Vaccinia Virus-Mediated Inhibition of Type I Interferon Responses Is a Multifactorial Process Involving the Soluble Type I Interferon Receptor B18 and Intracellular Components

Poxviruses such as virulent vaccinia virus (VACV) strain Western Reserve encode a broad range of immune modulators that interfere with host responses to infection. Upon more than 570 in vitro passages in chicken embryo fibroblasts (CEF), chorioallantois VACV Ankara (CVA) accumulated mutations that resulted in highly attenuated modified vaccinia virus Ankara (MVA). MVA infection of mice and of dendritic cells (DC) induced significant type I interferon (IFN) responses, whereas infection with VACV alone or in combination with MVA did not. These results implied that VACV expressed an IFN inhibitor(s) that was functionally deleted in MVA. To further characterize the IFN inhibitor(s), infection experiments were carried out with CVA strains isolated after 152 (CVA152) and 386 CEF passages (CVA386). Interestingly, neither CVA152 nor CVA386 induced IFN-α, whereas the latter variant did induce IFN-β. This pattern suggested a consecutive loss of inhibitors during MVA attenuation. Similar to supernatants of VACV- and CVA152-infected DC cultures, recombinantly expressed soluble IFN decoy receptor B18, which is encoded in the VACV genome, inhibited MVA-induced IFN-α but not IFN-β. In the same direction, a B18R-deficient VACV variant triggered only IFN-α, confirming B18 as the soluble IFN-α inhibitor. Interestingly, VACV infection inhibited IFN responses induced by a multitude of different stimuli, including oligodeoxynucleotides containing CpG motifs, poly(I:C), and vesicular stomatitis virus. Collectively, the data presented show that VACV-mediated IFN inhibition is a multistep process involving secreted factors such as B18 plus intracellular components that cooperate to efficiently shut off systemic IFN-α and IFN-β responses.     

Weak Functional Coupling of the Melanocortin-1 Receptor Expressed in Human Adipocytes

The melanocortin (MC) receptor type-1 (MC1-R) is the only one of the five MC receptor subtypes expressed in human adipose tissue explants, human mesenchymal stem cells (MSCs), and MSC-derived adipocytes. Following our recent expression studies (Obesity 2007, 15, 40–49), we now investigated the functional role of MC1-R in these tissues and cells to deduce the coupling state of MC1-R to intracellular output signals in human fat cells and tissue. Expression of MC1-R by undifferentiated and differentiated MSCs was quantified by real-time TaqMan PCR. Intracellular output signals (cAMP, lipolysis, secretion of IL-6, IL-10, and TNF-α), as well as effects on the metabolic rate and proliferation of human MSCs were analyzed by standard assays, exposing undifferentiated and differentiated MSCs and, in part, human adipose tissue explants to the potent MC1-R agonist, [Nle⁴, D-Phe⁷]-α -MSH (NDP-MSH). This agonist induced a weak cAMP signal in MSC-derived adipocytes. However, it did not affect lipolysis in these cells or in adipose tissue explants, nor did it modulate cytokine release and mRNA expression of IL-6, IL-8, and TNF-α upon LPS stimulation. In undifferentiated MSCs, NDP-MSH did not alter the metabolic rate, but it showed a significant antiproliferative effect. Therefore, it appears that MC1-R–effector coupling in (differentiated) human adipocytes is too weak to induce a regulatory effect on lipolysis or inflammation; by contrast, MC1-R stimulation in undifferentiated MSCs induces an inhibitory signal on cell proliferation.     

The Fetal Hypothalamus Has the Potential to Generate Cells with a Gonadotropin Releasing Hormone (GnRH) Phenotype

Background

Neurospheres (NS) are colonies of neural stem and precursor cells capable of differentiating into the central nervous system (CNS) cell lineages upon appropriate culture conditions: neurons, and glial cells. NS were originally derived from the embryonic and adult mouse striatum subventricular zone. More recently, experimental evidence substantiated the isolation of NS from almost any region of the CNS, including the hypothalamus.

Methodology/Findings

Here we report a protocol that enables to generate large quantities of NS from both fetal and adult rat hypothalami. We found that either FGF-2 or EGF were capable of inducing NS formation from fetal hypothalamic cultures, but that only FGF-2 is effective in the adult cultures. The hypothalamic-derived NS are capable of differentiating into neurons and glial cells and most notably, as demonstrated by immunocytochemical detection with a specific anti-GnRH antibody, the fetal cultures contain cells that exhibit a GnRH phenotype upon differentiation.

Conclusions/Significance

This in vitro model should be useful to study the molecular mechanisms involved in GnRH neuronal differentiation.     

