Neurotrophin-3 and FLT3 tyrosine kinase receptor in perinatal life

Our aim is to determine--in 30 healthy full-term infants and their mothers--circulating levels of neurotrophin-3 (NT-3) (important for antenatal and postnatal brain development and implicated in the immune response) and FLT3 tyrosine kinase receptor (FLT3) (controlling hematopoiesis and found in the nervous tissue), in the fetal and neonatal life. NT-3 levels, in contrast to FLT3 ones, increased significantly on the fourth postnatal day in relation to the low levels found in the mother, fetus, and day 1 neonate (P = .03, respectively). Maternal and umbilical NT3 levels positively correlated with respective FLT3 levels (P = .003 and P = .03). Circulating NT-3 levels increased in early neonatal life, possibly due to exposure to various stimuli soon after birth. FLT3 levels do not seem to behave accordingly, although these two substances probably synergize.     

Peptidoglycan N-acetylglucosamine deacetylases from Bacillus cereus, highly conserved proteins in Bacillus anthracis

The genomes of Bacillus cereus and its closest relative Bacillus anthracis contain 10 polysaccharide deacetylase homologues. Six of these homologues have been proposed to be peptidoglycan N-acetylglucosamine deacetylases. Two of these genes, namely bc1960 and bc3618, have been cloned and expressed in Escherichia coli, and the recombinant enzymes have been purified to homogeneity and further characterized. Both enzymes were effective in deacetylating cell wall peptidoglycan from the Gram(+) Bacillus cereus and Bacillus subtilis and the Gram(-) Helicobacter pylori as well as soluble chitin substrates and N-acetylchitooligomers. However, the enzymes were not active on acetylated xylan. These results provide insight into the substrate specificity of carbohydrate esterase family 4 enzymes. It was revealed that both enzymes deacetylated only the GlcNAc residue of the synthetic muropeptide N-acetyl-D-glucosamine-(beta-1,4)-N-acetylmuramyl-L-alanine-D-isoglutamine. Analysis of the constituent muropeptides of peptidoglycan from B. subtilis and H. pylori resulting from incubation of the enzymes BC1960 and BC3618 with these polymers and subsequent hydrolysis by Cellosyl and mutanolysin, respectively, similarly revealed that both enzymes deacetylate GlcNAc residues of peptidoglycan. Kinetic analysis toward GlcNAc(2-6) revealed that GlcNAc4 was the favorable substrate for both enzymes. Identification of the sequence of N-acetychitooligosaccharides (GlcNAc(2-4)) following enzymatic deacetylation by using 1H NMR revealed that both enzymes deacetylate all GlcNAc residues of the oligomers except the reducing end ones. Enzymatic deacetylation of chemically acetylated vegetative peptidoglycan from B. cereus by BC1960 and BC3618 resulted in increased resistance to lysozyme digestion. This is the first biochemical study of bacterial peptidoglycan N-acetylglucosamine deacetylases.     

Dominant role for TL1A/DR3 pathway in IL-12 plus IL-18-induced IFN-gamma production by peripheral blood and mucosal CCR9+ T lymphocytes

The TNF-like cytokine TL1A augments IFN-gamma production by anti-CD3 plus anti-CD28 and IL-12/IL-18-stimulated peripheral blood (PB) T cells. However, only a small subset of PB T cells respond to TL1A stimulation with IFN-gamma production. PB CCR9+ T cells represent a small subset of circulating T cells with mucosal T cell characteristics and a Th1/Tr1 cytokine profile. In the current study, we show that TL1A enhanced IFN-gamma production by TCR- or CD2/CD28-stimulated CCR9(+)CD4+ PB T cells. However, TL1A had the most pronounced effect on augmenting IFN-gamma production by IL-12/IL-18-primed CCR9(+)CD4+ PB T cells. TL1A enhanced both the percentage and the mean fluorescence intensity of IFN-gamma in CCR9(+)CD4+ T cells as assessed by intracellular cytokine staining. IL-12 plus IL-18 up-regulated DR3 expression in CCR9(+)CD4+ T cells but had negligible effect on CCR9(-)CD4+ T cells. CCR9(+)CD4+ T cells isolated from the small intestine showed a 37- to 105-fold enhancement of IFN-gamma production when TL1A was added to the IL-12/IL18 cytokine combination. Cell membrane-expressed TL1A was preferentially expressed in CCR9(+)CD4+ PB T cells, and a blocking anti-TL1A mAb inhibited IFN-gamma production by cytokine-primed CCR9(+)CD4+ T cells by approximately 50%. Our data show that the TL1A/DR3 pathway plays a dominant role in the ultimate level of cytokine-induced IFN-gamma production by CCR9+ mucosal and gut-homing PB T cells and could play an important role in Th1-mediated intestinal diseases, such as Crohn's disease, where increased expression of IL-12, IL-18, TL1A, and DR3 converge in the inflamed intestinal mucosa.     

