Copy Link
Add to Bookmark
Report
dictyNews Volume 43 Number 25
dictyNews
Electronic Edition
Volume 43, number 25
October 20, 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
=========
GPCR-controlled Membrane Recruitment of Negative Regulator
C2GAP1 Locally Inhibits Ras Signaling for Adaptation and
Long-range Chemotaxis
Xuehua Xua, Xi Wen, Douwe M. Veltman, Ineke Keizer-Gunnink,
Henderikus Pots, Arjan Kortholt, and Tian Jin
PNAS, USA, accepted
Eukaryotic cells chemotax in a wide range of chemoattractant
concentration gradients, and thus need inhibitory processes that
terminate cell responses to reach adaptation while maintaining
sensitivity to higher-concentration stimuli. However, the molecular
mechanisms underlying inhibitory processes are still poorly
understood. Here, we reveal a locally controlled inhibitory process in
a GPCR-mediated signaling network for chemotaxis in Dictyostelium
discoideum. We identified a novel negative regulator of Ras signaling,
C2GAP1, which localizes at the leading edge of chemotaxing cells
and is activated by and essential for GPCR-mediated Ras signaling.
We show that both C2 and GAP domains are required for the
membrane targeting of C2GAP1, and that GPCR-triggered Ras
activation is necessary to recruit C2GAP1 from the cytosol and retains
it on the membrane to locally inhibit Ras signaling. C2GAP1-deficient
c2gapA- cells have altered Ras activation that results in impaired
gradient sensing, excessive polymerization of F-actin, and subsequent
defective chemotaxis. Remarkably, these cellular defects of c2gapA-
cells are chemoattractant concentration-dependent. Thus, we have
uncovered a novel inhibitory mechanism required for adaptation and
long-range chemotaxis.
submitted by: Xuehua Xu [xxu@niaid.nih.gov]
——————————————————————————————————————
The fate of multilamellar bodies produced and secreted by
Dictyostelium discoideum amoebae
Alix M. Denoncourt1,2,3, Alicia F. Durocher1,2,3, Valérie E.
Paquet1,2,3 and Steve J. Charette1,2,3*
1. Institut de Biologie Intégrative et des Systèmes, Pavillon Charles-
Eugène-Marchand, Université Laval, Quebec City, QC, Canada
2. Centre de recherche de l’Institut universitaire de cardiologie et de
pneumologie de Québec, Hôpital Laval, Quebec City, QC, Canada
3. Département de biochimie, de microbiologie et de bio-informatique,
Faculté des sciences et de génie, Université Laval, Quebec City, QC,
Canada
European Journal of Cell Biology, accepted
The amoeba Dictyostelium discoideum produces and secretes
multilamellar bodies (MLBs) mainly composed of amoebal membranes
upon digestion of bacteria. After their secretion, the fate of these MLBs
remains unknown. The aim of this study was to determine if protozoa
can internalize and digest secreted D. discoideum MLBs. Our results
showed that MLBs were ingested by naive axenic D. discoideum cells
(i. e. cells not exposed to bacteria and consequently not producing
MLBs). Only a small fraction of the ingested MLBs were found in cells’
post-lysosomes compared to undigestible beads suggesting that naive
amoebae digest them. D. discoideum MLBs were also ingested by the
ciliates Tetrahymena pyriformis and Tetrahymena thermophila. MLBs
internalized by the ciliates were compacted into pellets and expelled in
the extracellular medium without obvious signs of degradation. The
results of this study provide new insights on the biological function of
MLBs and, considering that MLBs are also involved in bacteria
packaging, suggest additional layers of complexity in microbial
interactions.
submitted by: Steve Charette [steve.charette@bcm.ulaval.ca]
——————————————————————————————————————
G-Protein Dependent Signal Transduction and Ubiquitination in
Dictyostelium
Barbara Pergolizzi , Salvatore Bozzarro and Enrico Bracco
Int. J. Mol. Sci. 2017, accepted
Signal transduction through G-protein-coupled receptors (GPCRs) is
central for the regulation of virtually all cellular functions, and it has
been widely implicated in human diseases.These receptors activate
a common molecular switch that is represented by the heterotrimeric
G-protein generating a number of second messengers (cAMP, cGMP,
DAG, IP3, Ca2+ etc.), leading to a plethora of diverse cellular responses.
Spatiotemporal regulation of signals generated by a given GPCR is
crucial for proper signalling and is accomplished by a series of
biochemical modifications. Over the past few years, it has become
evident that many signalling proteins also undergo ubiquitination, a
posttranslational modification that typically leads to protein degradation,
but also mediates processes such as protein-protein interaction and
protein subcellular localization. The social amoeba Dictyostelium
discoideum has proven to be an excellent model to investigate
signal transduction triggered by GPCR activation, as cAMP signalling
via GPCR is a major regulator of chemotaxis, cell differentiation, and
multicellular morphogenesis. Ubiquitin ligases have been recently
involved in these processes. In the present review, we will summarize
the most significant pathways activated upon GPCRs stimulation and
discuss the role played by ubiquitination in Dictyostelium cells.
submitted by: Barbara Pergolizzi [barbara.pergolizzi@unito.it]
==============================================================
[End dictyNews, volume 43, number 25]
