-
BioRxiv : the Preprint Server For... Mar 2024Many cells adhere to extracellular matrix for efficient cell migration. This adhesion is mediated by focal adhesions, a protein complex linking the extracellular matrix...
Many cells adhere to extracellular matrix for efficient cell migration. This adhesion is mediated by focal adhesions, a protein complex linking the extracellular matrix to the intracellular cytoskeleton. Focal adhesions have been studied extensively in mesenchymal cells, but recent research in physiological contexts and amoeboid cells suggest focal adhesion regulation differs from the mesenchymal focal adhesion paradigm. We used to uncover new mechanisms of focal adhesion regulation, as are amoeboid cells that form focal adhesion-like structures for migration. We show that PaxillinB, the homologue of Paxillin, localizes to dynamic focal adhesion-like structures during migration. Unexpectedly, reduced PaxillinB recruitment to these structures increases cell migration. Quantitative analysis of focal adhesion size and dynamics show that lack of PaxillinB recruitment to focal adhesions does not alter focal adhesion size, but rather increases focal adhesion turnover. These findings are in direct contrast to Paxillin function at focal adhesions during mesenchymal migration, challenging the established focal adhesion model.
PubMed: 38562712
DOI: 10.1101/2024.03.19.585764 -
Scientific Reports Apr 2024The social amoeba Dictyostelium discoideum switches between solitary growth and social fruitification depending on nutrient availability. Under starvation, cells...
The social amoeba Dictyostelium discoideum switches between solitary growth and social fruitification depending on nutrient availability. Under starvation, cells aggregate and form fruiting bodies consisting of spores and altruistic stalk cells. Once cells socially committed, they complete fruitification, even if a new source of nutrients becomes available. This social commitment is puzzling because it hinders individual cells from resuming solitary growth quickly. One idea posits that traits that facilitate premature de-commitment are hindered from being selected. We studied outcomes of the premature de-commitment through forced refeeding. Our results show that when refed cells interacted with non-refed cells, some of them became solitary, whereas a fraction was redirected to the altruistic stalk, regardless of their original fate. The refed cells exhibited reduced cohesiveness and were sorted out during morphogenesis. Our findings provide an insight into a division of labor of the social amoeba, in which less cohesive individuals become altruists.
Topics: Humans; Dictyostelium; Amoeba; Cell Differentiation; Morphogenesis; Cell Movement
PubMed: 38561423
DOI: 10.1038/s41598-024-58277-3 -
Biology of the Cell May 2024Two pore channels (TPCs) are voltage-gated ion channel superfamily members that release Ca from acidic intracellular stores and are ubiquitously present in both animals...
BACKGROUND INFORMATION
Two pore channels (TPCs) are voltage-gated ion channel superfamily members that release Ca from acidic intracellular stores and are ubiquitously present in both animals and plants. Starvation initiates multicellular development in Dictyostelium discoideum. Increased intracellular calcium levels bias Dictyostelium cells towards the stalk pathway and thus we decided to analyze the role of TPC2 in development, differentiation, and autophagy.
RESULTS
We showed TPC2 protein localizes in lysosome-like acidic vesicles and the in situ data showed stalk cell biasness. Deletion of tpc2 showed defective and delayed development with formation of multi-tipped structures attached to a common base, while tpc2 cells showed faster development with numerous small-sized aggregates and wiry fruiting bodies. The tpc2 cells showed higher intracellular cAMP levels as compared to the tpc2 cells while pinocytosis was found to be higher in the tpc2 cells. Also, TPC2 regulates cell-substrate adhesion and cellular morphology. Under nutrient starvation, deletion of tpc2 reduced autophagic flux as compared to Ax2. During chimera formation, tpc2 cells showed a bias towards the prestalk/stalk region while tpc2 cells showed a bias towards the prespore/spore region. tpc2 deficient strain exhibits aberrant cell-type patterning and loss of distinct boundary between the prestalk/prespore regions.
CONCLUSION
TPC2 is required for effective development and differentiation in Dictyostelium and supports autophagic cell death and cell-type patterning.
SIGNIFICANCE
Decreased calcium due to deletion of tpc2 inhibit autophagic flux.
