dictyNews Volume 41 Number 08

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dictyNews 
Electronic Edition 
Volume 41, number 8 
April 24, 2015 

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========= 
Abstracts 
========= 

The phenotypes of ATG9, ATG16 and ATG9/16 knock-out mutants  
imply autophagy-dependent and -independent functions 

Qiuhong Xiong1, Can †nal2,3, Jan Matthias1, Michael Steinert2,4  
and Ludwig Eichinger1 

1 Zentrum fŸr Biochemie, Medizinische FakultŠt, UniversitŠt  
zu Kšln, Joseph-Stelzmann-Str. 52, D-50931 Kšln 
2 Institut fŸr Mikrobiologie, Technische UniversitŠt Braunschweig,  
Spielmannstr. 7, D-38106 Braunschweig 
3 Fen FakŸltesi, TŸrk-Alman-†niversitesi, 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 [ludwig.eichinger@uni-koeln.de]  
---------------------------------------------------------------------- 

 
Evolution of centrosomes and the nuclear lamina: Amoebozoan  
assets 

Ralph GrŠf, Petros Batsios and Irene Meyer 

UniversitŠt Potsdam, Institut fŸr 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 GrŠf [rgraef@uni-potsdam.de] 
============================================================== 
[End dictyNews, volume 41, number 8]