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dictyNews Volume 40 Number 02
dictyNews
Electronic Edition
Volume 40, number 2
January 10, 2014
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
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Abstracts
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PIP3-dependent macropinocytosis is incompatible with chemotaxis
Douwe M. Veltman(1), Michael G. Lemieux (2), David A. Knecht (2)
and Robert H. Insall (1)*
(1) Beatson Institute for Cancer Research, Switchback Road,
Glasgow G61 1BD, UK
(2) Department of Molecular and Cell Biology, University of Connecticut,
Storrs, CT 06269, U.S.A.
Journal of Cell Biology, in press
In eukaryotic chemotaxis, the mechanisms connecting external signals to
the motile apparatus remain unclear. The role of the lipid PIP3 has been
particularly controversial. PIP3 has many cellular roles, notably in growth
control and macropinocytosis as well as cell motility. Here we show that
PIP3 is not only unnecessary for Dictyostelium to migrate towards folate,
but actively inhibits chemotaxis. We find that macropinosomes, but not
pseudopods, in growing cells are dependent on PIP3. PIP3 patches in
these cells show no directional bias, and overall only PIP3-free pseudopods
orient up-gradient. The pseudopod driver SCAR/WAVE is not recruited to
centre of PIP3 patches, just the edges, where it causes macropinosome
formation. Wild type cells, unlike the widely-used axenic mutants, show little
macropinocytosis and few large PIP3 patches, but migrate more efficiently
towards folate. Tellingly, folate chemotaxis in axenic cells is rescued by
knocking out PI3-kinases. Thus PIP3 promotes macropinocytosis and
interferes with pseudopod orientation during chemotaxis of growing cells.
Submitted by Douwe Veltman [dveltman@mrc-lmb.cam.ac.uk]
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Cell-to-cell coordination for the spontaneous cAMP oscillation in Dictyostelium
Seido Nagano & Shunsuke Sakurai
Physical Review E88, 062710(2013)
We propose a new cellular dynamics scheme for the spontaneous cAMP
oscillations in Dictyostelium discoideum.Our scheme seamlessly integrates
both receptor dynamics andG-protein dynamics into our previously developed
cellular dynamics scheme. Extensive computer simulation studies based on
our new cellular dynamics scheme were conducted in mutant cells to evaluate
the molecular network. The validity of our proposed molecular network as well
as the controversial PKA-dependent negative feedback mechanism was
supported by our simulation studies. Spontaneous cAMP oscillations were not
observed in a single mutant cell. However, multicellular states of various
mutant cells consistently initiated spontaneous cAMP oscillations. Therefore,
cell-to-cell coordination via the cAMP receptor is essential for the robust
initiation of spontaneous cAMP oscillations.
Submitted by Seido Nagano [nagano@sk.ritsumei.ac.jp]]
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[End dictyNews, volume 40, number 2]
