Biostructural analysis of the metal-sensor domain of CnrX from <Emphasis Type="Italic">Cupriavidus metallidurans</Emphasis> CH34

In Cupriavidus metallidurans CH34, the proteins CnrX, CnrY, and CnrH regulate the expression of the cnrCBA operon that codes for a cation-efflux pump involved in cobalt and nickel resistance. The periplasmic part of CnrX can be defined as the metal sensor in the signal transduction complex composed of the membrane-bound anti-sigma factor CnrY and the extra-cytoplasmic function sigma factor CnrH. A soluble form of CnrX was overproduced and purified. This protein behaves as a dimer in solution as judged from gel filtration, sedimentation velocity experiments, and NMR. Native crystals diffracting to 2.3 A using synchrotron radiation were obtained using the hanging-drop vapor-diffusion method. They belong to the primitive monoclinic space group P2(1), with unit cell parameters a = 31.87, b = 74.80, c = 93.67 A, beta = 90.107 degrees. NMR data and secondary structure prediction suggest that this protein is essentially formed by helices.     

Purification of the blue-green pigment “marennine” from the marine tychopelagic diatom Haslea ostrearia (Gaillon/Bory) Simonsen

The diatom Haslea ostrearia that lives in oyster ponds has the distinctive feature of synthesizing “marennine”, a blue-green pigment of which the chemical nature still remains unknown. This pigment is responsible for the greening of oyster gills. Here, we report a new method for extraction and purification of intracellular (accumulated in the apex of the cell) and extracellular (released into the external medium) forms of the pigment. Intracellular marennine is obtained by extraction from blue algal pellets with a carbonate buffer. The extract is then centrifuged and filtered. Extracellular marennine is obtained by clarification of blue-coloured culture medium. Both extracts are then purified by a semi-preparative process, using ultrafiltration through membranes and anion-exchange chromatography. This procedure allows us to produce native pigment displaying the degree of purity required to enter upon the molecular characterisation of marennine. By this process, about 35% of the initial amount of pigment can be recovered. If necessary, this method could be easily scaled up to a larger production system to accommodate potential industrial applications.     

HIV-1 trafficking to the dendritic cell-T-cell infectious synapse uses a pathway of tetraspanin sorting to the immunological synapse

Dendritic cells (DCs) are essential components of the early events of HIV infection. Here, we characterized the trafficking pathways that HIV-1 follows during its capture by DCs and its subsequent presentation to CD4(+) T cells via an infectious synapse. Immunofluorescence microscopy indicates that the virus-containing compartment in mature DCs (mDCs) co-labels for the tetraspanins CD81, CD82, and CD9 but contains little CD63 or LAMP-1. Using ratio imaging of pH-reporting fluorescent virions in live DCs, we show that HIV-1 is internalized in an intracellular endocytic compartment with a pH of 6.2. Significantly, we demonstrate that the infectivity of cell-free virus is more stable at mildly acidic pH than at neutral pH. Using electron microscopy, we confirm that HIV-1 accumulates in intracellular vacuoles that contain CD81 positive internal membranes but overlaps only partially with CD63. When allowed to contact T cells, HIV-1-loaded DCs redistribute CD81, and CD9, as well as internalized HIV-1, but not the immunological synapse markers MHC-II and T-cell receptor to the infectious synapse. Together, our results indicate that HIV-1 is internalized into a non-conventional, non-lysosomal, endocytic compartment in mDCs and further suggest that HIV-1 is able to selectively subvert components of the intracellular trafficking machinery required for formation of the DC-T-cell immunological synapse to facilitate its own cell-to-cell transfer and propagation.     

