Iron metabolism in the social amoeba Dictyostelium discoideum: A role for ferric chelate reductases.

Iron is the most abundant transition metal in all living organisms and is essential for several cellular activities, including respiration, oxygen transport, energy production and regulation of gene expression. Iron starvation is used by professional phagocytes, from Dictyostelium to macrophages, as a form of defense mechanism against intracellular pathogens. Previously, we showed that Dictyostelium cells express the proton-driven iron transporter Nramp1 (Natural Resistance-Associated Macrophage Protein 1) and the homolog NrampB (Nramp2) in membranes of macropinosomes and phagosomes or of the contractile vacuole network, respectively.

The Dynamics of Aerotaxis in a Simple Eukaryotic Model.

In aerobic organisms, oxygen is essential for efficient energy production, and it acts as the last acceptor of the mitochondrial electron transport chain and as regulator of gene expression. However, excessive oxygen can lead to production of deleterious reactive oxygen species. Therefore, the directed migration of single cells or cell clumps from hypoxic areas toward a region of optimal oxygen concentration, named aerotaxis, can be considered an adaptive mechanism that plays a major role in biological and pathological processes.

Characterization of Transport Activity of SLC11 Transporters in Oocytes by Fluorophore Quenching.

Membrane proteins are involved in different physiological functions and are the target of pharmaceutical and abuse drugs. oocytes provide a powerful heterologous expression system for functional studies of these proteins. Typical experiments investigate transport using electrophysiology and radiolabeled uptake.

Dictyostelium as model for studying ubiquitination and deubiquitination.

By protein quality control and degradation, the ubiquitin system drives many essential regulatory processes such as cell cycle and division, signalling, DNA replication and repair. Therefore, dysfunctions in the ubiquitin system lead to many human disease states. However, despite the immense progress made over the last couple of decades, it appears that the ubiquitin system is more complex and multi-faced than formerly expected.

The past, present and future of Dictyostelium as a model system.

The social amoeba Dictyostelium discoideum has been a preferred model organism during the last 50 years, particularly for the study of cell motility and chemotaxis, phagocytosis and macropinocytosis, intercellular adhesion, pattern formation, caspase-independent cell death and more recently autophagy and social evolution. Being a soil amoeba and professional phagocyte, thus exposed to a variety of potential pathogens, D. discoideum has also proven to be a powerful genetic and cellular model for investigating host-pathogen interactions and microbial infections.

Two conserved glycine residues in mammalian and Rictor are required for mTORC2 activity and integrity.

Mammalian, or mechanistic, target of rapamycin complex 2 (mTORC2) regulates a variety of vital cellular processes, and its aberrant functioning is often associated with various diseases. Rictor is a peculiar and distinguishing mTORC2 component playing a pivotal role in controlling its assembly and activity. Among extant organisms, Rictor is conserved from unicellular eukaryotes to metazoans.

Dictyostelium Host Response to Legionella Infection: Strategies and Assays.

The professional phagocyte Dictyostelium discoideum is a well-established model organism to study host-pathogen interactions. Dictyostelium amoebae grow as separate, independent cells; they divide by binary fission and take up bacteria and yeast via phagocytosis. In the year 2000, D.

Is the admission test for a course in medicine a good predictor of academic performance? A case-control experience at the school of medicine of Turin.

Objectives: The usefulness of university admission tests to medical schools has been discussed in recent years. In the academic year 2014-15 in Italy, several students who failed the admission test appealed to the regional administrative court ('Tribunale Amministrativo Regionale'-TAR) requesting to be included, despite their test results, and all were admitted to their respective courses. The existence of this population of students generated a control group, in order to evaluate the predictive capacity of the admission test.

[Admission test to the degree course in Medicine and Surgery and university career: the experience in the campuses of Piedmont Region (Northern Italy)].

Objectives: to consider the admission test to the degree course in Medicine and Surgery in the three campus of Piedmont Region (Northern Italy) in order to discuss the ability of this test to predict the academic outcome of the students.

Design: cohort study considering all the students enrolled in the first year of medicine during the academic year 2014-2015. Their academic career is monitored during the period January 2015-February 2016.

G-Protein Dependent Signal Transduction and Ubiquitination in Dictyostelium.

Signal transduction through G-protein-coupled receptors (GPCRs) is central for the regulation of virtually all cellular functions, and it has been widely implicated in human diseases. These receptors activate a common molecular switch that is represented by the heterotrimeric G-protein generating a number of second messengers (cAMP, cGMP, DAG, IP3, Ca etc.), leading to a plethora of diverse cellular responses.

A new HECT ubiquitin ligase regulating chemotaxis and development in Dictyostelium discoideum.

Cyclic AMP (cAMP) binding to G-protein-coupled receptors (GPCRs) orchestrates chemotaxis and development in Dictyostelium. By activating the RasC-TORC2-PKB (PKB is also known as AKT in mammals) module, cAMP regulates cell polarization during chemotaxis. TORC2 also mediates GPCR-dependent stimulation of adenylyl cyclase A (ACA), enhancing cAMP relay and developmental gene expression.

Dictyostelium Nramp1, which is structurally and functionally similar to mammalian DMT1 transporter, mediates phagosomal iron efflux.

The Nramp (Slc11) protein family is widespread in bacteria and eukaryotes, and mediates transport of divalent metals across cellular membranes. The social amoeba Dictyostelium discoideum has two Nramp proteins. Nramp1, like its mammalian ortholog (SLC11A1), is recruited to phagosomal and macropinosomal membranes, and confers resistance to pathogenic bacteria.

Iron metabolism and resistance to infection by invasive bacteria in the social amoeba Dictyostelium discoideum.

