Research Articles
A cobalt concentration sensitive Btu-like system facilitates cobalamin uptake in Anabaena sp. PCC 7120
Julia Graf1, Leonard Fresenborg1,2, Hans-Michael Seitz2,3, Rafael Pernil1 and Enrico Schleiff1,2,4,5
Metal homeostasis is central to all forms of life, as metals are essential micronutrients with toxic effects at elevated levels. Our results provide novel information on the uptake of cobalamin and the regulation of the cellular cobalt content in cyanobacteria.
Predictable regulation of survival by intratumoral microbe-immune crosstalk in patients with lung adenocarcinoma
Shuo Shi1, Yuwen Chu2,3, Haiyan Liu4,5, Lan Yu6,7,8, Dejun Sun8,9, Jialiang Yang2,3,5, Geng Tian2,3, Lei Ji2,3, Cong Zhang10 and Xinxin Lu11
Intratumoral microbiota can regulate the tumor immune microenvironment (TIME) and mediate tumor prognosis by promoting inflammatory response or inhibiting anti-tumor effects. Our study demonstrated that intratumoral microbiota-immune crosstalk was strongly associated with prognosis in LUAD patients, which would provide new targets for the development of precise therapeutic strategies.
Two TonB-dependent outer membrane transporters involved in heme uptake in Anabaena sp. PCC 7120
Julia Graf1, Martin Schöpperle1,2, Rafael Pernil1 and Enrico Schleiff1,3,4
Low availability of micronutrients such as iron has enforced the evolution of uptake systems in all kingdoms of life. In our study, we conclude that heme transport might not be restricted to Anabaena, but at the same time is not specific to a cyanobacterial order and thus might be related to the habitat of origin, a notion which needs to be challenged in the future.
The last two transmembrane helices in the APC-type FurE transporter act as an intramolecular chaperone essential for concentrative ER-exit
Yiannis Pyrris1, Georgia F. Papadaki1, Emmanuel Mikros2 and George Diallinas1,3
FurE is a H+ symporter specific for the cellular uptake of uric acid, allantoin, uracil, and toxic nucleobase analogues in the fungus Aspergillus nidulans. Being member of the NCS1 protein family, FurE is structurally related to the APC-superfamily of transporters.
Extracellular DNA secreted in yeast cultures is metabolism-specific and inhibits cell proliferation
Elisabetta de Alteriis1, Guido Incerti2, Fabrizio Cartenì3, Maria Luisa Chiusano3, Chiara Colantuono3, Emanuela Palomba4, Pasquale Termolino4, Francesco Monticolo3,5, Alfonso Esposito3, Giuliano Bonanomi3,6, Rosanna Capparelli3, Marco Iannaccone3,7, Alessandro Foscari2, Carmine Landi8, Palma Parascandola8, Massimo Sanchez9, Valentina Tirelli9, Bruna de Falco3, Virginia Lanzotti3 and Stefano Mazzoleni3,6
Our study demonstrates that extracellular DNA released by living cells can impact the growth rate of Saccharomyces cerevisiae cultures, showing similarities to extrachromosomal circular DNA and leading to cell cycle arrest in the S phase, suggesting potential new functional roles of exDNA.
Basal level of ppGpp coordinates Escherichia coli cell heterogeneity and ampicillin resistance and persistence
Paulina Katarzyna Grucela1 and Yong Everett Zhang1
The universal stringent response alarmone ppGpp (guanosine penta and tetra phosphates) plays a crucial role in various aspects of fundamental cell physiology (e.g., cell growth rate, cell size) and thus bacterial tolerance to and survival of external stresses, including antibiotics. In tihs study, we discuss the fundamental role of basal level of ppGpp in regulating cell homogeneity and ampicillin persistence.
