dictyNews
Electronic Edition
Volume 34, number 13
April 23, 2010
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Abstracts
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The secreted proteome profile of developing Dictyostelium discoideum
cells
Deenadayalan Bakthavatsalam and Richard H.Gomer
Rice University, Department of Biochemistry and Cell Biology,
Houston, TX 77005. USA
Proteomics, in press
Dictyostelium discoideum is a unicellular eukaryote that, when starved,
aggregates to form multicellular structures. In this report, we
identified the
proteins secreted by developing Dictyostelium cells using mass
spectrometry based proteomics. A total of 349 different secreted
proteins
were identified, indicating that at least 2.6% of the 13600 predicted
proteins
in the Dictyostelium genome are secreted. Gene ontology (GO) analysis
suggests that many of the secreted proteins are involved in protein and
carbohydrate metabolism, and proteolysis.
Submitted by Richard Gomer [[log in to unmask]]
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Preparation of an antibody that recognizes and neutralizes Dictyostelium
differentiation-inducing factor-1
Yuzuru Kubohara*, Haruhisa Kikuchi, Koji Nakamura, Yusuke Matsuo,
Yoshiteru Oshima
*Institute for Molecular and Cellular Regulation (IMCR), Gunma
University,
Maebashi 371-8512, Japan.
BBRC, in press
In the development of the cellular slime mold Dictyostelium discoideum,
the differentiation-inducing factor-1 (DIF-1; 1-(3,5-dichloro-2,6-
dihydroxy-4-
methoxyphenyl)hexan-1-one) plays an important role in the regulation
of cell
differentiation and chemotaxis; however, the cellular signaling systems
involving DIF-1 remain to be elucidated. To obtain a probe for DIF-1, we
synthesized a DIF derivative (DIF-1-NH2; 6-amino-1-(3,5-dichloro-2,6-
dihydroxy-4-methoxyphenyl)hexan-1-one), and prepared an anti-DIF-1
antibody using a DIF-1-NH2-conjugated macromolecule as the immunogen.
A 100-fold dilution of the antibody bound to DIF-1-NH2-conjugated resin,
and this binding was inhibited by co-addition of 20 uM DIF-1 or
DIF-1-NH2. In a monolayer culture of HM44 cells, a DIF-deficient
D. discoideum strain, 0.5 nM exogenous DIF-1 induced stalk cell
formation
in ~60% of the cells; this induction was dose-dependently inhibited by
the
antibody (diluted 12.5- or 25-fold). Furthermore, this inhibition by the
antibody was recovered by co-addition of 2.5 or10 nM DIF-1. The results
indicate that the anti-DIF-1 antibody recognizes DIF-1 and neutralizes
its function.
Submitted by Yuzuru Kubohara [[log in to unmask]]
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The Onset of Collective Behavior in Social Amoebae
Thomas Gregor1, Koichi Fujimoto2, Noritaka Masaki2 and
Satoshi Sawai 1,2*
1Graduate School of Arts and Sciences, University of Tokyo,
2ERATO Complex Systems Biology Project, JST, Tokyo 153-8902, Japan
*To whom correspondence should be addressed.
Science, in press
In the social amoebae Dictyostelium discoideum, periodic synthesis and
release of extracellular cyclic AMP (cAMP) guides cell aggregation and
commitment to form fruiting bodies. It is unclear whether these
oscillations
represent an intrinsic property of individual cells or if they only
exist as a
population-level phenomenon. Here we show by live-cell imaging of
intact
cell populations that pulses originate from a discrete location despite
constant exchange of cells to and from the region. In a perfusion
chamber,
both isolated single cells and cell populations switch from quiescence
to
rhythmic activity depending on the level of extracellular cAMP. A
quantitative analysis shows that stochastic pulsing of individual
cells below
the threshold concentration of extracellular cAMP plays a critical
role in
the onset of collective behavior.
Submitted by Satoshi Sawai [[log in to unmask]]
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[End dictyNews, volume 34, number 13]
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