-
MBio Apr 2022Interorganellar cross talk is often mediated by membrane contact sites (MCSs), which are zones where participating membranes come within 30 nm of one another. MCSs...
Interorganellar cross talk is often mediated by membrane contact sites (MCSs), which are zones where participating membranes come within 30 nm of one another. MCSs have been found in organelles, including the endoplasmic reticulum, Golgi bodies, endosomes, and mitochondria. Despite its seeming ubiquity, reports of MCS involving mitochondrion-related organelles (MROs) present in a few anaerobic parasitic protozoa remain lacking. Entamoeba histolytica, the etiological agent of amoebiasis, possesses an MRO called the mitosome. We previously discovered several -specific transmembrane mitosomal proteins (ETMPs) from and cell-biological analyses. One of them, ETMP1 (EHI_175060), was predicted to have one transmembrane domain and two coiled-coil regions and was demonstrated to be mitosome membrane integrated based on carbonate fractionation and immunoelectron microscopy (IEM) data. Immunoprecipitation analysis detected a candidate interacting partner, EH domain-containing protein (EHD1; EHI_105270). We expressed hemagglutinin (HA)-tagged EHD1 in E. histolytica, and subsequent immunofluorescence and IEM data indicated an unprecedented MCS between the mitosome and the endosome. Live imaging of a green fluorescent protein (GFP)-EHD1-expressing strain demonstrated that EHD1 is involved in early endosome formation and is observed in MCS between endosomes of various sizes. assays using recombinant His-EHD1 demonstrated ATPase activity. MCSs are involved in lipid transfer, ion homeostasis, and organelle dynamics. The serendipitous discovery of the ETMP1-interacting partner EHD1 led to the observation of the mitosome-endosome contact site in E. histolytica. It opened a new view of how the relic mitochondria of may likewise be involved in organelle cross talk, a conserved feature of mitochondria and other organelles in general. Membrane contact sites (MCSs) are key regulators of interorganellar communication and have been widely demonstrated between various organelles. However, studies on MCSs involving mitochondrion-related organelles (MROs), present in some anaerobic parasitic protozoans, remain scarce. Entamoeba histolytica, the etiological agent of amoebiasis, possesses an MRO called the mitosome. This organelle is crucial for cellular differentiation and disease transmission, thereby significantly contributing to the amoeba's parasitic lifestyle. Our recent discovery of the interaction between the -specific transmembrane mitosomal protein (ETMP1) and EH domain-containing protein (EHD1) showcases a newly found mitosome-endosome contact site in E. histolytica. This finding reflects the idea that despite their substantially divergent and reduced nature, MROs like mitosomes conserve mechanisms for interorganellar cross talk. We posit lipid and ion transport, mitosome fission, and quality control as potential processes that are mediated by the ETMP1-EHD1-tethered mitosome-endosome contact site in E. histolytica.
Topics: Amebiasis; Endosomes; Entamoeba; Entamoeba histolytica; Humans; Lipids; Membrane Proteins; Mitochondria; Vesicular Transport Proteins
PubMed: 35404118
DOI: 10.1128/mbio.03849-21 -
Biophysical Journal Dec 2022Cell shape change processes, such as proliferation, polarization, migration, and cancer metastasis, rely on a dynamic network of macromolecules. The proper function of...
Cell shape change processes, such as proliferation, polarization, migration, and cancer metastasis, rely on a dynamic network of macromolecules. The proper function of this network enables mechanosensation, the ability of cells to sense and respond to mechanical cues. Myosin II and cortexillin I, critical elements of the cellular mechanosensory machinery, preassemble in the cytoplasm of Dictyostelium cells into complexes that we have termed contractility kits (CKs). Two IQGAP proteins then differentially regulate the mechanoresponsiveness of the cortexillin I-myosin II elements within CKs. To investigate the mechanism of CK self-assembly and gain insight into possible molecular means for IQGAP regulation, we developed a coarse-grained excluded volume molecular model in which all protein polymers are represented by nm-sized spheres connected by spring-like links. The model is parameterized using experimentally measured parameters acquired through fluorescence cross-correlation spectroscopy and fluorescence correlation spectroscopy, which describe the interaction affinities and diffusion coefficients for individual molecular components, and which have also been validated via several orthogonal methods. Simulations of wild-type and null-mutant conditions implied that the temporal order of assembly of these kits is dominated by myosin II dimer formation and that IQGAP proteins mediate cluster growth. In addition, our simulations predicted the existence of "ambiguous" CKs that incorporate both classes of IQGAPs, and we confirmed this experimentally using fluorescence cross-correlation spectroscopy. The model serves to describe the formation of the CKs and how their assembly enables and regulates mechanosensation at the molecular level.