A root chicory MADS box sequence and the Arabidopsis flowering repressor FLC share common features that suggest conserved function in vernalization and de‐vernalization responses

Root chicory (Cichorium intybus var. sativum) is a biennial crop, but is harvested to obtain root inulin at the end of the first growing season before flowering. However, cold temperatures may vernalize seeds or plantlets, leading to incidental early flowering, and hence understanding the molecular basis of vernalization is important. A MADS box sequence was isolated by RT‐PCR and named FLC‐LIKE1 (CiFL1) because of its phylogenetic positioning within the same clade as the floral repressor Arabidopsis FLOWERING LOCUS C (AtFLC). Moreover, over‐expression of CiFL1 in Arabidopsis caused late flowering and prevented up‐regulation of the AtFLC target FLOWERING LOCUS T by photoperiod, suggesting functional conservation between root chicory and Arabidopsis. Like AtFLC in Arabidopsis, CiFL1 was repressed during vernalization of seeds or plantlets of chicory, but repression of CiFL1 was unstable when the post‐vernalization temperature was favorable to flowering and when it de‐vernalized the plants. This instability of CiFL1 repression may be linked to the bienniality of root chicory compared with the annual lifecycle of Arabidopsis. However, re‐activation of AtFLC was also observed in Arabidopsis when a high temperature treatment was used straight after seed vernalization, eliminating the promotive effect of cold on flowering. Cold‐induced down‐regulation of a MADS box floral repressor and its re‐activation by high temperature thus appear to be conserved features of the vernalization and de‐vernalization responses in distant species.     

Apolipoprotein E and Low-Density Lipoprotein Binding and Internalization in Primary Cultures of Rat Astrocytes: Isoform-Specific Alterations

Abstract: Apolipoprotein (apo) E is likely involved in redistributing cholesterol and phospholipids during compensatory synaptogenesis in the injured CNS. Three common isoforms of apoE exist in human (E2, E3, and E4). The apoE4 allele frequency is markedly increased in both late-onset sporadic and familial Alzheimer's disease (AD). ApoE concentration in the brain of AD subjects follows a gradient: ApoE levels decrease as a function of E2 > E3 ? E4. It has been proposed that the poor reinnervation capacity reported in AD may be caused by impairment of the apoE/low-density lipoprotein (LDL) receptor activity. To understand further the role of this particular axis in lipid homeostasis in the CNS, we have characterized binding, internalization, and degradation of human ¹²⁵I-LDL to primary cultures of rat astrocytes. Specific binding was saturable, with a K_D of 1.8 nM and a B_max of 0.14 pmol/mg of proteins. Excess unlabeled human LDL or very LDL (VLDL) displaced 70% of total binding. Studies at 37°C confirmed that astrocytes bind, internalize, and degrade ¹²⁵I-LDL by a specific, saturable mechanism. Reconstituted apoE (E2, E3, and E4)-liposomes were labeled with ¹²⁵I and incubated with primary cultures of rat astrocytes and hippocampal neurons to examine specific binding. Human LDL and VLDL displaced binding and internalization of all apoE isoforms similarly in both astrocytes and neurons. ¹²⁵I-ApoE2 binding was significantly lower than that of the other ¹²⁵I-apoE isoforms in both cell types. ¹²⁵I-ApoE4 binding was similar to that of ¹²⁵I-apoE3 in both astrocytes and neurons. On the other hand, ¹²⁵I-apoE3 binding was significantly higher in neurons than in astrocytes. These isoform-specific alterations in apoE-lipoprotein pathway could explain some of the differences reported in the pathophysiology of AD subjects carrying different apoE alleles.     

Aggression in low functioning children and adolescents with autistic disorder

Background

Parents, caregivers and mental health professionals have often reported violence and aggression in children or adolescents with autistic disorder. However, most of these observations derived from anecdotal reports, and studies on frequency and characterization of aggression in autism remain limited. Our objective was to better characterize and understand the different types of aggressive behaviors displayed by a large group of individuals with autism in different observational situations.

