Marburgvirus-Neutralizing Human Monoclonal Antibody MR191 Targets a Conserved Site to Block Virus Receptor Binding

Since their first identification 50 years ago, marburgviruses have emerged several times, with 83%–90% lethality in the largest outbreaks. Although no vaccines or therapeutics are available for human use, the human antibody MR191 provides complete protection in non-human primates when delivered several days after inoculation of a lethal marburgvirus dose. The detailed neutralization mechanism of MR191 remains outstanding. Here we present a 3.2 Å crystal structure of MR191 complexed with a trimeric marburgvirus surface glycoprotein (GP). MR191 neutralizes by occupying the conserved receptor-binding site and competing with the host receptor Niemann-Pick C1. The structure illuminates previously disordered regions of GP including the stalk, fusion loop, CX_6CC switch, and an N-terminal region of GP2 that wraps about the outside of GP1 to anchor a marburgvirus-specific “wing” antibody epitope. Virus escape mutations mapped far outside the MR191 receptor-binding site footprint suggest a role for these other regions in the GP quaternary structure

Genome-Wide Expression Analysis Identifies a Modulator of Ionizing Radiation-Induced p53-Independent Apoptosis in Drosophila melanogaster

Tumor suppressor p53 plays a key role in DNA damage responses in metazoa, yet more than half of human tumors show p53 deficiencies. Therefore, understanding how therapeutic genotoxins such as ionizing radiation (IR) can elicit DNA damage responses in a p53-independent manner is of clinical importance. Drosophila has been a good model to study the effects of IR because DNA damage responses as well as underlying genes are conserved in this model, and because streamlined gene families make loss-of-function analyses feasible. Indeed, Drosophila is the only genetically tractable model for IR-induced, p53-independent apoptosis and for tissue regeneration and homeostasis after radiation damage. While these phenomenon occur only in the larvae, all genome-wide gene expression analyses after irradiation to date have been in embryos. We report here the first analysis of IR-induced, genome-wide gene expression changes in wild type and p53 mutant Drosophila larvae. Key data from microarrays were confirmed by quantitative RT-PCR. The results solidify the central role of p53 in IR-induced transcriptome changes, but also show that nearly all changes are made of both p53-dependent and p53-independent components. p53 is found to be necessary not just for the induction of but also for the repression of transcript levels for many genes in response to IR. Furthermore, Functional analysis of one of the top-changing genes, EF1a-100E, implicates it in repression of IR-induced p53-independent apoptosis. These and other results support the emerging notion that there is not a single dominant mechanism but that both positive and negative inputs collaborate to induce p53-independent apoptosis in response to IR in Drosophila larvae