Field response of Mediterranean fruit fly (Diptera: Tephritidae) to ceralure B1: evaluations of enantiomeric B1 ratios on fly captures

(-)-Ceralure B1 (ethyl-cis-5-iodo-trans-2-methylcyclohexane-1-carboxylate), a male attractant for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is significantly more attractive than trimedlure (tert-butyl esters of 4(5)-chloro-2-methylcyclohexane-1-carboxylate), the current standard male attractant used in detection programs. This article reports studies that compare the effectiveness of racemic ceralure B1, mixtures of racemic ceralure B1 and pure (-)-ceralure B1, and trimedlure in field tests conducted in Hawaii, Africa, and Spain with wild Mediterranean fruit flies and in Florida with sterile released Mediterranean fruit fly. Trapping results showed that doses of (-)-ceralure B1 of 87.5 and 75% are just as effective as the 98% (-)-ceralure B1 and the racemic form to be almost as attractive. In nearly all studies, the racemic ceralure B1 was significantly better than trimedlure. These studies suggest that the racemic ceralure B1 could be a viable replacement for trimedlure in areawide detection programs for Mediterranean fruit fly. Synthesizing racemic ceralure B1 instead of a specific stereoselective enantiomer of ceralure B1 would likely be more cost-effective to produce and also might be useful in control as well as detection of this pest.     

Fasciola hepatica: humoral and cytokine responses to a member of the saposin-like protein family following delivery as a DNA vaccine in mice

The humoral and cellular responses to DNA vaccination of BALB/c mice with a novel antigen from the Fasciola hepatica saposin-like protein family (FhSAP-2) have been investigated. Two constructs were produced containing the FhSAP-2 DNA sequence, one intended for extracellular secretion of FhSAP-2 protein, and one expressing FhSAP-2 in the cytoplasm of a transfected cell. The constructs were tested in HEK 293T cells, with the secretory construct producing less detectable FhSAP-2 relative to cytoplasmic construct when observed by fluorescence. The size of expressed protein was confirmed by Western blot of cell lysate, but FhSAP-2 was undetectable in cell supernatants. Both, secretory and cytoplasmic constructs as well as FhSAP-2 recombinant protein were tested in mice. The antibody response elicited in mice vaccinated with the rFhSAP-2 induced high levels of IgG(1), IgG(2), and IgE as well as high levels of IL-10 and IFNgamma indicating a mixed Th1/Th2 response. Vaccination of mice intramuscularly with the cytoplasmic FhSAP-2 construct resulted in a dominant IgG(2a) isotype antibody as well as a dominant IFNgamma cytokine, with significant IgE, IgG(1), and IL-10 responses also present, suggesting a mixed Th1/Th2 profile. Isotype and cytokine profiles elicited by the FhSAP-2 secretory construct were similar to those obtained with the cytoplasmic construct but at levels that were significantly lower. The results demonstrate that FhSAP-2 can be delivered as a DNA vaccine construct and induces a stronger Th1 response than the recombinant protein alone. This could result in an improvement in the immunoprophylactic potential of this candidate vaccine against F. hepatica.     

Identification of a rat model for usher syndrome type 1B by N-ethyl-N-nitrosourea mutagenesis-driven forward genetics

The rat is the most extensively studied model organism and is broadly used in biomedical research. Current rat disease models are selected from existing strains and their number is thereby limited by the degree of naturally occurring variation or spontaneous mutations. We have used ENU mutagenesis to increase genetic variation in laboratory rats and identified a recessive mutant, named tornado, showing aberrant circling behavior, hyperactivity, and stereotypic head shaking. More detailed analysis revealed profound deafness due to disorganization and degeneration of the organ of Corti that already manifests at the onset of hearing. We set up a single nucleotide polymorphism (SNP)-based mapping strategy to identify the affected gene, revealing strong linkage to the central region of chromosome 1. Candidate gene resequencing identified a point mutation that introduces a premature stopcodon in Myo7a. Mutations in human MYO7A result in Usher syndrome type 1B, a severe autosomal inherited recessive disease that involves deafness and vestibular dysfunction. Here, we present the first characterized rat model for this disease. In addition, we demonstrate proof of principle for the generation and cloning of human disease models in rat using ENU mutagenesis, providing good perspectives for systematic phenotypic screens in the rat.     

Robustness of downhill folding: guidelines for the analysis of equilibrium folding experiments on small proteins

Previously, we identified the protein BBL as a downhill folder. This conclusion was based on the statistical mechanical analysis of equilibrium experiments performed in two variants of BBL, one with a fluorescent label at the N-terminus, and another one labeled at both ends. A recent report has claimed that our results are an artifact of label-induced aggregation and that BBL with no fluorescent labels and a longer N-terminal tail folds in a two-state fashion. Here, we show that singly and doubly labeled BBL do not aggregate, unfold reversibly, and have the same thermodynamic properties when studied under appropriate experimental conditions (e.g., our original conditions (1)). With an elementary analysis of the available data on the nonlabeled BBL (2), we also show that this slightly more stable BBL variant is not a two-state folder. We discuss the problems that led to its previous misclassification and how they can be avoided. Finally, we investigate the equilibrium unfolding of the singly labeled BBL with both ends protected by acetylation and amidation. This variant has the same thermodynamic stability of the nonlabeled BBL and displays all the equilibrium signatures of downhill folding. From all these observations, we conclude that fluorescent labels do not perturb the thermodynamic properties of BBL, which consistently folds downhill regardless of its stability and specific protein tails. The work on BBL illustrates the shortcomings of applying conventional procedures intended to distinguish between two-state and three-state folding models to small fast-folding proteins.     