Topics: Dictyostelium; Autophagy; Protozoan Proteins; Gene Deletion; Calcium Channels; Calcium; Cell Differentiation
PubMed: 38537110
DOI: 10.1111/boc.202300067 -
Proceedings of the National Academy of... Apr 2024Consumers range from specialists that feed on few resources to generalists that feed on many. Generalism has the clear advantage of having more resources to exploit, but...
Consumers range from specialists that feed on few resources to generalists that feed on many. Generalism has the clear advantage of having more resources to exploit, but the costs that limit generalism are less clear. We explore two understudied costs of generalism in a generalist amoeba predator, , feeding on naturally co-occurring bacterial prey. Both involve costs of combining prey that are suitable on their own. First, amoebas exhibit a reduction in growth rate when they switched to one species of prey bacteria from another compared to controls that experience only the second prey. The effect was consistent across all six tested species of bacteria. These switching costs typically disappear within a day, indicating adjustment to new prey bacteria. This suggests that these costs are physiological. Second, amoebas usually grow more slowly on mixtures of prey bacteria compared to the expectation based on their growth on single prey. There were clear mixing costs in three of the six tested prey mixtures, and none showed significant mixing benefits. These results support the idea that, although amoebas can consume a variety of prey, they must use partially different methods and thus must pay costs to handle multiple prey, either sequentially or simultaneously.
Topics: Animals; Dictyostelium; Eukaryota; Diet; Bacteria; Amoeba; Predatory Behavior; Food Chain
PubMed: 38530891
DOI: 10.1073/pnas.2313203121 -
Biophysical Journal May 2024Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) is a signaling lipid on the plasma membrane that plays a fundamental role in cell signaling with a strong impact on...
Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) is a signaling lipid on the plasma membrane that plays a fundamental role in cell signaling with a strong impact on cell physiology and diseases. It is responsible for the protruding edge formation, cell polarization, macropinocytosis, and other membrane remodeling dynamics in cells. It has been shown that the membrane confinement and curvature affects the wave formation of PIP3 and F-actin. But, even in the absence of F-actin, a complex self-organization of the spatiotemporal PIP3 waves is observed. In recent findings, we have shown that these waves can be guided and pinned on strongly bended Dictyostelium membranes caused by molecular crowding and curvature-limited diffusion. Based on these experimental findings, we investigate the spatiotemporal PIP3 wave dynamics on realistic three-dimensional cell-like membranes to explore the effect of curvature-limited diffusion, as observed experimentally. We use an established stochastic reaction-diffusion model with enzymatic Michaelis-Menten-type reactions that mimics the dynamics of Dictyostelium cells. As these cells mimic the three-dimensional shape and size observed experimentally, we found that the PIP3 wave directionality can be explained by a Hopf-like and a reverse periodic-doubling bifurcation for uniform diffusion and curvature-limited diffusion properties. Finally, we compare the results with recent experimental findings and discuss the discrepancy between the biological and numerical results.
Topics: Cell Membrane; Dictyostelium; Phosphatidylinositol Phosphates; Models, Biological; Diffusion
PubMed: 38515298
DOI: 10.1016/j.bpj.2024.03.022 -
Frontiers in Cell and Developmental... 2024Eukaryotic cells exhibit random migration in the absence of extracellular directional cues. This random migration acts as basal motility for various migratory responses... (Review)
Review
Eukaryotic cells exhibit random migration in the absence of extracellular directional cues. This random migration acts as basal motility for various migratory responses such as chemotaxis. The self-organization of random motility requires the internal signals that determine the anterior side of the migrating cell be generated spontaneously from the intrinsic activities of intracellular signaling networks. Recent studies have identified an excitable system as the mechanism of the spontaneous signal generation. Here, we discuss how the excitable system of Ras, a small G protein, regulates signaling networks in as a model organism. The excitability produces a domain where an active form of Ras is enriched on the cell membrane without extracellular directional cues, such that Ras serves as the anterior signal. The typical spatiotemporal characteristics are mathematically explained by reaction-diffusion models. These models further enable a quantitative analysis of the dynamics that depends on the internal cellular states and surrounding environments. Downstream of the Ras excitable system, a phosphoinositide metabolic network composed of PI3K, PTEN, PI(3,4,5)P and PI(4,5)P exhibits bistability to discretize the anterior and posterior regions of the cell membrane. Upstream, a local excitation and global inhibition local excitation global inhibition network, which works for gradient sensing in the presence of chemoattractant gradients, spatiotemporally biases the excitability of Ras for chemotaxis. In parallel with the Ras excitable system, the cGMP signaling pathway constitutes another excitable system of its own periodicity to ensure flexible migratory dynamics. In addition to these intracellular signaling networks, an intercellular signaling network activated by secreted cAMP is coupled with the Ras excitable system for collective cell migration. Finally, we discuss how the excitable system of Ras operates as a platform of information integration by receiving multiple intrinsic and extrinsic signals to ensure spontaneous cellular activity and robust responses in eukaryotic cell migration under natural complex environments.
