Immunocytochemical analyses and targeted gene disruption of GTPBP1

GTP-Binding Protein 1-Like (GTPBP1l) Regulates Vascular Patterning during Zebrafish Development

Genetic regulation of vascular patterning is not fully understood. Here, we report a novel gene, gtpbp1l (GTP-binding protein 1-like), that regulates vascular development in zebrafish. Amino acid sequence comparison and a phylogenetic study showed that gtpbp1l is conserved in vertebrates. Gtpbp1l mRNA is expressed in the vasculature during embryogenesis. Knockdown of gtpbp1l by morpholino impairs the patterning of the intersegmental vessel (ISV) and caudal vein plexus (CVP), indicating the role of gtpbp1l in vasculature. Further apoptosis assays and transgenic fish tests suggested that vascular defects in gtpbp1l morphants are not due to cell death but are likely caused by the impairment of migration and proliferation. Moreover, the altered expression of vessel markers is consistent with the vascular defects in gtpbp1l morphants. Finally, we revealed that gtpbp1l is regulated by VEGF/notch and BMP signaling. Collectively, these findings showed that gtpbp1l plays a critical role in vascular patterning during zebrafish development.

Heterozygous variants in GATA2 contribute to DCML deficiency in mice by disrupting tandem protein binding

Accumulating lines of clinical evidence support the emerging hypothesis that loss-of-function mutations of GATA2 cause inherited hematopoietic diseases, including Emberger syndrome; dendritic cell, monocyte B and NK lymphoid (DCML) deficiency; and MonoMAC syndrome. Here, we show that mice heterozygous for an arginine-to-tryptophan substitution mutation in GATA2 (G2^R398W/+), which was found in a patient with DCML deficiency, substantially phenocopy human DCML deficiency. Mice heterozygous for the GATA2-null mutation (G2^-/+) do not show such phenotypes. The G2^R398W protein possesses a decreased DNA-binding affinity but obstructs the function of coexpressed wild-type GATA2 through specific cis-regulatory regions, which contain two GATA motifs in direct-repeat arrangements. In contrast, G2^R398W is innocuous in mice containing single GATA motifs. We conclude that the dominant-negative effect of mutant GATA2 on wild-type GATA2 through specific enhancer/silencer of GATA2 target genes perturbs the GATA2 transcriptional network, leading to the development of the DCML-like phenotype. The present mouse model provides an avenue for the understanding of molecular mechanisms underlying the pathogenesis of GATA2-related hematopoietic diseases.

GTPBP1 resolves paused ribosomes to maintain neuronal homeostasis

Ribosome-associated quality control pathways respond to defects in translational elongation to recycle arrested ribosomes and degrade aberrant polypeptides and mRNAs. Loss of a tRNA gene leads to ribosomal pausing that is resolved by the translational GTPase GTPBP2, and in its absence causes neuron death. Here, we show that loss of the homologous protein GTPBP1 during tRNA deficiency in the mouse brain also leads to codon-specific ribosome pausing and neurodegeneration, suggesting that these non-redundant GTPases function in the same pathway to mitigate ribosome pausing. As observed in Gtpbp2-/- mice (Ishimura et al., 2016), GCN2-mediated activation of the integrated stress response (ISR) was apparent in the Gtpbp1-/- brain. We observed decreased mTORC1 signaling which increased neuronal death, whereas ISR activation was neuroprotective. Our data demonstrate that GTPBP1 functions as an important quality control mechanism during translation elongation and suggest that translational signaling pathways intricately interact to regulate neuronal homeostasis during defective elongation.

Overexpression of isoform B of Dgp-1 gene enhances locomotor activity in senescent Drosophila males and under heat stress

Here, we describe the longevity and locomotor behavior of senescent Drosophila males with altered expression of Dgp-1 gene. In comparison with the wild-type Canton-S (CS) males, six characteristics of the phenotype of Dgp-1[843k] mutant were found: (1) low expression of isoform A; (2) augmented expression of isoform B; (3) reduction in the mean lifespan; (4) decrease in the running speed in 3-day-old flies; (5) maintenance of a high run frequency in senescent flies; and (6) resistance to heat stress manifested as maintenance of a high run frequency at 29 °C. After cessation of "cantonization" process, mean lifespan of the mutant males drifted from low to high values finally exceeding that for CS. In contrast, behavioral phenotype of the mutant was robust. Using the GAL4/UAS system, we showed that neurospecific overexpression of isoform B resulted in a slight decrease of longevity and a high level of run frequency in the senescent flies, similar to that in Dgp-1[843K] mutant. In addition, a decreased level of reactive oxygen species was found in Dgp-1[843K] mutant males maintained under stress conditions. The elevated resistance to oxidative stress probably explains the two distinctive features of the mutation: resistance to aging processes and thermal stress displayed at behavioral level.

