dictyNews
Electronic Edition
Volume 41, number 9
May 1, 2015
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Abstracts
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Evolutionary diversity of social amoebae N-glycomes may support
interspecific autonomy
Christa L. Feasley, Hanke van der Wel, and Christopher M. West
Dept. of Biochemistry & Molecular Biology, Oklahoma Center for
Medical Glycobiology, University of Oklahoma Health Sciences
Center, Oklahoma City, OK USA 73104 USA
Glycoconjugate Journal, in press
Multiple species of cellular slime mold (CSM) amoebae share
overlapping subterranean environments near the soil surface.
Despite similar life-styles, individual species form independent
starvation-induced fruiting bodies whose spores can renew the life
cycle. N-glycans associated with the cell surface glycocalyx have
been predicted to contribute to interspecific avoidance, resistance
to pathogens, and prey preference. N-glycans from five CSM species
that diverged 300-600 million years ago and whose genomes have been
sequenced were fractionated into neutral and acidic pools and
profiled by MALDI-TOF-MS. Glycan structure models were refined using
linkage specific antibodies, exoglycosidase digestions, MALDI-MS/MS,
and chromatographic studies. Amoebae of the type species
Dictyostelium discoideum express modestly trimmed high mannose
N-glycans variably modified with core alpha-3-linked Fuc and
peripherally decorated with 0-2 residues each of beta-GlcNAc,
Fuc, methylphosphate and/or sulfate, as reported previously.
Comparative analyses of D. purpureum, D. fasciculatum,
Polysphondylium pallidum, and Actyostelium subglobosum revealed
that each displays a distinctive spectrum of high-mannose species
with quantitative variations in the extent of these modifications,
and qualitative differences including retention of Glc, mannose
methylation, and absence of a peripheral GlcNAc, fucosylation, or
sulfation. Starvation-induced development modifies the pattern in
all species but, except for universally observed increased
mannose-trimming, the N-glycans do not converge to a common profile.
Correlations with glycogene repertoires will enable future reverse
genetic studies to eliminate N-glycomic differences to test their
functions in interspecific relations and pathogen evasion.
Submitted by Chris West [[log in to unmask]]
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Oxygen Sensing by Protozoans: How They Catch Their Breath
Christopher M. West (1) and Ira J. Blader (2)
(1) Department of Biochemistry & Molecular Biology, Oklahoma Center
for Medical Glycobiology, University of Oklahoma Health Sciences
Center, 975 NE 10th St. - BRC 417, Oklahoma City, OK 73104 USA
(2) Department of Microbiology and Immunology, University at
Buffalo School of Medicine, 347 Biomedical Research Building,
3435 Main Street, Buffalo, NY 14214 USA
Current Opinion in Microbiology, in press
Cells must know the local levels of available oxygen and either
adapt accordingly or relocate to more favorable environments.
Prolyl 4-hydroxylases are emerging as universal cellular oxygen
sensors. In animals, these oxygen sensors respond to decreased
oxygen availability by up-regulating hypoxia-inducible transcription
factors. In protozoa, the prolyl 4-hydroxylases appear to activate
E3-SCF ubiquitin ligase complexes potentially to turn over their
proteomes. Intracellular parasites are impacted by both types of
oxygen-sensing pathways. Since parasites are exposed to diverse
oxygen tensions during their life cycles, this review identifies
emerging oxygen-sensing mechanisms and discusses how these
mechanisms likely contribute to the regulation of unicellular
eukaryotes.
Submitted by Chris West [[log in to unmask]]
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Dictyostelium acetoacetyl-CoA thiolase is a dual-localizing enzyme
that localizes to peroxisomes, mitochondria, and the cytosol
Nana Isezaki(1), Atsushi Sekiba(1), Shoko Itagaki(1),
Koki Nagayama(1)†, Hiroshi Ochiai(1,2),
and Tetsuo Ohmachi(1)*
(1) Department of Biochemistry and Molecular Biology, Faculty of
Agriculture and Life Science, Hirosaki University, Hirosaki, Japan,
(2) Division of Biological Sciences, Graduate School of Science,
Hokkaido University, Sapporo, Japan
†Present address: Department of Life Science, University of
Manchester, Manchester, M13 9PT, UK
Microbiology, in press
Acetoacetyl-CoA thiolase (Acat) is an enzyme that catalyzes both
the CoA-dependent thiolytic cleavage of acetoacetyl-CoA and the
reverse condensation reaction. In Dictyostelium disciodeum,
acetoacetyl-CoA thiolase (DdAcat) is encoded by a single acat gene.
The aim of this study was to assess the localization of DdAcat and
to determine the mechanism of its cellular localization.
Subcellular localization of DdAcat was investigated using its
fusion protein with the green fluorescent protein (GFP), and it
was found to be localized to peroxisomes. The findings showed that
the targeting signal of DdAcat to peroxisomes is a unique
nonapeptide sequence (15RMYTTAKNL23) similar to the conserved
peroxisomal targeting signal-2 (PTS-2). Cell fractionation
experiments revealed that DdAcat also exists in the cytosol.
Distribution in the cytosol was caused by translational initiation
from the second Met codon at position 16. The first 18 N-terminal
residues also exhibited function as a mitochondrial targeting
signal (MTS). These results indicate that DdAcat is a
dual-localizing enzyme that localizes to peroxisomes, mitochondria,
and the cytosol using both PTS-2 and MTS signals, which overlap
each other near the N terminus, and the alternative utilisation
of start codons.
Submitted by Tetsuo Ohmachi [[log in to unmask]]
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[End dictyNews, volume 41, number 9]
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