dictyNews
Electronic Edition
Volume 33, number 3
July 24, 2009
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Abstracts
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How a Cell Crawls and the Role of Cortical Myosin II
David R. Soll, Deborah Wessels, Spencer Kuhl, and Daniel F. Lusche
Eukaryotic Cell, in press
Employing 3D-DIAS software, Dictyostelium discoideum amoebae
translocating
on a glass surface in the absence of chemoattractant have been
reconstructed
at five second intervals and motion-analyzed. A morphometric analysis of
pseudopods, the main cell body and the uropod provides a comprehensive
description of the basic motile behavior of a cell in 4D, resulting in
a list
of 18 characteristics. A similar analysis of the myosin II
phosphorylation
mutant 3XASP reveals a role for the cortical localization of myosin II
in the
suppression of lateral pseudopods, the formation of the uropod,
cytoplasmic
distribution of cytoplasm in the main cell body and efficient
motility. The
analysis suggests that pseudopods, the main cell body, and the uropod
represent three motility compartments that must be coordinated for
efficient translocation. It provides a contextual framework for
interpreting
the effects of mutations, inhibitors and chemoattractants on the basic
motile behavior of D. discoideum. The generality of the characteristics
of the basic motile behavior of D. discoideum must now be tested by
similar 4D analyses of the motility of higher eukaryotic cells, in
particular
human polymorphonuclear leukocytes.
Submitted by Deb Wessels [[log in to unmask]]
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Development of Dictyostelium discoideum is associated with alteration of
fucosylated N-glycan structures
Birgit Schiller, Alba Hykollari, Josef Voglmeir, Gerald Pöltl, Karin
Hummel,
Ebrahim Razzazi-Fazeli, Rudolf Geyer and Iain B. H. Wilson
Department für Chemie, Universität für Bodenkultur, Vienna A-1190,
Austria
Biochem. J., in press (doi:10.1042/BJ20090786)
The social amoeba Dictyostelium discoideum has become established
as a simple model for the examination of cell-cell interactions and
early
studies suggested that shifts in glycosylation profiles take place
during
its life cycle. In the present study, we have applied HPLC and mass
spectrometric methods to show that the major N-glycans in axenic
cultures
of the AX3 strain are oligomannosidic forms, most of which carry core
fucose
and/or intersecting and bisecting N-acetylglucosamine residues,
including
the major structure with the composition Man8GlcNAc4Fuc1. The postulated
alpha1,3-linkage of the core fucose which correlates with the cross-
reactivity
of Dictyostelium glycoproteins with an anti-horseradish peroxidase
antiserum;
a corresponding core alpha1,3-fucosyltransferase activity capable of
modifying
oligomannosidic N-glycans was detected in axenic Dictyostelium extracts.
The presence of fucose on the N-glycans and the reactivity to the
antiserum,
but not the fucosyltransferase activity, are abolished in the fucose-
deficient
HL250 strain. In later stages of development, N-glycans at the mound and
culmination stages show a reduction in both the size and the degree of
modification by intersecting/bisecting residues as compared to mid-log
phase cultures, consistent with the hypothesis that glycosidase and
glycosyltransferase expression levels are altered during the slime mould
life cycle.
Submitted by Iain Wilson [[log in to unmask]]
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Differentiation-Inducing Factor-1 and -2 Function Also as Modulators for
Dictyostelium Chemotaxis
Hidekazu Kuwayama 1 and Yuzuru Kubohara 2,*
1 Graduate School of Life and Environmental Sciences, University of
Tsukuba,
Tsukuba 305-8572, Japan
2 Department of Molecular and Cellular Biology, Institute for
Molecular and
Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512, Japan
PLoS ONE, in press
Background: In the early stages of development of the cellular slime
mold
Dictyostelium discoideum, chemotaxis toward cAMP plays a pivotal role in
organizing discrete cells into a multicellular structure. In this
process,
a series of signaling molecules, such as G-protein-coupled cell surface
receptors for cAMP, phosphatidylinositol metabolites, and cyclic
nucleotides,
function as the signal transducers for controlling dynamics of
cytoskeleton.
Differentiation-inducing factor-1 and -2 (DIF-1 and DIF-2) were
originally
identified as the factors (chlorinated alkylphenones) that induce
Dictyostelium stalk cell differentiation, but it remained unknown
whether
the DIFs had any other physiologic functions.
Methodology/Principal Findings: To further elucidate the functions of
DIFs,
in the present study we investigated their effects on chemotaxis under
various
conditions. Quite interestingly, in shallow cAMP gradients, DIF-1
suppressed
chemotaxis whereas DIF-2 promoted it greatly. Analyses with various
mutants
revealed that DIF-1 may inhibit chemotaxis, at least in part, via GbpB
(a phosphodiesterase) and a decrease in the intracellular cGMP
concentration
([cGMP]i). DIF-2, by contrast, may enhance chemotaxis, at least in part,
via RegA (another phosphodiesterase) and an increase in [cGMP]i. Using
null
mutants for DimA and DimB, the transcription factors that are required
for
DIF-dependent prestalk differentiation, we also showed that the
mechanisms
for the modulation of chemotaxis by DIFs differ from those for the
induction
of cell differentiation by DIFs, at least in part.
Conclusions/Significance: Our findings indicate that DIF-1 and DIF-2
function as negative and positive modulators for Dictyostelium
chemotaxis,
respectively. To our knowledge, this is the first report in any
organism of
physiologic modulators (small molecules) for chemotaxis having
differentiation-inducing activity.
Yuzuru Kubohara [[log in to unmask]]
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Regulation of IL-2 production in Jurkat cells by Dictyostelium-derived
factors
Katsunori Takahashi, Masami Murakami, Kohei Hosaka, Haruhisa Kikuchi,
Yoshiteru Oshima, Yuzuru Kubohara*
*Department of Molecular and Cellular Biology, Institute for Molecular
and
Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
Life Sciences , in press
Aims: Differentiation-inducing factors (DIFs) are chlorinated
alkylphenones
found in the cellular slime mold Dictyostelium discoideum. DIF
derivatives
exhibit antiproliferative activities and promote glucose consumption in
mammalian cells in vitro. In this study, we assessed the ability of
DIFs to
regulate the immune system and investigated their mechanisms of action.
Main methods: We examined the effects of 30 DIF derivatives on
concanavalin
A–induced IL-2 production (CIIP) in Jurkat T-cells. We also examined the
effects of some DIF derivatives on the activity of AP-1 (activator
protein-1),
NFAT (nuclear factor of activated T-cells), and NFkB (nuclear factor
kappa B),
which are transcription factors required for CIIP.
Key findings: Of the derivatives tested, some compounds suppressed
CIIP as
well as the known immunosuppressants cyclosporine A and FK506. A
reporter
gene assay revealed that 4 DIF derivatives tested suppressed CIIP, at
least
in part, by inhibiting the activity of AP-1, NFAT, and/or NFkB. Unlike
cyclosporine A and FK506, the DIF derivatives had little effect on
concanavalin A–induced interferon-gamma production in Jurkat cells.
Significance: The present results suggest that DIF derivatives could be
developed as novel immunosuppressive drugs.
Submitted by: Yuzuru Kubohara [[log in to unmask]]
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[End dictyNews, volume 33, number 3]
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