Project description:The chemokine CXCL12 and its receptor CXCR4 play important roles in signaling and migration of T-cells, but little is known about the transcriptional events involved in CXCL12-mediated T-cell migration. In this study we performed microarray analysis on CXCL12- treated T-cells, and found that the Wnt family of proteins was significantly upregulated during CXCL12 treatment. Confirmation of these results by real-time PCR and Western analysis indicated that the non-canonical Wnt pathway was specifically upregulated during CXCL12 treatment. In vitro and in vivo knockdown studies confirm that b-catenin (the key mediator of canonical Wnt signaling) is not involved in the CXCL12-mediated migration of T-cells. However, Wnt5A, a non-canonical Wnt protein, increases signaling through the CXCL12/ CXCR4 axis via Protein Kinase C (PKC). Our results demonstrated that CXCL12 required Wnt5A to mediate T-cell migration, and the treatment of T-cells with recombinant Wnt5A sensitized T-cells to CXCL12 induced migration. Additionally, Wnt5A expression was required for the sustained expression of CXCR4, both transcriptionally and translationally. These results could be translated in vivo, using EL4 thymoma metastasis as a model of T-cell migration. Taken together our data indicate, for the first time, that Wnt5A is a critical mediator of the CXCL12/ CXCR4 signaling axis. Keywords: Wnt5A, CXCL12, CXCL12, CXCR4, T-cell Migration
Project description:The chemokine CXCL12 and its receptor CXCR4 play important roles in signaling and migration of T-cells, but little is known about the transcriptional events involved in CXCL12-mediated T-cell migration. In this study we performed microarray analysis on CXCL12- treated T-cells, and found that the Wnt family of proteins was significantly upregulated during CXCL12 treatment. Confirmation of these results by real-time PCR and Western analysis indicated that the non-canonical Wnt pathway was specifically upregulated during CXCL12 treatment. In vitro and in vivo knockdown studies confirm that b-catenin (the key mediator of canonical Wnt signaling) is not involved in the CXCL12-mediated migration of T-cells. However, Wnt5A, a non-canonical Wnt protein, increases signaling through the CXCL12/ CXCR4 axis via Protein Kinase C (PKC). Our results demonstrated that CXCL12 required Wnt5A to mediate T-cell migration, and the treatment of T-cells with recombinant Wnt5A sensitized T-cells to CXCL12 induced migration. Additionally, Wnt5A expression was required for the sustained expression of CXCR4, both transcriptionally and translationally. These results could be translated in vivo, using EL4 thymoma metastasis as a model of T-cell migration. Taken together our data indicate, for the first time, that Wnt5A is a critical mediator of the CXCL12/ CXCR4 signaling axis. Experiment Overall Design: Primary T cells were treated with human CXCL12 (Peprotech, Rocky Hill, NJ) at 100 ng/ml per 10 million cells overnight in a humidified incubator at 37ºC with 5% CO2. Control cells were incubated in media only. Cells were harvested and washed with ice cold PBS for 2 times followed by the addition of ice cold TRIzol (Invitrogen, Carlsbad, CA) and frozen at -80ºC overnight. Total RNA was isolated using the RNA isolation kit manufactured by Qiagen (Valencia, CA). The cDNA was prepared from equal amount of RNA using a cDNA preparation kit (Bio-Rad, Hercules, CA) followed by preparation of cRNA according to manufacturerâs instructions (Agilent, Santa Clara, CA). The cRNA was amplified and labeled with either Cy-3 or Cy-5, using the Agilent low-input linear amplification kit, according to manufacturerâs protocols. Labeled cRNA were applied to the Human 44K whole genome oligo array slides (Agilent, Santa Clara, CA). Slides were hybridized in a rotating chamber overnight at 60ºC in 6X SSC. Next day, slides were washed with 0.005% Triton X-102 for 10 minutes, and then in 0.1X SSC, 0.005% Triton X-102 for 5 minutes on ice. Slides were dried using a nitrogen-filled air gun, and scanned using an Agilent scanner. Images were analyzed using the Agilent Feature Extractor Software, Version A.7.5.1 and ratios for each spot were calculated.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:Cytokines constitute a family of proteins that are secreted by a broad variety of cells and modulate the immune response. CXCL12, along with its receptor CXCR4, are essential players in numerous biological processes. Dysregulation of their function can underlie the mechanisms(s) of several pathologies, including malignancies. Here, we demonstrate a rather unexpected effect of the cytokine and its receptor: in both cells and animal models, CXCL12 restricts tumorigenicity of the glioblastoma cells U87-MG and U-118, and of the breast cancer cell PyMT. Overexpression of CXCL12 inhibits activation of the proto-oncogene Ras which results in downregulation of its proliferative signals, such as reduced phosphorylation of the extracellular signal-regulated kinase 1/2 (ERK1/2), inhibition of c-Myc expression, and subsequent inhibition of cell cycle. Furthermore, CXCL12 induces downregulation of the growth differentiation factor 15 (GDF15), insulin-like growth factor-binding protein 6 (IGFBP6), and matrix metalloproteinase-3 (MMP3), which are implicated in the metastatic process. Indeed, monitoring cell migration in vitro and generation of metastases in mice demonstrate that CXCL12 slows the migration of U87-MG and PyMT cells. Remarkably, overexpression of CXCL12 also downregulates the cell surface immune checkpoint protein programmed cell death-ligand 1 (PDL1), as is evidence by enhanced recruitment of cytotoxic CD8 T cells. Overall, CXCL12 inhibits tumor growth through several distinct mechanisms: inhibition of cell cycle and migration, as well as impairment of immune checkpoint, thereby stimulating a strong host’s immune response. The mechanism(s) that renders CXCL12 a tumor promoting agent in certain cells, and a tumor suppressor in others has remained elusive.