Ligand modulation of lateral segregation of a G-protein-coupled receptor into lipid microdomains in sphingomyelin/phosphatidylcholine solid-supported bilayers

A growing body of evidence supports the idea that the plasma membrane bilayer is characterized by a laterally inhomogeneous mixture of lipids, having an organized structure in which lipid molecules segregate into small domains or patches. Such microdomains are characterized by high contents of sphingolipids that form thicker liquid-ordered regions that are resistant to extraction with nonionic detergents. The existence of lipid lateral segregation has been demonstrated in both model and biological membranes, although its role in protein sorting and membrane function still remains unclear. In these studies, plasmon-waveguide resonance (PWR) spectroscopy was employed to investigate the properties of microdomains in a model system consisting of a solid-supported lipid bilayer composed of a 1:1 mixture of palmitoyloleoylphosphatidylcholine (POPC) and brain sphingomyelin (SM), and their influence on the partitioning and functioning of the human delta opioid receptor (hDOR), a G-protein coupled receptor (GPCR). Resonance signals corresponding to two microdomains (POPC-rich and SM-rich) were observed in such bilayers, and the sorting of the receptor into each domain was highly dependent on the type of ligand that was bound. When no ligand was bound, the receptor was incorporated preferentially into the POPC-rich domain; when an agonist or antagonist was bound, the receptor was incorporated preferentially into the SM-rich component, although with a 2-fold greater propensity for this microdomain in the case of the agonist. Binding of G-protein to the agonist-bound receptor in the SM-rich domain occurred with a 30-fold higher affinity than binding to the receptor in the PC-rich domain. The binding of the agonist to an unliganded receptor in the bilayer produced receptor trafficking from the PC-rich to the SM-rich component. Since the SM-rich domain is thicker than the PC-rich domain, and previous studies with the hDOR have shown that the receptor is elongated upon agonist activation, we propose that hydrophobic matching between the receptor and the lipid is a driving force for receptor trafficking to the SM-rich component.     

Functional analysis of backbone cyclic peptides bearing the arm domain of the HIV-1 Rev protein: characterization of the karyophilic properties and inhibition of Rev-induced gene expression

This work describes the synthesis and activity of a novel backbone cyclic (BC) peptide library based on the sequence of the HIV-1 Rev arginine-rich motif (ARM). All the peptides in the library possess the same sequence but differ in their ring-moiety properties. The BC peptides were synthesized using simultaneous multiple-peptide synthesis and were fully assembled using bis(trichloromethyl)carbonate as a coupling agent. All the peptides in the library had inhibitory effects on the binding of Rev-GFP to importin beta in vitro. Studies performed with one of the BC Rev-ARM analogues, Rev-13, demonstrated that, like its parental linear peptide, it is karyophilic; i.e., it is able to mediate the nuclear import of conjugated bovine serum albumin (BSA) molecules. The cell penetrating properties of the BC peptides were assessed utilizing an ELISA-based system. This assay provides a quantitative evaluation of cell penetration. Most of the peptides from the library were able to penetrate intact Colo-205 cells to varying degrees. Furthermore, these BC peptides were able to carry BSA into intact Colo-205 cells. In addition to its cell penetrating and binding properties, the BC Rev-13 analogue inhibited Rev-induced gene expression in HeLa cells by 60-70% in the low micromolar range and exhibited no cell toxicity. The potential of BC peptides bearing ARM domains as lead compounds for the production of anti-HIV drugs is discussed.     

X-ray crystal structures of HMG-CoA synthase from Enterococcus faecalis and a complex with its second substrate/inhibitor acetoacetyl-CoA

Biosynthesis of the isoprenoid precursor, isopentenyl diphosphate, is a critical function in all independently living organisms. There are two major pathways for this synthesis, the non-mevalonate pathway found in most eubacteria and the mevalonate pathway found in animal cells and a number of pathogenic bacteria. An early step in this pathway is the condensation of acetyl-CoA and acetoacetyl-CoA into HMG-CoA, catalyzed by the enzyme HMG-CoA synthase. To explore the possibility of a small molecule inhibitor of the enzyme functioning as a non-cell wall antibiotic, the structure of HMG-CoA synthase from Enterococcus faecalis (MVAS) was determined by selenomethionine MAD phasing to 2.4 A and the enzyme complexed with its second substrate, acetoacetyl-CoA, to 1.9 A. These structures show that HMG-CoA synthase from Enterococcus is a member of the family of thiolase fold enzymes and, while similar to the recently published HMG-CoA synthase structures from Staphylococcus aureus, exhibit significant differences in the structure of the C-terminal domain. The acetoacetyl-CoA binary structure demonstrates reduced coenzyme A and acetoacetate covalently bound to the active site cysteine through a thioester bond. This is consistent with the kinetics of the reaction that have shown acetoacetyl-CoA to be a potent inhibitor of the overall reaction, and provides a starting point in the search for a small molecule inhibitor.     

