scholarly journals Regulation of polarized growth initiation and termination cycles by the polarisome and Cdc42 regulators

2004 ◽  
Vol 164 (2) ◽  
pp. 207-218 ◽  
Author(s):  
Scott Bidlingmaier ◽  
Michael Snyder
Keyword(s):  
Cell Differentiation ◽  
Cell Growth ◽  
Fusion Proteins ◽  
Eukaryotic Cell ◽  
Yeast Cells ◽  
Polarized Growth ◽  
High Concentration ◽  
Dynamic Regulation ◽  
Polarized Cell Growth ◽  
Growth Initiation

The dynamic regulation of polarized cell growth allows cells to form structures of defined size and shape. We have studied the regulation of polarized growth using mating yeast as a model. Haploid yeast cells treated with high concentration of pheromone form successive mating projections that initiate and terminate growth with regular periodicity. The mechanisms that control the frequency of growth initiation and termination under these conditions are not well understood. We found that the polarisome components Spa2, Pea2, and Bni1 and the Cdc42 regulators Cdc24 and Bem3 control the timing and frequency of projection formation. Loss of polarisome components and mutation of Cdc24 decrease the frequency of projection formation, while loss of Bem3 increases the frequency of projection formation. We found that polarisome components and the cell fusion proteins Fus1 and Fus2 are important for the termination of projection growth. Our results define the first molecular regulators that control the timing of growth initiation and termination during eukaryotic cell differentiation.

scholarly journals Specification of sites for polarized growth in Saccharomyces cerevisiae and the influence of external factors on site selection.

1992 ◽  
Vol 3 (9) ◽  
pp. 1025-1035 ◽  
Author(s):  
K Madden ◽  
M Snyder
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Types ◽  
Growth Conditions ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Polarized Growth ◽  
Mating Partner ◽  
Polarized Cell Growth ◽  
External Conditions

Many eucaryotic cell types exhibit polarized cell growth and polarized cell division at nonrandom sites. The sites of polarized growth were investigated in G1 arrested haploid Saccharomyces cerevisiae cells. When yeast cells are arrested during G1 either by treatment with alpha-factor or by shifting temperature-sensitive cdc28-1 cells to the restrictive temperature, the cells form a projection. Staining with Calcofluor reveals that in both cases the projection usually forms at axial sites (i.e., next to the previous bud scar); these are the same sites where bud formation is expected to occur. These results indicate that sites of polarized growth are specified before the end of G1. Sites of polarized growth can be influenced by external conditions. Cells grown to stationary phase and diluted into fresh medium preferentially select sites for polarized growth opposite the previous bud scar (i.e., distal sites). Incubation of cells in a mating mixture results in projection formation at nonaxial sites: presumably cells form projections toward their mating partner. These observations have important implications in understanding three aspects of cell polarity in yeast: 1) how yeast cell shape is influenced by growth conditions 2) how sites of polarized growth are chosen, and 3) the pathway by which polarity is affected and redirected during the mating process.

Cdc42 regulates polarized growth and cell integrity in fission yeast

2014 ◽  
Vol 42 (1) ◽  
pp. 201-205 ◽  
Author(s):  
Sergio A. Rincón ◽  
Miguel Estravís ◽  
Pilar Pérez
Keyword(s):  
Cell Growth ◽  
Fission Yeast ◽  
Rho Gtpase ◽  
Short Review ◽  
Model Systems ◽  
Polarized Growth ◽  
Cell Integrity ◽  
Polarized Cell Growth ◽  
New Material ◽  
High Level

Polarized cell growth requires a well-orchestrated number of events, namely selection of growth site, organization of cytoskeleton elements and delivery of new material to the growth region. The small Rho GTPase Cdc42 has emerged as a major organizer of polarized growth through its participation in many of these events. In the present short review, we focus on the regulation of Cdc42 activity and localization as well as how it controls downstream events necessary for polarized cell growth in Schizosaccharomyces pombe. Owing to the high level of similarity of the polarity pathways, analogies between fission yeast and other model systems can be useful to decipher how cells can actively define their shape by polarized growth.

scholarly journals Regulation of cortical actin cytoskeleton assembly during polarized cell growth in budding yeast.

