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dictyNews Volume 19 Number 06
Dicty News
Electronic Edition
Volume 19, number 6
August 31, 2002
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to dicty@northwestern.edu.
Back issues of Dicty-News, the Dicty Reference database and other useful
information is available at DictyBase--http://dictybase.org.
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Abstracts
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The evolution of development in the cellular slime molds.
John Bonner
Department of Ecology and Evolutionary Biology, Princeton University,
Princeton, NJ 08540, USA
Evolution and Development, in press.
How might the successive stages in the life cycle of Dictyostelium
discoideum have evolved? It has been estimated that cellular slime
molds must have come into being something in the order of a billion
years ago and during this vast span of time have evolved into the
complex forms we find today. First I will compare the various stages
of the D. discoideum life cycle with other forms that exist today,
whose mature state corresponds to one of the earlier stages of the
development of D. discoideum. This is a component of my larger
argument that each stage of D. discoideum development is adaptive.
Those simpler forms would not exist today if they were not competing
successfully in their natural environment. Finally, I discuss the
possible evolutionary sequence of the steps in the development of D.
discoideum.
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Receptor-Dependent and Tyrosine Phosphatase-Mediated Inhibition of GSK3
Regulates Cell Fate Choice
Leung Kim 1, Adrian Harwood 2, and Alan R. Kimmel 1,3
1 Laboratory of Cellular and Developmental Biology (Bldg. 50/3351), NIDDK
National Institutes of Health, Bethesda, MD 20892-8028, USA
2 MRC Laboratory for Molecular Cell Biology & Dept of Biology, University
College London, London, WCIE 6BT, UK
Developmental Cell, On Press
Summary
Asymmetric body axis formation is central to metazoan development.
Dictyostelium establishes an anterior/posterior axis utilizing 7-TM cAMP
morphogen receptors (CARs) and GSK3-mediated signal transductions that has
a parallel with metazoan Wnt/Frizzled-GSK3 pathways. In Dictyostelium, GSK3
promotes posterior cell patterning but inhibits anterior cell
differentiation. Tyrosine kinase ZAK1 mediates GSK3 activation. We now show
that CAR4 regulates a tyrosine phosphatase that inhibits GSK3 activity. We
have also identified essential phospho-tyrosines in GSK3, confirmed their
role in activated/de-activated regulation and cell fate decisions, and
relate them to the predicted 3D-structure of GSK3b. CARs differentially
regulate GSK3 activity by selectively activating a tyrosine phosphatase or
kinase for pattern formation. The findings may provide a comparative
understanding of CAR-GSK3 and Wnt/Frizzled-GSK3 pathways.
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Loss of the F-actin binding and vesicle associated protein comitin leads to
a phagocytosis defect
Thomas Schreiner1), Martina R. Mohrs1), Rosemarie Blau-Wasser1), Alfred von
Krempelhuber2), Michael Steinert3), Michael Schleicher4) and Angelika A.
Noegel 1) *
1) Center for Biochemistry, Medical Faculty, University of Cologne, 50931
Koeln, Germany, 2) Max-Planck-Institut fuer Biochemie, 82152 Martinsried,
Germany, 3) Institut fr Molekulare Infektionsbiologie, Universitt Wrzburg,
97070 Wuerzburg, Germany, 4) Institut fr Zellbiologie, Ludwig-Maximilians-
Universitaet, 80336 Muenchen, Germany
Eukaryotic Cell
Abstract
Comitin is an F-actin binding and membrane associated protein from
Dictyostelium which is present on Golgi and vesicle membranes and changes
its localization in response to agents affecting the cytoskeleton. To
investigate its in vivo functions we have generated knock out mutants by
gene replacement. Based on comitin's in vitro functions we examined properties
related to vesicular transport and microfilament function. Whereas cell growth,
pinocytosis, secretion, chemotaxis, motility and development were unaltered,
comitin minus cells were impaired in the early steps of phagocytosis of yeast
particles and of E. coli, whereas uptake of latex beads was unaffected.
Furthermore, the lack of comitin positively affected survival of pathogenic
bacteria. Mutant cells also showed an altered response to hyperosmotic shock
in comparison to wild type. The redistribution of comitin during hyperosmotic
shock in wild type cells and its presence on early phagosomes suggest a
direct involvement of comitin in these processes.
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Functions of LIM proteins in cell polarity and chemotactic motility
Bharat Khurana*+1, Taruna Khurana*+2, Nandkumar Khaire and Angelika A.
Noegel
Center for Biochemistry, Medical Faculty, University of Cologne, Joseph-
Stelzmann-Str. 52, D-50931 Cologne, FRG
+present address:
1Laboratory of Viral Diseases
Building 4, Room 131
National Institute of Allergy and Infectious Diseases (NIAID)
2Laboratory of Cellular and Developmental Biology
Building 50, Room 3345
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
National Institutes of Health, Bethesda, Maryland 20892-8028, USA
EMBO Journal
Abstract
LimC and LimD are two novel LIM proteins of Dictyostelium, which are
comprised of double- and single-copy of LIM domains, respectively. Green
fluorescent protein (GFP)-fused LimC and LimD proteins preferentially
accumulate at areas of the cell-cortex where they colocalize with actin
and associate transiently with cytoskeleton-dependent dynamic structures
like phagosomes, macropinosomes and pseudopods. Furthermore, both LimC and
LimD interact directly with F-actin in vitro. Mutant cells that lack either
LimC or LimD or both exhibit normal growth. They are, however, significantly
impaired in growth under stress conditions and are highly sensitive towards
osmotic shock, suggesting that LimC and LimD contribute towards the
maintenance of the cortical strength. Moreover, we noted an altered
morphology and F-actin distribution in LimD- and LimC/D- mutants and changes
in chemotactic motility associated with an increased pseudopod formation.
Our results reveal both unique and overlapping roles for LimC and LimD and
suggest that both act directly on the actin cytoskeleton and provide
rigidity to the cortex.
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[End Dicty News, volume 19, number 6]