Role of growth hormone receptor signaling in osteogenesis from murine bone marrow progenitor cells

Growth hormone (GH) regulates many of the factors responsible for controlling the development of bone marrow progenitor cells (BMPCs). The aim of this study was to elucidate the role of GH in osteogenic differentiation of BMPCs using GH receptor null mice (GHRKO). BMPCs from GHRKO and their wild-type (WT) littermates were quantified by flow cytometry and their osteogenic differentiation in vitro was determined by cell morphology, real-time RT-PCR, and biochemical analyses. We found that freshly harvested GHRKO marrow contains 3% CD34 (hematopoietic lineage), 43.5% CD45 (monocyte/macrophage lineage), and 2.5% CD106 positive (CFU-F/BMPC) cells compared to 11.2%, 45%, and 3.4% positive cells for (WT) marrow cells, respectively. When cultured for 14 days under conditions suitable for CFU-F expansion, GHRKO marrow cells lost CD34 positivity, and were markedly reduced for CD45, but 3- to 4-fold higher for CD106. While WT marrow cells also lost CD34 expression, they maintained CD45 and increased CD106 levels by 16-fold. When BMPCs from GHRKO mice were cultured under osteogenic conditions, they failed to elongate, in contrast to WT cells. Furthermore, GHRKO cultures expressed less alkaline phosphatase, contained less mineralized calcium, and displayed lower osteocalcin expression than WT cells. However, GHRKO cells displayed similar or higher expression of cbfa-1, collagen I, and osteopontin mRNA compared to WT. In conclusion, we show that GH has an effect on the proportions of hematopoietic and mesenchymal progenitor cells in the bone marrow, and that GH is essential for both the induction and later progression of osteogenesis.     

Sequential immune escape and shifting of T cell responses in a long-term survivor of melanoma

Immune-mediated control of tumors may occur, in part, through lysis of malignant cells by CD8(+) T cells that recognize specific Ag-HLA class I complexes. However, tumor cell populations may escape T cell responses by immune editing, by preventing formation of those Ag-HLA complexes. It remains unclear whether the human immune system can respond to immune editing and recognize newly arising escape variants. We report an example of shifting immune responses to escape variants in a patient with sequential metastases of melanoma and long-term survival after surgery alone. Tumor cells in the first metastasis escaped immune recognition via selective loss of an HLA haplotype (HLA-A11, -B44, and -Cw17), but maintained expression of HLA-A2. In the second metastasis, immune escape from an immunodominant MART-1-specific T cell response was mediated by HLA class I down-regulation, resulting in a failure to present this epitope, but persistent presentation of a tyrosinase-derived epitope. Consequent to this modification in tumor Ag presentation, the dominant CTL response shifted principally toward a tyrosinase-targeted response, even though tyrosinase-specific CTL had been undetectable during the initial metastatic event. Thus, in response to immune editing of tumor cells, a patient's spontaneous T cell response adapted, gaining the ability to recognize and to lyse "edited" tumor targets. The observation of both immune editing and immune adaptation in a patient with long-term survival after surgery alone demonstrates an example of immune system reactivity to counteract the escape mechanism(s) developed by tumor cells, which may contribute to the clinical outcome of malignant disease.     

A role for TLRs in the regulation of immune cell migration by first trimester trophoblast cells

Normal pregnancy is characterized by the presence of innate immune cells at the maternal-fetal interface. Originally, it was postulated that the presence of these leukocytes was due to an immune response toward paternal Ags expressed by the invading trophoblasts. Instead, we and others postulate that these innate immune cells are necessary for successful implantation and pregnancy. However, elevated leukocyte infiltration may be an underlying cause of pregnancy complications, such as preterm labor or preeclampsia. Furthermore, such conditions have been attributed to an intrauterine infection. Therefore, we hypothesize that first trimester trophoblast cells, upon recognition of microbes through TLRs, may coordinate an immune response by recruiting cells of the innate immune system to the maternal-fetal interface. In this study, we have demonstrated that human first trimester trophoblast cells constitutively secrete the chemokines growth-related oncogene, growth-related oncogene alpha, IL-8, and MCP-1 and are able to recruit monocytes and NK cells, and to a lesser degree, neutrophils. Following the ligation of TLR-3 by the viral ligand, poly(I:C), or TLR-4 by bacterial LPS, trophoblast secretion of chemokines is significantly increased and this in turn results in elevated monocyte and neutrophil chemotaxis. In addition, TLR-3 stimulation also induces trophoblast cells to secrete RANTES. These results suggest a novel mechanism by which first trimester trophoblast cells may differentially modulate the maternal immune system during normal pregnancy and in the presence of an intrauterine infection. Such altered trophoblast cell responses might contribute to the pathogenesis of certain pregnancy complications.