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.

scholarly journals Assembly of normal actomyosin rings in the absence of Mid1p and cortical nodes in fission yeast

2008 ◽  
Vol 183 (6) ◽  
pp. 979-988 ◽  
Author(s):  
Yinyi Huang ◽  
Hongyan Yan ◽  
Mohan K. Balasubramanian
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Ring Structure ◽  
Contractile Ring ◽  
Ring Assembly ◽  
Cell Biol ◽  
In Cells

Cytokinesis in many eukaryotes depends on the function of an actomyosin contractile ring. The mechanisms regulating assembly and positioning of this ring are not fully understood. The fission yeast Schizosaccharomyces pombe divides using an actomyosin ring and is an attractive organism for the study of cytokinesis. Recent studies in S. pombe (Wu, J.Q., V. Sirotkin, D.R. Kovar, M. Lord, C.C. Beltzner, J.R. Kuhn, and T.D. Pollard. 2006. J. Cell Biol. 174:391–402; Vavylonis, D., J.Q. Wu, S. Hao, B. O'Shaughnessy, and T.D. Pollard. 2008. Science. 319:97–100) have suggested that the assembly of the actomyosin ring is initiated from a series of cortical nodes containing several components of this ring. These studies have proposed that actomyosin interactions bring together the cortical nodes to form a compacted ring structure. In this study, we test this model in cells that are unable to assemble cortical nodes. Although the cortical nodes play a role in the timing of ring assembly, we find that they are dispensable for the assembly of orthogonal actomyosin rings. Thus, a mechanism that is independent of cortical nodes is sufficient for the assembly of normal actomyosin rings.

In vivo direct patulin-induced fluidization of the plasma membrane of fission yeast Schizosaccharomyces pombe

2010 ◽  
Vol 48 (7) ◽  
pp. 1898-1904 ◽  
Author(s):  
Eszter Horváth ◽  
Gábor Papp ◽  
József Belágyi ◽  
Zoltán Gazdag ◽  
Csaba Vágvölgyi ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast

scholarly journals Amiloride Uptake and Toxicity in Fission Yeast Are Caused by the Pyridoxine Transporter Encoded by bsu1+ (car1+)

2005 ◽  
Vol 4 (2) ◽  
pp. 319-326 ◽  
Author(s):  
Jürgen Stolz ◽  
Heike J. P. Wöhrmann ◽  
Christian Vogl
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Plasma Membrane ◽  
Multidrug Resistance ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Vitamin B ◽  
Acidic Ph ◽  
Ph Optimum ◽  
Sodium Transporters ◽  
High Affinity

ABSTRACT Amiloride, a diuretic drug that acts by inhibition of various sodium transporters, is toxic to the fission yeast Schizosaccharomyces pombe. Previous work has established that amiloride sensitivity is caused by expression of car1 +, which encodes a protein with similarity to plasma membrane drug/proton antiporters from the multidrug resistance family. Here we isolated car1 + by complementation of Saccharomyces cerevisiae mutants that are deficient in pyridoxine biosynthesis and uptake. Our data show that Car1p represents a new high-affinity, plasma membrane-localized import carrier for pyridoxine, pyridoxal, and pyridoxamine. We therefore propose the gene name bsu1 + (for vitamin B6 uptake) to replace car1 +. Bsu1p displays an acidic pH optimum and is inhibited by various protonophores, demonstrating that the protein works as a proton symporter. The expression of bsu1 + is associated with amiloride sensitivity and pyridoxine uptake in both S. cerevisiae and S. pombe cells. Moreover, amiloride acts as a competitor of pyridoxine uptake, demonstrating that both compounds are substrates of Bsu1p. Taken together, our data show that S. pombe and S. cerevisiae possess unrelated plasma membrane pyridoxine transporters. The S. pombe protein may be structurally related to the unknown human pyridoxine transporter, which is also inhibited by amiloride.

scholarly journals A Link between Aurora Kinase and Clp1/Cdc14 Regulation Uncovered by the Identification of a Fission Yeast Borealin-Like Protein

2009 ◽  
Vol 20 (16) ◽  
pp. 3646-3659 ◽  
Author(s):  
K. Adam Bohnert ◽  
Jun-Song Chen ◽  
Dawn M. Clifford ◽  
Craig W. Vander Kooi ◽  
Kathleen L. Gould
Keyword(s):  
Cell Division ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Kinase Activity ◽  
Sequence Similarity ◽  
Aurora Kinase ◽  
Genetic Interactions ◽  
Aurora B ◽  
Contractile Ring ◽  
Chromosomal Passenger

