scholarly journals Kif2 microtubule depolymerase is required for unequal cell division and localizes to a subdomain of cortical endoplasmic reticulum

2017 ◽  
Author(s):  
Vlad Costache ◽  
Celine Hebras ◽  
Gerard Pruliere ◽  
Lydia Besnardeau ◽  
Margaux Failla ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Division ◽  
Cell Size ◽  
Microtubule Depolymerization ◽  
Spindle Positioning ◽  
Fundamental Process ◽  
Cortical Endoplasmic Reticulum ◽  
First Time ◽  
Invertebrate Chordate ◽  
Size Asymmetry

AbstractUnequal cell division (UCD) is a fundamental process responsible for creating sibling cell size asymmetry; however, how microtubules are specifically depolymerized on one aster of the mitotic spindle creating a smaller sibling cell during UCD has remained elusive. Using invertebrate chordate embryos (ascidian) that possess a large cortical structure (CAB) that causes UCD, we identified a microtubule depolymerase (Kif2) involved in creating cell size asymmetry. Kif2 localizes to the cortical subdomain of endoplasmic reticulum in the CAB. During three successive UCDs, Kif2 protein accumulates at the CAB during interphase and is delocalized from the CAB in mid mitosis. Rapid imaging of microtubule dynamics at the cortex revealed that microtubules do not penetrate the CAB during interphase. Inhibition of Kif2 function prevents the development of mitotic aster asymmetry and centrosome movement towards the CAB thereby blocking UCD, whereas locally increasing microtubule depolymerization causes exaggerated asymmetric spindle positioning. This study provides insights into the fundamental process of UCD and for the first time shows that a microtubule depolymerase is localized to a cortical site controlling UCD.

scholarly journals Moesin is involved in polarity maintenance and cortical remodeling during asymmetric cell division

2018 ◽  
Vol 29 (4) ◽  
pp. 419-434 ◽  
Author(s):  
Namal Abeysundara ◽  
Andrew J. Simmonds ◽  
Sarah C. Hughes
Keyword(s):  
Cell Division ◽  
Cell Size ◽  
Asymmetric Cell Division ◽  
Developing Brain ◽  
Actin Binding ◽  
Cell Cortex ◽  
Asymmetric Distribution ◽  
Mitotic Progression ◽  
Apical Polarity ◽  
Size Asymmetry

An intact actomyosin network is essential for anchoring polarity proteins to the cell cortex and maintaining cell size asymmetry during asymmetric cell division of Drosophila neuroblasts (NBs). However, the mechanisms that control changes in actomyosin dynamics during asymmetric cell division remain unclear. We find that the actin-binding protein, Moesin, is essential for NB proliferation and mitotic progression in the developing brain. During metaphase, phosphorylated Moesin (p-Moesin) is enriched at the apical cortex, and loss of Moesin leads to defects in apical polarity maintenance and cortical stability. This asymmetric distribution of p-Moesin is determined by components of the apical polarity complex and Slik kinase. During later stages of mitosis, p-Moesin localization shifts more basally, contributing to asymmetric cortical extension and myosin basal furrow positioning. Our findings reveal Moesin as a novel apical polarity protein that drives cortical remodeling of dividing NBs, which is essential for polarity maintenance and initial establishment of cell size asymmetry.

scholarly journals Alternative Modes of Organellar Segregation during Sporulation in Saccharomyces cerevisiae

2007 ◽  
Vol 6 (11) ◽  
pp. 2009-2017 ◽  
Author(s):  
Yasuyuki Suda ◽  
Hideki Nakanishi ◽  
Erin M. Mathieson ◽  
Aaron M. Neiman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Cell Division ◽  
Plasma Membranes ◽  
De Novo ◽  
Leading Edge ◽  
Protein Coat ◽  
Prospore Membrane ◽  
Cortical Endoplasmic Reticulum ◽  
Mitotic Cells

ABSTRACT Formation of ascospores in the yeast Saccharomyces cerevisiae is driven by an unusual cell division in which daughter nuclei are encapsulated within de novo-formed plasma membranes, termed prospore membranes. Generation of viable spores requires that cytoplasmic organelles also be captured along with nuclei. In mitotic cells segregation of mitochondria into the bud requires a polarized actin cytoskeleton. In contrast, genes involved in actin-mediated transport are not essential for sporulation. Instead, efficient segregation of mitochondria into spores requires Ady3p, a component of a protein coat found at the leading edge of the prospore membrane. Other organelles whose mitotic segregation is promoted by actin, such as the vacuole and the cortical endoplasmic reticulum, are not actively segregated during sporulation but are regenerated within spores. These results reveal that organellar segregation into spores is achieved by mechanisms distinct from those in mitotic cells.

