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Frontiers in Cell and Developmental... 2021The haploid social amoeba is a powerful model organism to study vesicle trafficking, motility and migration, cell division, developmental processes, and host... (Review)
Review
The haploid social amoeba is a powerful model organism to study vesicle trafficking, motility and migration, cell division, developmental processes, and host cell-pathogen interactions. Dynamin superfamily proteins (DSPs) are large GTPases, which promote membrane fission and fusion, as well as membrane-independent cellular processes. Accordingly, DSPs play crucial roles for vesicle biogenesis and transport, organelle homeostasis, cytokinesis and cell-autonomous immunity. Major progress has been made over the last years in elucidating the function and structure of mammalian DSPs. produces at least eight DSPs, which are involved in membrane dynamics and other processes. The function and structure of these large GTPases has not been fully explored, despite the elaborate genetic and cell biological tools available for . In this review, we focus on the current knowledge about mammalian and DSPs, and we advocate the use of the genetically tractable amoeba to further study the role of DSPs in cell and infection biology. Particular emphasis is put on the virulence mechanisms of the facultative intracellular bacterium .
PubMed: 34746129
DOI: 10.3389/fcell.2021.731964 -
Frontiers in Cellular and Infection... 2023
Topics: Animals; Communicable Diseases; Disease Models, Animal
PubMed: 37389208
DOI: 10.3389/fcimb.2023.1225129 -
Frontiers in Cell and Developmental... 2021For decades, the social amoeba has been an invaluable tool for dissecting the biology of eukaryotic cells. Its short growth cycle and genetic tractability make it ideal... (Review)
Review
For decades, the social amoeba has been an invaluable tool for dissecting the biology of eukaryotic cells. Its short growth cycle and genetic tractability make it ideal for a variety of biochemical, cell biological, and biophysical assays. Dictyostelium have been widely used as a model of eukaryotic cell motility because the signaling and mechanical networks which they use to steer and produce forward motion are highly conserved. Because these migration networks consist of hundreds of interconnected proteins, perturbing individual molecules can have subtle effects or alter cell morphology and signaling in major unpredictable ways. Therefore, to fully understand this network, we must be able to quantitatively assess the consequences of abrupt modifications. This ability will allow us better control cell migration, which is critical for development and disease, . Here, we review recent advances in imaging, synthetic biology, and computational analysis which enable researchers to tune the activity of individual molecules in single living cells and precisely measure the effects on cellular motility and signaling. We also provide practical advice and resources to assist in applying these approaches in .
PubMed: 34676215
DOI: 10.3389/fcell.2021.740205 -
Frontiers in Cell and Developmental... 2021Chemotaxis describes directional motility along ambient chemical gradients and has important roles in human physiology and pathology. Typical chemotactic cells, such as... (Review)
Review
Chemotaxis describes directional motility along ambient chemical gradients and has important roles in human physiology and pathology. Typical chemotactic cells, such as neutrophils and cells, can detect spatial differences in chemical gradients over a background concentration of a 10 scale. Studies of cells have elucidated the molecular mechanisms of gradient sensing involving G protein coupled receptor (GPCR) signaling. GPCR transduces spatial information through its cognate heterotrimeric G protein as a guanine nucleotide change factor (GEF). More recently, studies have revealed unconventional regulation of heterotrimeric G protein in the gradient sensing. In this review, we explain how multiple mechanisms of GPCR signaling ensure the broad range sensing of chemical gradients in cells as a model for eukaryotic chemotaxis.
PubMed: 34414196
DOI: 10.3389/fcell.2021.724797 -
Molecular and Cellular Biochemistry Jul 2019Caffeine is commonly used in Dictyostelium to inhibit the synthesis of the chemoattractant cAMP and, therefore, its secretion and the autocrine stimulation of cells, in...
