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dictyNews Volume 35 Number 05
dictyNews
Electronic Edition
Volume 35, number 5
August 13, 2010
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to dicty@northwestern.edu
or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.
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=========
Abstracts
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cAMP diffusion in Dictyostelium discoideum: A Green’s function method
Daniel S. Calovi, Leonardo G. Brunnet, and Rita M. C. de Almeida
Instituto de Física, Universidade Federal do Rio Grande do Sul, Av.
Bento Gonçalves 9500, P.B. 15051, 91501-970 Porto Alegre, RS,
Brazil
Physical review, E 82, 011909 2010
A Green’s function method is developed to approach the spatiotemporal
equations describing the cAMP production in Dictyostelium discoideum,
markedly reducing numerical calculations times: cAMP concentrations
and gradients are calculated just at the amoeba locations. A single set
of parameters is capable of reproducing the different observed behaviors,
from cAMP synchronization, spiral waves and reaction-diffusion patterns
to streaming and mound formation. After aggregation, the emergence
of a circular motion of amoebas, breaking the radial cAMP field
symmetry, is observed.
Submitted by Daniel Calovi [calovi@if.ufrgs.br]
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The ROCO kinase QkgA is necessary for proliferation inhibition by
autocrine signals in Dictyostelium discoideum
Jonathan E. Phillips and Richard H. Gomer
Eukaryotic Cell, in press
AprA and CfaD are secreted proteins that function as autocrine signals
to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking
AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells
slows proliferation. Cells lacking the ROCO kinase QkgA proliferate
rapidly, with a doubling time 83% that of wild type, and overexpression
of a QkgA-GFP fusion protein slows cell proliferation. We found that
qkgA¯ cells accumulate normal levels of extracellular AprA and CfaD.
Exogenous AprA or CfaD does not slow the proliferation of cells lacking
qkgA, and expression of QkgA-GFP in qkgA¯ cells rescues this
insensitivity. Like cells lacking AprA or CfaD, cells lacking QkgA tend
to be multinucleate, accumulate nuclei rapidly, and show a mass and
protein accumulation per nucleus like that of wild type, suggesting that
QkgA negatively regulates proliferation but not growth. Despite their
rapid proliferation, cells lacking AprA, CfaD, or QkgA expand as a
colony on bacteria less rapidly than wild type. Unlike AprA and CfaD,
QkgA does not affect spore viability following multicellular development.
Together, these results indicate that QkgA is necessary for proliferation
inhibition by AprA and CfaD, that QkgA mediates some but not all of
the effects of AprA and CfaD, and that QkgA may function downstream
of these proteins in a signal transduction pathway regulating proliferation.
Submitted by Richard Gomer [rgomer@tamu.edu]
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[End dictyNews, volume 35, number 5]
