-
Journal of Immunology (Baltimore, Md. :... Jul 2022A considerable amount is known about how eukaryotic cells move toward an attractant, and the mechanisms are conserved from to human neutrophils. Relatively little is...
A considerable amount is known about how eukaryotic cells move toward an attractant, and the mechanisms are conserved from to human neutrophils. Relatively little is known about chemorepulsion, where cells move away from a repellent signal. We previously identified pathways mediating chemorepulsion in , and here we show that these pathways, including Ras, Rac, protein kinase C, PTEN, and ERK1 and 2, are required for human neutrophil chemorepulsion, and, as with chemorepulsion, PI3K and phospholipase C are not necessary, suggesting that eukaryotic chemorepulsion mechanisms are conserved. Surprisingly, there were differences between male and female neutrophils. Inhibition of Rho-associated kinases or Cdc42 caused male neutrophils to be more repelled by a chemorepellent and female neutrophils to be attracted to the chemorepellent. In the presence of a chemorepellent, compared with male neutrophils, female neutrophils showed a reduced percentage of repelled neutrophils, greater persistence of movement, more adhesion, less accumulation of PI(3,4,5)P, and less polymerization of actin. Five proteins associated with chemorepulsion pathways are differentially abundant, with three of the five showing sex dimorphism in protein localization in unstimulated male and female neutrophils. Together, this indicates a fundamental difference in a motility mechanism in the innate immune system in men and women.
Topics: Actins; Chemotaxis; Dictyostelium; Female; Humans; Male; Neutrophils; Sex Characteristics
PubMed: 35793910
DOI: 10.4049/jimmunol.2101103 -
Structure (London, England : 1993) Aug 2019In this issue of Structure, Jasnin et al. (2019) shows how actin waves on the ventral membrane of Dictyostelium cells propagate by de novo nucleation of oblique...
In this issue of Structure, Jasnin et al. (2019) shows how actin waves on the ventral membrane of Dictyostelium cells propagate by de novo nucleation of oblique filaments that are polarized toward the ventral membrane without a preference to the wave direction.
Topics: Actins; Cytoskeleton; Dictyostelium; Electron Microscope Tomography
PubMed: 31390543
DOI: 10.1016/j.str.2019.07.010 -
MBio Oct 2023Tuberculosis still remains a global burden and is one of the top infectious diseases from a single pathogen. , the causative agent, has perfected many ways to replicate...
Tuberculosis still remains a global burden and is one of the top infectious diseases from a single pathogen. , the causative agent, has perfected many ways to replicate and persist within its host. While mycobacteria induce vacuole damage to evade the toxic environment and eventually escape into the cytosol, the host recruits repair machineries to restore the MCV membrane. However, how lipids are delivered for membrane repair is poorly understood. Using advanced fluorescence imaging and volumetric correlative approaches, we demonstrate that this involves the recruitment of the endoplasmic reticulum (ER)-Golgi lipid transfer protein OSBP8 in the / system. Strikingly, depletion of OSBP8 affects lysosomal function accelerating mycobacterial growth. This indicates that an ER-dependent repair pathway constitutes a host defense mechanism against intracellular pathogens such as .
Topics: Humans; Vacuoles; Dictyostelium; Endoplasmic Reticulum; Mycobacterium marinum; Mycobacterium tuberculosis; Tuberculosis
PubMed: 37676004
DOI: 10.1128/mbio.00943-23 -
Scientific Reports Jul 2022Genome-wide screening is powerful method used to identify genes and pathways associated with a phenotype of interest. The simple eukaryote Dictyostelium discoideum has a...
Genome-wide screening is powerful method used to identify genes and pathways associated with a phenotype of interest. The simple eukaryote Dictyostelium discoideum has a unique life cycle and is often used as a crucial research model for a wide range of biological processes and rare metabolites. To address the inadequacies of conventional genetic screening approaches, we developed a highly efficient CRISPR/Cas9-based genome-wide screening system for Dictyostelium. A genome-wide library of 27,405 gRNAs and a kinase library of 4,582 gRNAs were compiled and mutant pools were generated. The resulting mutants were screened for defects in cell growth and more than 10 candidate genes were identified. Six of these were validated and five recreated mutants presented with growth abnormalities. Finally, the genes implicated in developmental defects were screened to identify the unknown genes associated with a phenotype of interest. These findings demonstrate the potential of the CRISPR/Cas9 system as an efficient genome-wide screening method.
