bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–08–06
ten papers selected by
Valentina Piano, Uniklinik Köln



  1. PLoS Biol. 2023 Aug 03. 21(8): e3002224
      Both the spindle microtubule-organizing centers and the nuclear pore complexes (NPCs) are convoluted structures where many signaling pathways converge to coordinate key events during cell division. Interestingly, despite their distinct molecular conformation and overall functions, these structures share common components and collaborate in the regulation of essential processes. We have established a new link between microtubule-organizing centers and nuclear pores in budding yeast by unveiling an interaction between the Bfa1/Bub2 complex, a mitotic exit inhibitor that localizes on the spindle pole bodies, and the Nup159 nucleoporin. Bfa1/Bub2 association with Nup159 is reduced in metaphase to not interfere with proper spindle positioning. However, their interaction is stimulated in anaphase and assists the Nup159-dependent autophagy pathway. The asymmetric localization of Bfa1/Bub2 during mitosis raises the possibility that its interaction with Nup159 could differentially promote Nup159-mediated autophagic processes, which might be relevant for the maintenance of the replicative lifespan.
    DOI:  https://doi.org/10.1371/journal.pbio.3002224
  2. EMBO Rep. 2023 Aug 02. e53408
      Monoamine transporters retrieve serotonin (SERT), dopamine (DAT), and norepinephrine (NET) from the synaptic cleft. Transporter internalization contributes to the regulation of their surface expression. Clathrin-mediated endocytosis of plasma membrane proteins requires adaptor protein-2 (AP2), which recruits cargo to the nascent clathrin cage. However, the intracellular portions of monoamine transporters are devoid of a conventional AP2-binding site. Here, we identify a MAD2 (mitotic arrest deficient-2) interaction motif in the C-terminus of SERT, which binds the closed conformation of MAD2 and allows for the recruitment of two additional mitotic spindle assembly checkpoint (SAC) proteins, BubR1 and p31comet , and of AP2. We visualize MAD2, BubR1, and p31comet in dorsal raphe neurons, and depletion of MAD2 in primary serotonergic rat neurons decreases SERT endocytosis in the soma. Our findings do not only provide mechanistic insights into transporter internalization but also allow for rationalizing why SAC proteins are present in post-mitotic neurons.
    Keywords:  endocytosis; mitotic checkpoint; raphe neurons; recycling endosome; serotonin transporter
    DOI:  https://doi.org/10.15252/embr.202153408
  3. J Cell Sci. 2023 Jul 31. pii: jcs.261416. [Epub ahead of print]
      Accurate genome segregation in mitosis requires that all chromosomes are bioriented on the spindle. Cells monitor biorientation by sensing tension across sister centromeres. Chromosomes that are not bioriented have low centromere tension, which allows Aurora B (yeast Ipl1) to perform error correction that locally loosens kinetochore-microtubule attachments to allow detachment of microtubules and fresh attempts at achieving biorientation. However, it is not known if low tension recruits Aurora B to centromeres or, alternatively, if low tension directly activates Aurora B already localized at centromeres. In this work, we experimentally induced low tension in metaphase yeast cells, then monitored Ipl1 localization. We find low tension recruits Ipl1 to centromeres. Further, low tension induced Ipl1 recruitment depended on Bub1, which is known to provide a binding site for Ipl1. In contrast, Top2, which can also recruit Ipl1 to centromeres, was not required. Our results demonstrate cells are sensitive to low tension at centromeres and respond by actively recruiting Ip1l for error correction.