Functions of unconventional mammalian translational GTPases GTPBP1 and GTPBP2

In this study, Zinoviev et al. investigated how translational GTPases (GTPBPs) function in mRNA surveillance and ribosome-associated quality control. They demonstrate that GTPBP1 possesses eEF1A-like elongation activity, delivering cognate aa-tRNA to the ribosomal A site in a GTP-dependent manner, and that GTPBP2's binding to GTP was stimulated by Phe-tRNA^Phe, lacked elongation activity, and did not stimulate exosomal degradation. Their results indicate that GTPBP1 and GTPBP2 have different functions.

GTP-binding protein 1 (GTPBP1) and GTPBP2 comprise a divergent group of translational GTPases with obscure functions, which are most closely related to eEF1A, eRF3, and Hbs1. Although recent reports implicated GTPBPs in mRNA surveillance and ribosome-associated quality control, how they perform these functions remains unknown. Here, we demonstrate that GTPBP1 possesses eEF1A-like elongation activity, delivering cognate aminoacyl-transfer RNA (aa-tRNA) to the ribosomal A site in a GTP-dependent manner. It also stimulates exosomal degradation of mRNAs in elongation complexes. The kinetics of GTPBP1-mediated elongation argues against its functioning in elongation per se but supports involvement in mRNA surveillance. Thus, GTP hydrolysis by GTPBP1 is not followed by rapid peptide bond formation, suggesting that after hydrolysis, GTPBP1 retains aa-tRNA, delaying its accommodation in the A site. In physiological settings, this would cause ribosome stalling, enabling GTPBP1 to elicit quality control programs; e.g., by recruiting the exosome. GTPBP1 can also deliver deacylated tRNA to the A site, indicating that it might function via interaction with deacylated tRNA, which accumulates during stresses. Although GTPBP2's binding to GTP was stimulated by Phe-tRNA^Phe, suggesting that its function might also involve interaction with aa-tRNA, GTPBP2 lacked elongation activity and did not stimulate exosomal degradation, indicating that GTPBP1 and GTPBP2 have different functions.

Identification of mutation in GTPBP2 in patients of a family with neurodegeneration accompanied by iron deposition in the brain

We aimed to identify the genetic cause of a neurologic disorder accompanied with mental deficiency in a consanguineous family with 3 affected siblings by linkage analysis and exome sequencing. Iron accumulation in the brain of the patients was a notable phenotypic feature. A full-field electroretinography revealed generalized dysfunction of photoreceptors, bipolar cells, and amacrine cells. A splice site mutation in GTPBP2 that encodes GTP-binding protein 2 was identified in the patients and considered possible cause of their disease. The mutation was empirically shown to cause deletion of exon 9 of the gene and result in production of a truncated protein-lacking conserved C-terminus domains. GTPBP2 is a member of the GTPase superfamily of proteins. A recent report of identification of another splice site mutation in GTPBP2 in mice that causes neurodegeneration, and retinal damage provides supportive evidence for our finding. The conditions in the affected individuals of the family studied may define a novel form of neurodegeneration with brain iron accumulation, and GTPBP2 may be a novel neurodegeneration with brain iron accumulation gene.

Translation in giant viruses: a unique mixture of bacterial and eukaryotic termination schemes

Mimivirus and Megavirus are the best characterized representatives of an expanding new family of giant viruses infecting Acanthamoeba. Their most distinctive features, megabase-sized genomes carried in particles of size comparable to that of small bacteria, fill the gap between the viral and cellular worlds. These giant viruses are also uniquely equipped with genes coding for central components of the translation apparatus. The presence of those genes, thought to be hallmarks of cellular organisms, revived fundamental interrogations on the evolutionary origin of these viruses and the link they might have with the emergence of eukaryotes. In this work, we focused on the Mimivirus-encoded translation termination factor gene, the detailed primary structure of which was elucidated using computational and experimental approaches. We demonstrated that the translation of this protein proceeds through two internal stop codons via two distinct recoding events: a frameshift and a readthrough, the combined occurrence of which is unique to these viruses. Unexpectedly, the viral gene carries an autoregulatory mechanism exclusively encountered in bacterial termination factors, though the viral sequence is related to the eukaryotic/archaeal class-I release factors. This finding is a hint that the virally-encoded translation functions may not be strictly redundant with the one provided by the host. Lastly, the perplexing occurrence of a bacterial-like regulatory mechanism in a eukaryotic/archaeal homologous gene is yet another oddity brought about by the study of giant viruses.

