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Role of NAV3 in glioblastoma cells invasiveness
Legátová, Anna ; Brábek, Jan (advisor) ; Libusová, Lenka (referee)
The invasion of tumor cells from the primary lesion and the formation of metastases are the main reasons for the severe impact of cancer diseases. An option for dealing with this poor impact is the development of drugs (so-called migrastatics) that would target these processes and thus limit the spread of tumor cells from the site of the primary tumor. However, to develop such drugs, it is essential to clarify the molecular mechanisms that control or promote cell migration. One of the possible strategies for migrastatics development is the targeting of cytoskeletal structures, which play an indispensable role in cell migration. This work is focused on Neuron navigator 3 (NAV3), a protein that binds to + ends of microtubules (MTs), participates in their stabilization, and is able to mediate crosstalk between MTs and the actin network. The function of NAV3 is important for directing MTs into growing axons and proper neurite outgrowth, which is necessary for brain development. The results of this thesis suggest that NAV3 could act as a pro-tumor factor, which localizes not only to the + ends of MTs, but also to the cell protrusions, and whose presence supports the cell expansion and increases the invasive potential of glioblastoma cell lines. Key words: neuron navigator 3, microtubules, cancer,...
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Intermediate filament proteins of Preaxostyla flagellates
Švagr, Ezra ; Hampl, Vladimír (advisor) ; Varga, Vladimír (referee)
5 Abstract Monocercomonoides exilis and Paratrimastix pyriformis are protists from within the group Preaxostyla (Metamonada), they possess an excavate morphology that is presumed to be an ancestral cytoskeletal organisation of eukaryotic cells. A significant part of eukaryotic but specifically excavate morphology is fibers composed of unidentified proteins. The hypothesis on which this thesis builds upon is that these fibers are composed of Intermediate Filament proteins (IF proteins). IF proteins are a polyphyletic group of proteins involved in the assembly of mechano-elastically important fibers in eukaryotes. The most widespread group of these proteins is a family called SF-assemblins, homologues of which were identified first in Chlamydomonas reinhardii, and giardins a protein family first discovered in Giardia intestinalis, which were also found to be related to this group. Nested into the bigger hypothesis is an idea, that SF-assemblins are present in M. exilis and P. pyriformis, further strengthening their position as a universally present eukaryotic feature. The goal of this work was to find support for the morphological hypothesis that LECA possessed an excavate morphology in protein composition of the cytoskeleton. Two approaches were employed. First, identifying proteins in cytoskeletal fraction...
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Cytoskeletal orchestration of early mammalian development
Novotný, Jan ; Libusová, Lenka (advisor) ; Mašek, Jan (referee)
Structures of the cytoskeleton play a critical role in early mammalian development. Microtubules, intermediate filaments and actin microfilaments provide structural and mechanical basis for major developmental transitions of preimplantation development. Microvilli supported by bundles of actin filaments become restricted to one pole of the blastomere during the process of polarisation. All components of the cytoskeleton network undergo apparent reorganisation in embryo compaction. Cells flatten and adhere to each other thanks to the formation of cytoskeleton-linked intercellular junctions and oscillatory contractions generated by actomyosin complexes. Filopodia, actin based protrusions, are debated for their potential role in blastomere apposition and cell signalling. The first process of cell line specification in mammalian development is that which defines outer cells of morula as presumptive trophectoderm and inner cells as presumptive inner cell mass. Proteins and structures of cytoskeleton are asymmetrically distributed between these two populations helping to determine the fate of each blastomere. The aim of the thesis is to summarise the roles of cytoskeleton in blastomere polarisation, embryo compaction and specification of inner and outer cell populations in mammalian preimplantation...
