scholarly journals Roles of Mso1 and the SM protein Sec1 in efficient vesicle fusion during fission yeast cytokinesis

2020 ◽  
Vol 31 (15) ◽  
pp. 1570-1583
Author(s):  
Kenneth S. Gerien ◽  
Sha Zhang ◽  
Alexandra C. Russell ◽  
Yi-Hua Zhu ◽  
Vedud Purde ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Fission Yeast ◽  
Vesicle Fusion ◽  
Contractile Ring ◽  
Division Site ◽  
Ring Constriction ◽  
Sm Protein

Mso1 and the SM protein Sec1 aid in the efficient fusion of vesicles at the division site in fission yeast, which is important for proper contractile-ring constriction and plasma-membrane closure during cytokinesis.

scholarly journals Profilin-mediated Competition between Capping Protein and Formin Cdc12p during Cytokinesis in Fission Yeast

2005 ◽  
Vol 16 (5) ◽  
pp. 2313-2324 ◽  
Author(s):  
David R. Kovar ◽  
Jian-Qiu Wu ◽  
Thomas D. Pollard
Keyword(s):  
Fission Yeast ◽  
Actin Filament ◽  
Actin Filaments ◽  
Cell Separation ◽  
The Other ◽  
Temperature Sensitive ◽  
Contractile Ring ◽  
Capping Protein ◽  
Division Site ◽  
Ring Constriction

Fission yeast capping protein SpCP is a heterodimer of two subunits (Acp1p and Acp2p) that binds actin filament barbed ends. Neither acp1 nor acp2 is required for viability, but cells lacking either or both subunits have cytokinesis defects under stressful conditions, including elevated temperature, osmotic stress, or in combination with numerous mild mutations in genes important for cytokinesis. Defects arise as the contractile ring constricts and disassembles, resulting in delays in cell separation. Genetic and biochemical interactions show that the cytokinesis formin Cdc12p competes with capping protein for actin filament barbed ends in cells. Deletion of acp2 partly suppresses cytokinesis defects in temperature-sensitive cdc12-112 cells and mild overexpression of capping protein kills cdc12-112 cells. Biochemically, profilin has opposite effects on filaments capped with Cdc12p and capping protein. Profilin depolymerizes actin filaments capped by capping protein but allows filaments capped by Cdc12p to grow at their barbed ends. Once associated with a barbed end, either Cdc12p or capping protein prevents the other from influencing polymerization at that end. Given that capping protein arrives at the division site 20 min later than Cdc12p, capping protein may slowly replace Cdc12p on filament barbed ends in preparation for filament disassembly during ring constriction.

scholarly journals The Actomyosin Ring Recruits Early Secretory Compartments to the Division Site in Fission Yeast

2008 ◽  
Vol 19 (3) ◽  
pp. 1125-1138 ◽  
Author(s):  
Aleksandar Vjestica ◽  
Xin-Zi Tang ◽  
Snezhana Oliferenko
Keyword(s):  
Endoplasmic Reticulum ◽  
Fission Yeast ◽  
Membrane Trafficking ◽  
Secretory Pathway ◽  
Physical Force ◽  
Daughter Cells ◽  
Division Site ◽  
Ring Assembly ◽  
Membrane Barrier ◽  
Ring Constriction

The ultimate goal of cytokinesis is to establish a membrane barrier between daughter cells. The fission yeast Schizosaccharomyces pombe utilizes an actomyosin-based division ring that is thought to provide physical force for the plasma membrane invagination. Ring constriction occurs concomitantly with the assembly of a division septum that is eventually cleaved. Membrane trafficking events such as targeting of secretory vesicles to the division site require a functional actomyosin ring suggesting that it serves as a spatial landmark. However, the extent of polarization of the secretion apparatus to the division site is presently unknown. We performed a survey of dynamics of several fluorophore-tagged proteins that served as markers for various compartments of the secretory pathway. These included markers for the endoplasmic reticulum, the COPII sites, and the early and late Golgi. The secretion machinery exhibited a marked polarization to the division site. Specifically, we observed an enrichment of the transitional endoplasmic reticulum (tER) accompanied by Golgi cisternae biogenesis. These processes required actomyosin ring assembly and the function of the EFC-domain protein Cdc15p. Cdc15p overexpression was sufficient to induce tER polarization in interphase. Thus, fission yeast polarizes its entire secretory machinery to the cell division site by utilizing molecular cues provided by the actomyosin ring.

scholarly journals Roles of putative Rho-GEF Gef2 in division-site positioning and contractile-ring function in fission yeast cytokinesis

