dictyNews
Electronic Edition
Volume 43, number 26
November 10, 2017
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Abstracts
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Cln5 is secreted and functions as a glycoside hydrolase in Dictyostelium
Robert J. Huber and Sabateeshan Mathavarajah
Department of Biology, Trent University, Peterborough, Ontario, Canada
Cellular Signalling, in press
Ceroid lipofuscinosis neuronal 5 (CLN5) is a member of a family of
proteins that are linked to neuronal ceroid lipofuscinosis (NCL). This
devastating neurological disorder, known commonly as Batten disease,
affects all ages and ethnicities and is currently incurable. The precise
function of CLN5, like many of the NCL proteins, remains to be
elucidated. In this study, we report the localization, molecular function,
and interactome of Cln5, the CLN5 homolog in the social amoeba
Dictyostelium discoideum. Residues that are glycosylated in human
CLN5 are conserved in the Dictyostelium homolog as are residues
that are mutated in patients with CLN5 disease. Dictyostelium Cln5
contains a putative signal peptide for secretion and we show that the
protein is secreted during growth and starvation. We also reveal that
both Dictyostelium Cln5 and human CLN5 are glycoside hydrolases,
providing the first evidence in any system linking a molecular function
to CLN5. Finally, immunoprecipitation coupled with mass spectrometry
identified 61 proteins that interact with Cln5 in Dictyostelium. Of the 61
proteins, 67% localize to the extracellular space, 28% to intracellular
vesicles, and 20% to lysosomes. A GO term enrichment analysis
revealed that a majority of the interacting proteins are involved in
metabolism, catabolism, proteolysis, and hydrolysis, and include other
NCL-like proteins (e.g., Tpp1/Cln2, cathepsin D/Cln10, cathepsin
F/Cln13) as well as proteins linked to Cln3 function in Dictyostelium
(e.g., AprA, CfaD, CadA). In total, this work reveals a CLN5 homolog
in Dictyostelium and further establishes this organism as a
complementary model system for studying the functions of proteins
linked to NCL in humans.
submitted by: Robert Huber [[log in to unmask]]
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WASP family proteins and Formins Compete in Pseudopod- and
Bleb-based Migration
Andrew Davidson, Clelia Amato, Peter Thomason and Robert Insall
J Cell Biol., accepted
Actin pseudopods induced by SCAR/WAVE drive normal migration
and chemotaxis in eukaryotic cells. Cells can also migrate using blebs,
in which the edge is driven forwards by hydrostatic pressure instead
of actin. In Dictyostelium, loss of SCAR is compensated by WASP
moving to the leading edge to generate morphologically normal
pseudopods. Here we use an inducible double knockout to show
that cells lacking both SCAR and WASP are unable to grow, make
pseudopods or, unexpectedly, migrate using blebs. Remarkably,
amounts and dynamics of actin polymerization are normal.
Pseudopods are replaced in double SCAR/WASP mutants by
aberrant filopods, induced by the formin dDia2. Further disruption
of the gene for dDia2 restores cells’ ability to initiate blebs and thus
migrate, though pseudopods are still lost. Triple knockout cells still
contain near-normal F-actin levels. This work shows that SCAR,
WASP and dDia2 compete for actin. Loss of SCAR and WASP
causes excessive dDia2 activity, maintaining F-actin levels but
blocking pseudopod and bleb formation and migration.
submitted by: Robert Insall [[log in to unmask]]
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Curcumin affects gene expression and reactive oxygen species via
a PKA dependent mechanism in Dictyostelium discoideum
William S. Swatson 1, Mariko Katoh-Kurasawa 2, Gad Shaulsky 2*,
Stephen Alexander 1*
1 Division of Biological Sciences, University of Missouri, Columbia,
MO 65211, United States
2 Department of Molecular and Human Genetics, Baylor College
of Medicine, Houston, TX 77030, United States
*Corresponding authors
Correspondence to Stephen Alexander, [log in to unmask],
and Gad Shaulsky, [log in to unmask]
PLOS ONE November 6, 2017, accepted
Botanicals are widely used as dietary supplements and for the
prevention and treatment of disease. Despite a long history of use,
there is generally little evidence supporting the efficacy and safety
of these preparations. Curcumin has been used to treat a myriad
of human diseases and is widely advertised and marketed for its
ability to improve health, but there is no clear understanding how
curcumin interacts with cells and affects cell physiology.
D. discoideum is a simple eukaryotic lead system that allows both
tractable genetic and biochemical studies. The studies reported
here show novel effects of curcumin on cell proliferation and
physiology, and a pleiotropic effect on gene transcription.
Transcriptome analysis showed that the effect is two-phased with
an early transient effect on the transcription of approximately 5%
of the genome, and demonstrates that cells respond to curcumin
through a variety of previously unknown molecular pathways.
This is followed by later unique transcriptional changes and a
protein kinase A dependent decrease in catalase A and three
superoxide dismutase enzymes. Although this results in an
increase in reactive oxygen species (ROS; superoxide and H2O2),
the effects of curcumin on transcription do not appear to be the
direct result of oxidation. This study opens the door to future
explorations of the effect of curcumin on cell physiology.
submitted by: Steven Alexander [[log in to unmask]]
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[End dictyNews, volume 43, number 26]
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