Copy Link
Add to Bookmark
Report
dictyNews Volume 43 Number 13
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]
