scholarly journals Septin ring assembly is regulated by Spt20, a structural subunit of the SAGA complex

2014 ◽  
Vol 127 (18) ◽  
pp. 4024-4036 ◽  
Author(s):  
B. Lei ◽  
N. Zhou ◽  
Y. Guo ◽  
W. Zhao ◽  
Y.-W. Tan ◽  
...  
Keyword(s):  
Saga Complex ◽  
Septin Ring ◽  
Ring Assembly ◽  
Structural Subunit

scholarly journals Septin ring assembly involves cycles of GTP loading and hydrolysis by Cdc42p

2002 ◽  
Vol 156 (2) ◽  
pp. 315-326 ◽  
Author(s):  
Amy S. Gladfelter ◽  
Indrani Bose ◽  
Trevin R. Zyla ◽  
Elaine S.G. Bardes ◽  
Daniel J. Lew
Keyword(s):  
Transcriptional Activation ◽  
Gtpase Activating Protein ◽  
Gtp Hydrolysis ◽  
Septin Ring ◽  
Turn On ◽  
Ring Assembly ◽  
Bud Emergence ◽  
Assembly Factor ◽  
Gtpase Cycle ◽  
Budding Yeast Cell Cycle

At the beginning of the budding yeast cell cycle, the GTPase Cdc42p promotes the assembly of a ring of septins at the site of future bud emergence. Here, we present an analysis of cdc42 mutants that display specific defects in septin organization, which identifies an important role for GTP hydrolysis by Cdc42p in the assembly of the septin ring. The mutants show defects in basal or stimulated GTP hydrolysis, and the septin misorganization is suppressed by overexpression of a Cdc42p GTPase-activating protein (GAP). Other mutants known to affect GTP hydrolysis by Cdc42p also caused septin misorganization, as did deletion of Cdc42p GAPs. In performing its roles in actin polarization and transcriptional activation, GTP-Cdc42p is thought to function by activating and/or recruiting effectors to the site of polarization. Excess accumulation of GTP-Cdc42p due to a defect in GTP hydrolysis by the septin-specific alleles might cause unphysiological activation of effectors, interfering with septin assembly. However, the recessive and dose-sensitive genetic behavior of the septin-specific cdc42 mutants is inconsistent with the septin defect stemming from a dominant interference of this type. Instead, we suggest that assembly of the septin ring involves repeated cycles of GTP loading and GTP hydrolysis by Cdc42p. These results suggest that a single GTPase, Cdc42p, can act either as a ras-like GTP-dependent “switch” to turn on effectors or as an EF-Tu–like “assembly factor” using the GTPase cycle to assemble a macromolecular structure.

scholarly journals Septin ring size scaling and dynamics require the coiled-coil region of Shs1p

2012 ◽  
Vol 23 (17) ◽  
pp. 3391-3406 ◽  
Author(s):  
Rebecca A. Meseroll ◽  
Louisa Howard ◽  
Amy S. Gladfelter
Keyword(s):  
Coiled Coil ◽  
Higher Order ◽  
Membrane Curvature ◽  
Negative Regulator ◽  
Ring Size ◽  
Septin Ring ◽  
Ring Assembly ◽  
Coiled Coil Domain ◽  
C Terminus ◽  
Important Negative Regulator

Septins are conserved GTP-binding proteins that assemble into heteromeric complexes that form filaments and higher-order structures in cells. What directs filament assembly, determines the size of higher-order septin structures, and governs septin dynamics is still not well understood. We previously identified two kinases essential for septin ring assembly in the filamentous fungus Ashbya gossypii and demonstrate here that the septin Shs1p is multiphosphorylated at the C-terminus of the protein near the predicted coiled-coil domain. Expression of the nonphosphorylatable allele shs1-9A does not mimic the loss of the kinase nor does complete truncation of the Shs1p C-terminus. Surprisingly, however, loss of the C-terminus or the predicted coiled-coil domain of Shs1p generates expanded zones of septin assemblies and ectopic septin fibers, as well as aberrant cell morphology. The expanded structures form coincident with ring assembly and are heteromeric. Interestingly, while septin recruitment to convex membranes is increased, septin localization is diminished at concave membranes in these mutants. Additionally, the loss of the coiled-coil leads to increased mobility of Shs1p. These data indicate the coiled-coil of Shs1p is an important negative regulator of septin ring size and mobility, and its absence may make septin assembly sensitive to local membrane curvature.

scholarly journals Rho1- and Pkc1-dependent phosphorylation of the F-BAR protein Syp1 contributes to septin ring assembly

2015 ◽  
Vol 26 (18) ◽  
pp. 3245-3262 ◽  
Author(s):  
Laura Merlini ◽  
Alessio Bolognesi ◽  
Maria Angeles Juanes ◽  
Franck Vandermoere ◽  
Thibault Courtellemont ◽  
...  
Keyword(s):  
Cell Types ◽  
Effector Protein ◽  
Cleavage Furrow ◽  
Membrane Remodeling ◽  
Septin Ring ◽  
Ring Assembly ◽  
Kinase C ◽  
Cell Wall Remodeling ◽  
Bud Neck ◽  
Ring Stability

