bims-micesi 2024-09-15 papers

bims-micesi

Biomed News

on Mitotic cell signalling

Issue of 2024–09–15
twelve papers selected by
Valentina Piano, Uniklinik Köln

The central spindle drives anaphase chromosome segregation.
Kinesin-7 CENP-E mediates centrosome organization and spindle assembly to regulate chromosome alignment and genome stability.
LAT1 supports mitotic progression through Golgi unlinking in an amino acid transport activity-independent manner.
Revisiting the role of the spindle assembly checkpoint in the formation of gross chromosomal rearrangements in Saccharomyces cerevisiae.
miR-31-mediated local translation at the mitotic spindle is important for early development.
Plasmodium NEK1 coordinates MTOC organisation and kinetochore attachment during rapid mitosis in male gamete formation.
Mechanisms of nuclear envelope expansion.
The cytokinetic midbody mediates asymmetric fate specification at mitotic exit during neural stem cell division.
Requirement of Nek2a and cyclin A2 for Wapl-dependent removal of cohesin from prophase chromatin.
Probing centromere-kinetochore core complex CENP-L/M assembly using cenpemlin.
Newton's cradle: Cell cycle regulation by two mutually inhibitory oscillators.
PP1 phosphatase controls both daughter cell formation and amylopectin levels in Toxoplasma gondii.

bioRxiv. 2024 Aug 30. pii: 2024.08.30.610502. [Epub ahead of print]

The central spindle drives anaphase chromosome segregation.

Geng-Yuan Chen, Changfeng Deng, David M Chenoweth, Michael A Lampson.

Anaphase chromosome segregation depends on forces exerted by spindle microtubules. In the current model, forces on chromosomes are mediated through the spindle poles: sliding of antiparallel microtubules in the central spindle pushes poles apart, while kinetochore microtubule (kMT) depolymerization pulls chromosomes towards the poles. Here we show that the central spindle is directly linked to the chromosomes rather than the poles in anaphase, based on three lines of evidence. Chromosomes in monopolar spindles can move away from the pole, consistent with forces exerted by antiparallel microtubule sliding. In bipolar spindles, kMT depolymerization is constrained by suppressing central spindle sliding, indicating kinetochore linkage to the central spindle. Finally, increasing the rate of kMT depolymerization slows pole separation without increasing chromosome separation velocity. We conclude that central spindle sliding drives anaphase chromosome separation, while kMT depolymerization limits spindle elongation.

DOI: https://doi.org/10.1101/2024.08.30.610502
Cell Prolif. 2024 Sep 12. e13745

Kinesin-7 CENP-E mediates centrosome organization and spindle assembly to regulate chromosome alignment and genome stability.

Jie Chen, Shan Wu, Jie-Jie He, Yu-Peng Liu, Zhao-Yang Deng, Han-Kai Fang, Jian-Fan Chen, Ya-Lan Wei, Zhen-Yu She.

Chromosome congression and alignment are essential for cell cycle progression and genomic stability. Kinesin-7 CENP-E, a plus-end-directed kinesin motor, is required for chromosome biorientation, congression and alignment in cell division. However, it remains unclear how chromosomes are aligned and segregated in the absence of CENP-E in mitosis. In this study, we utilize the CRISPR-Cas9 gene editing method and high-throughput screening to establish CENP-E knockout cell lines and reveal that CENP-E deletion results in defects in chromosome congression, alignment and segregation, which further promotes aneuploidy and genomic instability in mitosis. Both CENP-E inhibition and deletion lead to the dispersion of spindle poles, the formation of the multipolar spindle and spindle disorganization, which indicates that CENP-E is necessary for the organization and maintenance of spindle poles. In addition, CENP-E heterozygous deletion in spleen tissues also leads to the accumulation of dividing lymphocytes and cell cycle arrest in vivo. Furthermore, CENP-E deletion also disrupts the localization of key kinetochore proteins and triggers the activation of the spindle assembly checkpoint. In summary, our findings demonstrate that CENP-E promotes kinetochore-microtubule attachment and spindle pole organization to regulate chromosome alignment and spindle assembly checkpoint during cell division.

