David R M Graham

Johns Hopkins Medicine, Baltimore, MD, United States

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Publications (10)39.42 Total impact

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    ABSTRACT: Minocycline is a tetracycline family antibiotic that has anti-inflammatory and immunomodulatory properties. These properties have shown promise in the treatment of conditions such as rheumatoid arthritis, Huntington disease, and multiple sclerosis. As lymphocyte activation is involved in the pathogenesis of many of these diseases, T cells are postulated to be a primary target in minocycline therapy. Previous studies have demonstrated attenuation of CD4(+) T cell activation by minocycline, but a specific mechanism has not been elucidated. In this study, we investigated the effect of minocycline on the activity of three key transcription factors regulating CD4(+) T cell activation: NF-κB, AP-1 (activator protein 1), and NFAT (nuclear factor of activated T) cells. Our data demonstrate that minocycline selectively impairs NFAT-mediated transcriptional activation, a result of increased phosphorylation and reduced nuclear translocation of the isoform NFAT1. Minocycline increased the activity of the NFAT kinase GSK3 and decreased intracellular Ca(2+) flux, both of which facilitate NFAT1 phosphorylation. These findings provide a novel mechanism for minocycline induced suppression of CD4(+) T cell activation and may better inform the application of minocycline as an immunomodulatory agent.
    Journal of Biological Chemistry 01/2011; 286(13):11275-82. · 4.65 Impact Factor
  • Ravi Tharakan, Nathan Edwards, David R M Graham
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    ABSTRACT: With the proliferation of search engines for the analysis of MS data, multisearch techniques aimed at boosting the discriminating power of the search engines' score functions have recently become popular. Much statistical and algorithmic work has been done, therefore, in order to be able to combine and parse multiple search streams. However, multisearch techniques suffer from long run times, and may have little impact on false negatives because of similar peptide filtering heuristics between searches. This review focuses, rather, on multipass techniques, which use the results of one search to guide the selection of spectra, parameters and sequences in subsequent searches. This reduces the number of false-negative peptide identifications due to peptide candidate filtering while preserving statistical significance of existing (correct) identifications. Furthermore, this technique avoids substantial increases in running time and, by limiting the search space, does not reduce the statistical significance of correct identifications or introduce a statistically significant number of false-positive identifications. However, we argue that the existing combiner tools are not reliably applicable to these multipass situations, because of algorithmic assumptions about search space and statistical assumptions about the rate of true positives. Here we provide an overview of the advantages of and issues in multipass analysis techniques, the existing methods and workflows available to proteomic researchers, and the unsolved statistical and algorithmic issues amenable to future research.
    Proteomics 03/2010; 10(6):1160-71. · 4.43 Impact Factor
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    ABSTRACT: The glycosylation state of envelope glycoproteins in human and simian immunodeficiency viruses (HIV/SIV) is critical to viral infectivity and tropism, viral protein processing, and in virus evasion of the immune system. Using a rapid fluorescent 2-D gel-based method coupled with enzymatic pre-treatment of virus with PNGase F (Peptide: N-Glycosidase F) and fluorescent 2-D gels or 2-D gel Western blotting, we show significant differences in the glycosylation patterns of two SIV strains widely used in animal models of HIV disease and vaccine studies. We also demonstrate the modification of a host protein important in HIV biology (HLA-DR) by O-GlcNAc. Further, this experimental pipeline allows for the identification of the modified protein and the site of N-linked glycosylation by fluorescent 2-DE coupled with MS and the qualitative and semi-quantitative assessment of viral glycosylation. The method is fully compatible with downstream glycomics analysis. This approach will permit correlation of virus glycosylation status with pathological severity and may serve as a rapid screen of viruses from physiological samples for further study by more advanced MS methodology.
    Proteomics 01/2009; 8(23-24):4919-30. · 4.43 Impact Factor
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    ABSTRACT: Endothelial cell barrier dysfunction results in the increased vascular permeability observed in inflammation, tumor metastasis, angiogenesis, and atherosclerosis. Sphingosine 1-phosphate (S1P), a biologically active phosphorylated lipid growth factor released from activated platelets, enhances the endothelial cell barrier integrity in vitro and in vivo. To begin to identify the molecular mechanisms mediating S1P induced endothelial barrier enhancement, quantitative proteomics analysis (iTRAQ) was performed on membrane rafts isolated from human pulmonary artery endothelial cells in the absence or presence of S1P stimulation. Our results demonstrated that S1P mediates rapid and specific recruitment (1 microM, 5 min) of myristoylated alanine-rich protein kinase C substrate (MARCKS) and MARCKS-related protein (MRP) to membrane rafts. Western blot experiments confirmed these findings with both MARCKS and MRP. Finally, small interfering RNA-mediated silencing of MARCKS or MRP or both attenuates S1P-mediated endothelial cell barrier enhancement. These data suggest the regulation of S1P-mediated endothelial cell barrier enhancement via the cell specific localization of MARCKS and MRP and validate the utility of proteomics approaches in the identification of novel molecular targets.
    Molecular &amp Cellular Proteomics 05/2007; 6(4):689-96. · 7.25 Impact Factor