In many cell types, septins assemble into filaments and rings at the neck of cellular appendages and/or at the cleavage furrow to help compartmentalize the plasma membrane and support cytokinesis. How septin ring assembly is coordinated with membrane remodeling and controlled by mechanical stress at these sites is unclear. Through a genetic screen, we uncovered an unanticipated link between the conserved Rho1 GTPase and its effector protein kinase C (Pkc1) with septin ring stability in yeast. Both Rho1 and Pkc1 stabilize the septin ring, at least partly through phosphorylation of the membrane-associated F-BAR protein Syp1, which colocalizes asymmetrically with the septin ring at the bud neck. Syp1 is displaced from the bud neck upon Pkc1-dependent phosphorylation at two serines, thereby affecting the rigidity of the new-forming septin ring. We propose that Rho1 and Pkc1 coordinate septin ring assembly with membrane and cell wall remodeling partly by controlling Syp1 residence at the bud neck.

scholarly journals Dynamics of septin ring and collar formation in Saccharomyces cerevisiae

2011 ◽  
Vol 392 (8-9) ◽  
pp. 689-697 ◽  
Author(s):  
Hsin Chen ◽  
Audrey S. Howell ◽  
Alex Robeson ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Septin Ring ◽  
Ring Assembly ◽  
Bud Emergence ◽  
Steady Rate ◽  
Constant Rate ◽  
Bud Neck ◽  
Quantitative Analyses ◽  
Reduced Rate ◽  
Mother Cells

Abstract Although the septin ring and collar in budding yeast were described over 20 years ago, there is still controversy regarding the organization of septin filaments within these structures and about the way in which the ring first forms and about how it converts into a collar at the mother-bud neck. Here we present quantitative analyses of the recruitment of fluorescently-tagged septins to the ring and collar through the cell cycle. Septin ring assembly began several minutes after polarity establishment and this interval was longer in daughter than in mother cells, suggesting asymmetric inheritance of septin regulators. Septins formed an initial faint and irregular ring, which became more regular as septins were recruited at a constant rate. This steady rate of septin recruitment continued for several minutes after the ring converted to a collar at bud emergence. We did not detect a stepwise change in septin fluorescence during the ring-to-collar transition. After collar formation, septins continued to accumulate at the bud neck, though at a reduced rate, until the onset of cytokinesis when the amount of neck-localized septins rapidly decreased. Implications for the mechanism of septin ring assembly are discussed.

scholarly journals Septin Ring Assembly Requires Concerted Action of Polarisome Components, a PAK Kinase Cla4p, and the Actin Cytoskeleton inSaccharomyces cerevisiae

2004 ◽  
Vol 15 (12) ◽  
pp. 5329-5345 ◽  
Author(s):  
Jun Kadota ◽  
Takaharu Yamamoto ◽  
Shiro Yoshiuchi ◽  
Erfei Bi ◽  
Kazuma Tanaka
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
Small Gtpase ◽  
Septin Ring ◽  
Ring Assembly ◽  
Actin Cable ◽  
Family Protein ◽  
Latrunculin A ◽  
Actin Cables ◽  
Initial Assembly

Septins are filament-forming proteins that function in cytokinesis in a wide variety of organisms. In budding yeast, the small GTPase Cdc42p triggers the recruitment of septins to the incipient budding site and the assembly of septins into a ring. We herein report that Bni1p and Cla4p, effectors of Cdc42p, are required for the assembly of the septin ring during the initiation of budding but not for its maintenance after the ring converts to a septin collar. In bni1Δ cla4-75-td mutant, septins were recruited to the incipient budding site. However, the septin ring was not assembled, and septins remained at the polarized growing sites. Bni1p, a formin family protein, is a member of the polarisome complex with Spa2p, Bud6p, and Pea2p. All spa2Δ cla4-75-td, bud6Δ cla4-75-td, and pea2Δ cla4-75-td mutants showed defects in septin ring assembly. Bni1p stimulates actin polymerization for the formation of actin cables. Point mutants of BNI1 that are specifically defective in actin cable formation also exhibited septin ring assembly defects in the absence of Cla4p. Consistently, treatment of cla4Δ mutant with the actin inhibitor latrunculin A inhibited septin ring assembly. Our results suggest that polarisome components and Cla4p are required for the initial assembly of the septin ring and that the actin cytoskeleton is involved in this process.

A cucurbituril-pillararene ring-on-ring complex

2021 ◽  
Author(s):  
Dejun Zhang ◽  
Hao Tang ◽  
Guozhen Zhang ◽  
Lingyun Wang ◽  
Derong Cao
Keyword(s):  
Ring Assembly ◽  
Ring Complex ◽  
New Type

A new type of non-intertwined ring-on-ring assembly was formed by the portal binding between a perfunctionalized polycationic pillar[5]arene and a cucurbit[10]uril, demonstrating a facile approach to solubilize a large macrocycle...

Design a Kind of Oblique-Cone-Sliding-Ring Assembly Seal Device

2014 ◽  
Vol 496-500 ◽  
pp. 1007-1011
Author(s):  
Jian Hua Fang ◽  
Wei Yan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Work Stress ◽  
Contact Stress ◽  
Element Analysis ◽  
Ring Assembly ◽  
User Demand ◽  
Oblique Cone

The design of seal device that can be used in carbide actor is a real problems.This paper presents a kind of oblique-cone-slid-ring (OCSR) assembly seal device that can self-compensate the seal wear in application. The max contact stress on the seal surface and other contact face is far bigger than the work stress of sealed medium in carbide actor. That means the design satisfies the user demand . Keywords: oblique-cone-sliding-ring (OCSR) assembly seal; self-compensation to seal wear; finite element analysis; contact stress;

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