dictyNews
Electronic Edition
Volume 35, number 11
October 21, 2010
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Abstracts
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Functional analyses of lissencephaly-related proteins in Dictyostelium
Irene Meyer, Oliver Kuhnert, Ralph Gräf
Seminars in Cell and Developmental Biology, in press
Lissencephaly is a severe brain developmental disease in human infants,
which is usually caused by mutations in either of two genes, LIS1 and
DCX. These genes encode proteins interacting with both the microtubule
and actin systems. Here we review the implications of data on
Dictyostelium LIS1 for the elucidation of LIS1 function in higher cells
and emphasize the role of LIS1 and nuclear envelope proteins in nuclear
positioning, which is also important for coordinated cell migration during
neocortical development. Furthermore, for the first time we characterize
Dictyostelium DCX, the only bona fide orthologue of human DCX
outside the animal kingdom. We show that DCX functionally interacts
with LIS1 and that both proteins have a cytoskeleton-independent
function in chemotactic signaling during development. Dictyostelium
LIS1 is also required for proper attachment of the centrosome to the
nucleus and, thus, nuclear positioning, where the association of these
two organelles has turned out to be crucial. It involves not only dynein
and dynein-associated proteins such as LIS1 but also SUN proteins
of the nuclear envelope. Analyses of Dictyostelium SUN1 mutants
have underscored the importance of these proteins for the linkage
of centrosomes and nuclei and for the maintenance of chromatin
integrity. Taken together, we show that Dictyostelium amoebae,
which provide a well established model to study the basic aspects
of chemotaxis, cell migration and development, are well suited for
the investigation of the molecular and cell biological basis of
developmental diseases such as lissencephaly.
Submitted by Ralph Gräf [[log in to unmask]]
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Molecular characterization of the evolution
of phagosomes
Jonathan Boulais, Matthias Trost, Christian Landry,
Régis Dieckmann, Emmanuel Levy, Thierry Soldati,
Stephen Michnick, Pierre Thibault, and Michel Desjardins
Molecular Systems Biology
(http://www.ncbi.nlm.nih.gov/pubmed/20959821)
Amoeba use phagocytosis to internalize bacteria as a source of
nutrients, whereas multicellular organisms utilize this process as
a defense mechanism to kill microbes and, in vertebrates, initiate
a sustained immune response. By using a large-scale approach to
identify and compare the proteome and phosphoproteome of
phagosomes isolated from distant organisms, and by comparative
analysis over 39 taxa, we identified an ‘ancient’ core of phagosomal
proteins around which the immune functions of this organelle have
likely organized. Our data indicated that a larger proportion of the
phagosome proteome, compared with the whole cell proteome,
has been acquired through gene duplication at a period coinciding
with the emergence of innate and adaptive immunity. Our study
also characterized in detail the acquisition of novel proteins and
the significant remodeling of the phagosome phosphoproteome
that contributed to modify the core constituents of this organelle in
evolution. Our work thus provides the first thorough analysis of the
changes that enabled the transformation of the phagosome from a
phagotrophic compartment into an organelle fully competent for
antigen presentation.
Submitted by Thierry Soldati [[log in to unmask]]
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[End dictyNews, volume 35, number 11]
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