The chromosomal passenger complex (CPC) regulates various events in cell division. This complex is composed of a catalytic subunit, Aurora B kinase, and three nonenzymatic subunits, INCENP, Survivin, and Borealin. Together, these four subunits interdependently regulate CPC function, and they are highly conserved among eukaryotes. However, a Borealin homologue has never been characterized in the fission yeast, Schizosaccharomyces pombe . Here, we isolate a previously uncharacterized S. pombe protein through association with the Cdc14 phosphatase homologue, Clp1/Flp1, and identify it as a Borealin-like member of the CPC. Nbl1 (novel Borealin-like 1) physically associates with known CPC components, affects the kinase activity and stability of the S. pombe Aurora B homologue, Ark1, colocalizes with known CPC subunits during mitosis, and shows sequence similarity to human Borealin. Further analysis of the Clp1–Nbl1 interaction indicates that Clp1 requires CPC activity for proper accumulation at the contractile ring (CR). Consistent with this, we describe negative genetic interactions between mutant alleles of CPC and CR components. Thus, this study characterizes a fission yeast Borealin homologue and reveals a previously unrecognized connection between the CPC and the process of cytokinesis in S. pombe .

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.

Functional expression and cellular localization of the Na+/H+ exchanger Sod2 of the fission yeast Schizosaccharomyces pombe

2005 ◽  
Vol 83 (7) ◽  
pp. 565-572 ◽  
Author(s):  
Larry Fliegel ◽  
Christine Wiebe ◽  
Gordon Chua ◽  
Paul G Young
Keyword(s):  
Plasma Membrane ◽  
Membrane Protein ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Cellular Localization ◽  
Functional Expression ◽  
Cation Binding ◽  
Plasma Membrane Protein ◽  
Gfp Fusion Protein ◽  
Growing Cell

In the fission yeast Schizosaccharomyces pombe, the Na+/H+ exchanger, Sod2, plays a major role in the removal of excess intracellular sodium, and its disruption results in a sodium-sensitive phenotype. We examined the subcellular distribution and dynamics of Sod2 expression in S. pombe using a sod2-GFP fusion protein under the control of an attenuated version of the inducible nmt promoter. Sod2 was localized throughout the plasma membrane, the nuclear envelope, and some internal membrane systems. In exponentially growing cells, in which sod2-GFP was expressed and then the promoter turned-off, previously synthesized sod2-GFP was stable for long periods and found localized to the plasma membrane in the medial regions of the cell. It was not present at the actively growing cell ends. This suggests that these regions of the cell contain old plasma membrane protein vs. newly synthesized plasma membrane without Sod2 at the growing ends. Sod2 localization was not affected by salt stress. The results suggest that Sod2 is both a plasma membrane protein and is present in intracellular membranes. It is likely tethered within discrete regions of the plasma membrane and is not free to diffuse throughout the bilayer. Key words: Na+/H+ exchanger, Schizosaccharomyces pombe, cation binding, salt tolerance.

scholarly journals The Clp1/Cdc14 phosphatase contributes to the robustness of cytokinesis by association with anillin-related Mid1

2008 ◽  
Vol 181 (1) ◽  
pp. 79-88 ◽  
Author(s):  
Dawn M. Clifford ◽  
Benjamin A. Wolfe ◽  
Rachel H. Roberts-Galbraith ◽  
W. Hayes McDonald ◽  
John R. Yates ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Cell Cycle Control ◽  
Physical Property ◽  
Cyclin Dependent Kinase ◽  
Contractile Ring ◽  
Protein Mobility ◽  
Functional Consequences

Cdc14 phosphatases antagonize cyclin-dependent kinase–directed phosphorylation events and are involved in several facets of cell cycle control. We investigate the role of the fission yeast Cdc14 homologue Clp1/Flp1 in cytokinesis. We find that Clp1/Flp1 is tethered at the contractile ring (CR) through its association with anillin-related Mid1. Fluorescent recovery after photobleaching analyses indicate that Mid1, unlike other tested CR components, is anchored at the cell midzone, and this physical property is likely to account for its scaffolding role. By generating a mutation in mid1 that selectively disrupts Clp1/Flp1 tethering, we reveal the specific functional consequences of Clp1/Flp1 activity at the CR, including dephosphorylation of the essential CR component Cdc15, reductions in CR protein mobility, and CR resistance to mild perturbation. Our evidence indicates that Clp1/Flp1 must interact with the Mid1 scaffold to ensure the fidelity of Schizosaccharomyces pombe cytokinesis.

scholarly journals Sterol biosensor reveals LAM-family Ltc1-dependent sterol flow to endosomes upon Arp2/3 inhibition