Giant viruses, such as Mimivirus and Megavirus, have huge near-micron-sized particles and possess more genes than several cellular organisms. Furthermore their genomes encode functions not supposed to be in a virus, such as components of the protein translation apparatus. Since Lwoff in 1957, viruses are defined as ultimate obligate intracellular parasites from their need to hijack the peptide synthesis machinery of their host to replicate. We looked at the Mimivirus and Megavirus proteins that recognize the stop codons, the translation termination factors. We found that these genes contain two internal stop codons, meaning that their translation bypasses two distinct stop codons to produce a functional translation termination factor. These types of autoregulatory mechanisms are found in bacterial termination factors, although it involves only a single internal stop codon and not two, and are absent from their eukaryotic and archaeal homologs. Despite these bacterial-like features, giant viruses' termination factors have sequences that do not resemble bacterial genes but are clearly related to the eukaryotic and archaeal termination factors. Thus, giant viruses' termination factors surprisingly combine elements from eukaryotes/archaea and bacteria.

Immunohistochemical demonstration of airway epithelial cell markers of guinea pig

The guinea pig (Cavea porcellus) is a mammalian non-rodent species in the Caviidae family. The sensitivity of the respiratory system and the susceptibility to infectious diseases allows the guinea pig to be a useful model for both infectious and non-infectious lung diseases such as asthma and tuberculosis. In this report, we demonstrated for the first time, the major cell types and composition in the guinea pig airway epithelium, using cell type-specific markers by immunohistochemical staining using the commercial available immunological reagents that cross-react with guinea pig. Our results revealed the availability of antibodies cross-reacting with airway epithelial cell types of basal, non-ciliated columnar, ciliated, Clara, goblet and alveolar type II cells, as well as those cells expressing Mucin 5AC, Mucin 2, Aquaporin 4 and Calcitonin Gene Related Peptide. The distribution of these various cell types were quantified in the guinea pig airway by immunohistochemical staining and were comparable with morphometric studies using an electron microscopy assay. Moreover, this study also demonstrated that goblet cells are the main secretory cell type in the guinea pig's airway, distinguishing this species from rats and mice. These results provide useful information for the understanding of airway epithelial cell biology and mechanisms of epithelial-immune integration in guinea pig models.

Assembling the archaeal ribosome: roles for translation-factor-related GTPases

The assembly of ribosomal subunits from their individual components (rRNA and ribosomal proteins) requires the assistance of a multitude of factors in order to control and increase the efficiency of the assembly process. GTPases of the TRAFAC (translation-factor-related) class constitute a major type of ribosome-assembly factor in Eukaryota and Bacteria. They are thought to aid the stepwise assembly of ribosomal subunits through a 'molecular switch' mechanism that involves conformational changes in response to GTP hydrolysis. Most conserved TRAFAC GTPases are involved in ribosome assembly or other translation-associated processes. They typically interact with ribosomal subunits, but in many cases, the exact role that these GTPases play remains unclear. Previous studies almost exclusively focused on the systems of Bacteria and Eukaryota. Archaea possess several conserved TRAFAC GTPases as well, with some GTPase families being present only in the archaeo-eukaryotic lineage. In the present paper, we review the occurrence of TRAFAC GTPases with translation-associated functions in Archaea.