    Keywords:  Aurora B; Bub1; Centromere tension; Ipl1; Top2
    DOI:  https://doi.org/10.1242/jcs.261416
  4. Curr Drug Targets. 2023 Jul 31.
      Microtubules are a well-known target in cancer chemotherapy because of their critical role in cell division. Chromosome segregation during mitosis depends on the establishment of the mitotic spindle apparatus through microtubule dynamics. The disruption of microtubule dynamics through the stabilization or destabilization of microtubules results in the mitotic arrest of the cells. Microtubule-targeted drugs, which interfere with microtubule dynamics, inhibit the growth of cells at the mitotic phase and induce apoptotic cell death. The principle of microtubule-targeted drugs is to arrest the cells at mitosis and reduce their growth because cancer is a disease of unchecked cell proliferation. Many anti-microtubule agents produce significant inhibition of cancer cell growth and are widely used as chemotherapeutic drugs for the treatment of cancer. The drugs that interact with microtubules generally bind at one of the three sites vinblastine site, taxol site, or colchicine site. Colchicine binds to the interface of tubulin heterodimer and induces the depolymerization of microtubules. The colchicine binding site on microtubules is a much sought-after target in the history of anti-microtubule drug discovery. Many colchicine-binding site inhibitors have been discovered, but their use in the treatment of cancer is limited due to their dose-limiting toxicity and resistance in humans. Combination therapy can be a new treatment strategy to overcome these drawbacks of currently available microtubule-targeted anticancer drugs. This review discusses the significance of microtubules as a potential pharmacological target for cancer and stresses the necessity of finding new microtubule inhibitors to fight the disease.
    Keywords:  apoptosis; cytoskeleton; mitosis; motor proteins; tubulin
    DOI:  https://doi.org/10.2174/1389450124666230731094837
  5. MicroPubl Biol. 2023 ;2023
      Mitosis is usually shorter than other phases of the cell cycle and maintains a consistent duration despite variations in cell size and spindle size. This suggests the existence of a compensatory mechanism that ensures a short duration, possibly as a protective measure against irreversible damage, such as DNA damage. To explore the link between prolonged mitosis and DNA damage, we develop a microscopy-based assay utilizing Rad52-GFP as a marker for mitotic DNA damage. Through this assay, we provide evidence that mutants with prolonged mitosis exhibit increased Rad52 puncta, indicating an elevation in endogenous DNA damage.
    DOI:  https://doi.org/10.17912/micropub.biology.000911
  6. Curr Biol. 2023 Jul 21. pii: S0960-9822(23)00916-8. [Epub ahead of print]
      Cytoplasmic linker-associated proteins (CLASPs) form a conserved family of microtubule-associated proteins (MAPs) that maintain microtubules in a growing state by promoting rescue while suppressing catastrophe.1 CLASP function involves an ordered array of tumor overexpressed gene (TOG) domains and binding to multiple protein partners via a conserved C-terminal domain (CTD).2,3 In migrating cells, CLASPs concentrate at the cortex near focal adhesions as part of cortical microtubule stabilization complexes (CMSCs), via binding of their CTD to the focal adhesion protein PHLDB2/LL5β.4,5 Cortical CLASPs also stabilize a subset of microtubules, which stimulate focal adhesion turnover and generate a polarized microtubule network toward the leading edge of migrating cells. CLASPs are also recruited to the trans-Golgi network (TGN) via an interaction between their CTD and the Golgin protein GCC185.6 This allows microtubule growth toward the leading edge of migrating cells, which is required for Golgi organization, polarized intracellular transport, and cell motility.7 In dividing cells, CLASPs are essential at kinetochores for efficient chromosome segregation and anaphase spindle integrity.8,9 Both CENP-E and ASTRIN bind and target CLASPs to kinetochores,10,11 although the CLASP domain required for this interaction is not known. Despite its high evolutionary conservation, the CTD remains structurally uncharacterized. Here, we find that the CTD can be structurally modeled as a TOG domain. We identify a surface-exposed and conserved arginine residue essential for CLASP CTD interaction with partner proteins. Together, our results provide a structural mechanism by which the CLASP CTD directs diverse sub-cellular localizations throughout the cell cycle.