DEF6, a novel PH-DH-like domain protein, is an upstream activator of the Rho GTPases Rac1, Cdc42, and RhoA

In this paper, we describe the characterization of DEF6, a novel PH-DH-like protein related to SWAP-70 that functions as an upstream activator of Rho GTPases. In NIH 3T3 cells, stimulation of the PI 3-kinase signaling pathway with either H2O2 or platelet-derived growth factor (PDGF) resulted in the translocation of an overexpressed DEF6-GFP fusion protein to the cell membrane and induced the formation of filopodia and lamellipodia. In contrast to full-length DEF6, expression of the DH-like (DHL) domain as a GFP fusion protein potently induced actin polymerization, including stress fiber formation in COS-7 cells, in the absence of PI 3-kinase signaling, indicating that it was constitutively active. The GTP-loading of Cdc42 was strongly enhanced in NIH 3T3 cells expressing the DH domain while filopodia formation, membrane ruffling, and stress fiber formation could be inhibited by the co-expression of the DH domain with dominant negative mutants of either N17Rac1, N17Cdc42, or N19RhoA, respectively. This indicated that DEF6 acts upstream of the Rho GTPases resulting in the activation of the Cdc42, Rac1, and RhoA signaling pathways. In vitro, DEF6 specifically interacted with Rac1, Rac2, Cdc42, and RhoA, suggesting a direct role for DEF6 in the activation of Rho GTPases. The ability of DEF6 to both stimulate actin polymerization and bind to filamentous actin suggests a role for DEF6 in regulating cell shape, polarity, and movement.     

Fluid shear regulates the kinetics and receptor specificity of Staphylococcus aureus binding to activated platelets

The interaction between surface components on the invading pathogen and host cells such as platelets plays a key role in the regulation of endovascular infections. However, the mechanisms mediating Staphylococcus aureus binding to platelets under shear remain largely unknown. This study was designed to investigate the kinetics and molecular requirements of platelet-S. aureus interactions in bulk suspensions subjected to a uniform shear field. Hydrodynamic shear-induced collisions augment platelet-S. aureus binding, which is further potentiated by platelet activation with stromal derived factor-1beta. Peak adhesion efficiency occurs at low shear (100 s(-1)) and decreases with increasing shear. The molecular interaction of platelet alpha(IIb)beta(3) with bacterial clumping factor A through fibrinogen bridging is necessary for stable bacterial binding to activated platelets under shear. Although this pathway is sufficient at low shear (相似文献   

TL1A synergizes with IL-12 and IL-18 to enhance IFN-gamma production in human T cells and NK cells

TL1A, a recently described TNF-like cytokine that interacts with DR3, costimulates T cells and augments anti-CD3 plus anti-CD28 IFN-gamma production. In the current study we show that TL1A or an agonistic anti-DR3 mAb synergize with IL-12/IL-18 to augment IFN-gamma production in human peripheral blood T cells and NK cells. TL1A also enhanced IFN-gamma production by IL-12/IL-18 stimulated CD56(+) T cells. When expressed as fold change, the synergistic effect of TL1A on cytokine-induced IFN-gamma production was more pronounced on CD4(+) and CD8(+) T cells than on CD56(+) T cells or NK cells. Intracellular cytokine staining showed that TL1A significantly enhanced both the percentage and the mean fluorescence intensity of IFN-gamma-producing T cells in response to IL-12/IL-18. The combination of IL-12 and IL-18 markedly up-regulated DR3 expression in NK cells, whereas it had minimal effect in T cells. Our data suggest that TL1A/DR3 pathway plays an important role in the augmentation of cytokine-induced IFN-gamma production in T cells and that DR3 expression is differentially regulated by IL-12/IL-18 in T cells and NK cells.     

