Members of the Entamoeba histolytica transmembrane kinase family play non-redundant roles in growth and phagocytosis

Entamoeba histolytica contains a large and novel family of transmembrane kinases (TMKs). The expression patterns of the E. histolytica TMKs in individual trophozoites and the roles of the TMKs for sensing and responding to extracellular cues were incompletely characterised. Here we provide evidence that single cells express multiple TMKs and that TMK39 and TMK54 likely serve non-redundant cellular functions. Laser-capture microdissection was used in conjunction with microarray analysis to demonstrate that single trophozoites express more than one TMK gene. Anti-peptide antibodies were raised against unique regions in the extracellular domains of TMK39, TMK54 and PaTMK, and TMK expression was analysed at the protein level. Flow cytometric assays revealed that populations of trophozoites homogeneously expressed TMK39, TMK54 and PaTMK, while confocal microscopy identified different patterns of cell surface expression for TMK39 and TMK54. The functions of TMK39 and TMK54 were probed by the inducible expression of dominant-negative mutants. While TMK39 co-localised with ingested beads and expression of truncated TMK39 interfered with trophozoite phagocytosis of apoptotic lymphocytes, expression of a truncated TMK54 inhibited growth of amoebae and altered the surface expression of the heavy subunit of the E. histolytica Gal/GalNAc lectin. Overall, our data indicates that multiple members of the novel E. histolytica TMK family are utilised for non-redundant functions by the parasite.     

Genetic dissection of vasculitis, myeloperoxidase-specific antineutrophil cytoplasmic autoantibody production, and related traits in spontaneous crescentic glomerulonephritis-forming/Kinjoh mice

The spontaneous crescentic glomerulonephritis-forming/Kinjoh (SCG/Kj) mouse is a model of human crescentic glomerulonephritis and vasculitis associated with the production of the myeloperoxidase (MPO)-specific antineutrophil cytoplasmic autoantibody (MPO-ANCA). Although the disease is mediated initially by mutation of the Fas gene (lpr), SCG/Kj mice also have non-Fas predisposing genetic factors. To define these factors, genome-wide quantitative trait locus (QTL) mapping was performed on female (B(6)x SCG/Kj) F(2) intercross mice. Fourteen non-Fas QTLs were identified. QTLs of glomerulonephritis were located on chromosomes 1, 10, 13, 16, and 17, vasculitis on chromosomes 1 and 17, splenomegaly on chromosome 1, hypergammaglobulinemia on chromosomes 1, 2, 4, 6, 7, 11, 13, and 17, antinuclear Ab on chromosomes 1, 8, 10, and 12, and MPO-ANCA production on chromosomes 1 and 10. Significant QTLs derived from SCG/Kj on chromosomes 1, 2, 7, and 13 were designated Scg-1 to Scg-5, respectively, and those derived from B(6) on chromosomes 4, 6, 17, and 10 were designated Sxb-1 to Sxb-4, respectively. Two loci linked to MPO-ANCA production on chromosomes 1 and 10 were designated Man-1 and Man-2 (for MPO-ANCA), respectively. Although both Scg-1 and Scg-2 were on chromosome 1 and shared several functions, it was of interest that aberrant MPO-ANCA production was exclusively controlled by Man-1, the centromeric half region of the Scg-2 chromosomal segment. We also examined the epistatic effects between the lpr mutation and non-Fas susceptibility genes. QTLs are discussed in relation to previously described loci, with emphasis on their candidate genes.     

Resistance of C57BL/6 mice to amoebiasis is mediated by nonhemopoietic cells but requires hemopoietic IL-10 production

Resistance to intestinal amoebiasis is mouse strain dependent. C57BL/6 (B6) mice clear Entamoeba histolytica within hours of challenge, whereas C3H and CBA strains are susceptible to infection and disease. In this study, we show using bone marrow (BM) chimeric mice that mouse strain-dependent resistance is mediated by nonhemopoietic cells; specifically, B6 BM --> CBA recipients remained susceptible as measured by amoeba score and culture, whereas CBA BM --> B6 recipients remained resistant. Interestingly, hemopoietic IL-10 was required for maintaining the resistance of B6 mice, in that B6 IL-10-deficient mice and IL-10(-/-) BM --> wild-type recipients, but not IL-10(+/+) BM --> IL-10(-/-) recipients, exhibited higher amoeba scores than their wild-type controls. Additionally, C57BL/10 IL-10(-/-)Rag2(-/-) mice exhibited diminished amoeba scores and culture rates vs IL-10(-/-) mice, indicating that lymphocytes potentiated the susceptibility of IL-10-deficient mice. We conclude that nonhemopoietic cells mediate the natural resistance to intestinal amoebiasis of B6 mice, yet this resistance depends on hemopoietic IL-10 activity.     