    Keywords:  CLASP; Golgi; TOG domain; cell division; focal adhesion; microtubules
    DOI:  https://doi.org/10.1016/j.cub.2023.07.009
  7. Cell Death Differ. 2023 Jul 29.
      Faithful eucaryotic cell division requires spatio-temporal orchestration of multiple sequential events. To ensure the dynamic nature of these molecular and morphological transitions, a swift modulation of key regulatory pathways is necessary. The molecular process that most certainly fits this description is phosphorylation, the post-translational modification provided by kinases, that is crucial to allowing the progression of the cell cycle and that culminates with the separation of two identical daughter cells. In detail, from the early stages of the interphase to the cytokinesis, each critical step of this process is tightly regulated by multiple families of kinases including the Cyclin-dependent kinases (CDKs), kinases of the Aurora, Polo, Wee1 families, and many others. While cell-cycle-related CDKs control the timing of the different phases, preventing replication machinery errors, the latter modulate the centrosome cycle and the spindle function, avoiding karyotypic abnormalities typical of chromosome instability. Such chromosomal abnormalities may result from replication stress (RS) and chromosome mis-segregation and are considered a hallmark of poor prognosis, therapeutic resistance, and metastasis in cancer patients. Here, we discuss recent advances in the understanding of how different families of kinases concur to govern cell cycle, preventing RS and mitotic infidelity. Additionally, considering the growing number of clinical trials targeting these molecules, we review to what extent and in which tumor context cell-cycle-related kinases inhibitors are worth exploiting as an effective therapeutic strategy.
    DOI:  https://doi.org/10.1038/s41418-023-01196-z
  8. Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2023 Aug 03.
      Mitosis is a key step of eukaryote proliferation.Endosomal sorting complex required for transport, a protein complex closely associated with membrane shearing, is involved in endosome maturation, virus budding, and autophagy.The structural and functional abnormalities of the complex are associated with the occurrence and progression of cancer and other diseases.In this paper, we summarized the roles of the endosomal sorting complex required for transport in different stages of mitosis and reviewed the studies about the role of the complex in regulating mitosis in diseases.
    Keywords:  cancer; endosomal sorting complex required for transport; mitosis; spindle assembly checkpoint
    DOI:  https://doi.org/10.3881/j.issn.1000-503X.15609
  9. EMBO Rep. 2023 Aug 03. e57108
      The H3K4 methyltransferase SETD1A plays a crucial role in leukemia cell survival through its noncatalytic FLOS domain-mediated recruitment of cyclin K and regulation of DNA damage response genes. In this study, we identify a functional nuclear localization signal in and interaction partners of the FLOS domain. Our screen for FLOS domain-binding partners reveals that the SETD1A FLOS domain binds mitosis-associated proteins BuGZ/BUB3. Inhibition of both cyclin K and BuGZ/BUB3-binding motifs in SETD1A shows synergistic antileukemic effects. BuGZ/BUB3 localize to SETD1A-bound promoter-TSS regions and SETD1A-negative H3K4me1-positive enhancer regions adjacent to SETD1A target genes. The GLEBS motif and intrinsically disordered region of BuGZ are required for both SETD1A-binding and leukemia cell proliferation. Cell-cycle-specific SETD1A restoration assays indicate that SETD1A expression at the G1/S phase of the cell cycle promotes both the expression of DNA damage response genes and cell cycle progression in leukemia cells.
    Keywords:  BuGZ; DNA repair; Leukemia; SETD1A; Transcription
    DOI:  https://doi.org/10.15252/embr.202357108
  10. Cell Death Differ. 2023 Aug 03.
      The discrimination of protein biological functions in different phases of the cell cycle is limited by the lack of experimental approaches that do not require pre-treatment with compounds affecting the cell cycle progression. Therefore, potential cycle-specific biological functions of a protein of interest could be biased by the effects of cell treatments. The OsTIR1/auxin-inducible degron (AID) system allows "on demand" selective and reversible protein degradation upon exposure to the phytohormone auxin. In the current format, this technology does not allow to study the effect of acute protein depletion selectively in one phase of the cell cycle, as auxin similarly affects all the treated cells irrespectively of their proliferation status. Therefore, the AID system requires coupling with cell synchronization techniques, which can alter the basal biological status of the studied cell population, as with previously available approaches. Here, we introduce a new AID system to Regulate OsTIR1 Levels based on the Cell Cycle Status (ROLECCS system), which induces proteolysis of both exogenously transfected and endogenous gene-edited targets in specific phases of the cell cycle. We validated the ROLECCS technology by down regulating the protein levels of TP53, one of the most studied tumor suppressor genes, with a widely known role in cell cycle progression. By using our novel tool, we observed that TP53 degradation is associated with increased number of micronuclei, and this phenotype is specifically achieved when TP53 is lost in S/G2/M phases of the cell cycle, but not in G1. Therefore, we propose the use of the ROLECCS system as a new improved way of studying the differential roles that target proteins may have in specific phases of the cell cycle.
    DOI:  https://doi.org/10.1038/s41418-023-01191-4