AgDscam, a hypervariable immunoglobulin domain-containing receptor of the Anopheles gambiae innate immune system

Activation of the insect innate immune system is dependent on a limited number of pattern recognition receptors (PRRs) capable of interacting with pathogen-associated molecular pattern. Here we report a novel role of an alternatively spliced hypervariable immunoglobulin domain-encoding gene, Dscam, in generating a broad range of PRRs implicated in immune defense in the malaria vector Anopheles gambiae. The mosquito Down syndrome cell adhesion molecule gene, AgDscam, has a complex genome organization with 101 exons that can produce over 31,000 potential alternative splice forms with different combinations of adhesive domains and interaction specificities. AgDscam responds to infection by producing pathogen challenge-specific splice form repertoires. Transient silencing of AgDscam compromises the mosquito's resistance to infections with bacteria and the malaria parasite Plasmodium. AgDscam is mediating phagocytosis of bacteria with which it can associate and defend against in a splice form–specific manner. AgDscam is a hypervariable PRR of the A. gambiae innate immune system.     

Structural, photolysis and biological studies of the bis(μ2-chloro)-tris(triphenylphosphine)-di-copper(I) and chloro-tris(triphenylphosphine)-copper(I) complexes. Study of copper(I)-copper(I) interactions

Direct reaction of copper(I) chloride with triphenylphosphine (tpp) in molar ratio 2:3 and 1:3, results in the formation of the [(tpp)Cu(μ₂-Cl)₂Cu(tpp)₂] (1) and {[CuCl(tpp)₃]·(CH₃CN)} (2) complexes. The complexes have been characterized by melting point, FT-IR, UV-Vis spectroscopic data and X-ray crystallography. Complex 1 is di-nuclear. Two μ₂-Cl atoms bridge two copper(I) ions with tetrahedral and trigonal geometry respectively. The short copper-copper bond distance of 2.9039(6) ? in case of 1 indicates d¹⁰-d¹⁰ interaction between metal centers. Thus, our studies were extended here in the determination of the quasi-aromaticity, which results in strong Cu-Cu interactions, using the computational method of nucleus-independent chemical shifts (NICS). The NICS calculated at the inner region of the Cu₂Cl₂P₃ core in complex 1 is shielded up to −6.05 ppm. Complex 2 is mono-nuclear where three phosphorus and one chloride atoms form a tetrahedron around the copper(I) ion. Photolysis of both complexes 1 and 2, results in the formation of triphenylphosphine oxide.The complexes 1 and 2, were tested for their in vitro cytotoxic activity against leiomyosarcoma cells (LMS) and human breast adenocarcinoma cells (MCF-7). The type of LMS cell death caused by the complexes was also evaluated by use of a flow cytometry assay. The results show that at concentration of 5 μΜ of complexes 1 and 2, 34.1% (1) and 19.6 (2)% of LMS cells undergo programmed cell death (apoptosis), while at 10 μΜ, 80.4% (1) and 65.2% (2) of LMS cells undergo apoptosis. The light sensitivity of the complex is discussed in relation with the biological activity.     

A mutation in the pericentrin gene causes abnormal interneuron migration to the olfactory bulb in mice

Precise control of neuronal migration is essential for proper function of the brain. Taking a forward genetic screen, we isolated a mutant mouse with defects in interneuron migration. By genetic mapping, we identified a frame shift mutation in the pericentrin (Pcnt) gene. The Pcnt gene encodes a large centrosomal coiled-coil protein that has been implicated in schizophrenia. Recently, frame shift and premature termination mutations in the pericentrin (PCNT) gene were identified in individuals with Seckel syndrome and microcephalic osteodysplastic primordial dwarfism (MOPD II), both of which are characterized by greatly reduced body and brain sizes. The mouse Pcnt mutant shares features with the human syndromes in its overall growth retardation and reduced brain size. We found that dorsal lateral ganglionic eminence (dLGE)-derived olfactory bulb interneurons are severely affected and distributed abnormally in the rostral forebrain in the mutant. Furthermore, mutant interneurons exhibit abnormal migration behavior and RNA interference knockdown of Pcnt impairs cell migration along the rostal migratory stream (RMS) into the olfactory bulb. These findings indicate that pericentrin is required for proper migration of olfactory bulb interneurons and provide a developmental basis for association of pericentrin function with interneuron defects in human schizophrenia.