Topics: Dictyostelium
PubMed: 36273263
DOI: 10.1016/j.bpj.2022.10.031 -
Genes Mar 2021Multicellularity evolved repeatedly in the history of life, but how it unfolded varies greatly between different lineages. Dictyostelid social amoebas offer a good... (Comparative Study)
Comparative Study Review
Multicellularity evolved repeatedly in the history of life, but how it unfolded varies greatly between different lineages. Dictyostelid social amoebas offer a good system to study the evolution of multicellular complexity, with a well-resolved phylogeny and molecular genetic tools being available. We compare the life cycles of the Dictyostelids with closely related amoebozoans to show that complex life cycles were already present in the unicellular common ancestor of Dictyostelids. We propose frost resistance as an early driver of multicellular evolution in Dictyostelids and show that the cell signalling pathways for differentiating spore and stalk cells evolved from that for encystation. The stalk cell differentiation program was further modified, possibly through gene duplication, to evolve a new cell type, cup cells, in Group 4 Dictyostelids. Studies in various multicellular organisms, including Dictyostelids, volvocine algae, and metazoans, suggest as a common principle in the evolution of multicellular complexity that unicellular regulatory programs for adapting to environmental change serve as "proto-cell types" for subsequent evolution of multicellular organisms. Later, new cell types could further evolve by duplicating and diversifying the "proto-cell type" gene regulatory networks.
Topics: Amoeba; Biological Evolution; Cold Temperature; Dictyostelium; Evolution, Molecular; Life Cycle Stages; Phylogeny; Signal Transduction; Stress, Physiological
PubMed: 33801615
DOI: 10.3390/genes12040487 -
The EMBO Journal Dec 2023Motile cells encounter microenvironments with locally heterogeneous mechanochemical composition. Individual compositional parameters, such as chemokines and...
Motile cells encounter microenvironments with locally heterogeneous mechanochemical composition. Individual compositional parameters, such as chemokines and extracellular matrix pore sizes, are well known to provide guidance cues for pathfinding. However, motile cells face diverse cues at the same time, raising the question of how they respond to multiple and potentially competing signals on their paths. Here, we reveal that amoeboid cells require nuclear repositioning, termed nucleokinesis, for adaptive pathfinding in heterogeneous mechanochemical micro-environments. Using mammalian immune cells and the amoeba Dictyostelium discoideum, we discover that frequent, rapid and long-distance nucleokinesis is a basic component of amoeboid pathfinding, enabling cells to reorientate quickly between locally competing cues. Amoeboid nucleokinesis comprises a two-step polarity switch and is driven by myosin-II forces that readjust the nuclear to the cellular path. Impaired nucleokinesis distorts path adaptions and causes cellular arrest in the microenvironment. Our findings establish that nucleokinesis is required for amoeboid cell navigation. Given that many immune cells, amoebae, and some cancer cells utilize an amoeboid migration strategy, these results suggest that nucleokinesis underlies cellular navigation during unicellular biology, immunity, and disease.
Topics: Animals; Cell Movement; Dictyostelium; Amoeba; Extracellular Matrix; Mammals
PubMed: 37987147
DOI: 10.15252/embj.2023114557 -
Viruses Feb 2023One quarter of the Northern hemisphere is underlain by permanently frozen ground, referred to as permafrost. Due to climate warming, irreversibly thawing permafrost is...