2012 ◽  
Vol 23 (7) ◽  
pp. 1181-1195 ◽  
Author(s):  
Yanfang Ye ◽  
I-Ju Lee ◽  
Kurt W. Runge ◽  
Jian-Qiu Wu
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Nucleotide Exchange ◽  
Contractile Ring ◽  
Division Plane ◽  
Cell Functions ◽  
Division Site ◽  
Ring Assembly ◽  
And Function ◽  
Rho Gef

Cytokinesis is crucial for integrating genome inheritance and cell functions. In multicellular organisms, Rho-guanine nucleotide exchange factors (GEFs) and Rho GTPases are key regulators of division-plane specification and contractile-ring formation during cytokinesis, but how they regulate early steps of cytokinesis in fission yeast remains largely unknown. Here we show that putative Rho-GEF Gef2 and Polo kinase Plo1 coordinate to control the medial cortical localization and function of anillin-related protein Mid1. The division-site positioning defects of gef2∆ plo1-ts18 double mutant can be partially rescued by increasing Mid1 levels. We find that Gef2 physically interacts with the Mid1 N-terminus and modulates Mid1 cortical binding. Gef2 localization to cortical nodes and the contractile ring depends on its last 145 residues, and the DBL-homology domain is important for its function in cytokinesis. Our data suggest the interaction between Rho-GEFs and anillins is an important step in the signaling pathways during cytokinesis. In addition, Gef2 also regulates contractile-ring function late in cytokinesis and may negatively regulate the septation initiation network. Collectively, we propose that Gef2 facilitates and stabilizes Mid1 binding to the medial cortex, where the localized Mid1 specifies the division site and induces contractile-ring assembly.

scholarly journals Fission yeast Cyk3p is a transglutaminase-like protein that participates in cytokinesis and cell morphogenesis

2012 ◽  
Vol 23 (13) ◽  
pp. 2433-2444 ◽  
Author(s):  
Luther W. Pollard ◽  
Masayuki Onishi ◽  
John R. Pringle ◽  
Matthew Lord
Keyword(s):  
Fission Yeast ◽  
Primary Role ◽  
Cell Integrity ◽  
Cell Morphogenesis ◽  
Contractile Ring ◽  
Physiological Importance ◽  
Complex Process ◽  
Catalytic Active Site ◽  
Thiol Proteases ◽  
Ring Constriction

Cell morphogenesis is a complex process that relies on a diverse array of proteins and pathways. We have identified a transglutaminase-like protein (Cyk3p) that functions in fission yeast morphogenesis. The phenotype of a cyk3 knockout strain indicates a primary role for Cyk3p in cytokinesis. Correspondingly, Cyk3p localizes both to the actomyosin contractile ring and the division septum, promoting ring constriction, septation, and subsequent cell separation following ring disassembly. In addition, Cyk3p localizes to polarized growth sites and plays a role in cell shape determination, and it also appears to contribute to cell integrity during stationary phase, given its accumulation as dynamic puncta at the cortex of such cells. Our results and the conservation of Cyk3p across fungi point to a role in cell wall synthesis and remodeling. Cyk3p possesses a transglutaminase domain that is essential for function, even though it lacks the catalytic active site. In a wider sense, our work illustrates the physiological importance of inactive members of the transglutaminase family, which are found throughout eukaryotes. We suggest that the proposed evolution of animal transglutaminase cross-linking activity from ancestral bacterial thiol proteases was accompanied by the emergence of a subclass whose function does not depend on enzymatic activity.

scholarly journals The number of cytokinesis nodes in mitotic fission yeast scales with cell volume

2021 ◽  
Author(s):  
Wasim A Sayyad ◽  
Thomas D Pollard
Keyword(s):  
Plasma Membrane ◽  
Fission Yeast ◽  
Large Population ◽  
Yeast Cells ◽  
Wild Type ◽  
Contractile Ring ◽  
Node Number ◽  
Nmt1 Promoter ◽  
Wide Range ◽  
Mutant Cells

Cytokinesis nodes are assemblies of stoichiometric ratios of proteins associated with the plasma membrane, which serve as precursors for the contractile ring during cytokinesis by fission yeast. The total number of nodes is uncertain, because of the limitations of the methods used previously. Here we used the ~140 nm resolution of Airyscan confocal microscopy to resolve a large population of dim, unitary cytokinesis nodes in 3D reconstructions of whole fission yeast cells. Wild-type fission yeast cells make about 200 unitary cytokinesis nodes. Most, but not all of these nodes condense into a contractile ring. The number of cytokinesis nodes scales with cell size in four strains tested, although wide rga4Δ mutant cells form somewhat fewer cytokinesis nodes than expected from the overall trend. The surface density of Pom1 kinase on the plasma membrane around the equators of cells is similar with a wide range of node numbers, so Pom1 does not control cytokinesis node number. However, varying protein concentrations with the nmt1 promoter showed that the numbers of nodes increase above a baseline of about 200 with the total cellular concentration of either Pom1 or the kinase Cdr2.

