dictyNews
Electronic Edition
Volume 32, number 10
April 10, 2009
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Abstracts
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Dictyostelium discoideum – a model for many reasons
Sarah J. Annesley and Paul R. Fisher
Department of Microbiology, La Trobe University VIC 3086, Australia
Molecular and Cellular Biochemistry, in press.
The social amoeba or cellular slime mould Dictyostelium discoideum is
a “professional” phagocyte that has long been recognized for its value
as a biomedical model organism, particularly in studying the actomyosin
cytoskeleton and chemotactic motility in non-muscle cells. The complete
genome sequence of D. discoideum is known, it is genetically tractable,
readily grown clonally as a eukaryotic microorganism and is highly
accessible for biochemical, cell biological and physiological studies.
These are properties it shares with other microbial model organisms.
However Dictyostelium combines these with a unique life style, with
motile unicellular and multicellular stages, and multiple cell types
that offer for study an unparalleled variety of phenotypes and
associated
signalling pathways. These advantages have led to its recent emergence
as valuable model organism for studying the molecular pathogenesis and
treatment of human disease, including a variety of infectious diseases
caused by bacterial and fungal pathogens. Perhaps surprisingly, this
organism, without neurons or brain, has begun to yield novel insights
into the cytopathology of mitochondrial diseases as well as other
genetic and idiopathic disorders affecting the central nervous system.
Dictyostelium has also contributed significantly to our understanding
of NDP kinase, as it was the Dictyostelium enzyme whose structure was
first determined and related to enzymatic activity. The phenotypic
richness and tractability of Dictyostelium should provide a fertile
arena for future exploration of NDPK’s cellular roles.
Submitted by: Paul R Fisher [[log in to unmask]]
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Switching direction in electric-signal-induced cell migration by cyclic
guanosine monophosphate and phosphatidylinositol signaling.
Sato MJ, Kuwayama H, van Egmond WN, Takayama AL, Takagi H,
van Haastert PJ, Yanagida T, Ueda M.
Proc Natl Acad Sci USA, in press
Switching between attractive and repulsive migration in cell movement in
response to extracellular guidance cues has been found in various cell
types and is an important cellular function for translocation during
cellular and developmental processes. Here we show that the preferential
direction of migration during electrotaxis in Dictyostelium cells can
be reversed by genetically modulating both guanylyl cyclases (GCases)
and the cyclic guanosine monophosphate (cGMP)-binding protein C (GbpC)
in combination with the inhibition of phosphatidylinositol-3-OH kinases
(PI3Ks). The PI3K-dependent pathway is involved in cathode-directed
migration under a direct-current electric field. The catalytic domains
of soluble GCase (sGC) and GbpC also mediate cathode-directed signaling
via cGMP, whereas the N-terminal domain of sGC mediates anode-directed
signaling in conjunction with both the inhibition of PI3Ks and cGMP
production. These observations provide an identification of the genes
required for directional switching in electrotaxis and suggest that
a parallel processing of electric signals, in which multiple-signaling
pathways act to bias cell movement toward the cathode or anode, is
used to determine the direction of migration.
Submitted by: Masayuki Sato [[log in to unmask]]
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[End dictyNews, volume 32, number 10]
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