DOI: https://doi.org/10.1111/cpr.13745
J Biol Chem. 2024 Sep 11. pii: S0021-9258(24)02262-2. [Epub ahead of print] 107761

LAT1 supports mitotic progression through Golgi unlinking in an amino acid transport activity-independent manner.

Sakura Yanagida, Ryuzaburo Yuki, Youhei Saito, Yuji Nakayama.

  Amino acid transporters play a vital role in cellular homeostasis by maintaining protein synthesis. L-type amino acid transporter 1 (LAT1/SLC7A5/CD98lc) is a major transporter of large neutral amino acids in cancer cells because of its predominant expression. Although amino acid restriction with various amino acid analog treatments is known to induce mitotic defects, the involvement of amino acid transporters in cell division remains unclear. In this study, we identified that LAT1 is responsible for mitotic progression in a transport activity-independent manner. LAT1 knockdown activates the spindle assembly checkpoint, leading to a delay in metaphase. LAT1 maintains proper spindle orientation with confinement of the lateral cortex localization of the NuMA protein, which mediates the pulling force against the mitotic spindle toward the lateral cortex. Unexpectedly, JPH203, an inhibitor of LAT1 amino acid transport activity, does not affect mitotic progression. Moreover, the transport activity-deficient LAT1 mutant maintains the proper spindle orientation and mitotic progression. LAT1 forms a heterodimer with CD98 (SLC3A2/CD98hc) both in interphase and mitosis. Although CD98 knockdown decreases the plasma membrane localization of LAT1, it does not affect mitotic progression. LAT1 is localized to the Golgi and ER not only at the plasma membrane in interphase, and promotes Golgi unlinking during the mitotic entry, leading to centrosome maturation. These results suggest that LAT1 supports mitotic progression in an amino acid transport activity-independent manner and that Golgi-localized LAT1 is important for mitotic progression through the acceleration of Golgi unlinking and centrosome maturation. These findings reveal a novel LAT1 function in mitosis.

Keywords:  Golgi; Golgi unlinking; LAT1; amino acid transport; centrosome; mitosis; mitotic spindle; spindle orientation

DOI:  https://doi.org/10.1016/j.jbc.2024.107761
Genetics. 2024 Sep 12. pii: iyae150. [Epub ahead of print]

Revisiting the role of the spindle assembly checkpoint in the formation of gross chromosomal rearrangements in Saccharomyces cerevisiae.

Yue Yao, Ziqing Yin, Fernando R Rosas Bringas, Jonathan Boudeman, Daniele Novarina, Michael Chang.

  Multiple pathways are known to suppress the formation of gross chromosomal rearrangements (GCRs), which can cause human diseases including cancer. In contrast, much less is known about pathways that promote their formation. The spindle assembly checkpoint (SAC), which ensures the proper separation of chromosomes during mitosis, has been reported to promote GCR, possibly by delaying mitosis to allow GCR-inducing DNA repair to occur. Here we show that this conclusion is the result of an experimental artifact arising from the synthetic lethality caused by disruption of the SAC and loss of the CIN8 gene, which is often lost in the genetic assay used to select for GCRs. After correcting for this artifact, we find no role of the SAC in promoting GCR.

Keywords:  chromosomal rearrangement; de novo telomere addition; interstitial telomere sequence; mitotic checkpoint; spindle assembly checkpoint; yeast

DOI:  https://doi.org/10.1093/genetics/iyae150
Development. 2024 Sep 01. pii: dev202619. [Epub ahead of print]151(17):

miR-31-mediated local translation at the mitotic spindle is important for early development.

