dictyNews Electronic Edition Volume 43, number 13 June 23, 2017 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 ========= Extracellular polyphosphate signals through Ras and Akt to prime Dictyostelium discoideum cells for development. Suess PM, Watson J, Chen W, Gomer RH Journal of Cell Science, in press Linear chains of five to hundreds of phosphates called polyphosphate are found in organisms ranging from bacteria to humans, but their function is poorly understood. In Dictyostelium, polyphosphate is used as a secreted signal that inhibits cytokinesis in an autocrine negative feedback loop. To elucidate how cells respond to this unusual signal, we did proteomic analysis of cells treated with physiological levels of polyphosphate and observed that polyphosphate causes cells to decrease levels of actin cytoskeleton proteins, possibly explaining how polyphosphate inhibits cytokinesis. Polyphosphate also causes proteasome protein levels to decrease, and in both Dictyostelium and human leukemia cells, decreases proteasome activity and cell proliferation. Polyphosphate also induces Dictyostelium cells to begin development by increasing expression of the cell-cell adhesion molecule CsA and causing aggregation, and this effect, as well as the inhibition of proteasome activity, is mediated by Ras and Akt. Surprisingly, Ras and Akt do not affect the ability of polyphosphate to inhibit proliferation, suggesting that a branching pathway mediates the effects of polyphosphate, with one branch affecting proliferation, and the other branch affecting development. submitted by: Patrick Suess [psuess@bio.tamu.edu] ——————————————————————————————————————— Breaking fat! How mycobacteria and other intracellular pathogens manipulate host lipid droplets Caroline Barisch & Thierry Soldati Department of Biochemistry, Faculty of Sciences, University of Geneva, 30 quai Ernest-Ansermet, Science II, 1211, Geneva-4, Switzerland Biochimie - https://doi.org/10.1016/j.biochi.2017.06.001 Tuberculosis (Tb) is a lung infection caused by Mycobacterium tuberculosis (Mtb). With one third of the world population latently infected, it represents the most prevalent bacterial infectious diseases worldwide. Typically, persistence is linked to so-called “dormant” slow-growing bacteria, which have a low metabolic rate and a reduced response to antibiotic treatments. However, dormant bacteria regain growth and virulence when the immune system is weakened, leading again to the active form of the disease. Fatty acids (FAs) released from host triacylglycerols (TAGs) and sterols are proposed to serve as sole carbon sources during infection. The metabolism of FAs requires beta-oxidation as well as gluconeogenesis and the glyoxylate shunt. Interestingly, the Mtb genome encodes more than hundred proteins involved in the five reactions of beta-oxidation, clearly demonstrating the importance of lipids as energy source. FAs have also been proposed to play a role during resuscitation, the resumption of replicative activities from dormancy. Lipid droplets (LDs) are energy and carbon reservoirs and have been described in all domains. TAGs and sterol esters (SEs) are stored in their hydrophobic core, surrounded by a phospholipid monolayer. Importantly, host LDs have been described as crucial for several intracellular bacterial pathogens and viruses and specifically translocate to the pathogen-containing vacuole (PVC) during mycobacteria infection. FAs released from host LDs are used by the pathogen as energy source and as building blocks for membrane synthesis. Despite their essential role, the mechanisms by which pathogenic mycobacteria induce the cellular redistribution of LDs and gain access to the stored lipids are still poorly understood. This review describes recent evidence about the dual interaction of mycobacteria with host LDs and membrane phospholipids and integrates them in a broader view of the underlying cellular processes manipulated by various intracellular pathogens to gain access to host lipids. submitted by: Caroline Barisch [caroline.barisch@unige.ch] ============================================================== [End dictyNews, volume 43, number 13]