Modulation of exosome-mediated mRNA turnover by interaction of GTP-binding protein 1 (GTPBP1) with its target mRNAs

Eukaryotic mRNA turnover is among most critical mechanisms that affect mRNA abundance and are regulated by mRNA-binding proteins and the cytoplasmic exosome. A functional protein, guanosine-triphosphate-binding protein 1 (GTPBP1), which associates with both the exosome and target mRNAs, was identified. The overexpression of GTPBP1 accelerated the target mRNA decay, whereas the reduction of the GTPBP1 expression with RNA interference stabilized the target mRNA. GTPBP1 has a putative guanosine-triphosphate (GTP)-binding domain, which is found in members of the G-protein family and Ski7p, a well-known core factor of the exosome-mediated mRNA turnover pathway in yeast. Analyses of protein interactions and mRNA decay demonstrated that GTPBP1 modulates mRNA degradation via GTP-binding-dependent target loading. Moreover, GTPBP1-knockout models displayed multiple mRNA decay defects, including elevated nocturnal levels of Aanat mRNA in pineal glands, and retarded degradation of TNF-α mRNA in lipopolysaccharide-treated splenocytes. The results of this study suggest that GTPBP1 is a regulator and adaptor of the exosome-mediated mRNA turnover pathway.

Phylogenetic and phyletic studies of informational genes in genomes highlight existence of a 4 domain of life including giant viruses

The discovery of Mimivirus, with its very large genome content, made it possible to identify genes common to the three domains of life (Eukarya, Bacteria and Archaea) and to generate controversial phylogenomic trees congruent with that of ribosomal genes, branching Mimivirus at its root. Here we used sequences from metagenomic databases, Marseillevirus and three new viruses extending the Mimiviridae family to generate the phylogenetic trees of eight proteins involved in different steps of DNA processing. Compared to the three ribosomal defined domains, we report a single common origin for Nucleocytoplasmic Large DNA Viruses (NCLDV), DNA processing genes rooted between Archaea and Eukarya, with a topology congruent with that of the ribosomal tree. As for translation, we found in our new viruses, together with Mimivirus, five proteins rooted deeply in the eukaryotic clade. In addition, comparison of informational genes repertoire based on phyletic pattern analysis supports existence of a clade containing NCLDVs clearly distinct from that of Eukarya, Bacteria and Archaea. We hypothesize that the core genome of NCLDV is as ancient as the three currently accepted domains of life.

Multiple antigen-targeted immunotherapy with alpha-galactosylceramide-loaded and genetically engineered dendritic cells derived from embryonic stem cells

Numerous tumor-associated antigens (TAA) have been identified and their use in immunotherapy is considered to be promising. For TAA-based immunotherapy to be broadly applied as standard anticancer medicine, methods for active immunization should be improved. In the present study, we demonstrated the efficacy of multiple TAA-targeted dendritic cell (DC) vaccines and also the additive effects of loading alpha-galactosylceramide to DC using mouse melanoma models. On the basis of previously established methods to generate DC from mouse embryonic stem cells (ES-DC), 4 kinds of genetically modified ES-DC, which expressed the melanoma-associated antigens, glypican-3, secreted protein acidic and rich in cysteine, tyrosinase-related protein-2, or gp100 were generated. Anticancer effects elicited by immunization with the ES-DC were assessed in preventive and also therapeutic settings in the models of peritoneal dissemination and spontaneous metastasis to lymph node and lung. The in vivo transfer of a mixture of 3 kinds of TAA-expressing ES-DC protected the recipient mice from melanoma cells more effectively than the transfer of ES-DC expressing single TAA, thus demonstrating the advantage of multiple as compared with single TAA-targeted immunotherapy. Loading ES-DC with alpha-galactosylceramide further enhanced the anticancer effects, suggesting that excellent synergic effects of TAA-specific cytotoxic T lymphocytes and natural killer T cells against metastatic melanoma can be achieved by using genetically modified ES-DC. With the aid of advancing technologies related to pluripotent stem cells, induced pluripotent stem cells, and ES cells, clinical application of DC highly potent in eliciting anticancer immunity will be realized in the near future.

Activation of antigen-specific cytotoxic T lymphocytes by beta 2-microglobulin or TAP1 gene disruption and the introduction of recipient-matched MHC class I gene in allogeneic embryonic stem cell-derived dendritic cells