TLR-dependent induction of IFN-beta mediates host defense against Trypanosoma cruzi

Host resistance to the intracellular protozoan parasite Trypanosoma cruzi depends on IFN-gamma production by T cells and NK cells. However, the involvement of innate immunity in host resistance to T. cruzi remains unclear. In the present study, we investigated host defense against T. cruzi by focusing on innate immunity. Macrophages and dendritic cells (DCs) from MyD88(-/-)TRIF(-/-) mice, in which TLR-dependent activation of innate immunity was abolished, were defective in the clearance of T. cruzi and showed impaired induction of IFN-beta during T. cruzi infection. Neutralization of IFN-beta in MyD88(-/-) macrophages led to enhanced T. cruzi growth. Cells from MyD88(-/-)IFNAR1(-/-) mice also showed impaired T. cruzi clearance. Furthermore, both MyD88(-/-)TRIF(-/-) and MyD88(-/-)IFNAR1(-/-) mice were highly susceptible to in vivo T. cruzi infection, highlighting the involvement of innate immune responses in T. cruzi infection. We further analyzed the molecular mechanisms for the IFN-beta-mediated antitrypanosomal innate immune responses. MyD88(-/-)TRIF(-/-) and MyD88(-/-)IFNAR1(-/-) macrophages and DCs exhibited defective induction of the GTPase IFN-inducible p47 (IRG47) after T. cruzi infection. RNA interference-mediated reduction of IRG47 expression in MyD88(-/-) macrophages resulted in increased intracellular growth of T. cruzi. These findings suggest that TLR-dependent expression of IFN-beta is involved in resistance to T. cruzi infection through the induction of IRG47.     

VopB1 and VopD1 are essential for translocation of type III secretion system 1 effectors of Vibrio parahaemolyticus

Vibrio parahaemolyticus is a pathogenic Vibrio species that causes food-borne acute gastroenteritis, often related to the consumption of raw or undercooked seafood. Vibrio parahaemolyticus has 2 type III secretion systems (T3SS1 and T3SS2). Here, we demonstrate that VP1657 (VopB1) and VP1656 (VopD1), which share sequence similarity with Pseudomonas genes popB (38%) and popD (36%), respectively, are essential for translocation of T3SS1 effectors into host cells. A VP1680CyaA fusion reporter system was constructed to observe effector translocation. Using this reporter assay we showed that the VopB1 and VopD1 deletion strains were unable to translocate VP1680 to host cell but that the secretion of VP1680 into the culture medium was not affected. VopB1 or VopD1 deletion strains did not enhance cytotoxicity and failed to activate mitogen-activated protein kinases and secretion of interleukin-8, which depend on VP1680. Thus, we conclude that VopB1 and VopD1 are essential components of the translocon. To target VopB1 and VopD1 may have therapeutic potential for the treatment or prevention in V.?parahaemolyticus infection.     

Heat shock factor 1 contributes to ischemia-induced angiogenesis by regulating the mobilization and recruitment of bone marrow stem/progenitor cells

Bone marrow (BM)-derived stem/progenitor cells play an important role in ischemia-induced angiogenesis in cardiovascular diseases. Heat shock factor 1 (HSF1) is known to be induced in response to hypoxia and ischemia. We examined whether HSF1 contributes to ischemia-induced angiogenesis through the mobilization and recruitment of BM-derived stem/progenitor cells using HSF1-knockout (KO) mice. After the induction of ischemia, blood flow and microvessel density in the ischemic hindlimb were significantly lower in the HSF1-KO mice than in the wild-type (WT) mice. The mobilization of BM-derived Sca-1- and c-kit-positive cells in peripheral blood after ischemia was significantly lower in the HSF1-KO mice than in the WT mice. BM stem/progenitor cells from HSF1-KO mice showed a significant decrease in their recruitment to ischemic tissue and in migration, adhesion, and survival when compared with WT mice. Blood flow recovery in the ischemic hindlimb significantly decreased in WT mice receiving BM reconstitution with donor cells from HSF1-KO mice. Conversely, blood flow recovery in the ischemic hindlimb significantly increased in HSF1-KO mice receiving BM reconstitution with donor cells from WT mice. These findings suggest that HSF1 contributes to ischemia-induced angiogenesis by regulating the mobilization and recruitment of BM-derived stem/progenitor cells.     