Carolyn M Remsburg, Kalin D Konrad, Michael D Testa, Nadezda Stepicheva, Kelvin Lee, Leila H Choe, Shawn Polson, Jaysheel Bhavsar, Hongzhan Huang, Jia L Song.

  miR-31 is a highly conserved microRNA that plays crucial roles in cell proliferation, migration and differentiation. We discovered that miR-31 and some of its validated targets are enriched on the mitotic spindle of the dividing sea urchin embryo and mammalian cells. Using the sea urchin embryo, we found that miR-31 inhibition led to developmental delay correlated with increased cytoskeletal and chromosomal defects. We identified miR-31 to directly suppress several actin remodeling transcripts, including β-actin, Gelsolin, Rab35 and Fascin. De novo translation of Fascin occurs at the mitotic spindle of sea urchin embryos and mammalian cells. Importantly, miR-31 inhibition leads to a significant a increase of newly translated Fascin at the spindle of dividing sea urchin embryos. Forced ectopic localization of Fascin transcripts to the cell membrane and translation led to significant developmental and chromosomal segregation defects, highlighting the importance of the regulation of local translation by miR-31 at the mitotic spindle to ensure proper cell division. Furthermore, miR-31-mediated post-transcriptional regulation at the mitotic spindle may be an evolutionarily conserved regulatory paradigm of mitosis.

Keywords:  Cell division; Cleavage stage; Cytoskeletal elements; Sea urchin

DOI:  https://doi.org/10.1242/dev.202619
PLoS Biol. 2024 Sep 10. 22(9): e3002802

Plasmodium NEK1 coordinates MTOC organisation and kinetochore attachment during rapid mitosis in male gamete formation.

Mohammad Zeeshan, Ravish Rashpa, David J Ferguson, George Mckeown, Raushan Nugmanova, Amit K Subudhi, Raphael Beyeler, Sarah L Pashley, Robert Markus, Declan Brady, Magali Roques, Andrew R Bottrill, Andrew M Fry, Arnab Pain, Sue Vaughan, Anthony A Holder, Eelco C Tromer, Mathieu Brochet, Rita Tewari.

Mitosis is an important process in the cell cycle required for cells to divide. Never in mitosis (NIMA)-like kinases (NEKs) are regulators of mitotic functions in diverse organisms. Plasmodium spp., the causative agent of malaria is a divergent unicellular haploid eukaryote with some unusual features in terms of its mitotic and nuclear division cycle that presumably facilitate proliferation in varied environments. For example, during the sexual stage of male gametogenesis that occurs within the mosquito host, an atypical rapid closed endomitosis is observed. Three rounds of genome replication from 1N to 8N and successive cycles of multiple spindle formation and chromosome segregation occur within 8 min followed by karyokinesis to generate haploid gametes. Our previous Plasmodium berghei kinome screen identified 4 Nek genes, of which 2, NEK2 and NEK4, are required for meiosis. NEK1 is likely to be essential for mitosis in asexual blood stage schizogony in the vertebrate host, but its function during male gametogenesis is unknown. Here, we study NEK1 location and function, using live cell imaging, ultrastructure expansion microscopy (U-ExM), and electron microscopy, together with conditional gene knockdown and proteomic approaches. We report spatiotemporal NEK1 location in real-time, coordinated with microtubule organising centre (MTOC) dynamics during the unusual mitoses at various stages of the Plasmodium spp. life cycle. Knockdown studies reveal NEK1 to be an essential component of the MTOC in male cell differentiation, associated with rapid mitosis, spindle formation, and kinetochore attachment. These data suggest that P. berghei NEK1 kinase is an important component of MTOC organisation and essential regulator of chromosome segregation during male gamete formation.

DOI: https://doi.org/10.1371/journal.pbio.3002802
Curr Opin Cell Biol. 2024 Sep 08. pii: S0955-0674(24)00104-2. [Epub ahead of print]91 102425

Mechanisms of nuclear envelope expansion.

Christopher Ptak, Saif Rehman, Richard W Wozniak.