Involvement of Smi1 in cell wall integrity and glucan synthase Bgs4 localization during fission yeast cytokinesis

2021 ◽  
Author(s):  
Larissa V. G. Longo ◽  
Evelyn G. Goodyear ◽  
Sha Zhang ◽  
Elena Kudryashova ◽  
Jian-Qiu Wu
Keyword(s):  
Fission Yeast ◽  
Cell Walls ◽  
Intrinsically Disordered Protein ◽  
Secretory Vesicles ◽  
Contractile Ring ◽  
Fungal Cell ◽  
Intrinsically Disordered ◽  
Disordered Protein ◽  
Division Site ◽  
Fungal Cell Walls

Cytokinesis is the final step of the cell-division cycle. In fungi, it relies on the coordination of constriction of an actomyosin contractile ring and construction of the septum at the division site. Glucan synthases synthesize glucans, which are the major components in fungal cell walls and division septa. It is known that Rho1 and Rho2 GTPases regulate glucan synthases Bgs1, Bgs4, and Ags1, and Sbg1 and the F-BAR protein Cdc15 play roles in Bgs1 stability and delivery to the plasma membrane. Here we characterize Smi1, an intrinsically disordered protein that interacts with Bgs4 and regulates its trafficking and localization in fission yeast. Smi1 is important for septum integrity, and its absence causes severe lysis during cytokinesis. Smi1 localizes to secretory vesicles and moves together with Bgs4 towards the division site. The concentrations of the glucan synthases Bgs1 and Bgs4 and the glucanases Agn1 and Bgl2 decrease at the division site in smi1 mutant, but Smi1 seems to be more specific to Bgs4. Mistargeting of Smi1 to mitochondria mislocalizes Bgs4, but not Bgs1. Together, our data reveal a novel regulator of glucan synthases and glucanases, Smi1, which is more important for Bgs4 trafficking, stability, and localization during cytokinesis. [Media: see text] [Media: see text]

scholarly journals The Localization of the Integral Membrane Protein Cps1p to the Cell Division Site is Dependent on the Actomyosin Ring and the Septation-Inducing Network inSchizosaccharomyces pombe

2002 ◽  
Vol 13 (3) ◽  
pp. 989-1000 ◽  
Author(s):  
Jianhua Liu ◽  
Xie Tang ◽  
Hongyan Wang ◽  
Snezhana Oliferenko ◽  
Mohan K. Balasubramanian
Keyword(s):  
Cell Division ◽  
Membrane Protein ◽  
Integral Membrane Protein ◽  
Wall Material ◽  
Contractile Ring ◽  
Division Site ◽  
Ring Assembly ◽  
Independent Mechanism ◽  
Ring Constriction ◽  
Initial Assembly

Schizosaccharomyces pombe cells divide by medial fission through the use of an actomyosin-based contractile ring. Constriction of the actomyosin ring is accompanied by the centripetal addition of new membranes and cell wall material. In this article, we characterize the mechanism responsible for the localization of Cps1p, a septum-synthesizing 1,3-β-glucan synthase, to the division site during cytokinesis. We show that Cps1p is an integral membrane protein that localizes to the cell division site late in anaphase. Neither F-actin nor microtubules are essential for the initial assembly of Cps1p to the medial division site. F-actin, but not microtubules, is however important for the eventual incorporation of Cps1p into the actomyosin ring. Assembly of Cps1p into the cell division ring is also dependent on the septation-inducing network (SIN) proteins that regulate division septum formation after assembly of the actomyosin ring. Fluorescence-recovery after-photobleaching experiments reveal that Cps1p does not diffuse appreciably within the plasma membrane and is retained at the division site by a mechanism that does not depend on an intact F-actin cytoskeleton. We conclude that the actomyosin ring serves as a spatial cue for Cps1p localization, whereas the maintenance of Cps1p at the division site occurs by a novel F-actin– and microtubule-independent mechanism. Furthermore, we propose that the SIN proteins ensure localization of Cps1p at the appropriate point in the cell cycle.

scholarly journals Cdc42 promotes Bgs1 recruitment for septum synthesis and glucanase localization for cell separation during cytokinesis in fission yeast

2019 ◽  
Author(s):  
Udo N. Onwubiko ◽  
Julie Robinson ◽  
Rose Albu Mustaf ◽  
Maitreyi E. Das
Keyword(s):  
Fission Yeast ◽  
Membrane Trafficking ◽  
Cell Separation ◽  
Nucleotide Exchange ◽  
Timely Initiation ◽  
Division Site ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Primary Septum ◽  
Ring Constriction