A method for the genetic modification of dendritic cells (DC) was previously established based on the in vitro differentiation of embryonic stem (ES) cells to DC (ES-DC). The unavailability of human ES cells genetically identical to the patients will be a problem in the future clinical application of this technology. This study attempted to establish a strategy to overcome this issue. The TAP1 or beta(2)-microglobulin (beta(2)m) gene was disrupted in 129 (H-2(b))-derived ES cells and then expression vectors for the H-2K(d) or beta(2)m-linked form of K(d) (beta2m-K(d)) were introduced, thus resulting in two types of genetically engineered ES-DC, TAP1(-/-)/K(d) ES-DC and beta(2)m(-/-)/beta(2)m-K(d) ES-DC. As intended, both of the transfectant ES-DC expressed K(d) but not the intrinsic H-2(b) haplotype-derived MHC class I. Beta(2)m(-/-)/beta(2)m-K(d) and TAP1(-/-)/K(d) ES-DC were not recognized by pre-activated H-2(b)-reactive CTL and did not prime H-2(b) reactive CTL in vitro or in vivo. Beta(2)m(-/-)/beta(2)m-K(d) ES-DC and TAP1(-/-)/K(d) ES-DC had a survival advantage in comparison to beta(2)m(+/-)/beta(2)m-K(d) ES-DC and TAP1(+/+)/K(d) ES-DC, when transferred into BALB/c mice. K(d)-restricted RSV-M2-derived peptide-loaded ES-DC could prime the epitope-specific CTL upon injection into the BALB/c mice, irrespective of the cell surface expression of intrinsic H-2(b) haplotype-encoded MHC class I. Beta(2)m(-/-)/beta(2)m-K(d) ES-DC were significantly more efficient in eliciting immunity against RSV M2 protein-expressing tumor cells than beta(2)m(+/-)/beta(2)m-K(d) ES-DC. The modification of the beta(2)m or TAP gene may therefore be an effective strategy to resolve the problem of HLA class I allele mismatch between human ES or induced pluripotent stem cells and the recipients to be treated.

Embryonic stem cell-derived dendritic cells expressing glypican-3, a recently identified oncofetal antigen, induce protective immunity against highly metastatic mouse melanoma, B16-F10

We have recently established a method to generate dendritic cells from mouse embryonic stem cells. By introducing exogenous genes into embryonic stem cells and subsequently inducing differentiation to dendritic cells (ES-DC), we can now readily generate transfectant ES-DC expressing the transgenes. A previous study revealed that the transfer of genetically modified ES-DC expressing a model antigen, ovalbumin, protected the recipient mice from a challenge with an ovalbumin-expressing tumor. In the present study, we examined the capacity of ES-DC expressing mouse homologue of human glypican-3, a recently identified oncofetal antigen expressed in human melanoma and hepatocellular carcinoma, to elicit protective immunity against glypican-3-expressing mouse tumors. CTLs specific to multiple glypican-3 epitopes were primed by the in vivo transfer of glypican-3-transfectant ES-DC (ES-DC-GPC3). The transfer of ES-DC-GPC3 protected the recipient mice from subsequent challenge with B16-F10 melanoma, naturally expressing glypican-3, and with glypican-3-transfectant MCA205 sarcoma. The treatment with ES-DC-GPC3 was also highly effective against i.v. injected B16-F10. No harmful side effects, such as autoimmunity, were observed for these treatments. The depletion experiments and immunohistochemical analyses suggest that both CD8+ and CD4+ T cells contributed to the observed antitumor effect. In conclusion, the usefulness of glypican-3 as a target antigen for antimelanoma immunotherapy was thus shown in the mouse model using the ES-DC system. Human dendritic cells expressing glypican-3 would be a promising means for therapy of melanoma and hepatocellular carcinoma.

Therapeutic effect of alpha-galactosylceramide-loaded dendritic cells genetically engineered to express SLC/CCL21 along with tumor antigen against peritoneally disseminated tumor cells

The close cooperation of both innate and acquired immunity is essential for the induction of truly effective antitumor immunity. We tested a strategy to enhance the cross-talk between NKT cells and conventional antigen-specific T cells with the use of alpha GalCer-loaded dendritic cells genetically engineered to express antigen plus chemokine, attracting both conventional T cells and NKT cells. DC genetically engineered to express a model antigen, OVA, along with SLC/CCL21 or monokine induced by IFN-gamma/CXCL9, had been generated using a method based on in vitro differentiation of DC from mouse ES cells. The ES-DC were loaded with alpha-GalCer and transferred to mice bearing MO4, an OVA-expressing melanoma, and their capacity to evoke antitumor immunity was evaluated. In vivo transfer of either OVA-expressing ES-DC, stimulating OVA-reactive T cells, or alpha-GalCer-loaded non-transfectant ES-DC, stimulating NKT cells, elicited a significant but limited degree of protection against the i.p. disseminated MO4. A more potent antitumor effect was observed when alpha-GalCer was loaded to ES-DC expressing OVA before in vivo transfer, and the effect was abrogated by the administration of anti-CD8, anti-NK1.1 or anti-asialo GM1 antibody. alpha-GalCer-loaded double transfectant ES-DC expressing SLC along with OVA induced the most potent antitumor immunity. Thus, alpha-GalCer-loaded ES-DC expressing tumor-associated antigen along with SLC can stimulate multiple subsets of effector cells to induce a potent therapeutic effect against peritoneally disseminated tumor cells. The present study suggests a novel way to use alpha-GalCer in immunotherapy for peritoneally