scholarly journals Spatiotemporally controlled Myosin relocalization and internal pressure cause biased cortical extension to generate sibling cell size asymmetry

2018 ◽  
Author(s):  
Tri Thanh Pham ◽  
Arnaud Monnard ◽  
Jonne Helenius ◽  
Erik Lund ◽  
Nicole Lee ◽  
...  
Keyword(s):  
Cell Division ◽  
Hydrostatic Pressure ◽  
Cell Size ◽  
Asymmetric Cell Division ◽  
Apical Cell ◽  
Basal Membrane ◽  
Cell Cortex ◽  
Subsequent Increase ◽  
Biophysical Forces ◽  
Size Asymmetry

AbstractMetazoan cells can generate unequal sized sibling cells during cell division. This form of asymmetric cell division depends on spindle geometry and Myosin distribution but the underlying mechanics are unclear. Here, we use atomic force microscopy and live cell imaging to elucidate the biophysical forces involved in the establishment of physical asymmetry in Drosophila neural stem cells. We show that the force driving initial apical membrane expansion is provided by hydrostatic pressure, peaking shortly after anaphase onset, and enabled by a relieve of actomyosin contractile tension on the apical cell cortex. The subsequent increase in contractile forces at the cleavage furrow, combined with the relocalization of basally located Myosin results in basal membrane extension and sustained apical expansion. We propose that spatiotemporally controlled actomyosin contractile tension and hydrostatic pressure enables stereotypic biased membrane expansion to generate sibling cell size asymmetry.

scholarly journals Phases of cortical actomyosin dynamics coupled to the neuroblast polarity cycle

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Chet Huan Oon ◽  
Kenneth E Prehoda
Keyword(s):  
Cell Division ◽  
Cell Size ◽  
Daughter Cell ◽  
Asymmetric Cell Division ◽  
Tightly Coupled ◽  
Size Asymmetry ◽  
Early Mitosis

The Par complex dynamically polarizes to the apical cortex of asymmetrically dividing Drosophila neuroblasts where it directs fate determinant segregation. Previously we showed that apically directed cortical movements that polarize the Par complex require F-actin (Oon and Prehoda, 2019). Here we report the discovery of cortical actomyosin dynamics that begin in interphase when the Par complex is cytoplasmic but ultimately become tightly coupled to cortical Par dynamics. Interphase cortical actomyosin dynamics are unoriented and pulsatile but rapidly become sustained and apically-directed in early mitosis when the Par protein aPKC accumulates on the cortex. Apical actomyosin flows drive the coalescence of aPKC into an apical cap that is depolarized in anaphase when the flow reverses direction. Together with the previously characterized role of anaphase flows in specifying daughter cell size asymmetry, our results indicate that multiple phases of cortical actomyosin dynamics regulate asymmetric cell division.

scholarly journals Interdependent YpsA- and YfhS-Mediated Cell Division and Cell Size Phenotypes in Bacillus subtilis

mSphere ◽  
2020 ◽  
Vol 5 (4) ◽  
Author(s):  
Robert S. Brzozowski ◽  
Brooke R. Tomlinson ◽  
Michael D. Sacco ◽  
Judy J. Chen ◽  
Anika N. Ali ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Cell Division ◽  
Cell Size ◽  
Unknown Function ◽  
Suppressor Mutation ◽  
Gram Positive ◽  
Content Type ◽  
Suppressor Mutations ◽  
Extragenic Suppressor ◽  
Cell Division Inhibition

