dictyNews Electronic Edition Volume 41, number 23 October 31, 2015 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 dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Reactive oxygen species and mitochondria: A nexus of cellular homeostasis. Dan Dunn J1, Alvarez LA2, Zhang X3, Soldati T4. 1Department of Biochemistry, University of Geneva, 30 quai Ernest Ansermet, Sciences II, CH-1211 Genève-4, Switzerland. 2National Children's Research Centre, Our Lady's Children's Hospital, Crumlin, Dublin 12, Ireland. 3Department of Biochemistry, University of Geneva, 30 quai Ernest Ansermet, Sciences II, CH-1211 Genève-4, Switzerland. 4Department of Biochemistry, University of Geneva, 30 quai Ernest Ansermet, Sciences II, CH-1211 Genève-4, Switzerland. In: Redox Biol. 2015 Sep 10;6:472-485. Reactive oxygen species (ROS) are integral components of multiple cellular pathways even though excessive or inappropriately localized ROS damage cells. ROS function as anti-microbial effector molecules and as signaling molecules that regulate such processes as NF-kB transcriptional activity, the production of DNA-based neutrophil extracellular traps (NETs), and autophagy. The main sources of cellular ROS are mitochondria and NADPH oxidases (NOXs). In contrast to NOX-generated ROS, ROS produced in the mitochondria (mtROS) were initially considered to be unwanted by-products of oxidative metabolism. Increasing evidence indicates that mtROS have been incorporated into signaling pathways including those regulating immune responses and autophagy. As metabolic hubs, mitochondria facilitate crosstalk between the metabolic state of the cell with these pathways. Mitochondria and ROS are thus a nexus of multiple pathways that determine the response of cells to disruptions in cellular homeostasis such as infection, sterile damage, and metabolic imbalance. In this review, we discuss the roles of mitochondria in the generation of ROS-derived anti-microbial effectors, the interplay of mitochondria and ROS with autophagy and the formation of DNA extracellular traps, and activation of the NLRP3 inflammasome by ROS and mitochondria. Submitted by Thierry Soldati [thierry.soldati@unige.ch] ———————————————————————————————————— Charged Solvatochromic Dyes as Signal Transducers in pH Independent Fluorescent and Colorimetric Ion Selective Nanosensors. Xie X1, Gutiérrez A1,2, Trofimov V2, Szilagyi I1, Soldati T2, Bakker E1. 1Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211, Geneva, Switzerland. 2Department of Biochemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211, Geneva, Switzerland. In: Anal Chem. 2015 Oct 6;87(19):9954-9. Ionophore-based ion selective optical nanosensors that operate independently of the sample pH are developed here by the use of electrically charged solvatochromic dyes as signal transducers. A series of dye molecules with a D-pi-A structure was synthesized and characterized in various solvents and incorporated into ion selective nanospheres for K(+), Na(+), and H(+). Since dye leakage was greatly suppressed when the solvatochromic dyes were encapsulated in the nanosphere core, ion sensing nanospheres were explored for cellular ion imaging in Dictyostelium discoideum live cells but spontaneous dye loss resulted in undesired staining of cells. The in vitro analysis of potassium in human plasma was successfully demonstrated with this approach. A theoretical model was developed for the response of the ion selective nanosensors containing charged solvatochromic dyes. The nanosensors exhibited a tunable response range, high sensitivity, and good stability. Submitted by Thierry Soldati [thierry.soldati@unige.ch] ——————————————————————————————————————— Adrenergic antagonists restrict replication of Legionella. Harrison CF1, Kicka S2, Kranjc A3, Finsel I1, Chiriano G3, Ouertatani-Sakouhi H4, Soldati T2, Scapozza L3, Hilbi H5. 1 Max von Pettenkofer Institute, Department of Medicine, Ludwig-Maximilians University Munich, 80336 Munich, Germany. 2 Department of Biochemistry, University of Geneva, 1211 Geneva, Switzerland. 3 School of Pharmaceutical Sciences, Department of Pharmaceutical Biochemistry, University of Geneva and University of Lausanne, 1211 Geneva, Switzerland. 4 Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland. 5 Institute of Medical Microbiology, Department of Medicine, University of Zurich, Gloriastrasse 30/32, 8006 Zurich, Switzerland. In: Microbiology. 2015 Jul;161(7):1392-406 Legionella pneumophila is a facultative intracellular bacterium, which upon inhalation can cause a potentially fatal pneumonia termed Legionnaires' disease. The opportunistic pathogen grows in environmental amoebae and mammalian macrophages within a unique membrane-bound compartment, the 'Legionella-containing vacuole'. Bacteria are exposed to many environmental cues including small signalling molecules from eukaryotic cells. A number of pathogenic bacteria sense and respond to catecholamine hormones, such as adrenalin and noradrenalin, a process mediated via the QseBC two-component system in some bacteria. In this study, we examined the effect of adrenergic compounds on L. pneumophila, and discovered that the adrenergic receptor antagonists benoxathian, naftopidil, propranolol and labetalol, as well as the QseC sensor kinase inhibitor LED209, reduced the growth of L. pneumophila in broth or amoebae, while replication in macrophages was enhanced. Growth restriction was common to members of the genus Legionella and Mycobacterium, and was observed for L. pneumophila in the replicative but not stationary phase of the biphasic life cycle. Deletion of the L. pneumophila qseBC genes indicated that growth inhibition by adrenergics or LED209 is mediated only to a minor extent by this two-component system, implying the presence of other adrenergic sensing systems. This study identifies adrenergic molecules as novel inhibitors of extra- and intracellular growth of Legionella and reveals LED209 as a potential lead compound to combat infections with Legionella or Mycobacterium spp. Submitted by Thierry Soldati [thierry.soldati@unige.ch] ——————————————————————————————————————— Live imaging of Mycobacterium marinum infection in Dictyostelium discoideum. Barisch C1, López-Jiménez AT, Soldati T. 1Département de Biochimie, Faculté des Sciences, Université de Genève, Sciences II, 30 Quai Ernest Ansermet, 1211, Genève-4, Switzerland. In; Methods Mol Biol. 2015;1285:369-85: The Dictyostelium discoideum-Mycobacterium marinum host-pathogen system is a recently established and powerful model system for mycobacterial infection. In this chapter, two simple protocols for live imaging of Dictyostelium discoideum infection are described. The first method is used to monitor the dynamics of recruitment of GFP-tagged Dictyostelium discoideum proteins at single time-points corresponding to the main stages of the infection (1.5-72 h post infection). The second method focuses at the early stages of the establishment of an infection (0-3 h post infection). In addition, several procedures to improve the imaging of the bacterium- containing compartment are described. Basic bacterial parameters such as bacterial growth and the recruitment of host proteins to the bacterium-containing compartment can be easily and precisely quantified using macros for ImageJ. These methods can be adapted to monitoring mycobacteria infection in other systems using mammalian cells. Submitted by Thierry Soldati [thierry.soldati@unige.ch] ============================================================== [End dictyNews, volume 41, number 23]