The Agnogene of the Human Polyomavirus BK Is Expressed

Primate polyomavirus genomes all contain an open reading frame at the 5′ end of the late coding region called the agnogene. A simian virus 40 agnoprotein with unknown functions has previously been demonstrated. We now show that a BK virus agnoprotein appears in the perinuclear area and cytoplasm late in the infectious cycle. It is phosphorylated in vivo and coimmunoprecipitates with a subset of host cell proteins.     

The Inner Nuclear Membrane Protein Nemp1 Is a New Type of RanGTP-Binding Protein in Eukaryotes

The inner nuclear membrane (INM) protein Nemp1/TMEM194A has previously been suggested to be involved in eye development in Xenopus, and contains two evolutionarily conserved sequences in the transmembrane domains (TMs) and the C-terminal region, named region A and region B, respectively. To elucidate the molecular nature of Nemp1, we analyzed its interacting proteins through those conserved regions. First, we found that Nemp1 interacts with itself and lamin through the TMs and region A, respectively. Colocalization of Nemp1 and lamin at the INM suggests that the interaction with lamin participates in the INM localization of Nemp1. Secondly, through yeast two-hybrid screening using region B as bait, we identified the small GTPase Ran as a probable Nemp1-binding partner. GST pulldown and co-immunoprecipitation assays using region B and Ran mutants revealed that region B binds directly to the GTP-bound Ran through its effector domain. Immunostaining experiments using transfected COS-7 cells revealed that full-length Nemp1 recruits Ran near the nuclear envelope, suggesting a role for Nemp1 in the accumulation of RanGTP at the nuclear periphery. At the neurula-to-tailbud stages of Xenopus embryos, nemp1 expression overlapped with ran in several regions including the eye vesicles. Co-knockdown using antisense morpholino oligos for nemp1 and ran caused reduction of cell densities and severe eye defects more strongly than either single knockdown alone, suggesting their functional interaction. Finally we show that Arabidopsis thaliana Nemp1-orthologous proteins interact with A. thaliana Ran, suggesting their evolutionally conserved physical and functional interactions possibly in basic cellular functions including nuclear transportation. Taken together, we conclude that Nemp1 represents a new type of RanGTP-binding protein.     

Receptor Tyrosine Kinase EphA5 Is a Functional Molecular Target in Human Lung Cancer

Lung cancer is often refractory to radiotherapy, but molecular mechanisms of tumor resistance remain poorly defined. Here we show that the receptor tyrosine kinase EphA5 is specifically overexpressed in lung cancer and is involved in regulating cellular responses to genotoxic insult. In the absence of EphA5, lung cancer cells displayed a defective G₁/S cell cycle checkpoint, were unable to resolve DNA damage, and became radiosensitive. Upon irradiation, EphA5 was transported into the nucleus where it interacted with activated ATM (ataxia-telangiectasia mutated) at sites of DNA repair. Finally, we demonstrate that a new monoclonal antibody against human EphA5 sensitized lung cancer cells and human lung cancer xenografts to radiotherapy and significantly prolonged survival, thus suggesting the likelihood of translational applications.     

The I Domain Is Required for Efficient Plasma Membrane Binding of Human Immunodeficiency Virus Type 1 Pr55Gag

The interaction of the human immunodeficiency virus type 1 (HIV-1) Pr55^Gag molecule with the plasma membrane of an infected cell is an essential step of the viral life cycle. Myristic acid and positively charged residues within the N-terminal portion of MA constitute the membrane-binding domain of Pr55^Gag. A separate assembly domain, termed the interaction (I) domain, is located nearer the C-terminal end of the molecule. The I domain is required for production of dense retroviral particles, but has not previously been described to influence the efficiency of membrane binding or the subcellular distribution of Gag. This study used a series of Gag-green fluorescent protein fusion constructs to define a region outside of MA which determines efficient plasma membrane interaction. This function was mapped to the nucleocapsid (NC) region of Gag. The minimal region in a series of C-terminally truncated Gag proteins conferring plasma membrane fluorescence was identified as the N-terminal 14 amino acids of NC. This same region was sufficient to create a density shift in released retrovirus-like particles from 1.13 to 1.17 g/ml. The functional assembly domain previously termed the I domain is thus required for the efficient plasma membrane binding of Gag, in addition to its role in determining the density of released particles. We propose a model in which the I domain facilitates the interaction of the N-terminal membrane-binding domain of Pr55^Gag with the plasma membrane.     