ABSTRACT Although many bacterial cell division factors have been uncovered over the years, evidence from recent studies points to the existence of yet-to-be-discovered factors involved in cell division regulation. Thus, it is important to identify factors and conditions that regulate cell division to obtain a better understanding of this fundamental biological process. We recently reported that in the Gram-positive organisms Bacillus subtilis and Staphylococcus aureus, increased production of YpsA resulted in cell division inhibition. In this study, we isolated spontaneous suppressor mutations to uncover critical residues of YpsA and the pathways through which YpsA may exert its function. Using this technique, we were able to isolate four unique intragenic suppressor mutations in ypsA (E55D, P79L, R111P, and G132E) that rendered the mutated YpsA nontoxic upon overproduction. We also isolated an extragenic suppressor mutation in yfhS, a gene that encodes a protein of unknown function. Subsequent analysis confirmed that cells lacking yfhS were unable to undergo filamentation in response to YpsA overproduction. We also serendipitously discovered that YfhS may play a role in cell size regulation. Finally, we provide evidence showing a mechanistic link between YpsA and YfhS. IMPORTANCE Bacillus subtilis is a rod-shaped Gram-positive model organism. The factors fundamental to the maintenance of cell shape and cell division are of major interest. We show that increased expression of ypsA results in cell division inhibition and impairment of colony formation on solid medium. Colonies that do arise possess compensatory suppressor mutations. We have isolated multiple intragenic (within ypsA) mutants and an extragenic suppressor mutant. Further analysis of the extragenic suppressor mutation led to a protein of unknown function, YfhS, which appears to play a role in regulating cell size. In addition to confirming that the cell division phenotype associated with YpsA is disrupted in a yfhS-null strain, we also discovered that the cell size phenotype of the yfhS knockout mutant is abolished in a strain that also lacks ypsA. This highlights a potential mechanistic link between these two proteins; however, the underlying molecular mechanism remains to be elucidated.

scholarly journals Shadowing the Actions of a Predator: Backlit Fluorescent Microscopy Reveals Synchronous Nonbinary Septation of Predatory Bdellovibrio inside Prey and Exit through Discrete Bdelloplast Pores

2010 ◽  
Vol 192 (24) ◽  
pp. 6329-6335 ◽  
Author(s):  
A. K. Fenton ◽  
M. Kanna ◽  
R. D. Woods ◽  
S.-I. Aizawa ◽  
R. E. Sockett
Keyword(s):  
Cell Division ◽  
Outer Membrane ◽  
Fluorescent Microscopy ◽  
Gram Negative Bacteria ◽  
Bacterial Cell Division ◽  
Prey Cell ◽  
Gram Negative ◽  
A Genome ◽  
Predatory Bacteria ◽  
First Time

ABSTRACT The Bdellovibrio are miniature “living antibiotic” predatory bacteria which invade, reseal, and digest other larger Gram-negative bacteria, including pathogens. Nutrients for the replication of Bdellovibrio bacteria come entirely from the digestion of the single invaded bacterium, now called a bdelloplast, which is bound by the original prey outer membrane. Bdellovibrio bacteria are efficient digesters of prey cells, yielding on average 4 to 6 progeny from digestion of a single prey cell of a genome size similar to that of the Bdellovibrio cell itself. The developmental intrabacterial cycle of Bdellovibrio is largely unknown and has never been visualized “live.” Using the latest motorized xy stage with a very defined z-axis control and engineered periplasmically fluorescent prey allows, for the first time, accurate return and visualization without prey bleaching of developing Bdellovibrio cells using solely the inner resources of a prey cell over several hours. We show that Bdellovibrio bacteria do not follow the familiar pattern of bacterial cell division by binary fission. Instead, they septate synchronously to produce both odd and even numbers of progeny, even when two separate Bdellovibrio cells have invaded and develop within a single prey bacterium, producing two different amounts of progeny. Evolution of this novel septation pattern, allowing odd progeny yields, allows optimal use of the finite prey cell resources to produce maximal replicated, predatory bacteria. When replication is complete, Bdellovibrio cells exit the exhausted prey and are seen leaving via discrete pores rather than by breakdown of the entire outer membrane of the prey.

scholarly journals The EF-Hand Ca2+-binding Protein p22 Plays a Role in Microtubule and Endoplasmic Reticulum Organization and Dynamics with Distinct Ca2+-binding Requirements

2004 ◽  
Vol 15 (2) ◽  
pp. 481-496 ◽  
Author(s):  
Josefa Andrade ◽  
Hu Zhao ◽  
Brian Titus ◽  
Sandra Timm Pearce ◽  
Margarida Barroso
Keyword(s):  
Endoplasmic Reticulum ◽  
Conformational Changes ◽  
Membrane Trafficking ◽  
Secretory Pathway ◽  
Network Formation ◽  
Binding Protein ◽  
Dependent Manner ◽  
Microtubule Depolymerization ◽  
Independent Manner ◽  
Ef Hand