Topics: CRISPR-Cas Systems; Dictyostelium; Gene Library; Genome; RNA, Guide, CRISPR-Cas Systems
PubMed: 35780186
DOI: 10.1038/s41598-022-15500-3 -
Cells May 2022Directional cell migration and the establishment of polarity play an important role in development, wound healing, and host cell defense. While actin polymerization...
Directional cell migration and the establishment of polarity play an important role in development, wound healing, and host cell defense. While actin polymerization provides the driving force at the cell front, the microtubule network assumes a regulatory function, in coordinating front protrusion and rear retraction. By using cells as a model for amoeboid movement in different 2D and 3D environments, the position of the centrosome relative to the nucleus was analyzed using live-cell microscopy. Our results showed that the centrosome was preferentially located rearward of the nucleus under all conditions tested for directed migration, while the nucleus was oriented toward the expanding front. When cells are hindered from straight movement by obstacles, the centrosome is displaced temporarily from its rearward location to the side of the nucleus, but is reoriented within seconds. This relocalization is supported by the presence of intact microtubules and their contact with the cortex. The data suggest that the centrosome is responsible for coordinating microtubules with respect to the nucleus. In summary, we have analyzed the orientation of the centrosome during different modes of migration in an amoeboid model and present evidence that the basic principles of centrosome positioning and movement are conserved between and human leukocytes.
Topics: Cell Movement; Cell Nucleus; Centrosome; Dictyostelium; Humans; Microtubules
PubMed: 35681473
DOI: 10.3390/cells11111776 -
MicroLife 2023Vesicular trafficking and membrane fusion are well-characterized, versatile, and sophisticated means of 'long range' intracellular protein and lipid delivery. Membrane... (Review)
Review
Vesicular trafficking and membrane fusion are well-characterized, versatile, and sophisticated means of 'long range' intracellular protein and lipid delivery. Membrane contact sites (MCS) have been studied in far less detail, but are crucial for 'short range' (10-30 nm) communication between organelles, as well as between pathogen vacuoles and organelles. MCS are specialized in the non-vesicular trafficking of small molecules such as calcium and lipids. Pivotal MCS components important for lipid transfer are the VAP receptor/tether protein, oxysterol binding proteins (OSBPs), the ceramide transport protein CERT, the phosphoinositide phosphatase Sac1, and the lipid phosphatidylinositol 4-phosphate (PtdIns(4)). In this review, we discuss how these MCS components are subverted by bacterial pathogens and their secreted effector proteins to promote intracellular survival and replication.
PubMed: 37223745
DOI: 10.1093/femsml/uqad018 -
The Journal of Biological Chemistry May 2024Recent research has identified the mechanistic Target of Rapamycin Complex 2 (mTORC2) as a conserved direct effector of Ras proteins. While previous studies suggested...
Recent research has identified the mechanistic Target of Rapamycin Complex 2 (mTORC2) as a conserved direct effector of Ras proteins. While previous studies suggested the involvement of the Switch I (SWI) effector domain of Ras in binding mTORC2 components, the regulation of the Ras-mTORC2 pathway is not entirely understood. In Dictyostelium, mTORC2 is selectively activated by the Ras protein RasC, and the RasC-mTORC2 pathway then mediates chemotaxis to cAMP and cellular aggregation by regulating the actin cytoskeleton and promoting cAMP signal relay. Here, we investigated the role of specific residues in RasC's SWI, C-terminal allosteric domain, and hypervariable region (HVR) related to mTORC2 activation. Interestingly, our results suggest that RasC SWI residue A31, which was previously implicated in RasC-mediated aggregation, regulates RasC's specific activation by the Aimless RasGEF. On the other hand, our investigation identified a crucial role for RasC SWI residue T36, with secondary contributions from E38 and allosteric domain residues. Finally, we found that conserved basic residues and the adjacent prenylation site in the HVR, which are crucial for RasC's membrane localization, are essential for RasC-mTORC2 pathway activation by allowing for both RasC's own cAMP-induced activation and its subsequent activation of mTORC2. Therefore, our findings revealed new determinants of RasC-mTORC2 pathway specificity in Dictyostelium, contributing to a deeper understanding of Ras signaling regulation in eukaryotic cells.
