dictyNews

Electronic Edition

Volume 44, number 22

August 4, 2018



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Abstracts

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Functions of the Dictyostelium LIMP-2/CD36 homologues in bacteria 

uptake,phagolysosome biogenesis and host cell defence



Natascha Sattler1&, Cristina Bosmani1&, Caroline Barisch1, Aurélie 

Guého1, Navin Gopaldass1,4, Marco Dias3, Florence Leuba1, 

Franz Bruckert2, Pierre Cosson3, and Thierry Soldati1*



&These authors contributed equally



1Départment de Biochimie, Faculté des Sciences, Université de Genève, 

Sciences II, 30 quai Ernest

Ansermet, CH-1211 Genève-4, Switzerland

2Laboratoire des Matériaux et du Génie Physique (LMGP), Grenoble 

Institute of Technology, 3

parvis Louis Néel, BP 257, 38016 Grenoble cedex 1, France

3Department of Cell Physiology and Metabolism, Centre Médical 

Universitaire, University of

Geneva, 1 rue Michel Servet, CH-1211 Geneva 4, Switzerland.

4Current address: Département de Biochimie, Faculté des Sciences, 

Université Lausanne, Chemin

des Boveresses 155 CH-1066 Epalinges, Switzerland





Journal of Cell Science , in press

http://jcs.biologists.org/content/early/2018/07/20/jcs.218040?papetoc



Phagocytic cells take up, kill and digest microbes by a process called 

phagocytosis. To this end these cells bind the particle, rearrange their 

actin cytoskeleton, and orchestrate transport of digestive factors to the 

particle-containing phagosome. The mammalian lysosomal membrane 

protein LIMP-2 and CD36, members of the class B of scavenger 

receptors, play a crucial role in lysosomal enzyme trafficking and uptake 

of mycobacteria, respectively, and generally in host cell defences 

against intracellular pathogens. Here, we show that the Dictyostelium 

discoideum LIMP-2 homologue LmpA regulates phagocytosis and 

phagolysosome biogenesis. The lmpA knockdown mutant is highly 

affected in actin-dependent processes such as particle uptake, cellular 

spreading and motility. Additionally, the cells are severely impaired in 

phagosomal acidification and proteolysis, likely explaining the higher 

susceptibility to infection with the pathogenic bacterium Mycobacterium 

marinum, a close cousin of the human pathogen Mycobacterium 

tuberculosis. Furthermore, we bring evidence that LmpB is a functional 

homologue of CD36 and specifically mediates uptake of mycobacteria. 

Altogether, these data indicate a role for LmpA and LmpB, ancestors of

 the LIMP-2/CD36 family, in lysosome biogenesis and host cell defence.





submitted by: Thierry Soldati [[log in to unmask]]

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Think zinc: Role of zinc poisoning in the intraphagosomal killing of 

bacteria by the amoeba Dictyostelium



Caroline Barisch1*, Vera Kalinina1,2, Louise H. Lefrançois1, Joddy 

Appiah1, and Thierry Soldati1



1Department of Biochemistry, Faculty of Science, University of Geneva, 

30 quai Ernest-Ansermet, Science II, 1211 Geneva-4, Switzerland

2 present address: Institute of Cytology, Russian Academy of Sciences, 

Tikhoretsky ave. 4, 194064 St. Petersburg, Russia



bioRxiv http://dx.doi.org/10.1101/356949





Professional phagocytes have developed an extensive repertoire of 

autonomous immunity strategies to ensure killing of bacteria. Besides 

phagosome acidification and the generation of reactive oxygen species, 

deprivation of nutrients and the lumenal accumulation of toxic metals 

are essential to kill ingested bacteria or inhibit growth of intracellular 

pathogens. We use the soil amoeba Dictyostelium discoideum, a 

professional phagocyte that digests bacteria for nutritional purposes, 

to decipher the role of zinc poisoning during phagocytosis of non-

pathogenic bacteria and visualize the temporal and spatial dynamics 

of compartmentalized, free zinc using fluorescent probes. Immediately 

after particle uptake, zinc is delivered to phagosomes by fusion with 

“zincosomes” of endosomal origin, but also by the action of one or more 

zinc transporters. We localize the four Dictyostelium ZnT transporters 

to endosomes, the contractile vacuole and the Golgi apparatus, and 

study the impact of znt knockouts on zinc homeostasis. Finally, we show 

that zinc is delivered into the lumen of Mycobacterium smegmatis-

containing vacuoles, and that Escherichia coli deficient in the zinc efflux 

P1B-type ATPase ZntA is killed faster than wild type bacteria.





submitted by: Thierry Soldati [[log in to unmask]]

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ESCRT and autophagy cooperate to repair ESX-1-dependent damage 

to the Mycobacterium-containing vacuole 



Ana T. López-Jiménez1, Elena Cardenal-Muñoz1, Florence Leuba1, Lilli 

Gerstenmaier2, Monica Hagedorn3, Jason S. King4 and Thierry Soldati1* 



1Department of Biochemistry, Faculty of Science, University of Geneva, 

Sciences II, 30 quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland. 