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Characterization of Euglena gracilis and their role in metaboly movement
Šmída, Adam ; Hampl, Vladimír (advisor) ; Pergner, Jiří (referee)
Euglena gracilis is a free-living freshwater flagellate from the class Euglenida (Euglenozoa, Discoba, Excavata). The synapomorphy of Euglenida group is their pellicle, a firm layer underneath the surface of the cell which is composed of proteinaceous stripes (pellicle strips). The strips are locked into each other and run along the cell`s surface underneath the plasma membrane. In E. gracilis these strips can move by parallel sliding, therefore contracting the cell and changing its surface which results in a characteristic peristaltic euglenoid movement called metaboly. The mechanism behind this movement is still unresolved, however, it is expected that the force is generated by the cytoskeletal structures beneath the pellicle strips which consist of microtubules and other unknown cytoskeletal fibers. This thesis tests a hypothesis which proposes that centrins are involved in the pellicle contraction. Centrins are small proteins capable of binding calcium ions, they are very conserved throughout the eukaryotic tree and serve many purposes in the cell, of which one is to form contractile structures in ciliates species e.g., Vorticella or Paramecium. Sequences of centrins were searched for in the transcriptome of E. gracilis and after comparison with the available proteomic dataset of the isolated...
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Cellular determinants of the distribution of PIN auxin transporters in the plasma membrane
Stelate, Ayoub ; Petrášek, Jan (advisor) ; Mravec, Jozef (referee) ; Nodzynski, Tomasz (referee)
Asymmetric localization of auxin carriers has always attracted the attention of many scientists around the world. However, to address this topic while focusing on the plasma membrane (PM), requires advanced microscopy techniques and knowledge of biophysics and biology. This doctoral work bridges the two disciplines to contribute to our understanding of the dynamics and distribution of PIN-FORMED auxin carriers from tobacco (NtPINs) within the PM. I have developed a novel correlative light electron microscopy (CLEM) method using total internal reflection fluorescence microscopy (TIRFM) and advanced environmental scanning electron microscopy (A-ESEM). To my knowledge, this is the first effort to achieve a correlation between immunofluorescence and electron microscopy imaging of plant integral PM proteins. As I have shown, individual NtPINs are organized differently within the PM. Dynamic analyses that quantify individual nanodomains' diffusion rates allowed me to show that NtPINs have constraints behavior with different diffusion rates. I have investigated the role of the cell wall and cytoskeleton in the organization and dynamics of NtPINs. Using pharmacological treatments, I have shown that they differentially affect the mobility and organization of NtPINs within the PM. Complete removal of the...
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The mechanism of impaired formation of head-tail coupling apparatus in centrobin deficient acephalic spermatozoa
Vlčková, Monika ; Frolíková, Michaela (advisor) ; Krejčová, Tereza (referee)
Acephalic sperm syndrome (ASS) is a rare form of teratozoospermia that is probably genetic in origin. The sperm of individuals with this syndrome have a damaged apparatus connecting the head and flagellum (HTCA), which leads to the formation of acephalic sperm, i.e. sperm with separate heads from flagella. Individuals affected by ASS are almost exclusively infertile. One of the proteins whose mutation causes ASS is SUN5. Together with KASH proteins, SUN proteins are part of the so-called LINC complex, which ensures the connection of the nucleoskeleton with the cytoskeleton. Centrobin is a protein involved in centriole duplication and assembly of the dividing spindle. Rats carrying a defective gene for centrobin have reduced fertility and exhibit an ASS phenotype. For that reason, this model organism was used in this work to study the possible interrelationships of proteins involved in the formation of ASS. Given the similar phenotype of centrobin and SUN5 mutated spermatozoa, there is a possibility that centrobin interacts with one of the LINC complex proteins and together they participate in the formation of the head-flagella junction. Sperm from rats with a defective centrobin gene also show significant damage to the flagella. Decreased Odf1 protein expression has previously been reported in ASS...
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The role of actin cytoskeleton in the targeting of auxin carriers to the plasma membrane.