Dictyostelium cells are forest soil amoebae, which feed on bacteria and proliferate as solitary cells until bacteria are consumed. Starvation triggers a change in life style, forcing cells to gather into aggregates to form multicellular organisms capable of cell differentiation and morphogenesis. As a soil amoeba and a phagocyte that grazes on bacteria as the obligate source of food, Dictyostelium could be a natural host of pathogenic bacteria.

The model organism Dictyostelium discoideum.

Much of our knowledge of molecular cellular functions is based on studies with a few number of model organisms that were established during the last 50 years. The social amoeba Dictyostelium discoideum is one such model, and has been particularly useful for the study of cell motility, chemotaxis, phagocytosis, endocytic vesicle traffic, cell adhesion, pattern formation, caspase-independent cell death, and, more recently, autophagy and social evolution. As nonmammalian model of human diseases D.

Dictyostelium host response to legionella infection: strategies and assays.

The professional phagocyte Dictyostelium discoideum is a simple eukaryotic microorganism, whose natural habitat is deciduous forest soil and decaying leaves, where the amoebae feed on bacteria and grow as separate, independent, single cells. In the last decade, the organism has been successfully used as a host for several human pathogens, including Legionella pneumophila, Mycobacterium avium and Mycobacterium marinum,Pseudomonas aeruginosa, Klebsiella pneumoniae, Cryptococcus neoformans, and Salmonella typhimurium. To dissect the complex cross-talk between host and pathogen Dictyostelium offers easy cultivation, a high quality genome sequence and excellent molecular genetic and biochemical tools.

The Nramp (Slc11) proteins regulate development, resistance to pathogenic bacteria and iron homeostasis in Dictyostelium discoideum.

The Dictyostelium discoideum genome harbors two genes encoding members of the Nramp superfamily, which is conserved from bacteria (MntH proteins) to humans (Slc11 proteins). Nramps are proton-driven metal ion transporters with a preference for iron and manganese. Acquisition of these metal cations is vital for all cells, as they act as redox cofactors and regulate key cellular processes, such as DNA synthesis, electron transport, energy metabolism and oxidative stress.

Salmonella typhimurium is pathogenic for Dictyostelium cells and subverts the starvation response.

In unicellular amoebae, such as Dictyostelium discoideum, bacterial phagocytosis is a food hunting device, while in higher organisms it is the first defence barrier against microbial infection. In both cases, pathogenic bacteria exploit phagocytosis to enter the cell and multiply intracellularly. Salmonella typhimurium, the agent of food-borne gastroenteritis, is phagocytosed by both macrophages and Dictyostelium cells.

Legionella pneumophila infection is enhanced in a RacH-null mutant of Dictyostelium.

Recently we reported that Dictyostelium cells ingest Legionella pneumophila by macropinocytosis, whereas other bacteria, such as Escherichia coli, Mycobacterium avium, Neisseria meningitidis or Salmonella typhimurium, are taken up by phagocytosis.1 In contrast to phagocytosis, macropinocytosis is partially inhibited by PI3K or PTEN inactivation, whereas both processes are sensitive to PLC inhibition. Independently from reduced uptake, L.

The professional phagocyte Dictyostelium discoideum as a model host for bacterial pathogens.

The use of simple hosts such as Dictyostelium discoideum in the study of host pathogen interactions offers a number of advantages and has steadily increased in recent years. Infection-specific genes can often only be studied in a very limited way in man and even in the mouse model their analysis is usually expensive, time consuming and technically challenging or sometimes even impossible. In contrast, their functional analysis in D.

Phosphoinositides differentially regulate bacterial uptake and Nramp1-induced resistance to Legionella infection in Dictyostelium.

Membrane phosphatidylinositides recruit cytosolic proteins to regulate phagocytosis, macropinocytosis and endolysosomal vesicle maturation. Here, we describe effects of inactivation of PI3K, PTEN or PLC on Escherichia coli and Legionella pneumophila uptake by the professional phagocyte Dictyostelium discoideum. We show that L.

Legionella pneumophila multiplication is enhanced by chronic AMPK signalling in mitochondrially diseased Dictyostelium cells.

Human patients with mitochondrial diseases are more susceptible to bacterial infections, particularly of the respiratory tract. To investigate the susceptibility of mitochondrially diseased cells to an intracellular bacterial respiratory pathogen, we exploited the advantages of Dictyostelium discoideum as an established model for mitochondrial disease and for Legionella pneumophila pathogenesis. Legionella infection of macrophages involves recruitment of mitochondria to the Legionella-containing phagosome.

Phagocytosis and host-pathogen interactions in Dictyostelium with a look at macrophages.

Research into phagocytosis and host-pathogen interactions in the lower eukaryote Dictyostelium discoideum has flourished in recent years. This chapter presents a glimpse of where this research stands, with emphasis on the cell biology of the phagocytic process and on the wealth of molecular genetic data that have been gathered. The basic mechanistic machinery and most of the underlying genes appear to be evolutionarily conserved, reflecting the fact that phagocytosis arose as an efficient way to ingest food in single protozoan cells devoid of a rigid cell wall.

Dictyostelium discoideum as a model host for meningococcal pathogenesis.

Background: The aim of the present study was to evaluate the possibility of studying meningococcal virulence in a new model organism, Dictyostelium discoideum, a haploid social soil amoeba that is an established host model for several human pathogens, leading to the discovery of novel virulence mechanisms.

Material/methods: A number of virulent and hyper-virulent N. meningitidis strains, including isogenic encapsulated, unencapsulated, and lipooligosaccharide (LOS) outer core-defective derivatives, were used to test the ability of D.