dictyNews
Electronic Edition
Volume 38, number 11
April 20, 2012

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Abstracts
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The isoform B of the Dictyostelium long-chain fatty-acyl-coenzyme A 
synthetase is initially inserted into the ER and subsequently provides 
peroxisomes with an activity important for efficient phagocytosis. 

Peggy Paschke, Nadine Pawolleck, Frauke Haenel, Heike Otto, 
Harald Rühling, and Markus Maniak

Abteilung Zellbiologie, Universität Kassel, 34109 Kassel, Germany


Eur. J. Cell Biol. in press

Long-chain fatty-acyl-coenzymeA synthetases activate fatty acids for 
anabolic or catabolic metabolism. They often localize to more than one 
organelle within eukaryotic cells. Dictyostelium contains two of these 
proteins, FcsA and FcsB with the latter being targeted to the membrane 
of the endoplasmic reticulum by virtue of an N-terminal signal sequence 
and from there appears to move on to peroxisomes. Deletion of this 
signal favours the peripheral association of the protein with the 
mitochondrial surface instead. A strain lacking the activity of the FcsB 
enzyme was constructed by homologous recombination. It has a severe 
deficiency in the phagocytic uptake of particles, which can be partially 
alleviated by a peroxisomally targeted, soluble FcsA enzyme. It is, 
however, not rescued by expressing FcsA in the cytoplasm or targeting 
it to the ER, indicating that peroxisomal beta-oxidation is important for 
phagocytosis. In a fcsA-/B- double mutant phagocytosis efficiency is 
similar to fcsB- cells. However, unlike the single mutants, the fcsA-/B- 
strain is delayed in morphogenesis, but forms viable spores, albeit 
within a small fruiting body. This developmental defect is also seen in 
other mutants affecting peroxisomal enzymes involved in ß-oxidation 
and the glyoxylate cycle.


Submitted by Markus Maniak [[log in to unmask]]
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A lamin in lower eukaryotes?

Petros Batsios, Tatjana Peter, Otto Baumann, Reimer Stick, 
Irene Meyer, Ralph Gräf

Dept. of Cell Biology, Institute for Biochemistry and Biology, 
University of Potsdam, Karl-Liebknecht-Strasse 24-25, 14469 
Potsdam-Golm, Germany


Nucleus, in press

Lamins are the major components of the nuclear lamina and serve 
not only as a mechanical support, but are also involved in chromatin 
organization, epigenetic regulation, transcription, and mitotic events. 
Despite these universal tasks, lamins have so far been found only in 
metazoans. Yet, recently we have identified Dictyostelium NE81 as 
the first lamin-like protein in a lower eukaryote. Based on the current 
knowledge, we draw a model for nuclear envelope organization in 
Dictyostelium in this Extra View and we review the experimental data 
that justified this classification. Furthermore we provide unpublished 
data underscoring the requirement of posttranslational CaaX-box 
processing for proper protein localization at the nuclear envelope. 
Sequence comparison of NE81 sequences from four Dictyostelia with 
bona fide lamins illustrates the evolutional relationship between these 
proteins. Under certain conditions these usually unicellular social 
amoebae congregate to form a multicellular body. We propose that 
the evolution of the lamin-like NE81 went along with the invention of 
multicellularity.


Submitted by Ralph Gräf [[log in to unmask]]
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[End dictyNews, volume 38, number 11]