One quarter of the Northern hemisphere is underlain by permanently frozen ground, referred to as permafrost. Due to climate warming, irreversibly thawing permafrost is releasing organic matter frozen for up to a million years, most of which decomposes into carbon dioxide and methane, further enhancing the greenhouse effect. Part of this organic matter also consists of revived cellular microbes (prokaryotes, unicellular eukaryotes) as well as viruses that have remained dormant since prehistorical times. While the literature abounds on descriptions of the rich and diverse prokaryotic microbiomes found in permafrost, no additional report about "live" viruses have been published since the two original studies describing pithovirus (in 2014) and mollivirus (in 2015). This wrongly suggests that such occurrences are rare and that "zombie viruses" are not a public health threat. To restore an appreciation closer to reality, we report the preliminary characterizations of 13 new viruses isolated from seven different ancient Siberian permafrost samples, one from the Lena river and one from Kamchatka cryosol. As expected from the host specificity imposed by our protocol, these viruses belong to five different clades infecting spp. but not previously revived from permafrost: Pandoravirus, Cedratvirus, Megavirus, and Pacmanvirus, in addition to a new Pithovirus strain.
Topics: Eukaryota; Permafrost; Eukaryotic Cells; Acanthamoeba; Carbon Dioxide
PubMed: 36851778
DOI: 10.3390/v15020564 -
PloS One 2022Free-living amoebae (FLA) are gaining attention due to the increasing number of related grave central nervous system (CNS) and sight-threatening eye infections and their...
Isolation and morphological and molecular characterization of waterborne free-living amoebae: Evidence of potentially pathogenic Acanthamoeba and Vahlkampfiidae in Assiut, Upper Egypt.
Free-living amoebae (FLA) are gaining attention due to the increasing number of related grave central nervous system (CNS) and sight-threatening eye infections and their role as Trojan horses for many bacteria and viruses. This study was conducted in Assiut City, Egypt to detect the presence of FLA in different water sources using morphological and molecular approaches and determine their potential pathogenicity. A total of 188 water samples (100 tap, 80 tank, and 8 swimming pool samples) were collected, cultivated on non-nutrient agar seeded with Escherichia coli, and inspected for FLA. Thermo- and osmo-tolerance assays were performed to determine their pathogenicity. Polymerase chain reaction and sequence analysis were performed to confirm the identification and analyze the genotype. Overall, 52 samples (27.7%) were positive for FLA. Of these, 20.7% were identified as Acanthamoeba, 1.6% as Vahlkampfiidae, and 5.3% as mixed Acanthamoeba and Vahlkampfiidae. Seven species of Acanthamoeba were recognized, of which A. triangularis, A. polyphaga, A. lenticulata, and A. culbertsoni are thermo- and osmo-tolerant, and A. astronyxis, A. comandoni, and A. echinulata are non-thermo- and non-osmo-tolerant. The phylogeny analysis revealed T4 and T7 genotypes. Among Vahlkampfiids, 61.5% were identified as thermo- and osmo-tolerant Vahlkampfia, and 30.8% were identified as non-pathogenic Naegleria. One isolate (7.7%) was identified as potentially pathogenic Allovahlkampfia, as confirmed by sequencing. This is the first report documenting the occurrence and phylogeny of waterborne FLA (Acanthamoeba/Vahlkampfiidae) in Assiut, Egypt. The presence of potentially pathogenic FLA highlights the possible health hazards and the need for preventive measures.
Topics: Acanthamoeba; Amoeba; Egypt; Naegleria; Water
PubMed: 35802617
DOI: 10.1371/journal.pone.0267591 -
Trends in Microbiology May 2024Metals and metalloids are used as weapons for predatory feeding by unicellular eukaryotes on prokaryotes. This review emphasizes the role of metal(loid) bioavailability... (Review)
Review
Metals and metalloids are used as weapons for predatory feeding by unicellular eukaryotes on prokaryotes. This review emphasizes the role of metal(loid) bioavailability over the course of Earth's history, coupled with eukaryogenesis and the evolution of the mitochondrion to trace the emergence and use of the metal(loid) prey-killing phagosome as a feeding strategy. Members of the genera Acanthamoeba and Dictyostelium use metals such as zinc (Zn) and copper (Cu), and possibly metalloids, to kill their bacterial prey after phagocytosis. We provide a potential timeline on when these capacities first evolved and how they correlate with perceived changes in metal(loid) bioavailability through Earth's history. The origin of phagotrophic eukaryotes must have postdated the Great Oxidation Event (GOE) in agreement with redox-dependent modification of metal(loid) bioavailability for phagotrophic poisoning. However, this predatory mechanism is predicted to have evolved much later - closer to the origin of the multicellular metazoans and the evolutionary development of the immune systems.