Investigation of the acetic acid stress response in Saccharomyces cerevisiae with mutated H3 residues
Nitu Saha1, Swati Swagatika1 and Raghuvir Singh Tomar1
Yeast cells respond to acetic acid in diverse ways. Here, we have elucidated the deleterious effects of acetic acid on different histone mutants
The coenzyme B12 precursor 5,6-dimethylbenzimidazole is a flavin antagonist in Salmonella
Lahiru Malalasekara1 and Jorge C. Escalante-Semerena1,*
Here we investigated why 5,6-dimethylbenzimidazole (DMB) inhibits in S. Typhimurium. Briefly, we determined that the structural similarities of the substituted benzene ring of DMB with the isoalloxazine moiety of flavins is responsible for the deleterious effects of this CoB12 precursor.
GFP fusions of Sec-routed extracellular proteins in Staphylococcus aureus reveal surface-associated coagulase in biofilms
Dominique C. S. Evans1,2,#, Amanda B. Khamas1,#, Lisbeth Marcussen1, Kristian S. Rasmussen3, Janne K. Klitgaard3, Birgitte H. Kallipolitis3, Janni Nielsen1, Daniel E. Otzen1, Mark C. Leake2,4 and Rikke L. Meyer1,5
We show that msfGFP can be used to generate extracellular fluorescent fusion proteins in S. aureus, applicable for proteins that are secreted through the Sec pathway. When fused to coagulase, msfGFP did not hinder the biological function, and the fusion protein localised to the fibrin pseudocapsule surrounding clusters of S. aureus cells.
The lysosomotropic drug LeuLeu-OMe induces lysosome disruption and autophagy-independent cell death in Trypanosoma brucei
July 30, 2015
Trypanosoma brucei is a blood-borne, protozoan parasite that causes African sleeping sickness in humans and nagana in animals. The current chemotherapy relies on only a handful of drugs that display undesirable toxicity, poor efficacy and drug-resistance. In this study, we explored the use of lysosomotropic drugs to induce bloodstream form T. brucei cell death via lysosome destabilization. We measured drug concentrations that inhibit cell proliferation by 50% (IC50) for several compounds, chosen based on their lysosomotropic effects previously reported in Plasmodium falciparum. The lysosomal effects and cell death induced by L-leucyl-L-leucyl methyl ester (LeuLeu-OMe) were further analyzed by flow cytometry and immunofluorescence analyses of different lysosomal markers...
In Entamoeba histolytica, a BspA family protein is required for chemotaxis toward tumour necrosis factor
July 6, 2015
Background: Entamoeba histolytica cell migration is essential for the development of human amoebiasis (an infectious disease characterized by tissue invasion and destruction). The tissue inflammation associated with tumour necrosis factor (TNF) secretion by host cells is a well-documented feature of amoebiasis. Tumour necrosis factor is a chemoattractant for E. histolytica, and the parasite may have a TNF receptor at its cell surface. Methods: confocal microscopy, RNA Sequencing, bioinformatics, RNA antisense techniques and histological analysis of human colon explants were used to characterize the interplay between TNF and E. histolytica. Results: an antibody against human TNF receptor 1 (TNFR1) stained the E. histolytica trophozoite...
Polyamines directly promote antizyme-mediated degradation of ornithine decarboxylase by the proteasome
May 20, 2015
Ornithine decarboxylase (ODC), a ubiquitin-independent substrate of the proteasome, is a homodimeric protein with a rate-limiting function in polyamine biosynthesis. Polyamines regulate ODC levels by a feedback mechanism mediated by ODC antizyme (OAZ). Higher cellular polyamine levels trigger the synthesis of OAZ and also inhibit its ubiquitin-dependent proteasomal degradation. OAZ binds ODC monomers and targets them to the proteasome. Here, we report that polyamines, aside from their role in the control of OAZ synthesis and stability, directly enhance OAZ-mediated ODC degradation by the proteasome. Using a stable mutant of OAZ, we show that polyamines promote ODC degradation in Saccharomyces cerevisiae cells even when OAZ levels are not changed. Furthermore, polyamines stimulated the in vitro degradation of ODC by the...