We have reported that p22, an N-myristoylated EF-hand Ca2+-binding protein, associates with microtubules and plays a role in membrane trafficking. Here, we show that p22 also associates with membranes of the early secretory pathway membranes, in particular endoplasmic reticulum (ER). On binding of Ca2+, p22's ability to associate with membranes increases in an N-myristoylation-dependent manner, which is suggestive of a nonclassical Ca2+-myristoyl switch mechanism. To address the intracellular functions of p22, a digitonin-based “bulk microinjection” assay was developed to load cells with anti-p22, wild-type, or mutant p22 proteins. Antibodies against a p22 peptide induce microtubule depolymerization and ER fragmentation; this antibody-mediated effect is overcome by preincubation with the respective p22 peptide. In contrast, N-myristoylated p22 induces the formation of microtubule bundles, the accumulation of ER structures along the bundles as well as an increase in ER network formation. An N-myristoylated Ca2+-binding p22 mutant, which is unable to undergo Ca2+-mediated conformational changes, induces microtubule bundling and accumulation of ER structures along the bundles but does not increase ER network formation. Together, these data strongly suggest that p22 modulates the organization and dynamics of microtubule cytoskeleton in a Ca2+-independent manner and affects ER network assembly in a Ca2+-dependent manner.

scholarly journals Structure of the Lectin Mannose 6-Phosphate Receptor Homology (MRH) Domain of Glucosidase II, an Enzyme That Regulates Glycoprotein Folding Quality Control in the Endoplasmic Reticulum

2013 ◽  
Vol 288 (23) ◽  
pp. 16460-16475 ◽  
Author(s):  
Linda J. Olson ◽  
Ramiro Orsi ◽  
Solana G. Alculumbre ◽  
Francis C. Peterson ◽  
Ivan D. Stigliano ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Three Dimensional ◽  
Binding Pocket ◽  
Dimensional Structure ◽  
Mannose Residue ◽  
Glucosidase Ii ◽  
Mannose 6 Phosphate ◽  
First Time ◽  
Conserved Residue

Here we report for the first time the three-dimensional structure of a mannose 6-phosphate receptor homology (MRH) domain present in a protein with enzymatic activity, glucosidase II (GII). GII is involved in glycoprotein folding in the endoplasmic reticulum. GII removes the two innermost glucose residues from the Glc3Man9GlcNAc2 transferred to nascent proteins and the glucose added by UDP-Glc:glycoprotein glucosyltransferase. GII is composed of a catalytic GIIα subunit and a regulatory GIIβ subunit. GIIβ participates in the endoplasmic reticulum localization of GIIα and mediates in vivo enhancement of N-glycan trimming by GII through its C-terminal MRH domain. We determined the structure of a functional GIIβ MRH domain by NMR spectroscopy. It adopts a β-barrel fold similar to that of other MRH domains, but its binding pocket is the most shallow known to date as it accommodates a single mannose residue. In addition, we identified a conserved residue outside the binding pocket (Trp-409) present in GIIβ but not in other MRHs that influences GII glucose trimming activity.

scholarly journals Remarks Using the SEM method Species Seeds of Gentiana occurring in Turkey

2017 ◽  
Vol 35 (0) ◽  
Author(s):  
E. ALÇITEPE ◽  
S. ERKEN ◽  
F. GÜLBAG ◽  
M.E. ÖZZAMBAK
Keyword(s):  
Cell Size ◽  
Morphological Character ◽  
Seed Shape ◽  
Different Types ◽  
Seed Micromorphology ◽  
Periclinal Walls ◽  
First Time ◽  
Seed Characteristics ◽  
Wing Cell

ABSTRACT Seeds of eleven perennial Gentiana collected from Turkey were analyzed using the SEM method. Other species excluding G. septemfida, G. boissieri, G. gelida were studied for the first time. They were identified and compared in terms of seed characteristics and surface ornamentations. Major characteristics including the outer periclinal walls of testa, sculpting of inner periclinal walls, seed shape, seed and testa cell, wing cell size, thickness of testa wall and seed shape have been proposed for Turkey Gentiana. They are divided into different types, such as no wing, chalazal wing, incomplete discoid wing, complete discoid wing according to the outer periclinal walls of testa. Considering primary sculpting of seeds, irregularly striate and shallowly reticulate type is observed. Anticlinal walls of G. olivieri, G. boissieri and G. gelida are curved, while others are straight. G. lutea has the largest mean seed (4.20 x 4.40 mm), while G. cruciata (0.67 x 0.60 mm) and G. olivieri have the smallest mean seeds (0.67 x 0.67 mm). Seed micromorphology can be used together with morphological character to form classifications in studied specimens for Gentiana genus.

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