Cancer prevention with semi-allogeneic ES cell-derived dendritic cells

Dendritic cells (DC) genetically modified to present tumor-associated antigen are a promising means for anti-cancer immunotherapy. By introducing expression vectors into ES cells and subsequently inducing differentiation to DC (ES-DC), we can generate transfectant DC expressing the transgenes. In the future clinical application of this technology, the unavailability of human ES cells genetically identical to the patients will be a problem. However, in most cases, semi-allogeneic ES cells sharing some of HLA alleles with recipients are expected to be available. In the present study, we observed that model tumor antigen (OVA)-expressing mouse ES-DC transferred into semi-allogeneic mice potently primed OVA-reactive CTL and elicited a significant protection against challenge with OVA-expressing tumor. Genetic modification of ES-DC to overexpress SPI-6, the specific inhibitor of granzyme B, further enhanced their capacity to prime antigen-specific CTL in semi-allogeneic recipient mice. These results suggest the potential of ES-DC as a novel means for anti-cancer immunotherapy.

Antigens from Ascaris suum trigger in vitro macrophage NO production

SUMMARY We investigated the in vitro effect of total excretory/secretory and somatic antigens from Ascaris suum adults (ESA and SA) and larvae 3 (ESL3 and SL3), and of 10 purified protein fractions from ESA components on rat alveolar macrophage nitric oxide (NO) production. Our results showed that in vitro incubation of macrophages with SA and SL3 antigens of A. suum did not result in NO release from cells, whereas incubation with ESA or ESL3 antigens resulted in the stimulation of NO production by these cells, both in a specific (inhibited by L-NAME and L-canavanine) and dose-dependent manner. In addition, we could demonstrate that a purified ESA fraction consisting of three Coomassie-stained bands of approximately 37, 44 and 46 kDa is involved in the in vitro triggering of NO production by host cells. These three bands were subjected to MALDI-peptide mass fingerprint, showing similarities with phosphoglycerate kinase, elongation factor Tu and enolase molecules, respectively. Future studies will focus on the characterization of these parasite-derived molecules.

Prevention of Experimental Autoimmune Encephalomyelitis by Transfer of Embryonic Stem Cell-Derived Dendritic Cells Expressing Myelin Oligodendrocyte Glycoprotein Peptide along with TRAIL or Programmed Death-1 Ligand

Experimental autoimmune encephalomyelitis (EAE) is caused by activation of myelin Ag-reactive CD4+ T cells. In the current study, we tested a strategy to prevent EAE by pretreatment of mice with genetically modified dendritic cells (DC) presenting myelin oligodendrocyte glycoprotein (MOG) peptide in the context of MHC class II molecules and simultaneously expressing TRAIL or Programmed Death-1 ligand (PD-L1). For genetic modification of DC, we used a recently established method to generate DC from mouse embryonic stem cells (ES cells) in vitro (ES-DC). ES cells were sequentially transfected with an expression vector for TRAIL or PD-L1 and an MHC class II-associated invariant chain-based MOG epitope-presenting vector. Subsequently, double-transfectant ES cell clones were induced to differentiate to ES-DC, which expressed the products of introduced genes. Treatment of mice with either of the double-transfectant ES-DC significantly reduced T cell response to MOG, cell infiltration into spinal cord, and the severity of MOG peptide-induced EAE. In contrast, treatment with ES-DC expressing MOG alone, irrelevant Ag (OVA) plus TRAIL, or OVA plus PD-L1, or coinjection with ES-DC expressing MOG plus ES-DC-expressing TRAIL or PD-L1 had no effect in reducing the disease severity. In contrast, immune response to irrelevant exogenous Ag (keyhole limpet hemocyanin) was not impaired by treatment with any of the genetically modified ES-DC. The double-transfectant ES-DC presenting Ag and simultaneously expressing immune-suppressive molecules may well prove to be an effective therapy for autoimmune diseases without inhibition of the immune response to irrelevant Ag.