Toxoplasma gondii inhibits cytochrome c-induced caspase activation in its host cell by interference with holo-apoptosome assembly
May 4, 2015
Inhibition of programmed cell death pathways of mammalian cells often facilitates the sustained survival of intracellular microorganisms. The apicomplexan parasite Toxoplasma gondii is a master regulator of host cell apoptotic pathways. Here, we have characterized a novel anti-apoptotic activity of T. gondii. Using a cell-free cytosolic extract model, we show that T. gondii interferes with the activities of caspase 9 and caspase 3/7 which have been induced by exogenous cytochrome c and dATP. Proteolytic cleavage of caspases 9 and 3 is also diminished suggesting inhibition of holo-apoptosome function. Parasite infection of Jurkat T cells and subsequent triggering of apoptosome formation by exogenous cytochrome c in vitro and in vivo indicated that...
Modeling human Coenzyme A synthase mutation in yeast reveals altered mitochondrial function, lipid content and iron metabolism
April 6, 2015
Mutations in nuclear genes associated with defective coenzyme A biosynthesis have been identified as responsible for some forms of neurodegeneration with brain iron accumulation (NBIA), namely PKAN and CoPAN. Yeast expressing a pathogenic mutation exhibited a temperature-sensitive growth defect in the absence of pantothenate and a reduced CoA content. Additional characterization revealed decreased oxygen consumption, reduced activities of mitochondrial respiratory complexes, higher iron content, increased sensitivity to oxidative stress and reduced amount of lipid droplets, thus partially recapitulating the phenotypes found in patients and establishing yeast as a potential model to clarify the pathogenesis underlying PKAN and CoPAN diseases.
Prokaryotic ancestry and gene fusion of a dual localized peroxiredoxin in malaria parasites
January 4, 2015
Horizontal gene transfer has emerged as a crucial driving force for the evolution of eukaryotes. This also includes Plasmodium falciparum and related economically and clinically relevant apicomplexan parasites, whose rather small genomes have been shaped not only by natural selection in different host populations but also by horizontal gene transfer following endosymbiosis. However, there is rather little reliable data on horizontal gene transfer between animal hosts or bacteria and apicomplexan parasites. Here we show that apicomplexan homologues of peroxiredoxin 5 (Prx5) have a prokaryotic ancestry and therefore represent a special subclass of Prx5 isoforms in eukaryotes. Using two different immunobiochemical approaches, we found that...
Two distinct and competitive pathways confer the cellcidal actions of artemisinins
January 1, 2015
The biological actions of artemisinin (ART), an antimalarial drug derived from Artemisia annua, remain poorly understood and controversial. This article concludes that ARTs are endowed with two major and distinct types of properties: a potent and specific mitochondria-dependent reaction and a more general and less specific heme-mediated reaction. The competitive nature of these two actions could be explained by their shared source of the consumable ARTs, so that inhibition of the heme-mediated degradation pathway would enable more ARTs to be available for the mitochondrial action. These properties of ARTs can be used to interpret the divergent antimalarial and anticancer actions of ARTs.
Measurement of apoptosis by SCAN©, a system for counting and analysis of fluorescently labelled nuclei
November 26, 2014
This work reports on a system for analyses of apoptosis-like programmed cell death in fungal hyphae that is composed of several modules, which enable automatic quantification of nuclei with chromatin condensation and DNA strand break in large datasets according to nuclei-associated fluorescent markers.
Rewiring yeast acetate metabolism through MPC1 loss of function leads to mitochondrial damage and decreases chronological lifespan
November 18, 2014
This work shows that MPC1-deficient cells make up for their impairment in mitochondrial pyruvate with a metabolic rewiring which involves several intermediates of the mitochondrially localized TCA cycle and the cytosolic glyoxylate shunt but ultimately results in a pro-aging process.