PubMed: 38481533
DOI: 10.3389/fcell.2024.1373609 -
Developmental and Comparative Immunology Jun 2024This study investigated the effects of two distinct probiotics, Leuconostoc mesenteroides B4 (B4) and Bacillus pumilus D5 (D5), along with their combination, on the diet...
This study investigated the effects of two distinct probiotics, Leuconostoc mesenteroides B4 (B4) and Bacillus pumilus D5 (D5), along with their combination, on the diet of white shrimp (Litopenaeus vannamei) during an eight-week feeding trial. The diets tested included B4 + dextran at 10 CFU/g feed (the B4 group), D5 alone at 10 CFU/g feed (the D5 group), and a combination of B4 + dextran and D5 at 5 × 10 CFU/g feed each (the B4+dextran + D5 group). Relative to the control group, those administered probiotics exhibited moderate enhancements in growth. By the eighth week, the weight gain for the B4, D5, and B4+D5 groups was 696.50 ± 78.15%, 718.53 ± 130.73%, and 693.05 ± 93.79%, respectively, outperforming the control group's 691.66 ± 31.10% gain. The feed conversion ratio was most efficient in the B4 group (2.16 ± 0.06), closely followed by B4+D5 (2.21 ± 0.03) and D5 (2.22 ± 0.06), with the control group having the highest ratio (2.27 ± 0.03). While phenoloxidase activity was somewhat elevated in the B4 and D5 groups, no significant differences were noted in respiratory burst activity or total hemocyte count across all groups. Challenge tests at weeks 4 and 8 showed that the B4 + D5 combination offered superior protection against AHPND-causing Vibrio parahaemolyticus. The 4-week cumulative survival rate was highest in shrimp treated with B4 + dextran + D5 (56.25%), followed by B4 + dextran (31.25%), control (18.75%), and lowest in D5 (12.5%). By week 8, the B4 + dextran + D5 (43.75%) and B4 + dextran (37.5%) groups significantly outperformed the control group (6.25%, p < 0.05), with no significant difference observed between the D5 group (37.5%) and the control group at day 56. Analysis of the shrimp's foregut microbiota revealed an increase in unique OTUs in the B4 and B4 + D5 groups. Compared to the control, Proteobacteria abundance was reduced in all probiotic groups. Potential pathogens like Vibrio, Bacteroides, Neisseria, Botrytis, Clostridioides, and Deltaentomopoxvirus were detected in the control but were reduced or absent in probiotic groups. Beneficial microbes such as Methanobrevibacter and Dictyostelium in the B4+D5 group, and Sugiyamaella in the B4 group, showed significant increases. Probiotics also led to higher transcript levels of nitric oxide synthase in the hemocytes, and lysozyme and transglutaminase in the midgut, along with lysozyme and α2-macroglobulin in the foregut. Notably, the combined B4 + D5 probiotics synergistically enhanced the expression of superoxide dismutase and prophenoloxidase in the foregut, indicating an improved immune response. In summary, this study demonstrates that the probiotics evaluated, especially when used in combination, significantly boost the expression of specific immune-related genes, enhance the bacterial diversity and richness of the intestine, and thus prevent the colonization and proliferation of Vibrio spp. in L. vannamei.
Topics: Animals; Disease Resistance; Bacillus; Muramidase; Leuconostoc mesenteroides; Leuconostoc; Dextrans; Dictyostelium; Vibrio parahaemolyticus; Probiotics; Diet; Penaeidae; Immunity, Innate
PubMed: 38467323
DOI: 10.1016/j.dci.2024.105158 -
BioRxiv : the Preprint Server For... Feb 2024The directed movement of eukaryotic cells is crucial for processes such as embryogenesis and immune cell trafficking. The enzyme Phosphatase and tensin homolog (PTEN)...