A stand-alone adenylation domain forms amide bonds in streptothricin biosynthesis

The streptothricin (ST) antibiotics, produced by Streptomyces bacteria, contain L-β-lysine ((3S)-3,6-diaminohexanoic acid) oligopeptides as pendant chains. Here we describe three unusual nonribosomal peptide synthetases (NRPSs) involved in ST biosynthesis: ORF 5 (a stand-alone adenylation (A) domain), ORF 18 (containing thiolation (T) and condensation (C) domains) and ORF 19 (a stand-alone A domain). We demonstrate that ST biosynthesis begins with adenylation of L-β-lysine by ORF 5, followed by transfer to the T domain of ORF 18. In contrast, L-β-lysine molecules adenylated by ORF 19 are used to elongate an L-β-lysine peptide chain on ORF 18, a reaction unexpectedly catalyzed by ORF 19 itself. Finally, the C domain of ORF 18 catalyzes the condensation of L-β-lysine oligopeptides covalently bound to ORF 18 with a freely diffusible intermediate to release the ST products. These results highlight an unusual activity for an A domain and unique mechanisms of crosstalk within NRPS machinery.     

Malaria parasites require TLR9 signaling for immune evasion by activating regulatory T cells

Malaria is still a life-threatening infectious disease that continues to produce 2 million deaths annually. Malaria parasites have acquired immune escape mechanisms and prevent the development of sterile immunity. Regulatory T cells (Tregs) have been reported to contribute to immune evasion during malaria in mice and humans, suggesting that activating Tregs is one of the mechanisms by which malaria parasites subvert host immune systems. However, little is known about how these parasites activate Tregs. We herein show that TLR9 signaling to dendritic cells (DCs) is crucial for activation of Tregs. Infection of mice with the rodent malaria parasite Plasmodium yoelii activates Tregs, leading to enhancement of their suppressive function. In vitro activation of Tregs requires the interaction of DCs with parasites in a TLR9-dependent manner. Furthermore, TLR9(-/-) mice are partially resistant to lethal infection, and this is associated with impaired activation of Tregs and subsequent development of effector T cells. Thus, malaria parasites require TLR9 to activate Tregs for immune escape.     

Glass Capillary Gas Chromatography of Secondary Amines in Foods with Flame Photometric Detection after Derivatization with Benzenesulfonyl Chloride

A simple and selective gas chromatographic method was established for determining naturally occurring secondary amines. Secondary amines separated from foods by extraction with dichloro-methane and reextraction with hydrochloric acid were readily converted into the corresponding sulfonamides by reaction with benzenesulfonyl chloride under alkaline condition. Gas chromatography was carried out with a capillary coated with OV-101 and a flame photometric detector. Column temperature was programmed from 170 to 230°C at a rate of 5°C/min.

The obtained sulfonamides were separated from one another within 40 min.

Eleven secondary amines examined were added to 5 kinds of foods and recovered from them. The mean recovery rates were in the range 71.3% (dimethylamine)–99.8% (piperidine).

The limits of detection varied from 0.002 ppm (dimethylamine) to 0.01 ppm (morpholine).     

CAST, a novel CD3epsilon-binding protein transducing activation signal for interleukin-2 production in T cells.

Antigen recognition through T cell receptor (TCR)-CD3 complex transduces signals into T cells, which regulate activation, function, and differentiation of T cells. The TCR-CD3 complex is composed of two signaling modules represented by CD3zeta and CD3epsilon. Signaling through CD3zeta has been extensively analyzed, but that via CD3epsilon, which is also crucial in immature thymocyte development, is still not clearly understood. We isolated cDNA encoding a novel CD3epsilon-binding protein CAST. CAST specifically interacts in vivo and in vitro with CD3epsilon but not with CD3zeta or FcRgamma via a unique membrane-proximal region of CD3epsilon. CAST is composed of 512 amino acids including a single tyrosine and undergoes tyrosine phosphorylation upon TCR stimulation. Overexpression of two dominant-negative types of CAST, a minimum CD3epsilon-binding domain and a tyrosine-mutant, strongly suppressed NFAT activation and interleukin-2 production. These results demonstrate that CAST serves as a component of preformed TCR complex and transduces activation signals upon TCR stimulation and represents a new signaling pathway via the CD3epsilon-containing TCR signaling module.