Dicty News Electronic Edition Volume 25, number 6 September 16, 2005 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= Function and mechanism of action of Dictyostelium Nramp1 (Slc11a1) in bacterial infection Barbara Peracino, Carina Wagner*, Alessandra Balest, Alessandra Balbo, Barbara Pergolizzi, Angelika A. Noegel�, Michael Steinert* and Salvatore Bozzaro Traffic, in press Dictyostelium amoebae are professional phagocytes, which ingest bacteria as the principal source of food. We have cloned the Dictyostelium homologue of human Nramp1 (Slc11a1), an endo-lysosomal membrane protein that confers on macrophages resistance to infection by a variety of intracellular bacteria and protozoa. The Dictyostelium Nramp1 gene encodes a protein of 53kDa with 11 putative transmembrane domains. The Nramp1 gene is transcribed during the growth-phase and down regulated to barely detectable levels upon starvation. To gain insights into their intracellular localization, Nramp1 or the vatB subunit of the V-H+ATPase were fused with GFP and expressed in cells. GFP-vatB was inserted in membranes of all acidic compartments and the contractile vacuole network, and decorated macropinosomes and phagosomes. GFP-Nramp1 decorated macropinosomes and phagosomes, in addition to intracellular vesicular compartments positive for endosomal SNARE protein Vti1 or vacuolin, a marker of the exocytic pathway. Nramp1 disruption generated mutants that were more permissive hosts than wild-type cells for intracellular growth of L. pneumophyla and M. avium. Nramp1 overexpression protected cells from L. pneumophila infection. Evidence is provided that Nramp1 transports metal cations out of the phago-lysosome in an ATP-dependent process, and that L. pneumophila and M. avium use different mechanisms to neutralize Nramp1 activity. Submitted by: Salvatore Bozzaro [salvatore.bozzaro@unito.it] ----------------------------------------------------------------------------- Dictyostelium transcriptional host cell response upon infection with Legionella Patrick Farbrother1, Carina Wagner2, Jianbo Na1, Budi Tunggal1, Takahiro Morio3, Hideko Urushihara3, Yoshimasa Tanaka3, Michael Schleicher4, Michael Steinert2 and Ludwig Eichinger1 1 Institut f�r Biochemie I, Medizinische Fakult�t, Universit�t zu K�ln, Joseph-Stelzmann-Str. 52, D-50931 K�ln 2 Institut f�r Molekulare Infektionsbiologie, Universit�t W�rzburg, R�ntgenring 11, D-97070 W�rzburg 3 Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan 4 Institut f�r Zellbiologie, Medizinische Fakult�t, Ludwig-Maximilians-Universit�t M�nchen, D-80336 M�nchen Cellular Microbiology, in press Differential gene expression of Dictyostelium discoideum after infection with Legionella pneumophila was investigated using DNA-microarrays. Investigation of a 48-hour time course of infection revealed several clusters of co-regulated genes, an enrichment of preferentially up- or down-regulated genes in distinct functional categories and also showed that most of the transcriptional changes occurred 24 hours after infection. A detailed analysis of the 24-hour time point post-infection was performed in comparison to three controls, uninfected cells and co-incubation with L. hackeliae and L. pneumophila DdotA. 131 differentially expressed D. discoideum genes were identified as common to all three experiments and are thought to be involved in the pathogenic response. Functional annotation of the differentially regulated genes revealed that apart from triggering a stress response Legionella apparently not only interferes with intracellular vesicle fusion and destination but also profoundly influences and exploits the metabolism of its host. For some of the identified genes e.g. RtoA involvement in the host response has been demonstrated in a recent study, for others such a role appears plausible. The results provide the basis for a better understanding of the complex host-pathogen interactions and for further studies on the Dictyostelium response to Legionella infection. Submitted by: Ludwig Eichinger [ludwig.eichinger@uni-koeln.de] ----------------------------------------------------------------------------- Comparative genomics of Dictyostelium discoideum and Entamoeba histolytica Ludwig Eichinger and Angelika A Noegel Centre for Biochemistry and Centre for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 K�ln, Germany Curr. Opin. Microbiol., in press Amoebozoa represent one of the earliest branches from the last common ancestor of all eukaryotes and contain some of the most dangerous human pathogens. Two amoebozoan genomes - from the model organism Dictyostelium discoideum and the human pathogen Entamoeba histolytica - have been published this year. Owing to their high A+T content, both genomes were difficult to sequence. In addition to nine amoebozoan expressed sequence tag projects, efforts are underway for comparative sequencing of four additional Entamoeba species. The completed genome sequences of D. discoideum and E. histolytica revealed unusual telomere structures, a high percentage of repetitive elements and a remarkably high gene content that is close to the one of Drosophila melanogaster. Finally, both organisms are brilliant examples of the influence of the lifestyle of an organism on its genome. Submitted by: Ludwig Eichinger [ludwig.eichinger@uni-koeln.de] ============================================================================== [End Dicty News, volume 25, number 6]