The directed movement of eukaryotic cells is crucial for processes such as embryogenesis and immune cell trafficking. The enzyme Phosphatase and tensin homolog (PTEN) dephosphorylates phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P ] to phosphatidylinositol 4,5-bisphosphate [PI(4,5)P ]. cells require both PTEN and the PTEN-like phosphatase CnrN to locally inhibit Ras activation to induce biased movement of cells away from the secreted chemorepellent protein AprA. Both PTEN and CnrN decrease basal levels of PI(3,4,5)P and increase basal numbers of macropinosomes, and AprA prevents this increase. AprA requires both PTEN and CnrN to increase PI(4,5)P levels, decrease PI(3,4,5)P levels, inhibit proliferation, decrease myosin II phosphorylation, and increase filopod sizes. AprA causes PTEN, similar to CnrN, to localize to the side of the cell towards AprA in an AprA gradient. However, PTEN and CnrN also have distinct roles in some signaling pathways. PTEN, but not CnrN, decreases basal levels of PI(4,5)P , AprA requires PTEN, but not CnrN, to induce cell roundness, and CnrN and PTEN have different effects on the number of filopods and pseudopods, and the sizes of filopods. Together, our results suggest that CnrN and PTEN play unique roles in signaling pathways, and possibly dephosphorylate PI(3,4,5)P in different membrane domains, to mediate chemorepulsion away from AprA.
PubMed: 38464111
DOI: 10.1101/2024.02.23.581751 -
Plant Communications Jun 2024Allelochemicals represent a class of natural products released by plants as root, leaf, and fruit exudates that interfere with the growth and survival of neighboring...
Allelochemicals represent a class of natural products released by plants as root, leaf, and fruit exudates that interfere with the growth and survival of neighboring plants. Understanding how allelochemicals function to regulate plant responses may provide valuable new approaches to better control plant function. One such allelochemical, Myrigalone A (MyA) produced by Myrica gale, inhibits seed germination and seedling growth through an unknown mechanism. Here, we investigate MyA using the tractable model Dictyostelium discoideum and reveal that its activity depends on the conserved homolog of the plant ethylene synthesis protein 1-aminocyclopropane-1-carboxylic acid oxidase (ACO). Furthermore, in silico modeling predicts the direct binding of MyA to ACO within the catalytic pocket. In D. discoideum, ablation of ACO mimics the MyA-dependent developmental delay, which is partially restored by exogenous ethylene, and MyA reduces ethylene production. In Arabidopsis thaliana, MyA treatment delays seed germination, and this effect is rescued by exogenous ethylene. It also mimics the effect of established ACO inhibitors on root and hypocotyl extension, blocks ethylene-dependent root hair production, and reduces ethylene production. Finally, in silico binding analyses identify a range of highly potent ethylene inhibitors that block ethylene-dependent response and reduce ethylene production in Arabidopsis. Thus, we demonstrate a molecular mechanism by which the allelochemical MyA reduces ethylene biosynthesis and identify a range of ultrapotent inhibitors of ethylene-regulated responses.
Topics: Ethylenes; Pheromones; Arabidopsis; Germination
PubMed: 38460510
DOI: 10.1016/j.xplc.2024.100846 -
Soft Matter Mar 2024Collective cellular behavior plays a crucial role in various biological processes, ranging from developmental morphogenesis to pathological processes such as cancer...
Collective cellular behavior plays a crucial role in various biological processes, ranging from developmental morphogenesis to pathological processes such as cancer metastasis. Our previous research has revealed that a mutant cell of exhibits collective cell migration, including chain migration and traveling band formation, driven by a unique tail-following behavior at contact sites, which we term "contact following locomotion" (CFL). Here, we uncover an imbalance of forces between the front and rear cells within cell chains, leading to an additional propulsion force in the rear cells. Drawing inspiration from this observation, we introduce a theoretical model that incorporates non-reciprocal cell-cell interactions. Our findings highlight that the non-reciprocal interaction, in conjunction with self-alignment interactions, significantly contributes to the emergence of the observed collective cell migrations. Furthermore, we present a comprehensive phase diagram, showing distinct phases at both low and intermediate cell densities. This phase diagram elucidates a specific regime that corresponds to the experimental system.
Topics: Dictyostelium; Cell Communication; Cell Movement; Locomotion; Morphogenesis
PubMed: 38436091
DOI: 10.1039/d3sm01752d