PubMed: 38815864
DOI: 10.1016/j.jbc.2024.107423 -
Frontiers in Immunology 2020is the causative agent of a severe pneumonia called Legionnaires' disease. The environmental bacterium replicates in free-living amoebae as well as in lung macrophages... (Review)
Review
is the causative agent of a severe pneumonia called Legionnaires' disease. The environmental bacterium replicates in free-living amoebae as well as in lung macrophages in a distinct compartment, the -containing vacuole (LCV). The LCV communicates with a number of cellular vesicle trafficking pathways and is formed by a plethora of secreted bacterial effector proteins, which target host cell proteins and lipids. Phosphoinositide (PI) lipids are pivotal determinants of organelle identity, membrane dynamics and vesicle trafficking. Accordingly, eukaryotic cells tightly regulate the production, turnover, interconversion, and localization of PI lipids. modulates the PI pattern in infected cells for its own benefit by (i) recruiting PI-decorated vesicles, (ii) producing effectors acting as PI interactors, phosphatases, kinases or phospholipases, and (iii) subverting host PI metabolizing enzymes. The PI conversion from PtdIns(3) to PtdIns(4) represents a decisive step during LCV maturation. In this review, we summarize recent progress on elucidating the strategies, by which subverts host PI lipids to promote LCV formation and intracellular replication.
Topics: Bacterial Proteins; Cell Membrane; Endoplasmic Reticulum; Host-Pathogen Interactions; Humans; Legionella pneumophila; Legionnaires' Disease; Macrophages; Phosphatidylinositols; Secretory Vesicles; Transport Vesicles; Vacuoles
PubMed: 32117224
DOI: 10.3389/fimmu.2020.00025 -
Nature Communications Feb 2023Self-organization of cells is central to a variety of biological systems and physical concepts of condensed matter have proven instrumental in deciphering some of their...
Self-organization of cells is central to a variety of biological systems and physical concepts of condensed matter have proven instrumental in deciphering some of their properties. Here we show that microphase separation, long studied in polymeric materials and other inert systems, has a natural counterpart in living cells. When placed below a millimetric film of liquid nutritive medium, a quasi two-dimensional, high-density population of Dictyostelium discoideum cells spontaneously assembles into compact domains. Their typical size of 100 μm is governed by a balance between competing interactions: an adhesion acting as a short-range attraction and promoting aggregation, and an effective long-range repulsion stemming from aerotaxis in near anoxic condition. Experimental data, a simple model and cell-based simulations all support this scenario. Our findings establish a generic mechanism for self-organization of living cells and highlight oxygen regulation as an emergent organizing principle for biological matter.
Topics: Dictyostelium; Chemotaxis
PubMed: 36781863
DOI: 10.1038/s41467-023-36395-2 -
International Journal of Molecular... Feb 2020is gaining increasing attention as a model organism for the study of calcium binding and calmodulin function in basic biological events as well as human diseases. After... (Review)
Review
is gaining increasing attention as a model organism for the study of calcium binding and calmodulin function in basic biological events as well as human diseases. After a short overview of calcium-binding proteins, the structure of Dictyostelium calmodulin and the conformational changes effected by calcium ion binding to its four EF hands are compared to its human counterpart, emphasizing the highly conserved nature of this central regulatory protein. The calcium-dependent and -independent motifs involved in calmodulin binding to target proteins are discussed with examples of the diversity of calmodulin binding proteins that have been studied in this amoebozoan. The methods used to identify and characterize calmodulin binding proteins is covered followed by the ways is currently being used as a system to study several neurodegenerative diseases and how it could serve as a model for studying calmodulinopathies such as those associated with specific types of heart arrythmia. Because of its rapid developmental cycles, its genetic tractability, and a richly endowed stock center, is in a position to become a leader in the field of calmodulin research.
Topics: Binding Sites; Calcium; Calcium Signaling; Calmodulin; Calmodulin-Binding Proteins; Dictyostelium; EF Hand Motifs; Humans; Models, Molecular; Protein Binding; Protozoan Infections; Protozoan Proteins
PubMed: 32054133
DOI: 10.3390/ijms21041210