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dictyNews Volume 41 Number 19
dictyNews
Electronic Edition
Volume 41, number 19
September 4, 2015
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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Allorecognition, via TgrB1 and TgrC1, mediates the
transition from unicellularity to multicellularity in
the social amoebae Dictyostelium discoideum
Shigenori Hirose1, Balaji Santhanam2,3, Mariko
Katoh-Kurosawa2, Gad Shaulsky2,3,#, and Adam Kuspa1,2,#
1 Verna and Marrs McLean Department of Biochemistry
and Molecular Biology
2 Department of Molecular and Human Genetics
3 Structural and Computational Biology and Molecular
Biophysics Program
# Corresponding Authors
Baylor College of Medicine, Houston, TX 77030 USA
Accepted to “Development”
SUMMARY
The social amoeba Dictyostelium discoideum integrates
into a multicellular organism when individual starving
cells aggregate and form a mound. The cells then integrate
into defined tissues and develop into a fruiting body that
consists of a stalk and spores. Aggregation is initially
orchestrated by waves of extracellular cyclic adenosine
monophosphate (cAMP) and previous theory suggested that
cAMP and other field-wide diffusible signals mediate
tissue integration and terminal differentiation as well.
Cooperation between cells depends on an allorecognition
system comprised of the polymorphic adhesion proteins
TgrB1 and TgrC1. Binding between compatible TgrB1 and
TgrC1 variants ensures that non-matching cells segregate
into distinct aggregates prior to terminal development.
Here, we have embedded a small number of cells with
incompatible allotypes within fields of developing cells
with compatible allotypes. We found that compatibility
of the allotype encoded by the tgrB1 and tgrC1 genes is
required for tissue integration, as manifested in cell
polarization, coordinated movement, and differentiation
into prestalk and prespore cells. Our results show that
the molecules that mediate allorecognition in D. discoideum
also control the integration of individual cells into a
unified developing organism and this acts as a gating step
for multicellularity.
Submitted by Adam Kuspa [akuspa@bcm.edu]
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Title: Dissecting the function of Atg1 complex in
Dictyostelium autophagy reveals a connection with the
pentose phosphate pathway enzyme transketolase
Ana Mesquita, Luis C. Tábara, Oscar Martinez-Costa,
Natalia Santos-Rodrigo, Olivier Vincent and
Ricardo Escalante
Open Biol. 2015 Aug;5(8).
Abstract
The network of protein-protein interactions of the
Dictyostelium discoideum autophagy pathway was
investigated by yeast two-hybrid screening of the
conserved autophagic proteins Atg1 and Atg8. These
analyses confirmed expected interactions described
in other organisms and also identified novel interactors
that highlight the complexity of autophagy regulation.
The Atg1 kinase complex, an essential regulator of
autophagy, was investigated in detail here. The
composition of the Atg1 complex in Dictyostelium
discoideum is more similar to mammalian cells than
to Saccharomyces cerevisiae since, besides Atg13,
it contains Atg101, a protein not conserved in this
yeast. We found that Atg101 interacts with Atg13 and
genetic disruption of these proteins in Dictyostelium
leads to an early block in autophagy, although the
severity of the developmental phenotype and the degree
of autophagic block is higher in Atg13 deficient cells.
We have also identified a protein containing zinc-finger
B-box and FNIP motifs that interacts with Atg101.
Disruption of this protein increases autophagic flux
suggesting that it functions as a negative regulator
of Atg101. We also describe the interaction of Atg1
kinase with the pentose phosphate pathway enzyme
transketolase. We found changes in the activity of
endogenous transketolase activity in strains lacking
or overexpressing Atg1 suggesting the presence of an
unsuspected regulatory pathway between autophagy and
the pentose phosphate pathway in Dictyostelium that
seems to be conserved in mammalian cells.
Submitted by Ricardo Escalante [rescalante@iib.uam.es] ==============================================================
[End dictyNews, volume 41, number 19]