The DEK Oncogene Is a Target of Steroid Hormone Receptor Signaling in Breast Cancer

Expression of estrogen and progesterone hormone receptors indicates a favorable prognosis due to the successful use of hormonal therapies such as tamoxifen and aromatase inhibitors. Unfortunately, 15–20% of patients will experience breast cancer recurrence despite continued use of tamoxifen. Drug resistance to hormonal therapies is of great clinical concern so it is imperative to identify novel molecular factors that contribute to tumorigenesis in hormone receptor positive cancers and/or mediate drug sensitivity. The hope is that targeted therapies, in combination with hormonal therapies, will improve survival and prevent recurrence. We have previously shown that the DEK oncogene, which is a chromatin remodeling protein, supports breast cancer cell proliferation, invasion and the maintenance of the breast cancer stem cell population. In this report, we demonstrate that DEK expression is associated with positive hormone receptor status in primary breast cancers and is up-regulated in vitro following exposure to the hormones estrogen, progesterone, and androgen. Chromatin immunoprecipitation experiments identify DEK as a novel estrogen receptor α (ERα) target gene whose expression promotes estrogen-induced proliferation. Finally, we report for the first time that DEK depletion enhances tamoxifen-induced cell death in ER+ breast cancer cell lines. Together, our data suggest that DEK promotes the pathogenesis of ER+ breast cancer and that the targeted inhibition of DEK may enhance the efficacy of conventional hormone therapies.     

Mitofilin Is a Transmembrane Protein of the Inner Mitochondrial Membrane Expressed as Two Isoforms

Mitofilin, also known as heart muscle protein, is a recently identified mitochondrial protein. We have isolated two human cDNAs that encode different isoforms of mitofilin. Using reverse PCR, we provide evidence that both isoforms are derived by alternative splicing and encode two proteins of 88 and 90 kDa that are detected in immunoblot analyses with mitofilin-specific antibodies. Immunofluorescence microscopy, fractionating of human osteosarcoma cells, and protease protection experiments with isolated mitochondria and mitoplasts indicate that mitofilin is an integral membrane protein of the inner mitochondrial membrane.³⁵S-labeled mitofilin is transported into isolated yeast mitochondria in a reaction that depends on the membrane potential across the inner mitochondrial membrane (ΔΨ). During mitochondrialin vitroimport, mitofilin is proteolytically processed to the mature protein that is also detected in cellular fractions, indicating that the amino-terminal leader sequence is removed. Sequence analysis and our results suggest that mitofilin is anchored in the inner mitochondrial membrane with an amino-terminal transmembrane domain, while the majority of the protein is extruding into the intermembrane space.     

Expression and Purification of a Functional Porcine Soluble Triggering Receptor Expressed on Myeloid Cells 1

Triggering receptor expressed on myeloid cells 1 (TREM-1) plays a vital role in the pathogen-triggered amplification loop required for proinflammatory responses. Blockade of TREM-1 signaling may inhibit expansion of sepsis and prolong survival of animals. In the present study, the gene of porcine soluble TREM-1 was cloned and expressed in E. coli. After purification, the bioactivity of recombinant porcine soluble TREM-1 was tested in vitro on porcine alveolar macrophages. The results showed that supplementation with the recombinant porcine sTREM-1 protein rapidly and dose-dependently attenuated the upregulation of cytokines (IL-1β, IL-2, IL-4, IL-8, IL-10, IL-12, IL-16, IL-18, and TNF-α) caused by LPS stimulation in the cultured porcine alveolar macrophages. These results indicate that the recombinant porcine sTREM-1 protein can prevent TREM-1-mediated hyperinflammatory responses after exposure to LPS.     

人白细胞抗原G3在稳定转染细胞细胞膜上的表达

人白细胞抗原G(HLA G)是一种在母婴耐受中起主要作用的非经典的HLA Ⅰ类分子 .其中HLA G3结构简单 ,仅具有α1结构域、穿膜区及胞浆区 ,其是否在细胞表面表达尚存在争议 .为了建立HLA G3稳定转染细胞株并确定其在细胞内的定位 ,采用RT PCR法从 9周人胎盘组织中获得了HLA G3的cDNA ,并构建到真核表达载体pcDNA3中 ,将所获得的真核表达质粒pcDNA G3转染至HLA Ⅰ (- )细胞株K5 6 2 ,经G4 18筛选后获得稳定转染的细胞株K5 6 2 G3.利用RT PCR、Western印迹检测方法证明在K5 6 2 G3细胞株中 ,HLA G3在mRNA水平和蛋白水平上均有表达 .进一步利用免疫荧光标记技术 ,证明HLA G3能够在转染细胞细胞膜上表达 .结果表明 ,稳定转染细胞株中HLA G3蛋白能够定位表达在细胞膜