Topics: Metals; Phagocytosis; Dictyostelium; Biological Evolution; Acanthamoeba; Animals; Phagosomes; Zinc; Metalloids; Copper; Biological Availability; Mitochondria
PubMed: 38103995
DOI: 10.1016/j.tim.2023.11.008 -
Journal of Cell Science Oct 2023Mitogen-activated protein kinases (MAPKs) have been the focus of many studies over the past several decades, but the understanding of one subgroup of MAPKs, orthologs of... (Review)
Review
Mitogen-activated protein kinases (MAPKs) have been the focus of many studies over the past several decades, but the understanding of one subgroup of MAPKs, orthologs of MAPK15, known as atypical MAPKs, has lagged behind others. In most organisms, specific activating signals or downstream responses of atypical MAPK signaling pathways have not yet been identified even though these MAPKs are associated with many eukaryotic processes, including cancer and embryonic development. In this Review, we discuss recent studies that are shedding new light on both the regulation and function of atypical MAPKs in different organisms. In particular, the analysis of the atypical MAPK in the amoeba Dictyostelium discoideum has revealed important roles in chemotactic responses and gene regulation. The rapid and transient phosphorylation of the atypical MAPK in these responses suggest a highly regulated activation mechanism in vivo despite the ability of atypical MAPKs to autophosphorylate in vitro. Atypical MAPK function can also impact the activation of other MAPKs in amoeba. These advances are providing new perspectives on possible MAPK roles in animals that have not been previously considered, and this might lead to the identification of potential targets for regulating cell movement in the treatment of diseases.
Topics: Animals; Amoeba; Dictyostelium; Phosphorylation; MAP Kinase Signaling System; Gene Expression Regulation; Mitogen-Activated Protein Kinase Kinases
PubMed: 37850857
DOI: 10.1242/jcs.261447 -
Mycologia 2023Based on a study of 255 collections from four continents and four floristic kingdoms, we describe 15 new species of the genus . The new species, all morphologically...
Based on a study of 255 collections from four continents and four floristic kingdoms, we describe 15 new species of the genus . The new species, all morphologically close to , and , differ from each other by the structure of the peridium and, in some cases, also by the color of the fresh spore mass and the ornamentation of the capillitium and spores. Species delimitation is confirmed by two independently inherited molecular markers, as well as previously performed tests of reproductive isolation and genetic distances. We studied authentic material of and and found fresh specimens of these species, which allowed us to obtain molecular barcodes and substantiate the separation of new species from these taxa. We propose to retain the name for the globally most abundant species, for which we provide a more precise description and a neotypification. Two formerly described species, and , we consider to be dubious. We do not recognize the species .
Topics: Microscopy, Electron, Scanning; Myxomycetes; Spores, Protozoan; Species Specificity; DNA, Protozoan; DNA Barcoding, Taxonomic
PubMed: 37224183
DOI: 10.1080/00275514.2023.2199109 -
Journal of Fish Diseases Jun 2021Paramoeba perurans causes amoebic gill disease (AGD), which is a major problem in aquaculture worldwide. The parasite can be cultured in vitro, but to this date, no...
Paramoeba perurans causes amoebic gill disease (AGD), which is a major problem in aquaculture worldwide. The parasite can be cultured in vitro, but to this date, no method for long-term storage of the clones exists. In this study, we describe a method for cryopreservation of Paramoeba perurans. The method was successfully employed on four out the five clones we tested. The thawing success rate, that is the percentage of successfully thawed vials relative to the total number of vials that were thawed, differed for the clones and ranged from 25% to 100%. The age of the clones seemed to have a negative impact on the ability to survive cryopreservation.
Topics: Amebiasis; Amoebozoa; Cryopreservation; Fish Diseases; Norway
PubMed: 33159703
DOI: 10.1111/jfd.13295