In actively dividing eukaryotic cells, the nuclear envelope membrane (NEM) expands during the cell cycle to accommodate increases in nuclear volume and formation of two nuclei as a cell passes through mitosis to form daughter cells. NEM expansion is driven by glycerophospholipid (GPL) synthesis that is regulated by the lipin family of phosphatidic acid phosphatases (PAPs). How, and when during the cell cycle, PAPs regulate membrane expansion differs between organisms undergoing a closed or open mitosis. Here, we discuss recent studies that shed light on the mechanisms of NE expansion. Moreover, we examine evidence that NEM expansion not only employs GPLs synthesized in the ER but also lipids whose synthesis is regulated by events at the inner nuclear membrane.

DOI: https://doi.org/10.1016/j.ceb.2024.102425
bioRxiv. 2024 Aug 28. pii: 2024.08.27.609974. [Epub ahead of print]

The cytokinetic midbody mediates asymmetric fate specification at mitotic exit during neural stem cell division.

Bryce LaFoya, Rhiannon R Penkert, Kenneth E Prehoda.

Asymmetric cell division (ACD) is a broadly used mechanism for generating cellular diversity. Molecules known as fate determinants are segregated during ACD to generate distinct sibling cell fates, but determinants should not be activated until fate can be specified asymmetrically. Determinants could be activated after cell division but many animal cells complete division long after mitosis ends, raising the question of how activation could occur at mitotic exit taking advantage of the unique state plasticity at this time point. Here we show that the midbody, a microtubule-rich structure that forms in the intercellular bridge connecting nascent siblings, mediates fate determinant activation at mitotic exit in neural stem cells (NSCs) of the Drosophila larval brain. The fate determinants Prospero (Pros) and Brain tumor (Brat) are sequestered at the NSC membrane at metaphase but are released immediately following nuclear division when the midbody forms, well before cell division completes. The midbody isolates nascent sibling cytoplasms, allowing determinant release from the membrane via the cell cycle phosphatase String, without influencing the fate of the incorrect sibling. Our results identify the midbody as a key facilitator of ACD that allows asymmetric fate determinant activation to be initiated before division.

DOI: https://doi.org/10.1101/2024.08.27.609974
EMBO J. 2024 Sep 13.

Requirement of Nek2a and cyclin A2 for Wapl-dependent removal of cohesin from prophase chromatin.

Susanne Hellmuth, Olaf Stemmann.

  Sister chromatid cohesion is mediated by the cohesin complex. In mitotic prophase cohesin is removed from chromosome arms in a Wapl- and phosphorylation-dependent manner. Sgo1-PP2A protects pericentromeric cohesion by dephosphorylation of cohesin and its associated Wapl antagonist sororin. However, Sgo1-PP2A relocates to inner kinetochores well before sister chromatids are separated by separase, leaving pericentromeric regions unprotected. Why deprotected cohesin is not removed by Wapl remains enigmatic. By reconstituting Wapl-dependent cohesin removal from chromatin in vitro, we discovered a requirement for Nek2a and Cdk1/2-cyclin A2. These kinases phosphorylate cohesin-bound Pds5b, thereby converting it from a sororin- to a Wapl-interactor. Replacement of endogenous Pds5b by a phosphorylation mimetic variant causes premature sister chromatid separation (PCS). Conversely, phosphorylation-resistant Pds5b impairs chromosome arm separation in prometaphase-arrested cells and suppresses PCS in the absence of Sgo1. Early mitotic degradation of Nek2a and cyclin A2 may therefore explain why only separase, but not Wapl, can trigger anaphase.

Keywords:  Cohesin; Cyclin A2; Nek2a; Sororin; Wapl

DOI:  https://doi.org/10.1038/s44318-024-00228-9
J Mol Cell Biol. 2024 Sep 06. pii: mjae035. [Epub ahead of print]

Probing centromere-kinetochore core complex CENP-L/M assembly using cenpemlin.