Kebrlová, Štěpánka ; Petrášek, Jan (advisor) ; Pernisová, Markéta (referee)
Auxin plays an important morphogenic role in plant development, mainly through its effect on gene expression, but also through a number of faster processes that are directly dependent on its concentration. Therefore, in many plant tissues, directional auxin transport using specific transporters in the plasma membrane, is important for the coordination of morphogenic stimuli. The amount of auxin carriers in the plasma membrane directly affects the resulting auxin concentration inside the cell. Although the localization of auxin transporters and their abundance in the plasma membrane could be determined primarily by the actin cytoskeleton and its involvement in vesicle transport processes, this relationship is currently still unclear. Therefore, in this study, we were interested in how the localization and function of auxin transporters is affected when the function of the actin cytoskeleton is affected in a given cell type. To this end, the localization of the auxin transporters PIN3, PIN4, PIN7, and AUX1 was studied in epidermal cells of cotyledons in young seedlings of Arabidopsis thaliana whose morphogenesis was affected by mutations in subunits of the actin nucleation complex ARP2/3. Crosses of mutants in the ARP2/3 complex subunits with marker lines carrying fluorescently labeled auxin carriers...
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Roles of tubulin post-translational modifications in regulation of microtubule-based processes
Šliková, Pavlína ; Novák, Petr (advisor) ; Libusová, Lenka (referee)
Microtubular cytoskeleton plays crucial roles during diverse cellular processes, such as intracellular transport, cell motility and chromosome segregation during cytokinesis. Tubulin, the building block of microtubules, undergoes numerous post-translational modifications which affect microtubular dynamics and organization as well as their interaction with associated proteins. Understanding the role post-translational modifications play in the diversification of functions and properties of microtubules is key for our comprehension of the dynamics of the complex microtubule cytoskeleton. However, mechanisms behind the effect of post-translational modifications on microtubule cytoskeleton are not fully understood. In this work, we focus on the influence of post-translational modifications on microtubule polymerization and interaction with molecular motor kinesin-1. Using total internal fluorescence and interference reflection microscopy techniques, we here show that high levels of post-translational modifications on microtubules decrease the time of microtubule-kinesin interaction whereas binding affinity and median velocity are not significantly different on modified and unmodified microtubules. Further, we show that the absence of polyglutamylation on tubulin isotypes leads to a faster microtubule...
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Mechanisms of symmetry breaking during embryogenesis
Ždímalová, Michaela ; Lánský, Zdeněk (advisor) ; Búran, Peter (referee)
Left-right symmetry breaking is crucial for correct body development of many organisms, including humans. The fact that the left-right asymmetry is established consistently in all healthy individuals of given species fascinates researchers for a long time. Although several models offering a mechanistic insight to this phenomenon were proposed or already accepted, they lack a sufficient molecular description or do not explain all cases. A model of acto-myosin flows - intracellular counter-rotating flows driven by an active torque generation in acto-myosin cortex - leading to the left-right symmetry breaking during embryogenesis is a topic of particular interest in current research. This thesis introduces the problematics of acto-myosin flows in a context of the previous research related to the left-right symmetry breaking. Since the left-right asymmetry is tightly associated with chirality at different scales, this thesis also discusses the current knowledge about possible processes of propagating chirality of molecules to the larger scale. 1
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Non-neuronal cell outgrowth in Caenorhabditis elegans model system
Smidžárová, Lucie ; Macůrková, Marie (advisor) ; Strouhalová, Kateřina (referee)
1 Abstract Oriented cell growth is an important process for regular tissue development, in which regulated changes in cell shapes occur. An important role in this mechanism is played by remodelling of cytoskeletal elements in the growing parts of the cell, which is regulated by many extracellular and intracellular factors. This bachelor's thesis is focused on oriented non-neuronal cells growth in the model organism Caenorhabditis elegans, specifically the growth of the excretory cell and the anchor cell invasion. The growth mechanism of the excretory canal cell is in many aspects similar to growth of neurons, however it also involves a unique mechanism of growth through extension of an intracellular lumen. In case of the anchor cell the growth mechanisms support the basement membrane disruption and invasive behavior reminiscent of metastatic cancer cells. Regulation of growth of these two cells thus could serve as a good model for human pathologies such as cystic kidney disease or cancer cell metastasis, and therefore further study in this area could lead to new insights into these diseases. At the end of the thesis, other non- neuronal cells with oriented growth in the model organism C.elegans are briefly described. Key words: cell outgrowth, excretory canal cell, anchor cell, signalling, cytoskeleton
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