Project description:As the evolution of miRNA genes has been found to be one of the important factors in formation of the modern type of man, we performed a comparative analysis of the evolution of miRNA genes in two archaic hominines, Homo sapiens neanderthalensis and Homo sapiens denisova, and elucidated the expression of their target mRNAs in bain.A comparative analysis of the genomes of primates, including species in the genus Homo, identified a group of miRNA genes having fixed substitutions with important implications for the evolution of Homo sapiens neanderthalensis and Homo sapiens denisova. The mRNAs targeted by miRNAs with mutations specific for Homo sapiens denisova exhibited enhanced expression during postnatal brain development in modern humans. By contrast, the expression of mRNAs targeted by miRNAs bearing variations specific for Homo sapiens neanderthalensis was shown to be enhanced in prenatal brain development.Our results highlight the importance of changes in miRNA gene sequences in the course of Homo sapiens denisova and Homo sapiens neanderthalensis evolution. The genetic alterations of miRNAs regulating the spatiotemporal expression of multiple genes in the prenatal and postnatal brain may contribute to the progressive evolution of brain function, which is consistent with the observations of fine technical and typological properties of tools and decorative items reported from archaeological Denisovan sites. The data also suggest that differential spatial-temporal regulation of gene products promoted by the subspecies-specific mutations in the miRNA genes might have occurred in the brains of Homo sapiens denisova and Homo sapiens neanderthalensis, potentially contributing to the cultural differences between these two archaic hominines.
Project description:Homing and engraftment of hematopoietic stem cells (HSCs) to the bone marrow (BM) involve a complex interplay between chemokines, cytokines, and non-peptide molecules. Extracellular nucleotides and their cognate P2 receptors are emerging as key-factors of inflammation and related chemotactic responses. In this study, we investigated the activity of extracellular adenosine-triphosphate (ATP) and uridine-triphosphate (UTP) on CXCL12-stimulated CD34+ HSC chemotaxis. In vitro, UTP significantly improved HSC migration, inhibited cell membrane CXCR4 down-regulation of migrating CD34+ cells and increased cell adhesion to fibronectin. In vivo, pre-incubation with UTP significantly enhanced the BM homing efficiency of human CD34+ cells in immunodeficient mice. Pertussis toxin blocked CXCL12- and UTP-dependent chemotactic responses, suggesting that G-protein alpha-subunits (Gαi) may provide a converging signal for CXCR4- and P2Y-activated transduction pathways. In addition, gene expression profiling of UTP-treated CD34+ cells and in vitro inhibition assays demonstrated that Rho guanosine 5â-triphosphatases (GTPase) Rac2 and downstream effectors Rho GTPaseâactivated kinases 1 and 2 (ROCK1/2) are involved in UTP-promoted/CXCL12-dependent HSC migration. Our data suggest that UTP may physiologically modulate the migration of HSCs and their homing to the BM, in concert with CXCL12, via the activation of converging signaling pathways between CXCR4 and P2Y receptors, involving Gαi proteins and RhoGTPases. Experiment Overall Design: Highly purified CD34+ cells from 6 healthy donors were seeded at 1000000 cells/ml in serum free medium (EX vivo 15) w/o cytokines and treated with 10 mM UTP, 150ng/ml CXCL12, or 10 mM UTP plus 150ng/ml CXCL12 respectively for 24 hours. As a control, CD34+ untreated cells were maintained in the same culture conditions at the same time.
Project description:PurposeWe investigated the evidence of recent positive selection in the human phototransduction system at single nucleotide polymorphism (SNP) and gene level.MethodsSNP genotyping data from the International HapMap Project for European, Eastern Asian, and African populations was used to discover differences in haplotype length and allele frequency between these populations. Numeric selection metrics were computed for each SNP and aggregated into gene-level metrics to measure evidence of recent positive selection. The level of recent positive selection in phototransduction genes was evaluated and compared to a set of genes shown previously to be under recent selection, and a set of highly conserved genes as positive and negative controls, respectively.ResultsSix of 20 phototransduction genes evaluated had gene-level selection metrics above the 90th percentile: RGS9, GNB1, RHO, PDE6G, GNAT1, and SLC24A1. The selection signal across these genes was found to be of similar magnitude to the positive control genes and much greater than the negative control genes.ConclusionsThere is evidence for selective pressure in the genes involved in retinal phototransduction, and traces of this selective pressure can be demonstrated using SNP-level and gene-level metrics of allelic variation. We hypothesize that the selective pressure on these genes was related to their role in low light vision and retinal adaptation to ambient light changes. Uncovering the underlying genetics of evolutionary adaptations in phototransduction not only allows greater understanding of vision and visual diseases, but also the development of patient-specific diagnostic and intervention strategies.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes