dictyNews
Electronic Edition
Volume 41, number 8
April 24, 2015
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Abstracts
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The phenotypes of ATG9, ATG16 and ATG9/16 knock-out mutants
imply autophagy-dependent and -independent functions
Qiuhong Xiong1, Can Ünal2,3, Jan Matthias1, Michael Steinert2,4
and Ludwig Eichinger1
1 Zentrum für Biochemie, Medizinische Fakultät, Universität
zu Köln, Joseph-Stelzmann-Str. 52, D-50931 Köln
2 Institut für Mikrobiologie, Technische Universität Braunschweig,
Spielmannstr. 7, D-38106 Braunschweig
3 Fen Fakültesi, Türk-Alman-Üniversitesi, 34820, Istanbul, Turkey
4 Helmholtz Centre for Infection Research, 38124,
Braunschweig, Germany
Open Biol. 2015 Apr;5(4). pii: 150008. doi: 10.1098/rsob.150008.
Macroautophagy is a highly conserved intracellular bulk
degradation system of all eukaryotic cells. It is governed by a
large number of autophagy proteins (ATGs) and is crucial for many
cellular processes. Here, we describe the phenotypes of
Dictyostelium discoideum ATG16(-) and ATG9(-)/16(-) cells and
compare them to the previously reported ATG9(-) mutant. ATG16
deficiency caused an increase in the expression of several core
autophagy genes, among them atg9 and the two atg8 paralogues.
The single and double ATG9 and ATG16 knock-out mutants had
complex phenotypes and displayed severe and comparable defects
in pinocytosis and phagocytosis. Uptake of Legionella pneumophila
was reduced. In addition, ATG9(-) and ATG16(-) cells had dramatic
defects in autophagy, development and proteasomal activity which
were much more severe in the ATG9(-)/16(-) double mutant. Mutant
cells showed an increase in poly-ubiquitinated proteins and
contained large ubiquitin-positive protein aggregates which
partially co-localized with ATG16-GFP in ATG9(-)/16(-) cells. The
more severe autophagic, developmental and proteasomal
phenotypes of ATG9(-)/16(-) cells imply that ATG9 and ATG16
probably function in parallel in autophagy and have in addition
autophagy-independent functions in further cellular processes.
Submitted by Ludwig Eichinger [[log in to unmask]]
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Evolution of centrosomes and the nuclear lamina: Amoebozoan
assets
Ralph Gräf, Petros Batsios and Irene Meyer
Universität Potsdam, Institut für Biochemie und Biologie,
Potsdam-Golm, Germany.
Eur. J. Cell Biol., in press
The current eukaryotic tree of life groups most eukaryotes
into one of five supergroups, the Opisthokonta, Amoebozoa,
Archaeplastida, Excavata and SAR (Stramenopile, Alveolata,
Rhizaria). Molecular and comparative morphological analyses
revealed that the last eukaryotic common ancestor (LECA)
already contained a rather sophisticated equipment of
organelles including a mitochondrion, an endomembrane system,
a nucleus with a lamina, a microtubule-organizing center
(MTOC), and a flagellar apparatus. Recent studies of MTOCs,
basal bodies/centrioles, and nuclear envelope organization
of organisms in different supergroups have clarified our
picture of how the nucleus and MTOCs co-evolved from LECA
to extant eukaryotes. In this review we summarize these
findings with special emphasis on valuable contributions
of research on a lamin-like protein, nuclear envelope
proteins, and the MTOC in the amoebozoan model organism
Dictyostelium discoideum.
Submitted by Ralph Gräf [[log in to unmask]]
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[End dictyNews, volume 41, number 8]
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