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    ABSTRACT: Two-dimensional gel electrophoresis (2-DE) is widely used for initial protein separation in proteomics. Commercial products using neutral pH sodium dodecyl sulfate-polyacrylamide gel electrophoresis ((SDS-PAGE)/(Bis (2-hydroxyethyl) imino-tris (hydroxymethyl) methane-HCl, or Bis-Tris)) have greatly improved this technique, but cost and limited sizes restrict their applications. An "in-house" system is presented, resulting in better resolution, separation, and new spot visualization and improved resolution when compared to Tris-HCl gels. Their utility is demonstrated using albumin-depleted serum samples, rabbit heart left ventricle, and human immunodeficiency virus type 1 (HIV-1).
    PROTEOMICS 07/2005; 5(9):2309-14. · 4.13 Impact Factor
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    ABSTRACT: Proteomics, the study of the proteome (the collection of all the proteins expressed from the genome in all isoforms, polymorphisms and post-translational modifications), is a rapidly developing field in which there are numerous new and often expensive technologies, making it imperative to use the most appropriate technology for the biological system and hypothesis being addressed. This review provides some guidelines on approaching a broad-based proteomics project, including strategies on refining hypotheses, choosing models and proteomic approaches with an emphasis on aspects of sample complexity (including abundance and protein characteristics), and separation technologies and their respective strengths and weaknesses. Finally, issues related to quantification, mass spectrometry and informatics strategies are discussed. The goal of this review is therefore twofold: the first section provides a brief outline of proteomic technologies, specifically with respect to their applications to broad-based proteomic approaches, and the second part provides more details about the application of these technologies in typical scenarios dealing with physiological and pathological processes. Proteomics at its best is the integration of carefully planned research and complementary techniques with the advantages of powerful discovery technologies that has the potential to make substantial contributions to the understanding of disease and disease processes.
    The Journal of Physiology 03/2005; 563(Pt 1):1-9. · 4.38 Impact Factor
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    ABSTRACT: Barrier-to-autointegration factor (BAF) is a conserved human chromatin protein exploited by retroviruses. Previous investigators showed that BAF binds double-stranded DNA nonspecifically and is a host component of preintegration complexes (PICs) isolated from cells infected with human immunodeficiency virus type 1 (HIV-1) or Moloney murine leukemia virus. BAF protects PIC structure and stimulates the integration of salt-stripped PICs into target DNA in vitro. PICs are thought to acquire BAF from the cytoplasm during infection. However, we identified two human tissues (of 16 tested) in which BAF mRNA was not detected: thymus and peripheral blood leukocytes, which are enriched in CD4(+) T lymphocytes and macrophage precursors, respectively. BAF protein was detected in activated but not resting CD4(+) T lymphocytes; thus, if BAF were essential for PIC function, we hypothesized that virions might "bring their own BAF." Supporting this model, BAF copurified with HIV-1 virions that were digested with subtilisin to remove microvesicle contaminants, and BAF was present in approximately zero to three copies per virion. In three independent assays, BAF bound directly to both p55 Gag (the structural precursor of HIV-1 virions) and its cleaved product, matrix. Using lysates from cells overexpressing Gag, endogenous BAF and Gag were coimmunoprecipitated by antibodies against Gag. Purified recombinant BAF had low micromolar affinities (1.1 to 1.4 micro M) for recombinant Gag and matrix. We conclude that BAF is present at low levels in incoming virions, in addition to being acquired from the cytoplasm of newly infected cells. We further conclude that BAF might contribute to the assembly or activity of HIV-1 PICs through direct binding to matrix, as well as DNA.
    Journal of Virology 01/2004; 77(24):13084-92. · 5.08 Impact Factor
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    ABSTRACT: Recent evidence suggests that human immunodeficiency virus type 1 (HIV-1) particles assemble and bud selectively through areas in the plasma membrane of cells that are highly enriched with glycosylphosphatidylinositol-anchored proteins and cholesterol, called lipid rafts. Since cholesterol is required to maintain lipid raft structure and function, we proposed that virion-associated cholesterol removal with the compound 2-hydroxy-propyl-beta-cyclodextrin (beta-CD) might be disruptive to HIV-1 and simian immunodeficiency virus (SIV). We examined the effect of beta-CD on the structure and infectivity of cell-free virions. We found that beta-CD inactivated HIV-1 and SIV in a dose-dependent manner and permeabilized the viral membranes, resulting in the loss of mature Gag proteins (capsid, matrix, nucleocapsid, p1, and p6) without loss of the envelope glycoproteins. SIV also lost reverse transcriptase (RT), integrase (IN), and viral RNA. IN appeared to be only slightly diminished in HIV-1, and viral RNA, RT, matrix, and nucleocapsid proteins were retained in HIV-1 but to a much lesser degree. Host proteins located internally in the virus (actin, moesin, and ezrin) and membrane-associated host proteins (major histocompatibility complex classes I and II) remained associated with the treated virions. Electron microscopy revealed that under conditions that permeabilized the viruses, holes were present in the viral membranes and the viral core structure was perturbed. These data provide evidence that an intact viral membrane is required to maintain mature virion core integrity. Since the viruses were not fixed before beta-CD treatment and intact virion particles were recovered, the data suggest that virions may possess a protein scaffold that can maintain overall structure despite disruptions in membrane integrity.
    Journal of Virology 09/2003; 77(15):8237-48. · 5.08 Impact Factor
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    Journal of Virology - J VIROL. 01/2003; 77(15):8237-8248.
  • David R. M. Graham, Steven T. Elliott, Jennifer E. Van Eyk

Publication Stats

258 Citations
65 Downloads
405 Views
39.42 Total Impact Points

Institutions

  • 2010
    • Johns Hopkins Medicine
      • Department of Medicine
      Baltimore, MD, United States
  • 2003–2009
    • Johns Hopkins University
      • • Department of Medicine
      • • Department of Pharmacology and Molecular Sciences
      Baltimore, MD, United States