2020 ◽  
Vol 219 (6) ◽  
Author(s):  
Magdalena Marek ◽  
Vincent Vincenzetti ◽  
Sophie G. Martin
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Biological Membranes ◽  
Time Lapse ◽  
Vesicular Trafficking ◽  
Actin Assembly ◽  
Contact Sites ◽  
Family Protein

Sterols are crucial components of biological membranes, which are synthetized in the ER and accumulate in the plasma membrane (PM). Here, by applying a genetically encoded sterol biosensor (D4H), we visualize a sterol flow between PM and endosomes in the fission yeast Schizosaccharomyces pombe. Using time-lapse and correlative light-electron microscopy, we found that inhibition of Arp2/3-dependent F-actin assembly promotes the reversible relocalization of D4H from the PM to internal sterol-rich compartments (STRIC) labeled by synaptobrevin Syb1. Retrograde sterol internalization to STRIC is independent of endocytosis or an intact Golgi, but depends on Ltc1, a LAM/StARkin-family protein localized to ER-PM contact sites. The PM in ltc1Δ cells over-accumulates sterols and upon Arp2/3 inhibition forms extended ER-interacting invaginations, indicating that sterol transfer contributes to PM size homeostasis. Anterograde sterol movement from STRIC is independent of canonical vesicular trafficking but requires Arp2/3, suggesting a novel role for this complex. Thus, transfer routes orthogonal to vesicular trafficking govern the flow of sterols in the cell.

scholarly journals Schizosaccharomyces pombe Pxl1 Is a Paxillin Homologue That Modulates Rho1 Activity and Participates in Cytokinesis

2008 ◽  
Vol 19 (4) ◽  
pp. 1727-1738 ◽  
Author(s):  
Mario Pinar ◽  
Pedro M. Coll ◽  
Sergio A. Rincón ◽  
Pilar Pérez
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Rho Gtpases ◽  
Actin Polymerization ◽  
Cell Integrity ◽  
Contractile Ring ◽  
Cytoskeleton Organization ◽  
Lim Domains ◽  
Actin Cytoskeleton Organization ◽  
Septation Initiation Network

Schizosaccharomyces pombe Rho GTPases regulate actin cytoskeleton organization and cell integrity. We studied the fission yeast gene SPBC4F6.12 based on its ability to suppress the thermosensitivity of cdc42-1625 mutant strain. This gene, named pxl1+, encodes a protein with three LIM domains that is similar to paxillin. Pxl1 does not interact with Cdc42 but it interacts with Rho1, and it negatively regulates this GTPase. Fission yeast Pxl1 forms a contractile ring in the cell division region and deletion of pxl1+ causes a delay in cell–cell separation, suggesting that it has a function in cytokinesis. Pxl1 N-terminal region is required and sufficient for its localization to the medial ring, whereas the LIM domains are necessary for its function. Pxl1 localization requires actin polymerization and the actomyosin ring, but it is independent of the septation initiation network (SIN) function. Moreover, Pxl1 colocalizes and interacts with Myo2, and Cdc15, suggesting that it is part of the actomyosin ring. Here, we show that in cells lacking Pxl1, the myosin ring is not correctly assembled and that actomyosin ring contraction is delayed. Together, these data suggest that Pxl1 modulates Rho1 GTPase signaling and plays a role in the formation and contraction of the actomyosin ring during cytokinesis.

scholarly journals A node organization in the actomyosin contractile ring generates tension and aids stability

2017 ◽  
Vol 28 (23) ◽  
pp. 3286-3297 ◽  
Author(s):  
Sathish Thiyagarajan ◽  
Shuyuan Wang ◽  
Ben O’Shaughnessy
Keyword(s):  
Mathematical Model ◽  
Plasma Membrane ◽  
Fission Yeast ◽  
Actin Filaments ◽  
Microscopy Study ◽  
Coarse Grained ◽  
Contractile Ring ◽  
Superresolution Microscopy

During cytokinesis, a contractile actomyosin ring constricts and divides the cell in two. How the ring marshals actomyosin forces to generate tension is not settled. Recently, a superresolution microscopy study of the fission yeast ring revealed that myosins and formins that nucleate actin filaments colocalize in plasma membrane-anchored complexes called nodes in the constricting ring. The nodes move bidirectionally around the ring. Here we construct and analyze a coarse-grained mathematical model of the fission yeast ring to explore essential consequences of the recently discovered ring ultrastructure. The model reproduces experimentally measured values of ring tension, explains why nodes move bidirectionally, and shows that tension is generated by myosin pulling on barbed-end-anchored actin filaments in a stochastic sliding-filament mechanism. This mechanism is not based on an ordered sarcomeric organization. We show that the ring is vulnerable to intrinsic contractile instabilities, and protection from these instabilities and organizational homeostasis require both component turnover and anchoring of components to the plasma membrane.

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