Methodology/Findings

The study was conducted on 74 children and adolescents with autism and 115 typically developing control individuals matched for sex, age and pubertal stage. Other-Injurious Behaviors (OIB) were assessed in three observational situations (parents at home, two caregivers at day-care, a nurse and a child psychiatrist during blood drawing) using validated scales. The frequency of OIB was significantly higher in individuals with autism compared to typically developing control individuals during the blood drawing (23% vs. 0%, P<0 .01). The parents observed significantly less OIB in their children than caregivers (34% vs. 58%, P<0.05). In addition, the most frequent concurrent behaviors occurring just before the appearance of OIB in individuals with autism were anxiety-related behaviors and excitation according to the parental as well as the caregiver observation.

Conclusions/Significance

The results suggest that in a stressful situation, such as the blood drawing, individuals with autism release their stress through behaviors such as OIB, whereas typically developing individuals regulate and express their stress through cognitive skills such as mental coping strategies, symbolization skills with representation and anticipation of the stressful situation, social interaction and verbal or non-verbal communication. The findings underline also the key role of the environment in assessing OIB and developing therapeutic perspectives, with an individual who modulates his/her behavior according to the environment, and an environment that perceives this behavior and reacts to it with different tolerance thresholds according to the observers.     

Melanoma Cells Treated with GGTI and IFN-γ Allow Murine Vaccination and Enhance Cytotoxic Response against Human Melanoma Cells

Background

Suboptimal activation of T lymphocytes by melanoma cells is often due to the defective expression of class I major histocompatibility antigens (MHC-I) and costimulatory molecules. We have previously shown that geranylgeranyl transferase inhibition (done with GGTI-298) stimulates anti-melanoma immune response through MHC-I and costimulatory molecule expression in the B16F10 murine model [1].

Methodology/Principal Findings

In this study, it is shown that vaccination with mIFN-gand GGTI-298 pretreated B16F10 cells induces a protection against untreated tumor growth and pulmonary metastases implantation. Furthermore, using a human melanoma model (LB1319-MEL), we demonstrated that in vitro treatment with hIFN-γ and GGTI-298 led to the up regulation of MHC-I and a costimulatory molecule CD86 and down regulation of an inhibitory molecule PD-1L. Co-culture experiments with peripheral blood mononuclear cells (PBMC) revealed that modifications induced by hIFN-γ and GGTI-298 on the selected melanoma cells, enables the stimulation of lymphocytes from HLA compatible healthy donors. Indeed, as compared with untreated melanoma cells, pretreatment with hIFN-γ and GGTI-298 together rendered the melanoma cells more efficient at inducing the: i) activation of CD8 T lymphocytes (CD8+/CD69+); ii) proliferation of tumor-specific CD8 T cells (MelanA-MART1/TCR+); iii) secretion of hIFN-γ; and iv) anti-melanoma specific cytotoxic cells.

Conclusions/Significance

These data indicate that pharmacological treatment of melanoma cell lines with IFN-γ and GGTI-298 stimulates their immunogenicity and could be a novel approach to produce tumor cells suitable for vaccination and for stimulation of anti-melanoma effector cells.     

Characterization of solute binding at human serum albumin site II and its geometry using a biochromatographic approach.

Chiral recognition mechanism relationships for binding at site II on human serum albumin (HSA) were investigated using D, L dansyl amino acids. Sodium phosphate salt was used as a solute-HSA interaction modifier. A new model was developed using a biochromatographic approach to describe the variation in the transfer equilibrium constant with the salt concentration, i.e., the nature of the interactions. The solute binding was divided into two salt concentration ranges c. For the low c values, below 0.03 M, the nonstereoselective interactions constituted the preponderant contribution to the variation in the solute binding with the salt concentration. For the high c values, above 0.03 M, the solute binding was governed by the hydrophobic effect and the stereoselective interactions. The different contributions implied in the binding process provided an estimation of both the surface charge density (sigma/F) and the surface area of the site II binding cavity accessible to solvent, which were found to be equal to around 10.10(-7) mol/m(2) and 2 nm(2). As well, the excess of sodium ions excluded by the solute transfer from the surface area of the pocket were about(-0.7) for dansyl norvaline and (-0.8) for dansyl tryptophan.