dictyNews
Electronic Edition
Volume 35, number 2
July 10, 2010
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Abstracts
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Redundant and unique roles of coronin proteins in Dictyostelium
Maria C. Shina, Annette Müller-Taubenberger, Can Ünal,
Michael Schleicher, Michael Steinert, Ludwig Eichinger, Rolf Müller,
Rosemarie Blau-Wasser, Gernot Glöckner, Angelika A. Noegel
Cellular and Molecular Life Sciences, in press
Dictyostelium discoideum harbors a short (CRN12) and a long coronin
(CRN7) composed of one and two beta-propellers, respectively. They are
primarily present in the cell cortex and cells lacking CRN12 (corA-) or
CRN7 (corB-) have defects in actin driven processes. We compared the
characteristics of a mutant cell line (corA-/corB-) lacking CRN12 and
CRN7
with the single mutants focusing on cytokinesis, phagocytosis,
chemotaxis
and development. Cytokinesis, uptake of small particles, and
developmental
defects were not enhanced in the corA-/corB- strain as compared to the
single mutants, whereas motility and phagocytosis of yeast particles
were
more severely impaired. It appears that although both proteins affect
the
same processes they do not act in a redundant manner. Rather, they often
act antagonistically which is in accordance with their proposed roles
in the
actin cytoskeleton where CRN12 acts in actin disassembly whereas CRN7
stabilizes actin filaments and protects them from disassembly.
Submitted by Angelika Nögel [[log in to unmask]]
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Synthesis and biological activity of peptides equivalent to the IP22
repeat
motif found in proteins from Dictyostelium and Mimivirus
Andrew Catalano a, Wei Luo b, Yali Wang b, and Danton H. O’Day a,b,*
aDepartment of Cell and Systems Biology, University of Toronto,
25 Harbord st., Toronto, Ontario, Canada, M5S 3G5
bDepartment of Biology, University of Toronto at Mississauga,
3359 Mississauga rd. N., Mississauga, Ontario, Canada, L5L 1C6
Peptides, in press
A novel IP22 repeat motif of unknown function was discovered
previously that
comprises almost the entire structure of cmbB, a calmodulin-binding
protein
from Dictyostelium discoideum. An analysis of over 2000 IP22 repeats
across
130 different proteins from different species allowed us to define a
prototypical
IP22 repeat: I/LPxxhxxhxhxxxhxxxhxxxx (where L = leucine,
I = isoleucine, h = any hydrophobic amino acid, x = any amino acid).
Here
we describe the synthesis of three peptide variants of the IP22 motif:
IP22-1(IPNSVTSLKFGDGFNQPLTPGT; 22aa);
IP22-2 (LPSTLKTISLSNSTDKKIFKNS; 22aa); and,
IP22-3 (IPKSLRSLFLGKGYNQPLEF; 20aa) plus a control peptide from
the N-term of cmbB (HNMNPFSPQLDEKKNSHIVEY; 21aa). The structure
and purity of synthesized peptides were verified by HPLC and mass
spectrometry. The peptides all dose-dependently enhanced random cell
motility
and cAMP-mediated chemotaxis in Dictyostelium but IP22-3 was most
effective
peaking in activity around 50μM. Fluorescein isothiocyanate (FITC) -
conjugated
IP22 peptides did not penetrate cells suggesting these peptides affect
cell
motility via cell surface interactions. Treatment of cells with FITC-
IP22
peptides also led to enhanced cell motility equivalent to the non-
conjugated
peptides. Treatment of IP22-3-stimulated cells with 50μM LY294002,
20μM
quinacrine or both suggests that IP22-3 requires both phosphoinositol
3-kinase and phospholipase A2 signaling to elicit its effects, a
mechanism
unique from EGFL motility-enhancing peptides. The mechanism of action
and potential uses of IP22 repeat peptides are discussed.
Submitted by Danton O'Day [[log in to unmask]]
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[End dictyNews, volume 35, number 2]
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