Caffeine is commonly used in Dictyostelium to inhibit the synthesis of the chemoattractant cAMP and, therefore, its secretion and the autocrine stimulation of cells, in order to prevent its interference with the study of chemoattractant-induced responses. However, the mechanism through which caffeine inhibits cAMP synthesis in Dictyostelium has not been characterized. Here, we report the effects of caffeine on the cAMP chemoattractant signaling network. We found that caffeine inhibits phosphatidylinositol 3-kinase (PI3K) and mechanistic target of rapamycin complex 2 (mTORC2). Both PI3K and mTORC2 are essential for the chemoattractant-stimulated cAMP production, thereby providing a mechanism for the caffeine-mediated inhibition of cAMP synthesis. Our results also reveal that caffeine treatment of cells leads to an increase in cAMP-induced RasG and Rap1 activation, and inhibition of the PKA, cGMP, MyoII, and ERK1 responses. Finally, we observed that caffeine has opposite effects on F-actin and ERK2 depending on the assay and Dictyostelium strain used, respectively. Altogether, our findings reveal that caffeine considerably affects the cAMP-induced chemotactic signaling pathways in Dictyostelium, most likely acting through multiple targets that include PI3K and mTORC2.
Topics: Caffeine; Chemotaxis; Cyclic AMP; Dictyostelium; Mechanistic Target of Rapamycin Complex 2; Phosphatidylinositol 3-Kinases; Protozoan Proteins; Second Messenger Systems
PubMed: 30879206
DOI: 10.1007/s11010-019-03520-z -
Interactome and evolutionary conservation of Dictyostelid small GTPases and their direct regulators.Small GTPases Jan 2022GTP binding proteins known as small GTPases make up one of the largest groups of regulatory proteins and control almost all functions of living cells. Their activity is...
GTP binding proteins known as small GTPases make up one of the largest groups of regulatory proteins and control almost all functions of living cells. Their activity is under, respectively, positive and negative regulation by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), which together with their upstream regulators and the downstream targets of the small GTPases form formidable signalling networks. While genomics has revealed the large size of the GTPase, GEF and GAP repertoires, only a small fraction of their interactions and functions have yet been experimentally explored. Dictyostelid social amoebas have been particularly useful in unravelling the roles of many proteins in the Rac-Rho and Ras-Rap families of GTPases in directional cell migration and regulation of the actin cytoskeleton. Genomes and cell-type specific and developmental transcriptomes are available for species that span the 0.5 billion years of evolution of the group from their unicellular ancestors. In this work, we identified all GTPases, GEFs and GAPs from genomes representative of the four major taxon groups and investigated their phylogenetic relationships and evolutionary conservation and changes in their functional domain architecture and in their developmental and cell-type specific expression. We performed a hierarchical cluster analysis of the expression profiles of the ~2000 analysed genes to identify putative interacting sets of GTPases, GEFs and GAPs, which highlight sets known to interact experimentally and many novel combinations. This work represents a valuable resource for research into all fields of cellular regulation.
Topics: Dictyostelium; GTPase-Activating Proteins; Guanine Nucleotide Exchange Factors; Monomeric GTP-Binding Proteins; Phylogeny
PubMed: 34565293
DOI: 10.1080/21541248.2021.1984829 -
Cells Apr 2020Wound repair of cell membrane is a vital physiological phenomenon. We examined wound repair in cells by using a laserporation, which we recently invented. We examined... (Review)
Review
Wound repair of cell membrane is a vital physiological phenomenon. We examined wound repair in cells by using a laserporation, which we recently invented. We examined the influx of fluorescent dyes from the external medium and monitored the cytosolic Ca after wounding. The influx of Ca through the wound pore was essential for wound repair. Annexin and ESCRT components accumulated at the wound site upon wounding as previously described in animal cells, but these were not essential for wound repair in cells. We discovered that calmodulin accumulated at the wound site upon wounding, which was essential for wound repair. The membrane accumulated at the wound site to plug the wound pore by two-steps, depending on Ca influx and calmodulin. From several lines of evidence, the membrane plug was derived from de novo generated vesicles at the wound site. Actin filaments also accumulated at the wound site, depending on Ca influx and calmodulin. Actin accumulation was essential for wound repair, but microtubules were not essential. A molecular mechanism of wound repair will be discussed.
Topics: Animals; Calcium; Calmodulin; Cell Membrane; Dictyostelium; Endosomal Sorting Complexes Required for Transport; Humans; Wound Healing
PubMed: 32340342
DOI: 10.3390/cells9041058 -
Journal of Cell Science Jun 2022Capping protein Arp2/3 myosin I linker (CARMIL) proteins are multi-domain scaffold proteins that regulate actin dynamics by regulating the activity of capping protein...
