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Planta Mar 2023STD1 specifically interacts with MAP65-5 in rice and they cooperatively control microtubule bundles in phragmoplast expansion during cell division. Microtubules play...
STD1 specifically interacts with MAP65-5 in rice and they cooperatively control microtubule bundles in phragmoplast expansion during cell division. Microtubules play critical roles during the cell cycle progression in the plant cell. We previously reported that STEMLESS DWARF 1 (STD1), a kinesin-related protein, was localized specifically to the phragmoplast midzone during telophase to regulate the lateral expansion of phragmoplast in rice (Oryza sativa). However, how STD1 regulates microtubule organization remains unknown. Here, we found that STD1 interacted directly with MAP65-5, a member of the microtubule-associated proteins (MAPs). Both STD1 and MAP65-5 could form homodimers and bundle microtubules individually. Compared with MAP65-5, the microtubules bundled by STD1 were disassembled completely into single microtubules after adding ATP. Conversely, the interaction of STD1 with MAP65-5 enhanced the microtubule bundling. These results suggest STD1 and MAP65-5 might cooperatively regulate microtubule organization in the phragmoplast at telophase.
Topics: Microtubule-Associated Proteins; Kinesins; Oryza; Microtubules; Mitosis
PubMed: 36862199
DOI: 10.1007/s00425-023-04106-2 -
Methods in Molecular Biology (Clifton,... 2023Cross-linking of microtubules by microtubule-associated proteins (MAPs) results in the formation of microtubule bundles. It has been shown that a majority of...
Cross-linking of microtubules by microtubule-associated proteins (MAPs) results in the formation of microtubule bundles. It has been shown that a majority of microtubules in interphase plant cells are bundled. Bundling can contribute to maintaining structural stability and sustaining spatial organization of microtubule arrays. While bundling can be readily detected by an electron or fluorescent microscope, quantifying this activity remains technically challenging. Here we describe a method for quantifying microtubule-bundling in vitro using green and red stable microtubules. Furthermore, this method distinguishes between different types of microtubule-microtubule interactions: bundling, annealing, and branching. Our technique can be used to compare bundling activity of different MAPs and generate parameters for modeling their contribution to organization and dynamics of microtubule arrays.
Topics: Microtubule-Associated Proteins; Microscopy; Microtubules; Cytoskeleton
PubMed: 36773221
DOI: 10.1007/978-1-0716-2867-6_1 -
Software Impacts May 2021JACFC is a Java web application (http://neuronanobiophysics.utsa.edu/) that provides both experts and non-experts in the field suitable tools for elucidating the...
JACFC is a Java web application (http://neuronanobiophysics.utsa.edu/) that provides both experts and non-experts in the field suitable tools for elucidating the molecular mechanisms modulating the electrical signal propagation, stability, and bundle formation of microtubules and actin filaments under different molecular (wild type, isoforms, mutants) and environmental (physiological and pathological) conditions. This acknowledgment might reveal the potential role of cytoskeleton filaments in neuronal activities, including molecular-level processing of information and neural regeneration. Molecular understanding of the polyelectrolyte properties of bionanowires, is also crucial for development of reliability, highly functioning small devices with biotechnological applications such as bionanosensors and computing bionanoprocessors.
PubMed: 34109318
DOI: 10.1016/j.simpa.2021.100072 -
Nature Communications Jun 2023Cell division is spatiotemporally precisely regulated, but the underlying mechanisms are incompletely understood. In the social bacterium Myxococcus xanthus, the...
Cell division is spatiotemporally precisely regulated, but the underlying mechanisms are incompletely understood. In the social bacterium Myxococcus xanthus, the PomX/PomY/PomZ proteins form a single megadalton-sized complex that directly positions and stimulates cytokinetic ring formation by the tubulin homolog FtsZ. Here, we study the structure and mechanism of this complex in vitro and in vivo. We demonstrate that PomY forms liquid-like biomolecular condensates by phase separation, while PomX self-assembles into filaments generating a single large cellular structure. The PomX structure enriches PomY, thereby guaranteeing the formation of precisely one PomY condensate per cell through surface-assisted condensation. In vitro, PomY condensates selectively enrich FtsZ and nucleate GTP-dependent FtsZ polymerization and bundle FtsZ filaments, suggesting a cell division site positioning mechanism in which the single PomY condensate enriches FtsZ to guide FtsZ-ring formation and division. This mechanism shares features with microtubule nucleation by biomolecular condensates in eukaryotes, supporting this mechanism's ancient origin.
