dictyNews
Electronic Edition
Volume 42, number 7
March 4, 2016

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=========
Abstracts
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Lysosomes appear as the auto-fluorescent vacuoles in Dictyostelium 
discoideum cells

Hiroki Kainuma*, Yuya Saito*, Ikuo Hatakeyama, Takako A. Omata and 
Saburo Uchiyama**

HK, IH, SU: Laboratory of Biology, Course of Science Education, 
Graduate School of Education, Iwate University, Ueda 3-18-33, 
Morioka 020-8550, Japan
YS:Laboratory of Biology, Division of Science Education,Faculty of 
Education, Iwate University, Morioka, Japan
TAO: Clinical Laboratory, University Hospital, Dokkyo Medical 
University, Mibu, Tochigi, Japan


Pteridines, accepted

Dictyostelium discoideum cells contain autofluorescent
vacuoles. To determine the identity of these vacuoles, t
he fluorescent dye 4-nitro-7-(1-piperazinyl)-2,1,3-
benzoxadiazole (NBD-PZ) was used to stain the lysosomes
in D. discoideum cells. Neither the auto-fluorescent
vacuoles nor lysosomes were observed in D. discoideum
cells immediately after they arose from spores or in 
stationary phase cells. However, both the auto-fluorescent
vacuoles and lysosomes were visible in cells that had
entered growth phase. Auto-fluorescent vacuoles and
lysosomes were also observed in stationary phase cells
incubated with chloroquine. When the cells were allowed
to phagocytose BioParticles Fluorescent Bacteria (orange
fluorescence) for 1 h, orange phagosomes and blue auto- 
fluorescent vacuoles were observed as independent moieties. 
However, after an additional 2 h of incubation, we
observed vacuoles with mixed fluorescence (orange and
blue) in the cells, suggestive of secondary lysosomes.
These results suggest that the auto-fluorescent vacuoles
in D. discoideum cells are lysosomes.


submitted by: Saburo Uchiyama [[log in to unmask]]
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Social amoebae trap and kill bacteria by casting DNA nets

Xuezhi Zhang, Olga Zhuchenko, Adam Kuspa, and Thierry Soldati


Nature Communications, 2016 Mar 1;7:10938. doi: 10.1038/ncomms10938

Extracellular traps (ETs) from neutrophils are reticulated nets of 
DNA decorated with antimicrobial granules, and are capable of 
trapping and killing extracellular pathogens. Various phagocytes 
of mammals and invertebrates produce ETs, however, the evolutionary 
history of this DNA-based host defence strategy is unclear. Here 
we report for the first time that Sentinel cells of the multicellular 
slug stage of the social amoeba Dictyostelium discoideum produce ETs 
upon stimulation with bacteria or lipopolysaccharide in a reactive 
oxygen species-dependent manner. The production of ETs by Sentinel 
cells requires a Toll/Interleukin-1 receptor domain-containing 
protein TirA and reactive oxygen species-generating NADPH oxidases. 
Disruption of these genes results in decreased clearance of bacterial 
infections. Our results demonstrate that D. discoideum is a powerful 
model organism to study the evolution and conservation of mechanisms 
of cell-intrinsic immunity, and suggest that the origin of DNA-based 
ETs as an innate immune defence predates the emergence of metazoans.


submitted by: Thierry Soldati [[log in to unmask]]
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[End dictyNews, volume 42, number 7]