Capping protein Arp2/3 myosin I linker (CARMIL) proteins are multi-domain scaffold proteins that regulate actin dynamics by regulating the activity of capping protein (CP). Here, we characterize CARMIL-GAP (GAP for GTPase-activating protein), a Dictyostelium CARMIL isoform that contains a ∼130 residue insert that, by homology, confers GTPase-activating properties for Rho-related GTPases. Consistent with this idea, this GAP domain binds Dictyostelium Rac1a and accelerates its rate of GTP hydrolysis. CARMIL-GAP concentrates with F-actin in phagocytic cups and at the leading edge of chemotaxing cells, and CARMIL-GAP-null cells exhibit pronounced defects in phagocytosis and chemotactic streaming. Importantly, these defects are fully rescued by expressing GFP-tagged CARMIL-GAP in CARMIL-GAP-null cells. Finally, rescue with versions of CARMIL-GAP that lack either GAP activity or the ability to regulate CP show that, although both activities contribute significantly to CARMIL-GAP function, the GAP activity plays the bigger role. Together, our results add to the growing evidence that CARMIL proteins influence actin dynamics by regulating signaling molecules as well as CP, and that the continuous cycling of the nucleotide state of Rho GTPases is often required to drive Rho-dependent biological processes.
Topics: Actin Capping Proteins; Actin Cytoskeleton; Actins; Carrier Proteins; Dictyostelium; GTPase-Activating Proteins; Microfilament Proteins
PubMed: 35583107
DOI: 10.1242/jcs.258704 -
Nucleus (Austin, Tex.) Dec 2022Dictyostelium amoebae perform a semi-closed mitosis, in which the nuclear envelope is fenestrated at the insertion sites of the mitotic centrosomes and around the...
Dictyostelium amoebae perform a semi-closed mitosis, in which the nuclear envelope is fenestrated at the insertion sites of the mitotic centrosomes and around the central spindle during karyokinesis. During late telophase the centrosome relocates to the cytoplasmic side of the nucleus, the central spindle disassembles and the nuclear fenestrae become closed. Our data indicate that Dictyostelium spastin (DdSpastin) is a microtubule-binding and severing type I membrane protein that plays a role in this process. Its mitotic localization is in agreement with a requirement for the removal of microtubules that would hinder closure of the fenestrae. Furthermore, DdSpastin interacts with the HeH/ LEM-family protein Src1 in BioID analyses as well as the inner nuclear membrane protein Sun1, and shows subcellular co-localizations with Src1, Sun1, the ESCRT component CHMP7 and the IST1-like protein filactin, suggesting that the principal pathway of mitotic nuclear envelope remodeling is conserved between animals and Dictyostelium amoebae.
Topics: Animals; Cell Nucleus Division; Dictyostelium; Mitosis; Nuclear Envelope; Spastin
PubMed: 35298348
DOI: 10.1080/19491034.2022.2047289 -
Seminars in Cell & Developmental Biology May 2023While the field of synthetic developmental biology has traditionally focused on the study of the rich developmental processes seen in metazoan systems, an attractive... (Review)
Review
While the field of synthetic developmental biology has traditionally focused on the study of the rich developmental processes seen in metazoan systems, an attractive alternate source of inspiration comes from microbial developmental models. Microbes face unique lifestyle challenges when forming emergent multicellular collectives. As a result, the solutions they employ can inspire the design of novel multicellular systems. In this review, we dissect the strategies employed in multicellular development by two model microbial systems: the cellular slime mold Dictyostelium discoideum and the biofilm-forming bacterium Bacillus subtilis. Both microbes face similar challenges but often have different solutions, both from metazoan systems and from each other, to create emergent multicellularity. These challenges include assembling and sustaining a critical mass of participating individuals to support development, regulating entry into development, and assigning cell fates. The mechanisms these microbial systems exploit to robustly coordinate development under a wide range of conditions offer inspiration for a new toolbox of solutions to the synthetic development community. Additionally, recreating these phenomena synthetically offers a pathway to understanding the key principles underlying how these behaviors are coordinated naturally.
Topics: Humans; Animals; Dictyostelium; Models, Biological
PubMed: 35537929
DOI: 10.1016/j.semcdb.2022.04.014