Genetic and genomic studies of Drosophila parkin mutants implicate oxidative stress and innate immune responses in pathogenesis

Loss-of-function mutations of the parkin gene, which encodes a ubiquitin-protein ligase, are a common cause of autosomal recessive juvenile parkinsonism (ARJP). Previous work has led to the identification of a number of Parkin substrates that implicate specific pathways in ARJP pathogenesis, including endoplasmic reticulum (ER) stress and cell cycle activation. To test the involvement of previously implicated pathways, as well as to identify novel pathways in ARJP pathogenesis, we are using genetic and genomic approaches to study Parkin function in the fruit fly Drosophila melanogaster. In previous work, we demonstrated that Drosophila parkin null mutants exhibit mitochondrial pathology and flight muscle degeneration. To further explore the mechanisms responsible for pathology in parkin mutants, we analyzed the transcriptional alterations that occur during muscle degeneration and performed a genetic screen for parkin modifiers. Results of these studies indicate that oxidative stress response components are induced in parkin mutants and that loss-of-function mutations in oxidative stress components enhance the parkin mutant phenotypes. Genes involved in the innate immune response are also induced in parkin mutants. In contrast, our studies did not reveal evidence for cell cycle or ER stress pathway induction in parkin mutants. These results suggest that oxidative stress and/or inflammation may play a fundamental role in the etiology of ARJP.

Genome wide analysis of common and specific stress responses in adult drosophila melanogaster

Background

During their life, multicellular organisms are challenged with oxidative stress. It is generated by several reactive oxygen species (ROS), may limit lifespan and has been related to several human diseases. ROS can generate a wide variety of defects in many cellular components and thus the response of the organism challenged with oxidative stress may share some features with other stress responses. Conversely, in spite of recent progress, a complete functional analysis of the transcriptional responses to different oxidative stresses in model organisms is still missing. In addition, the functional significance of observed transcriptional changes is still elusive.

Results

We used oligonucleotide microarrays to address the specificities of transcriptional responses of adult Drosophila to different stresses induced by paraquat and H₂O₂, two oxidative stressors, and by tunicamycin which induces an endoplasmic reticulum (ER) stress. Both specific and common responses to the three stressors were observed and whole genome functional analysis identified several important classes of stress responsive genes. Within some functional classes, we observed that isozymes do not all behave similarly, which may reflect unsuspected functional specificities. Moreover, genetic experiments performed on a subset of lines bearing mutations in genes identified in microarray experiments showed that a significant number of these mutations may affect resistance of adult Drosophila to oxidative stress.

Conclusions

A long term common stress response to paraquat- or H₂O₂-induced oxidative stresses and ER stress is observed for a significant number of genes. Besides this common response, the unexpected complexity of the stress responses to oxidative and ER stresses in Drosophila, suggest significant specificities in protective properties between genes associated to the same functional classes. According to our functional analysis, a large part of the genome may play a role in protective mechanisms against oxidative stress in Drosophila.

Identification of a novel human cancer/testis antigen, KM-HN-1, recognized by cellular and humoral immune responses

PURPOSE

We used serologic screening of a cDNA expression library of human testis to identify novel cancer/testis antigens that elicit both humoral and cellular immune responses in cancer patients.

EXPERIMENTAL DESIGN AND RESULTS

We identified a novel gene designated KM-HN-1 the expression of which is testis-specific among normal tissues; it contains coiled coil domains and a leucine zipper motif and encodes a putative protein consisting of 833 amino acids. KM-HN-1 expression was observed in various cancer tissues and cancer cell lines at both mRNA and protein levels. Immunofluorescence staining of an esophageal cancer cell line revealed that KM-HN-1 protein was present exclusively in the nucleus during mitosis. Recombinant KM-HN-1 protein was produced, and used for ELISA to quantitate levels of IgG antibody specific to KM-HN-1. Higher levels of IgG antibodies specific to KM-HN-1 were detected in many types and numbers of cancer patients but not in healthy donors. The CTL lines specific to KM-HN-1, generated from HLA-A*2402-positive healthy donors and cancer patients, killed human leukocyte antigen (HLA)-A24-positive cancer cells expressing KM-HN-1 but not cell lines that did not express either KM-HN-1 or HLA-A24.

