bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2023–04–16
seven papers selected by
Valentina Piano, Uniklinik Köln
  1. UBAP2L-dependent coupling of PLK1 localization and stability during mitosis.
  2. Structural insights into how augmin augments the mitotic spindle.
  3. In mitosis integrins reduce adhesion to extracellular matrix and strengthen adhesion to adjacent cells.
  4. Apical PAR-3 caps orient the mitotic spindle in C. elegans early embryos.
  5. 3,5-bis(styryl)pyrazole inhibits mitosis and induces cell death independent of BubR1 and p53 levels by depolymerizing microtubules.
  6. Cdc42 prevents precocious Rho1 activation during cytokinesis in a Pak1-dependent manner.
  7. The GPER Agonist LNS8801 Induces Mitotic Arrest and Apoptosis in Uveal Melanoma Cells.
  1. EMBO Rep. 2023 Apr 11. e56241
    UBAP2L-dependent coupling of PLK1 localization and stability during mitosis.
    Lucile Guerber, Aurore Vuidel, Yongrong Liao, Charlotte Kleiss, Erwan Grandgirard, Izabela Sumara, Evanthia Pangou.
      PLK1 is an important regulator of mitosis whose protein levels and activity fluctuate during the cell cycle. PLK1 dynamically localizes to various mitotic structures to regulate chromosome segregation. However, the signaling pathways linking localized PLK1 activity to its protein stability remain elusive. Here, we identify the Ubiquitin-Binding Protein 2-Like (UBAP2L) that controls both the localization and the protein stability of PLK1. We demonstrate that UBAP2L is a spindle-associated protein whose depletion leads to severe mitotic defects. UBAP2L-depleted cells are characterized by increased PLK1 protein levels and abnormal PLK1 accumulation in several mitotic structures such as kinetochores, centrosomes and mitotic spindle. UBAP2L-deficient cells exit mitosis and enter the next interphase in the presence of aberrant PLK1 kinase activity. The C-terminal domain of UBAP2L mediates its function on PLK1 independently of its role in stress response signaling. Importantly, the mitotic defects of UBAP2L-depleted cells are largely rescued by chemical inhibition of PLK1. Overall, our data suggest that UBAP2L is required to fine-tune the ubiquitin-mediated PLK1 turnover during mitosis as a means to maintain genome fidelity.
    Keywords:  PLK1; UBAP2L; cell cycle; mitosis; ubiquitin
    DOI:  https://doi.org/10.15252/embr.202256241
  2. Nat Commun. 2023 Apr 13. 14(1): 2073
    Structural insights into how augmin augments the mitotic spindle.
    Szymon W Manka.
      
    DOI:  https://doi.org/10.1038/s41467-023-37625-3
  3. Nat Commun. 2023 Apr 14. 14(1): 2143
    In mitosis integrins reduce adhesion to extracellular matrix and strengthen adhesion to adjacent cells.
    Maximilian Huber, Javier Casares-Arias, Reinhard Fässler, Daniel J Müller, Nico Strohmeyer.
      To enter mitosis, most adherent animal cells reduce adhesion, which is followed by cell rounding. How mitotic cells regulate adhesion to neighboring cells and extracellular matrix (ECM) proteins is poorly understood. Here we report that, similar to interphase, mitotic cells can employ integrins to initiate adhesion to the ECM in a kindlin- and talin-dependent manner. However, unlike interphase cells, we find that mitotic cells cannot engage newly bound integrins to actomyosin via talin or vinculin to reinforce adhesion. We show that the missing actin connection of newly bound integrins leads to transient ECM-binding and prevents cell spreading during mitosis. Furthermore, β1 integrins strengthen the adhesion of mitotic cells to adjacent cells, which is supported by vinculin, kindlin, and talin1. We conclude that this dual role of integrins in mitosis weakens the cell-ECM adhesion and strengthens the cell-cell adhesion to prevent delamination of the rounding and dividing cell.
    DOI:  https://doi.org/10.1038/s41467-023-37760-x
  4. bioRxiv. 2023 Mar 27. pii: 2023.03.27.534341. [Epub ahead of print]
    Apical PAR-3 caps orient the mitotic spindle in C. elegans early embryos.
    Naomi J Stolpner, Nadia I Manzi, Thomas Su, Daniel J Dickinson.
      During embryonic development, oriented cell divisions are important for patterned tissue growth and cell fate specification. Cell division orientation is controlled in part by asymmetrically localized polarity proteins, which establish functional domains of the cell membrane and interact with microtubule regulators to position the mitotic spindle. For example, in the 8-cell mouse embryo, apical polarity proteins form caps on the outside, contact-free surface of the embryo that position the mitotic spindle to execute asymmetric cell division. A similar radial or "inside-outside" polarity is established at an early stage in many other animal embryos, but in most cases it remains unclear how inside-outside polarity is established and how it influences downstream cell behaviors. Here, we explore inside-outside polarity in C. elegans somatic blastomeres using spatiotemporally controlled protein degradation and live embryo imaging. We show that PAR polarity proteins, which form apical caps at the center of the contact free membrane, localize dynamically during the cell cycle and contribute to spindle orientation and proper cell positioning. Surprisingly, apical PAR-3 can form polarity caps independently of actomyosin flows and the small GTPase CDC-42, and can regulate spindle orientation in cooperation with the key polarity kinase aPKC. Together, our results reveal a role for apical polarity caps in regulating spindle orientation in symmetrically dividing cells and provide novel insights into how these structures are formed.