Topics: Tubulin; Biomolecular Condensates; Polymerization; Cell Division; Myxococcus xanthus
PubMed: 37380708
DOI: 10.1038/s41467-023-39513-2 -
Physical Review Letters Oct 2021In microtubule-based active nematics, motor-driven extensile motion of microtubule bundles powers chaotic large-scale dynamics. We quantify the interfilament sliding...
In microtubule-based active nematics, motor-driven extensile motion of microtubule bundles powers chaotic large-scale dynamics. We quantify the interfilament sliding motion both in isolated bundles and in a dense active nematic. The extension speed of an isolated microtubule pair is comparable to the molecular motor stepping speed. In contrast, the net extension in dense 2D active nematics is significantly slower; the interfilament sliding speeds are widely distributed about the average and the filaments exhibit both contractile and extensile relative motion. These measurements highlight the challenge of connecting the extension rate of isolated bundles to the multimotor and multifilament interactions present in a dense 2D active nematic. They also provide quantitative data that is essential for building multiscale models.
PubMed: 34652175
DOI: 10.1103/PhysRevLett.127.148001 -
Nano Letters Sep 2020In nature, interactions between biopolymers and motor proteins give rise to biologically essential emergent behaviors. Besides cytoskeleton mechanics, active nematics...
In nature, interactions between biopolymers and motor proteins give rise to biologically essential emergent behaviors. Besides cytoskeleton mechanics, active nematics arise from such interactions. Here we present a study on 3D active nematics made of microtubules, kinesin motors, and depleting agent. It shows a rich behavior evolving from a nematically ordered space-filling distribution of microtubule bundles toward a flattened and contracted 2D ribbon that undergoes a wrinkling instability and subsequently transitions into a 3D active turbulent state. The wrinkle wavelength is independent of the ATP concentration and our theoretical model describes its relation with the appearance time. We compare the experimental results with a numerical simulation that confirms the key role of kinesin motors in cross-linking and sliding the microtubules. Our results on the active contraction of the network and the independence of wrinkle wavelength on ATP concentration are important steps forward for the understanding of these 3D systems.
Topics: Computer Simulation; Kinesins; Microtubules
PubMed: 32786934
DOI: 10.1021/acs.nanolett.0c01546 -
FASEB Journal : Official Publication of... May 2023Age-related oocyte aneuploidy occurs as a result of chromosome segregation errors in female meiosis-I and meiosis-II, and is caused by a progressive age-related...
Age-related oocyte aneuploidy occurs as a result of chromosome segregation errors in female meiosis-I and meiosis-II, and is caused by a progressive age-related deterioration of the chromosome segregation machinery. Here, we assess the impact of age upon the kinetochore, the multi-protein structure that forms the link between the chromosome and spindle microtubules. We find that in meiosis-I the outer kinetochore assembles at germinal vesicle breakdown, but that a substantially smaller outer kinetochore is assembled in oocytes from aged mice. We show this correlates with a weaker centromere in aged oocytes and, using nuclear transfer approaches to generate young-aged hybrid oocytes, we show that outer kinetochore assembly always mirrors the status of the centromere, regardless of cytoplasmic age. Finally, we show that weaker kinetochores in aged oocytes are associated with thinner microtubule bundles, that are more likely to be mis-attached. We conclude that progressive loss of the centromere with advancing maternal age underpins a loss of the outer kinetochore in meiosis-I, which likely contributes to chromosome segregation fallibility in oocytes from older females.
Topics: Female; Animals; Mice; Kinetochores; Centromere; Oocytes; Meiosis; Microtubules; Aging; Chromosome Segregation; Spindle Apparatus
PubMed: 37078553
DOI: 10.1096/fj.202300062R -
Molecular and Biochemical Parasitology May 2020Trypanosomatids are a monophyletic group of parasitic flagellated protists belonging to the order Kinetoplastida. Their cytoskeleton is primarily made up of microtubules... (Review)
Review
Trypanosomatids are a monophyletic group of parasitic flagellated protists belonging to the order Kinetoplastida. Their cytoskeleton is primarily made up of microtubules in which no actin microfilaments have been detected. Although all these parasites contain actin, it is widely thought that their actin cytoskeleton is reduced when compared to most eukaryotic organisms. However, there is increasing evidence that it is more complex than previously thought. As in other eukaryotic organisms, trypanosomatids encode for a conventional actin that is expected to form microfilament-like structures, and for members of three conserved actin-related proteins probably involved in microfilament nucleation (ARP2, ARP3) and in gene expression regulation (ARP6). In addition to these canonical proteins, also encode for an expanded set of actins and actin-like proteins that seem to be restricted to kinetoplastids. Analysis of their amino acid sequences demonstrated that, although very diverse in primary sequence when compared to actins of model organisms, modelling of their tertiary structure predicted the presence of the actin fold in all of them. Experimental characterization has been done for only a few of the trypanosomatid actins and actin-binding proteins. The most studied is the conventional actin of Leishmania donovani (LdAct), which unusually requires both ATP and Mg for polymerization, unlike other conventional actins that do not require ATP. Additionally, polymerized LdAct tends to assemble in bundles rather than in single filaments. Regulation of actin polymerization depends on their interaction with actin-binding proteins. In trypanosomatids, there is a reduced but sufficient core of actin-binding proteins to promote microfilament nucleation, turnover and stabilization. There are also genes encoding for members of two families of myosin motor proteins, including one lineage-specific. Homologues to all identified actin-family proteins and actin-binding proteins of trypanosomatids are also present in Paratrypanosoma confusum (an early branching trypanosomatid) and in Bodo saltans (a closely related free-living organism belonging to the trypanosomatid sister order of Bodonida) suggesting they were all present in their common ancestor. Secondary losses of these genes may have occurred during speciation within the trypanosomatids, with salivarian trypanosomes having lost many of them and stercorarian trypanosomes retaining most.