2Section Parasitology, Bernhard Nocht Institute for Tropical Medicine, 

20359 Hamburg, Germany. 

3Life Sciences and Chemistry, Jacobs University Bremen gGmbH, group

 Ribogenetics, Campus Ring 1, 28759 Bremen, Germany. 

4Department of Biomedical Science, University of Sheffield, Western 

Bank, Sheffield S10 2TN, United 17 Kingdom.





bioRxiv http://dx.doi.org/10.1101/334755



Phagocytes capture invader microbes within the bactericidal phagosome. 

Some pathogens subvert killing by damaging and escaping from this 

compartment. To prevent and fight bacterial escape, cells contain and 

repair the membrane damage, or finally eliminate the cytosolic escapees. 

All eukaryotic cells engage highly conserved mechanisms to ensure 

integrity of membranes in a multitude of physiological and pathological 

situations, including the Endosomal Sorting Complex Required for 

Transport (ESCRT) and autophagy machineries. In Dictyostelium 

discoideum, recruitment of the ESCRT-III protein Snf7/Chmp4/Vps32 and

 the ATPase Vps4 to sites of membrane repair relies on the ESCRT-I 

 component Tsg101 and occurs in absence of Ca2+. The ESX-1 

 dependent membrane perforations produced by the pathogen 

 Mycobacterium marinum separately engage both ESCRT and autophagy. 

 In absence of Tsg101, M. marinum escapes earlier to the cytosol, where 

 it is restricted by xenophagy. We propose that ESCRT has an evolutionary 

 conserved function in containing intracellular pathogens in intact 

 compartments.





submitted by: Thierry Soldati [[log in to unmask]]

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Proteobacterial origin of protein arginine methylation and regulation of 

Complex I assembly by MidA



Umar S. Hameed1,2, Oana Sanislav3, Sui T. Lay3, Sarah J. Annesley3, 

Chacko Jobichen2, Paul R. Fisher3, Kunchithapadam Swaminathan*,2, 

Stefan T. Arold*,1,4



1King Abdullah University of Science and Technology, Computational 

Bioscience Research Center, Division of Biological and Environmental 

Sciences and Engineering, Thuwal, 23955-6900, Saudi Arabia

2Department of Biological Sciences, National University of Singapore, 

Singapore 117543

3Department of Microbiology, La Trobe University, Plenty Rd., Bundoora, 

VIC, Australia, 3086

4Lead Contact

* Correspondence can be addressed to STA: [log in to unmask] 

and KS: [log in to unmask]





Cell Reports,in press



The human protein arginine methyl transferase NDUFAF7 controls the 

assembly of the ~1MDa mitochondrial Complex I (the NADH ubiquinone 

oxidoreductase), by methylating its subunit NDUFS2. We determined 

crystal structures of MidA, the Dictyostelium orthologue of NDUFAF7. The 

MidA catalytic core domain resembles other eukaryotic methyl transferases. 

However, three large core loops assemble into a novel regulatory domain 

that is likely to control ligand selection. Binding of MidA to NDUFS2 is 

weakened by demethylation, suggesting a mechanism for methylation-

controlled substrate release. Structural and bioinformatic analyses support 

that MidA/NDUFAF7 and their role in Complex I assembly are conserved 

from bacteria to humans, inferring that protein methylation already existed 

in proteobacteria. In vivo studies confirmed the critical role of the MidA 

methyltransferase activity for Complex I assembly, growth and phototaxis 

of Dictyostelium. Collectively, our data elucidate the origin of protein arginine 

methylation and its use by MidA/NDUFAF7 to regulate Complex I assembly.





submitted by: Paul Fisher [[log in to unmask]]

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Promoter-mediated diversification of transcriptional bursting dynamics 

following gene duplication



Edward Tunnacliffe, Adam M. Corrigan, and Jonathan R. Chubb



MRC Laboratory for Molecular Cell Biology and Department of Cell and 

Developmental Biology, University College London, Gower Street, London, 

WC1E 6BT, UK.





PNAS, in press



During the evolution of gene families, functional diversification of proteins 

often follows gene duplication. However, many gene families expand while 

preserving protein sequence. Why do cells maintain multiple copies of the 

same gene? Here we have addressed this question for an actin family with 

17 genes encoding an identical protein. The genes have divergent flanking 

regions and are scattered throughout the genome. Surprisingly, almost the 

entire family showed similar developmental expression profiles, with their 

expression also strongly coupled in single cells. Using live cell imaging, we 

show that differences in gene expression were apparent over shorter 

timescales, with family members displaying different transcriptional bursting 

dynamics. Strong “bursty” behaviors contrasted steady, more continuous 

activity, indicating different regulatory inputs to individual actin genes. To 

determine the sources of these different dynamic behaviors, we reciprocally 

exchanged the upstream regulatory regions of gene family members. This 

revealed that dynamic transcriptional behavior is directly instructed by 

upstream sequence, rather than features specific to genomic context. A 

residual minor contribution of genomic context modulates the gene OFF rate. 

Our data suggest promoter diversification following gene duplication could 

expand the range of stimuli that regulate the expression of essential genes. 

These observations contextualize the significance of transcriptional bursting.





submitted by:  Jonathan Chubb  [[log in to unmask]]

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[End dictyNews, volume 44, number 22]