dictyNews
Electronic Edition
Volume 49, number 30
December 1, 2023
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Abstracts
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Resolving exit strategies of mycobacteria in Dictyostelium
discoideum by combining high-pressure freezing with 3D-correlative
light and electron microscopy
Rico Franzkoch1,2,3,#, Aby Anand2,4,5,6,7,#, Leonhard
Breitsprecher1,2,3, Olympia E. Psathaki1,2,*,
Caroline Barisch2,4,5,6,7,*
#These two authors contributed equally to the work.
1iBiOs–integrated Bioimaging Facility, University of Osnabrück,
Osnabrück, Germany
2Center of Cellular Nanoanalytics, Osnabrück, Germany
3Division of Microbiology, Department of Biology, University of
Osnabrück, Osnabrück, Germany
4Division of Molecular Infection Biology, Department of Biology,
University of Osnabrück, Osnabrück, Germany
5Centre for Structural Systems Biology, Hamburg, Germany
6Research Center Borstel - Leibniz Lung Center (FZB), Borstel,
Germany
7Department of Biology, University of Hamburg, Hamburg,
Germany
Published in Molecular Microbiology
MMI-2023-19296.R2
The infection course of Mycobacterium tuberculosis is highly dynamic
and comprises sequential stages that require damaging and crossing
of several membranes to enable the translocation of the bacteria
into the cytosol or their escape from the host. Many important
breakthroughs such as the restriction of vacuolar and cytosolic
mycobacteria by the autophagy pathway and the recruitment of
sophisticated host repair machineries to the Mycobacterium-
containing vacuole have been gained in the Dictyostelium discoideum/
M. marinum system. Despite the availability of well-established
light and advanced electron microscopy techniques in this system,
a correlative approach integrating both methods with near-native
ultrastructural preservation is currently lacking.
This is most likely due to the low ability of D. discoideum to
adhere to surfaces, which results in cell loss even after fixation.
To address this problem, we improved the adhesion of cells and
developed a straightforward and convenient workflow for
3D-correlative light and electron microscopy. This approach includes
high-pressure freezing, which is an excellent technique for
preserving membranes. Thus, our method allows to monitor the
ultrastructural aspects of vacuole escape which is of central
importance for the survival and dissemination of bacterial pathogens.
Submitted by Caroline Barisch [[log in to unmask]]
________________________________________________________
Extracellular and intracellular destruction of Pseudomonas
aeruginosa by Dictyostelium discoideum phagocytes mobilize
different antibacterial mechanisms
Imen Ayadi, Otmane Lamrabet, Raphael Munoz-Ruiz, Tania Jauslin,
Cyril Guilhen, Pierre Cosson
28 November 2023
https://doi.org/10.1111/mmi.15197
Ingestion and killing of bacteria by phagocytic cells are critical
processes to protect the human body from bacterial infections. In
addition, some immune cells (neutrophils, NK cells) can release
microbicidal molecules in the extracellular medium to eliminate
non-ingested microorganism. Molecular mechanisms involved in the
resulting intracellular and extracellular killing are still
poorly understood. In this study, we used the amoeba Dictyostelium
discoideum as a model phagocyte to investigate the mechanisms
allowing intracellular and extra cellular killing of Pseudomonas
aeruginosa. When a D. discoideum cell establishes a close contact
with a P. aeruginosa bacterium, it can either ingest it and kill
it in phagosomes, or kill it extracellularly, allowing a direct
side-by-side comparison of these two killing modalities. Efficient
intracellular destruction of P. aeruginosanrequires the presence
of the Kil2 pump in the phagosomal membrane.On the contrary,
extracellular lysis is independent on Kil2 but requires the
expression of the superoxide-producing protein NoxA, and the
extracellular release of the AplA bacteriolytic protein. These
results shed new light on the molecular mechanisms allowing
elimination of P. aeruginosa bacteria by phagocytic cells.
Submitted by: Otmane Lamrabet [[log in to unmask]
_______________________________________________________
Adaptive pathfinding by nucleokinesis during amoeboid migration
Janina Kroll, Robert Hauschild, Artur Kuznetcov, Kasia Stefanowski,
Monika D Hermann, Jack Merrin, Lubuna Shafeek, Annette
Müller-Taubenberger, Jörg Renkawitz
EMBO Journal e114557https://doi.org/10.15252/embj.2023114557
Motile cells encounter microenvironments with locally heterogeneous
mechanochemical composition. Individual compositional parameters,
such as chemokines and extracellular matrix pore sizes, are well
known to provide guidance cues for pathfinding. However, motile
cells face diverse cues at the same time, raising the question of
how they respond to multiple and potentially competing signals on
their paths. Here, we reveal that amoeboid cells require nuclear
repositioning, termed nucleokinesis, for adaptive pathfinding in
heterogeneous mechanochemical micro-environments. Using mammalian
immune cells and the amoeba Dictyostelium discoideum, we discover
that frequent, rapid and long-distance nucleokinesis is a basic
component of amoeboid pathfinding, enabling cells to reorientate
quickly between locally competing cues. Amoeboid nucleokinesis
comprises a two-step polarity switch and is driven by myosin-II
forces that readjust the nuclear to the cellular path. Impaired
nucleokinesis distorts path adaptions and causes cellular arrest
in the microenvironment. Our findings establish that nucleokinesis
is required for amoeboid cell navigation. Given that many immune
cells, amoebae, and some cancer cells utilize an amoeboid
migration strategy, these results suggest that nucleokinesis
underlies cellular navigation during unicellular biology,
immunity, and disease.
Submitted by: Annette Müller-Taubenberger [[log in to unmask]]
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[End dictyNews, volume 49, number 30]
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