Olanrewaju Ayodeji Durojaye, Fengrui Yang, Xinjiao Gao, Felix Aikhionbare, Liangyu Zhang, Xing Liu, Xuebiao Yao.

DOI: https://doi.org/10.1093/jmcb/mjae035
Math Biosci. 2024 Sep 04. pii: S0025-5564(24)00151-2. [Epub ahead of print]377 109291

Newton's cradle: Cell cycle regulation by two mutually inhibitory oscillators.

Calin-Mihai Dragoi, John J Tyson, Béla Novák.

  The cell division cycle is a fundamental physiological process displaying a great degree of plasticity during the course of multicellular development. This plasticity is evident in the transition from rapid and stringently-timed divisions of the early embryo to subsequent size-controlled mitotic cycles. Later in development, cells may pause and restart proliferation in response to myriads of internal or external signals, or permanently exit the cell cycle following terminal differentiation or senescence. Beyond this, cells can undergo modified cell division variants, such as endoreplication, which increases their ploidy, or meiosis, which reduces their ploidy. This wealth of behaviours has led to numerous conceptual analogies intended as frameworks for understanding the proliferative program. Here, we aim to unify these mechanisms under one dynamical paradigm. To this end, we take a control theoretical approach to frame the cell cycle as a pair of arrestable and mutually-inhibiting, doubly amplified, negative feedback oscillators controlling chromosome replication and segregation events, respectively. Under appropriate conditions, this framework can reproduce fixed-period oscillations, checkpoint arrests of variable duration, and endocycles. Subsequently, we use phase plane and bifurcation analysis to explain the dynamical basis of these properties. Then, using a physiologically realistic, biochemical model, we show that the very same regulatory structure underpins the diverse functions of the cell cycle control network. We conclude that Newton's cradle may be a suitable mechanical analogy of how the cell cycle is regulated.

Keywords:  Bistability; Cell cycle; Checkpoints; Endocycles; Oscillations

DOI:  https://doi.org/10.1016/j.mbs.2024.109291
PLoS Biol. 2024 Sep 10. 22(9): e3002791

PP1 phosphatase controls both daughter cell formation and amylopectin levels in Toxoplasma gondii.

Asma Sarah Khelifa, Maanasa Bhaskaran, Tom Boissavy, Thomas Mouveaux, Tatiana Araujo Silva, Cerina Chhuon, Marcia Attias, Ida Chiara Guerrera, Wanderley De Souza, David Dauvillee, Emmanuel Roger, Mathieu Gissot.

Virulence of apicomplexan parasites is based on their ability to divide rapidly to produce significant biomass. The regulation of their cell cycle is therefore key to their pathogenesis. Phosphorylation is a crucial posttranslational modification that regulates many aspects of the eukaryotic cell cycle. The phosphatase PP1 is known to play a major role in the phosphorylation balance in eukaryotes. We explored the role of TgPP1 during the cell cycle of the tachyzoite form of the apicomplexan parasite Toxoplasma gondii. Using a conditional mutant strain, we show that TgPP1 regulates many aspects of the cell cycle including the proper assembly of the daughter cells' inner membrane complex (IMC), the segregation of organelles, and nuclear division. Unexpectedly, depletion of TgPP1 also results in the accumulation of amylopectin, a storage polysaccharide that is usually found in the latent bradyzoite form of the parasite. Using transcriptomics and phospho-proteomics, we show that TgPP1 mainly acts through posttranslational mechanisms by dephosphorylating target proteins including IMC proteins. TgPP1 also dephosphorylates a protein bearing a starch-binding domain. Mutagenesis analysis reveals that the targeted phospho-sites are linked to the ability of the parasite to regulate amylopectin steady-state levels. Therefore, we show that TgPP1 has pleiotropic roles during the tachyzoite cell cycle regulation, but also regulates amylopectin accumulation.

DOI: https://doi.org/10.1371/journal.pbio.3002791