Topics: Actin Cytoskeleton; Actins; Animals; Binding Sites; Gene Expression; Humans; Microfilament Proteins; Models, Molecular; Myosins; Phylogeny; Protein Binding; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Interaction Domains and Motifs; Protozoan Proteins; Trypanosomatina
PubMed: 32353561
DOI: 10.1016/j.molbiopara.2020.111278 -
Current Biology : CB Mar 2021The centrosome is the main organizer of microtubules and as such, its position is a key determinant of polarized cell functions. As the name says, the default position...
The centrosome is the main organizer of microtubules and as such, its position is a key determinant of polarized cell functions. As the name says, the default position of the centrosome is considered to be the cell geometrical center. However, the mechanism regulating centrosome positioning is still unclear and often confused with the mechanism regulating the position of the nucleus to which it is linked. Here, we used enucleated cells plated on adhesive micropatterns to impose regular and precise geometrical conditions to centrosome-microtubule networks. Although frequently observed there, the equilibrium position of the centrosome is not systematically at the cell geometrical center and can be close to cell edge. Centrosome positioning appears to respond accurately to the architecture and anisotropy of the actin network, which constitutes, rather than cell shape, the actual spatial boundary conditions the microtubule network is sensitive to. We found that the contraction of the actin network defines a peripheral margin in which microtubules appear bent by compressive forces. The progressive disassembly of the actin network at distance from the cell edges defines an inner zone where actin bundles were absent, where microtubules were more radially organized and where dynein concentration was higher. We further showed that the production of dynein-based forces on microtubules places the centrosome at the center of this zone. In conclusion, the spatial distribution of cell adhesion and the production of contractile forces define the architecture of the actin network with respect to which the centrosome-microtubule network is centered.
Topics: Actins; Centrosome; Dyneins; Microtubules; Myosins
PubMed: 33609453
DOI: 10.1016/j.cub.2021.01.002 -
Prilozi (Makedonska Akademija Na... Jul 2023The glomerulopathies associated with the deposition of extracellular fibrils in the glomeruli are subdivided into Congo red positive (amyloidosis) and Congo red negative...
The glomerulopathies associated with the deposition of extracellular fibrils in the glomeruli are subdivided into Congo red positive (amyloidosis) and Congo red negative (non-amyloidotic glomerulopathies) based on Congo red staining. The non-amyloidotic glomerulopathies are divided into immunoglobulin-derived and non-immunoglobulin-derived glomerulopathies. The immunoglobulin-derived glomerulopathies: fibrillary glomerulopathy (FGn) and immunotactoid glomerulopathy (ITG) are rare glomerulopathies. The diagnosis of fibrillary-immunotactoid glomerulopathy depends on electron microscopy, which shows the presence of microfibrils in the glomeruli. The microfibrils in FGn are randomly arranged with diameters less than 30 nm. The microfibrils in ITG are larger than 30 nm with a visible lumen (microtubules), focally arranged in parallel bundles. Patients with fibrillary-immunotactoid glomerulopathy present with proteinuria (usually in the nephrotic range), microscopic hematuria, arterial hypertension, and chronic kidney disease that progresses to kidney failure over months to years. Currently, there are no guidelines for the treatment of fibrillary-immunotactoid glomerulopathy, although immunotactoid glomerulopathy could be associated with underlying hematologic disorders with the need for clone-directed therapy.
Topics: Humans; Congo Red; Kidney Diseases; Kidney Glomerulus; Glomerulonephritis; Proteinuria
PubMed: 37453107
DOI: 10.2478/prilozi-2023-0030