scholarly journals Casein kinase 1γ acts as a molecular switch for cell polarization through phosphorylation of the polarity factor T ea1 in fission yeast

2015 ◽  
Vol 20 (12) ◽  
pp. 1046-1058 ◽  
Author(s):  
Takayuki Koyano ◽  
Karin Barnouin ◽  
Ambrosius P. Snijders ◽  
Kazunori Kume ◽  
Dai Hirata ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Molecular Switch ◽  
Casein Kinase ◽  
Cell Polarization ◽  
Polarity Factor

scholarly journals Activation of Cdc42 GTPase upon CRY2-Induced Cortical Recruitment Is Antagonized by GAPs in Fission Yeast

Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 2089 ◽  
Author(s):  
Iker Lamas ◽  
Nathalie Weber ◽  
Sophie G. Martin
Keyword(s):  
Fission Yeast ◽  
Positive Feedback ◽  
Antagonistic Activity ◽  
Cell Polarization ◽  
Small Gtpase ◽  
Nucleotide Exchange ◽  
Gtpase Activating Protein ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Cell Architecture

The small GTPase Cdc42 is critical for cell polarization in eukaryotic cells. In rod-shaped fission yeast Schizosaccharomyces pombe cells, active GTP-bound Cdc42 promotes polarized growth at cell poles, while inactive Cdc42-GDP localizes ubiquitously also along cell sides. Zones of Cdc42 activity are maintained by positive feedback amplification involving the formation of a complex between Cdc42-GTP, the scaffold Scd2, and the guanine nucleotide exchange factor (GEF) Scd1, which promotes the activation of more Cdc42. Here, we use the CRY2-CIB1 optogenetic system to recruit and cluster a cytosolic Cdc42 variant at the plasma membrane and show that this leads to its moderate activation also on cell sides. Surprisingly, Scd2, which binds Cdc42-GTP, is still recruited to CRY2-Cdc42 clusters at cell sides in individual deletion of the GEFs Scd1 or Gef1. We show that activated Cdc42 clusters at cell sides are able to recruit Scd1, dependent on the scaffold Scd2. However, Cdc42 activity is not amplified by positive feedback and does not lead to morphogenetic changes, due to antagonistic activity of the GTPase activating protein Rga4. Thus, the cell architecture is robust to moderate activation of Cdc42 at cell sides.

scholarly journals Roles of a Fimbrin and an α-Actinin-like Protein in Fission Yeast Cell Polarization and Cytokinesis

2001 ◽  
Vol 12 (4) ◽  
pp. 1061-1077 ◽  
Author(s):  
Jian-Qiu Wu ◽  
Jürg Bähler ◽  
John R. Pringle
Keyword(s):  
Fission Yeast ◽  
Protein Localization ◽  
Normal Growth ◽  
Growth Conditions ◽  
Cell Polarization ◽  
Dependent Manner ◽  
Cortical Actin ◽  
Ring Assembly ◽  
Or Organization

Eukaryotic cells contain many actin-interacting proteins, including the α-actinins and the fimbrins, both of which have actin cross-linking activity in vitro. We report here the identification and characterization of both an α-actinin-like protein (Ain1p) and a fimbrin (Fim1p) in the fission yeast Schizosaccharomyces pombe. Ain1p localizes to the actomyosin-containing medial ring in an F-actin–dependent manner, and the Ain1p ring contracts during cytokinesis. ain1 deletion cells have no obvious defects under normal growth conditions but display severe cytokinesis defects, associated with defects in medial-ring and septum formation, under certain stress conditions. Overexpression of Ain1p also causes cytokinesis defects, and the ain1 deletion shows synthetic effects with other mutations known to affect medial-ring positioning and/or organization. Fim1p localizes both to the cortical actin patches and to the medial ring in an F-actin–dependent manner, and several lines of evidence suggest that Fim1p is involved in polarization of the actin cytoskeleton. Although a fim1deletion strain has no detectable defect in cytokinesis, overexpression of Fim1p causes a lethal cytokinesis defect associated with a failure to form the medial ring and concentrate actin patches at the cell middle. Moreover, an ain1 fim1 double mutant has a synthetical-lethal defect in medial-ring assembly and cell division. Thus, Ain1p and Fim1p appear to have an overlapping and essential function in fission yeast cytokinesis. In addition, protein-localization and mutant-phenotype data suggest that Fim1p, but not Ain1p, plays important roles in mating and in spore formation.

scholarly journals A Molecular Switch for the Orientation of Epithelial Cell Polarization

