Lecudina tuzetae is a parasitic protozoan (Gregarine, Apicomplexa) living in the intestine of a marine polychaete annelid, Nereis diversicolor. Using electron and fluorescence microscopy, we have characterized the dynamic changes in microtubule organization during the sexual phase of the life cycle. The gametocyst excreted from the host worm into seawater consists of two (one male and one female) gamonts in which cortical microtubule arrays are discernible. Each gamont undergoes multiple nuclear divisions without cytokinesis, resulting in the formation of large multinucleate haploid cells. After cellularization, approximately 1000 individual gametes are produced from each gamont within 24 h. Female gametes are spherical and contain interphase cytoplasmic microtubule arrays emanating from a gamma-tubulin-containing site. In male gametes, both interphase microtubules and a flagellum with "6 + 0" axonemal microtubules extend from the same microtubule-organizing site. At the beginning of spore formation, each zygote secretes a wall to form a sporocyst. Following meiotic and mitotic divisions, each sporocyst gives rise to eight haploid cells that ultimately differentiate into sporozoites. The ovoid shaped sporocyst is asymmetric and forms at least two distinctive microtubule arrays: spindle microtubules and microtubule bundles originating from the protruding apical end corresponding to the dehiscence pole of the sporocyst. Because antibodies raised against mammalian centrosome components, such as gamma-tubulin, pericentrin, Cep135, and mitosis-specific phosphoproteins, react strongly with the microtubule-nucleating sites of Lecudina, this protozoan is likely to share common centrosomal antigens with higher eukaryotes.
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Cytoskeleton (Hoboken)
December 2024
Department of Biotechnology, University of Kerala, Kariavattom Campus, Thiruvananthapuram, India.
Cancer, a complex and heterogeneous disease, continues to be a major global health concern. Despite advancements in diagnostics and therapeutics, the aggressive nature of certain cancers remain a significant challenge, necessitating a deeper understanding of the underlying molecular mechanisms driving their severity and progression. Cancer severity and progression depend on cellular properties such as cell migration, cell division, cell shape changes, and intracellular transport, all of which are driven by dynamic cellular microtubules.
View Article and Find Full Text PDFTargeting of exocytosis enables cellular morphogenesis, motility and polarized transport, yet relatively little is known about the targeting mechanisms in cellular systems. Here we show that the SEC/MUNC protein KEULE is a dynamic marker for individual secretory events and employ it as a live cell probe, that together with high-precision image analysis of thousands of events, reveal that cortical microtubule arrays act as two-dimensional templates that pattern exocytosis at the nano-scale in higher plant cells. This mechanism is distinct from previously described mechanisms involving motor-driven transport and defines ordered and adjacent linear domains where secretory events are higher and lower than expected, effectively redistributing exocytosis over most of the cell membrane.
View Article and Find Full Text PDFDev Cell
December 2024
Department of Molecular Biosciences, University of Texas, Austin, Austin, TX 78712, USA. Electronic address:
Motile cilia are ancient, evolutionarily conserved organelles whose dysfunction underlies motile ciliopathies, a broad class of human diseases. Motile cilia contain a myriad of different proteins that assemble into an array of distinct machines, and understanding the interactions and functional hierarchies among them presents an important challenge. Here, we defined the protein interactome of motile axonemes using cross-linking mass spectrometry in Tetrahymena thermophila.
View Article and Find Full Text PDFiScience
December 2024
Department of Cancer Biology, Mayo Clinic, Jacksonville, FL 32224, USA.
While mitotic spindle inhibitors specifically kill proliferating tumor cells without the toxicities of microtubule poisons, resistance has limited their clinical utility. Treating glioblastomas with the spindle inhibitors ispinesib, alisertib, or volasertib creates a subpopulation of therapy induced senescent cells that resist these drugs by relying upon the anti-apoptotic and metabolic effects of activated STAT3. Furthermore, these senescent cells expand the repertoire of cells resistant to these drugs by secreting an array of factors, including TGFβ, which induce proliferating cells to exit mitosis and become quiescent-a state that also resists spindle inhibitors.
View Article and Find Full Text PDFSci Adv
November 2024
Key Laboratory of Plant Design, National Key Laboratory of Plant Molecular Genetics, Shanghai Center for Plant Stress Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Cell wall remodeling is important for plants to adapt to environmental stress. Under salt stress, cortical microtubules undergo a depolymerization-reassembly process to promote the biosynthesis of stress-adaptive cellulose, but the regulatory mechanisms underlying this process are still largely unknown. In this study, we reveal that FERONIA (FER), a potential cell wall sensor, interacts with COMPANION OF CELLULOSE SYNTHASE1 (CC1) and its closest homolog, CC2, two proteins that are required for cortical microtubule reassembly under salt stress.
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