CONCLUSIONS

We identified a novel cancer/testis antigen, KM-HN-1, which elicited humoral immune responses in patients with various types of cancer. Furthermore, KM-HN-1-specific CTLs could be generated from both healthy donors and cancer patients, which indicated that KM-HN-1 can be a candidate for an ideal target for cancer immunotherapy.

Enhanced Priming of Antigen-Specific CTLs In Vivo by Embryonic Stem Cell-Derived Dendritic Cells Expressing Chemokine Along with Antigenic Protein: Application to Antitumor Vaccination

Dendritic cell (DC)-based immunotherapy is regarded as a promising means for anti-cancer therapy. The efficiency of T cell-priming in vivo by transferred DCs should depend on their encounter with T cells. In the present study, we attempted to improve the capacity of DCs to prime T cells in vivo by genetic modification to express chemokine with a T cell-attracting property. For genetic modification of DCs, we used a recently established method to generate DCs from mouse embryonic stem cells. We generated double-transfectant DCs expressing a chemokine along with a model Ag (OVA) by sequential transfection of embryonic stem cells, and then induced differentiation to DCs. We comparatively evaluated the effect of three kinds of chemokines; secondary lymphoid tissue chemokine (SLC), monokine induced by IFN-gamma (Mig), and lymphotactin (Lptn). All three types of double transfectant DCs primed OVA-specific CTLs in vivo more efficiently than did DCs expressing only OVA, and the coexpression of SLC or Lptn was more effective than that of Mig. Immunization with DCs expressing OVA plus SLC or Mig provided protection from OVA-expressing tumor cells more potently than did immunization with OVA alone, and SLC was more effective than Mig. In contrast, coexpression of Lptn gave no additive effect on protection from the tumor. Collectively, among the three chemokines, expression of SLC was the most effective in enhancing antitumor immunity by transferred DCs in vivo. The findings provide useful information for the development of a potent DC-based cellular immunotherapy.

Generation and genetic modification of dendritic cells derived from mouse embryonic stem cells

We developed a method to generate dendritic cells (DCs) from mouse embryonic stem (ES) cells. We cultured ES cells for 10 days on feeder cell layers of OP9, in the presence of granulocyte-macrophage colony-stimulating factor in the latter 5 days. The resultant ES cell-derived cells were transferred to bacteriologic Petri dishes without feeder cells and further cultured. In about 7 days, irregularly shaped floating cells with protrusions appeared and these expressed major histocompatibility complex class II, CD11c, CD80, and CD86, with the capacity to stimulate primary mixed lymphocyte reaction (MLR) and to process and present protein antigen to T cells. We designated them ES-DCs (ES cell-derived dendritic cells), and the functions of ES-DCs were comparable with those of DCs generated from bone marrow cells. Upon transfer to new dishes and stimulation with interleukin-4 plus tumor necrosis factor alpha, combined with anti-CD40 monoclonal antibody or lipopolysaccharide, ES-DCs completely became mature DCs, characterized by a typical morphology and higher capacity to stimulate MLR. Using an expression vector containing the internal ribosomal entry site-puromycin N-acetyltransferase gene or a Cre-lox-mediated exchangeable gene-trap system, we could efficiently generate ES cell transfectants expressing the products of introduced genes after their differentiation to DCs. ES-DCs expressing invariant chain fused to a pigeon cytochrome C epitope presented the epitope efficiently in the context of E(k). We primed ovalbumin (OVA)-specific cytotoxic T lymphocytes in vivo by injecting mice with ES-DCs expressing OVA, thus demonstrating immunization with ES-DCs genetically engineered to express antigenic protein. The methods may be applicable to immunomodulation therapy and gene-trap investigations of DCs.

A novel GTP-binding protein hGBP3 interacts with NIK/HGK

A novel human guanylate-binding protein (GBP) hGBP3 was identified and characterized. Similar as the two human guanylate-binding proteins hGBP1 and hGBP2, hGBP3 has the first two motifs of the three classical guanylate-binding motifs, GXXXXGKS (T) and DXXG, but lacks the N (T) KXD motif. Escherichia coli-expressed hGBP3 protein specifically binds to guanosine triphosphate (GTP). Using a yeast two-hybrid system, it was revealed that the N-terminal region of hGBP3 binds to the C-terminal regulatory domain of NIK/HGK, a member of the group I GCK (germinal center kinase) family. This interaction was confirmed by in vitro glutathione-S-transferase (GST) pull-down and co-immunoprecipitation assays.