dictyNews
Electronic Edition
Volume 34, number 15
May 22, 2010
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Abstracts
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The glycopeptidome of a heavily N-glycosylated cell surface glycoprotein of
Dictyostelium implicated in cell adhesion
Christa L. Feasley, Jennifer M. Johnson, Christopher M. West, and
Catherine P. Chia
Department of Biochemistry & Molecular Biology and the Oklahoma Center
for Medical
Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma
City, OK 73104 USA;
School of Biological Sciences, University of Nebraska-Lincoln, Lincoln,
NE 68588-0118 USA
J. Proteome Res., in press
Genetic analysis has implicated the cell surface glycoprotein gp130 in cell
interactions of the social amoeba Dictyostelium, and information about the
utilization of the 18 N-glycosylation sequons present in gp130 is needed
to identify critical molecular determinants of its activity. Various
glycomics
strategies, including mass spectrometry of native and derivatized glycans,
monosaccharide analysis, exoglycosidase digestion and antibody binding,
were applied to characterize a non-anchored version secreted from
Dictyostelium.
s-gp130 is modified by a predominant Man8GlcNAc4 species containing
bisecting and
intersecting GlcNAc residues, and additional high-mannose N-glycans
substituted
with sulfate, methyl-phosphate and/or core alpha3-fucose. Site mapping
confirmed
the occupancy of 15 sequons, some variably, and glycopeptide analysis
confirmed
14 sites and revealed extensive heterogeneity at most sites. Glycopeptide
glycoforms ranged from Man6 to Man9, GlcNAc0-2 (peripheral),
Fuc0-2 (including core alpha3 and peripheral), (SO4)0-1, and (MePO4)0-1,
which represented elements of virtually the entire known cellular N-glycome
as inferred from prior metabolic labeling and mass spectrometry studies.
gp130,
and a family of 14 related predicted glycoproteins whose polypeptide
sequences
are rapidly diverging in the Dictyostelium lineage, may contribute a
functionally
important shroud of high-mannose N-glycans at the interface of the
amoebae with
each other, their predators and prey, and the soil environment.
Submitted by Chris West [[log in to unmask]]
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TWO NOVEL SH2 DOMAIN PROTEINS INTERACT TO REGULATE DICTYOSTELIUM GENE
EXPRESSION DURING GROWTH AND EARLY DEVELOPMENT
Christopher Sugden1, Susan Ross1, Gareth Bloomfield2, AlasdairIvens3,
JasonSkelton3,Annette Mueller-Taubenberger4 and Jeffrey G. Williams1
School of Life Sciences1,Universityof Dundee, Dow St.,
Dundee DD1 5EH, UK
Wellcome Trust Sanger Institute2,
Hinxton, UK
MRC Laboratory of Molecular Biology3,
Hills Road, Cambridge, CB2 2QH, UK
Institute for Cell Biology and Center for Integrated Protein
Science4, Munich (CIPSM),
Ludwig Maximilians University, Schillerstrasse 42, D-80336
Munich, Germany
JBC, in press
There are 13 Dictyostelium SH2 domain proteins, almost ten fold fewer
than in
mammals, and only three are functionally unassigned. One of these, LrrB,
contains a
novel combination of protein interaction domains: an SH2 domain and a
leucine-rich
repeat domain. Growth and early development appear normal in the mutant
but expressionprofiling
reveals that three genes active at these stages are greatly
under-expressed: the ttdA
metallo-hydrolase, the abcG10 small molecule transporter and the cinB
esterase. In contrast,
the multi-gene family encoding the lectin Discoidin 1 is over-expressed
in the disruptant
strain. LrrB binds to 14-3-3 protein and the level of binding is highest
during growth and
decreases during early development. Comparative TAP tagging shows that
LrrB also
interacts, via its SH2 domain and in a tyrosine phosphorylation
dependent manner, with two
novel proteins: CldA and CldB. Both these proteins contain a Clu domain;
a >200 amino
acid sequence present within highly conserved eukaryotic proteins
required for correct
mitochondrial dispersal. A functional interaction of LrrB with CldA is
supported by
the fact that a cldA disruptant mutant also under-expresses ttdA, abcG10
and cinB.
Significantly, CldA is itself one of the three functionally unassigned
SH2 domain proteins.
Thus, just as in metazoa, but on a vastly reduced numerical scale, an
interacting
network of SH2 domain proteins regulates specific Dictyostelium gene
expression.
Submitted by Jeff Williams [[log in to unmask]]
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Two species of dictyostelid cellular slime molds from Alaska
Maria Romeralo, John C. Landolt, James C. Cavender, Gary A. Laursen,
and Sandie L. Baldauf.
Mycologia 2010;102 588-595.
In sampling soils to survey dictyostelid cellular slime molds in Alaska
we encountered two groups of isolates that have morphologies that differ
from any previously described species within their group. We sequenced the
nuclear small subunit ribosomal RNA gene (SSU rDNA) of selected isolates
from
the two groups and found sequences from both groups to be distinct from all
previously described dictyostelid sequences. Phylogenetic analyses place one
novel species in dictyostelid Group 2 and the other in Group 4 (Schaap
et al. 2006).
In this paper we formally describe as new these two species of cellular
slime
molds, Dictyostelium ammophilum sp. nov. and Dictyostelium boreale sp. nov.,
based on the combination of morphological and molecular characters.
Submitted by Maria Romeralo [[log in to unmask]]
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