AbstractCytokinesis in fission yeast involves actomyosin ring constriction concurrent to septum synthesis followed by septum digestion resulting in cell separation. A recent report indicates that endocytosis is required for septum synthesis and cell separation. The conserved GTPase Cdc42 is required for membrane trafficking and promotes endocytosis. Cdc42 is activated by Guanine nucleotide exchange factors (GEFs). Cdc42 GEFs have been shown to promote timely initiation of septum synthesis and proper septum morphology. Here we show that Cdc42 promotes the recruitment of the major primary septum synthesizing enzyme Bgs1 and consequent ring constriction. Cdc42 is also required for proper localization of the septum digesting glucanases at the division site. Thus, Cdc42 is required to promote multiple steps during cytokinesis.

scholarly journals Contractile ring constriction and septation in fission yeast are integrated mutually stabilizing processes

2021 ◽  
Author(s):  
Sathish Thiyagarajan ◽  
Zachary A McDargh ◽  
Shuyuan Wang ◽  
Ben O'Shaughnessy
Keyword(s):  
Cell Wall ◽  
Fission Yeast ◽  
Growth Ring ◽  
Integrated System ◽  
Animal Cells ◽  
Contractile Ring ◽  
Cell Wall Growth ◽  
Ring Constriction ◽  
Wall Growth ◽  
In Cells

In common with other cellular machineries, the actomyosin contractile ring that divides cells during cytokinesis does not operate in isolation. Contractile rings in animal cells interact with contiguous actomyosin cortex, while ring constriction in many cell-walled organisms couples tightly to cell wall growth. In fission yeast, a septum grows in the wake of the constricting ring, ensuring cytokinesis leaves two daughter cells fully enclosed by cell wall. Here we mathematical modeled the integrated constriction-septation system in fission yeast, with a kinetic growth model evolving the 3D septum shape coupled to a molecularly explicit simulation of the contractile ring highly constrained by experimental data. Simulations revealed influences in both directions, stabilizing the ring-septum system as a whole. By providing a smooth circular anchoring surface for the ring, the inner septum leading edge stabilized ring organization and tension production; by mechanically regulating septum circularity and in-plane growth, ring tension stabilized septum growth and shape. Genetic or pharmacological perturbation of either subsystem destabilized this delicate balance, precipitating uncontrolled positive feedback with disastrous morphological and functional consequences. Thus, high curvature septum irregularities triggered bridging instabilities, in which contractile ring segments became unanchored. Bridging abolished the local tension-mediated septum shape regulation, exacerbating the irregularity in a mutually destabilizing runaway process. Our model explains a number of previously mysterious experimental observations, including unanchoring of ring segments observed in cells with mutations in the septum-growing β-glucan synthases, and irregular septa in cells with mutations in the contractile ring myosin-II Myo2. Thus, the contractile ring and cell wall growth cellular machineries operate as a single integrated system, whose stability relies on mutual regulation by the two subsystems.

scholarly journals Analysis of the contribution of phosphoinositides to medial septation in fission yeast highlights the importance of PI(4,5)P2 for medial contractile ring anchoring

2018 ◽  
Vol 29 (18) ◽  
pp. 2148-2155 ◽  
Author(s):  
Chloe E. Snider ◽  
Alaina H. Willet ◽  
HannahSofia T. Brown ◽  
Kathleen L. Gould
Keyword(s):  
Plasma Membrane ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Specific Role ◽  
Elevated Plasma ◽  
Contractile Ring ◽  
Nuclear Position

In Schizosaccharomyces pombe, loss of the plasma membrane PI4-kinase scaffold Efr3 leads to sliding of the cytokinetic ring (CR) away from the cell center during anaphase, implicating phosphoinositides (PIPs) in CR anchoring. However, whether other PIP regulators contribute to CR anchoring has not been investigated. Here we report that mutants of other PIP kinases and their regulators divide with off-center septa, similar to efr3∆. Using new biosensors for S. pombe PIPs, we confirm that these mutants have disrupted PIP composition. We extend a previous finding that a mutant known to decrease PI(3,5)P2 levels indirectly affects CR positioning by increasing vacuole size which disrupts nuclear position at the onset of mitosis. Indeed, we found that other mutants with increased vacuole size also disrupt medial division via this mechanism. Although elevated plasma membrane PI(4,5)P2 levels do not affect medial cytokinesis, mutants with decreased levels display CR sliding events indicating a specific role for PI(4,5)P2 in CR anchoring.

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