2014 ◽  
Vol 31 (2) ◽  
pp. 171-187 ◽  
Author(s):  
David M. Bryant ◽  
Julie Roignot ◽  
Anirban Datta ◽  
Arend W. Overeem ◽  
Minji Kim ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Molecular Switch ◽  
Cell Polarization

scholarly journals Casein Kinase 1γ Ensures Monopolar Growth Polarity under Incomplete DNA Replication Downstream of Cds1 and Calcineurin in Fission Yeast

2015 ◽  
Vol 35 (9) ◽  
pp. 1533-1542 ◽  
Author(s):  
Takayuki Koyano ◽  
Manabu Konishi ◽  
Sophie G. Martin ◽  
Yoshikazu Ohya ◽  
Dai Hirata ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Cell Polarity ◽  
Molecular Mechanisms ◽  
Kinase Activity ◽  
Developmental Stages ◽  
Casein Kinase ◽  
S Phase ◽  
Cellular Functions ◽  
C Terminus ◽  
Polarity Transition

Cell polarity is essential for various cellular functions during both proliferative and developmental stages, and it displays dynamic alterations in response to intracellular and extracellular cues. However, the molecular mechanisms underlying spatiotemporal control of polarity transition are poorly understood. Here, we show that fission yeast Cki3 (a casein kinase 1γ homolog) is a critical regulator to ensure persistent monopolar growth during S phase. Unlike the wild type,cki3mutant cells undergo bipolar growth when S phase is blocked, a condition known to delay transition from monopolar to bipolar growth (termed NETO [newendtakeoff]). Consistent with this role, Cki3 kinase activity is substantially increased, and cells lose their viability in the absence of Cki3 upon an S-phase block. Cki3 acts downstream of the checkpoint kinase Cds1/Chk2 and calcineurin, and the latter physically interacts with Cki3. Autophosphorylation in the C terminus is inhibitory toward Cki3 kinase activity, and calcineurin is responsible for its dephosphorylation. Cki3 localizes to the plasma membrane, and this localization requires the palmitoyltransferase complex Erf2-Erf4. Membrane localization is needed not only for proper NETO timing but also for Cki3 kinase activity. We propose that Cki3 acts as a critical inhibitor of cell polarity transition under S-phase arrest.

A PDE-DDE Model for Cell Polarization in Fission Yeast

2016 ◽  
Vol 76 (5) ◽  
pp. 1844-1870 ◽  
Author(s):  
Bin Xu ◽  
Paul C. Bressloff
Keyword(s):  
Fission Yeast ◽  
Cell Polarization

scholarly journals The Rho-GEF Gef3 interacts with the septin complex and activates the GTPase Rho4 during fission yeast cytokinesis

2015 ◽  
Vol 26 (2) ◽  
pp. 238-255 ◽  
Author(s):  
Ning Wang ◽  
Mo Wang ◽  
Yi-Hua Zhu ◽  
Timothy W. Grosel ◽  
Daokun Sun ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Cell Polarization ◽  
Nucleotide Exchange ◽  
Cellular Processes ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rho Gef

Rho GTPases, activated by Rho guanine nucleotide exchange factors (GEFs), are conserved molecular switches for signal transductions that regulate diverse cellular processes, including cell polarization and cytokinesis. The fission yeast Schizosaccharomyces pombe has six Rho GTPases (Cdc42 and Rho1–Rho5) and seven Rho GEFs (Scd1, Rgf1–Rgf3, and Gef1–Gef3). The GEFs for Rho2–Rho5 have not been unequivocally assigned. In particular, Gef3, the smallest Rho GEF, was barely studied. Here we show that Gef3 colocalizes with septins at the cell equator. Gef3 physically interacts with septins and anillin Mid2 and depends on them to localize. Gef3 coprecipitates with GDP-bound Rho4 in vitro and accelerates nucleotide exchange of Rho4, suggesting that Gef3 is a GEF for Rho4. Consistently, Gef3 and Rho4 are in the same genetic pathways to regulate septum formation and/or cell separation. In gef3∆ cells, the localizations of two potential Rho4 effectors—glucanases Eng1 and Agn1—are abnormal, and active Rho4 level is reduced, indicating that Gef3 is involved in Rho4 activation in vivo. Moreover, overexpression of active Rho4 or Eng1 rescues the septation defects of mutants containing gef3∆. Together our data support that Gef3 interacts with the septin complex and activates Rho4 GTPase as a Rho GEF for septation in fission yeast.

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