    DOI:  https://doi.org/10.1101/2023.03.27.534341
  5. J Biochem. 2023 Apr 11. pii: mvad031. [Epub ahead of print]
    3,5-bis(styryl)pyrazole inhibits mitosis and induces cell death independent of BubR1 and p53 levels by depolymerizing microtubules.
    Pooja J Batra, Anuradha Kumari, Vivian W Y Liao, David E Hibbs, Paul W Groundwater, Dulal Panda.
      Here, we show that 3,5-bis[(1E)-2-(2,6-dichlorophenyl)ethenyl]-1H-pyrazole 2l depolymerizes microtubules and reduces the number of growing tips of microtubules. The fluorescence recovery after photobleaching experiment in live MCF-7 cells showed that pyrazole 2l suppresses spindle microtubule dynamics. Further, the compound inhibits chromosome movements, activates the spindle assembly checkpoint, and blocks mitosis in MCF-7 cells. Pyrazole 2l treatment induced cell death in a variety of pathways. Pyrazole 2l induces cell death independent of BubR1 and p53 levels of MCF-7 cells upon microtubule depolymerization. Further, pyrazole 2l increases the interaction between NF-κB and microtubules and enhances the nuclear localization of NF-κB at its half-maximal proliferation inhibitory concentration while a high concentration of the compound reduced the nuclear localization of NF-κB. Interestingly, the compound exerted significantly stronger antiproliferative effects in cancerous cells than in non-cancerous cells. The results indicated that pyrazole 2l inhibits mitosis by targeting microtubules, induces several types of cell death stimuli, and suggest its potential as a lead in developing anticancer agent.
    Keywords:  Cell death; Chromosome dynamics; Congression index; Microtubule dynamics; Mitotic index
    DOI:  https://doi.org/10.1093/jb/mvad031
  6. J Cell Sci. 2023 Apr 11. pii: jcs.261160. [Epub ahead of print]
    Cdc42 prevents precocious Rho1 activation during cytokinesis in a Pak1-dependent manner.
    Udo N Onwubiko, Dhanya Kalathil, Emma Koory, Sahara Pokharel, Hayden Roberts, Ahmad Mitoubsi, Maitreyi Das.
      During cytokinesis a series of coordinated events partition a dividing cell. Accurate regulation of cytokinesis is essential for proliferation and genome integrity. In fission yeast, these coordinated events ensure that the actomyosin ring and septum start ingressing only after chromosome segregation. How cytokinetic events are coordinated remains unclear. The GTPase Cdc42 promotes recruitment of certain cell wall-building enzymes while the GTPase Rho1 activates these enzymes. We show that Cdc42 prevents early Rho1 activation during cytokinesis. Using an active Rho-probe, we find that although the Rho1 activators Rgf1 and Rgf3 localize to the division site in early anaphase, Rho1 is not activated until late anaphase, just before the onset of ring constriction. We find that loss of Cdc42 activation enables precocious Rho1 activation in early anaphase. Furthermore, we provide functional and genetic evidence that Cdc42-dependent Rho1 inhibition is mediated by the Cdc42 target Pak1 kinase. Our work proposes a mechanism of Rho1 regulation by active Cdc42 to coordinate timely septum formation and cytokinesis fidelity.
    Keywords:  Cdc42; Cytokinesis; Pak kinase; Rho1
    DOI:  https://doi.org/10.1242/jcs.261160
  7. Cancer Res Commun. 2023 Apr;3(4): 540-547
    The GPER Agonist LNS8801 Induces Mitotic Arrest and Apoptosis in Uveal Melanoma Cells.
    Grazia Ambrosini, Christopher A Natale, Elgilda Musi, Tina Garyantes, Gary K Schwartz.
      Uveal melanoma is the most common primary intraocular malignancy in adults and has a high incidence of metastatic disease. Current treatments have shown limited clinical activity in patients with uveal melanoma with metastasis and there is an urgent need for new effective therapies. Recent findings have shown that women with uveal melanoma have better survival rates than men. The G protein-coupled estrogen receptor-1 (GPER) has distinct functions from those of the classic estrogen receptors ERα/β and its activation by specific agonists has tumor-suppressive roles in several cancers. However, the role of GPER had not previously been investigated in uveal melanoma. We demonstrated that downregulation of GPER in uveal melanoma cells decreased expression of p53 and stimulated cell growth. In contrast, the clinical GPER agonist, LNS8801, upregulated p53 and p21, induced melanocytic differentiation markers, inhibited cell proliferation and cell migration, and induced apoptosis. Furthermore, LNS8801 treatment arrested the cells in G2-M-phase of the cell cycle with concomitant activation of mitotic markers and disruption of the mitotic spindle apparatus. LNS8801 significantly inhibited tumor growth of uveal melanoma xenografts in vivo, suggesting that GPER agonists may be a novel treatment for uveal melanoma.
    Significance: Current treatments against metastatic uveal melanoma have shown limited clinical activity and there is an urgent need for effective therapies. Here, we demonstrate that the GPER agonist LNS8801 induced both GPER-dependent and GPER-independent effects and elicited potent anticancer activities in vitro and in vivo. Our results complement and support the ongoing clinical trial of LNS8801 in advanced uveal melanoma.
    DOI:  https://doi.org/10.1158/2767-9764.CRC-22-0399
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