1995 ◽  
Vol 128 (4) ◽  
pp. 599-615 ◽  
Author(s):  
R Li ◽  
Y Zheng ◽  
D G Drubin
Keyword(s):  
Cell Growth ◽  
Actin Cytoskeleton ◽  
Actin Filaments ◽  
Budding Yeast ◽  
Yeast Cells ◽  
Actin Assembly ◽  
Cortical Actin ◽  
Polarized Cell Growth ◽  
Nucleation Activity

We have established an in vitro assay for assembly of the cortical actin cytoskeleton of budding yeast cells. After permeabilization of yeast by a novel procedure designed to maintain the spatial organization of cellular constituents, exogenously added fluorescently labeled actin monomers assemble into distinct structures in a pattern that is similar to the cortical actin distribution in vivo. Actin assembly in the bud of small-budded cells requires a nucleation activity provided by protein factors that appear to be distinct from the barbed ends of endogenous actin filaments. This nucleation activity is lost in cells that lack either Sla1 or Sla2, proteins previously implicated in cortical actin cytoskeleton function, suggesting a possible role for these proteins in the nucleation reaction. The rate and the extent of actin assembly in the bud are increased in permeabilized delta cap2 cells, providing evidence that capping protein regulates the ability of the barbed ends of actin filaments to grow in yeast cells. Actin incorporation in the bud can be stimulated by treating the permeabilized cells with GTP-gamma S, and, significantly, the stimulatory effect is eliminated by a mutation in CDC42, a gene that encodes a Rho-like GTP-binding protein required for bud formation. Furthermore, the lack of actin nucleation activity in the cdc42 mutant can be complemented in vitro by a constitutively active Cdc42 protein. These results suggest that Cdc42 is closely involved in regulating actin assembly during polarized cell growth.

scholarly journals ThePXL1Gene ofSaccharomyces cerevisiaeEncodes a Paxillin-like Protein Functioning in Polarized Cell Growth

2004 ◽  
Vol 15 (4) ◽  
pp. 1904-1917 ◽  
Author(s):  
Nancy A. Mackin ◽  
Tarek J. Sousou ◽  
Scott E. Erdman
Keyword(s):  
Cell Growth ◽  
Rho Gtpase ◽  
Cell Types ◽  
Scaffolding Protein ◽  
Polarized Growth ◽  
Lim Domain ◽  
Reading Frame ◽  
Growth Defects ◽  
Pathway Activation ◽  
Polarized Cell Growth

The Saccharomyces cerevisiae open reading frame YKR090w encodes a predicted protein displaying similarity in organization to paxillin, a scaffolding protein that organizes signaling and actin cytoskeletal regulating activities in many higher eucaryotic cell types. We found that YKR090w functions in a manner analogous to paxillin as a mediator of polarized cell growth; thus, we have named this gene PXL1 (Paxillin-like protein 1). Analyses of pxl1Δ strains show that PXL1 is required for the selection and maintenance of polarized growth sites during vegetative growth and mating. Genetic analyses of strains lacking both PXL1 and the Rho GAP BEM2 demonstrate that such cells display pronounced growth defects in response to different conditions causing Rho1 pathway activation. PXL1 also displays genetic interactions with the Rho1 effector FKS1. Pxl1p may therefore function as a modulator of Rho-GTPase signaling. A GFP::Pxl1 fusion protein localizes to sites of polarized cell growth. Experiments mapping the localization determinants of Pxl1p demonstrate the existence of localization mechanisms conserved between paxillin and Pxl1p and indicate an evolutionarily ancient and conserved role for LIM domain proteins in acting to modulate cell signaling and cytoskeletal organization during polarized growth.

scholarly journals Reciprocal regulation of TORC signaling and tRNA modifications by Elongator enforces nutrient-dependent cell fate

2019 ◽  
Vol 5 (6) ◽  
pp. eaav0184 ◽  
Author(s):  
Julie Candiracci ◽  
Valerie Migeot ◽  
Yok-Hian Chionh ◽  
Fanelie Bauer ◽  
Thomas Brochier ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Cell Growth ◽  
Cell Fate ◽  
Glycogen Synthase ◽  
Yeast Cells ◽  
Glycogen Synthase Kinase 3 ◽  
Trna Modification ◽  
Reciprocal Regulation ◽  
Trna Modifications ◽  
Dependent Cell

Nutrient availability has a profound impact on cell fate. Upon nitrogen starvation, wild-type fission yeast cells uncouple cell growth from cell division to generate small, round-shaped cells that are competent for sexual differentiation. The TORC1 (TOR complex 1) and TORC2 complexes exert opposite controls on cell growth and cell differentiation, but little is known about how their activity is coordinated. We show that transfer RNA (tRNA) modifications by Elongator are critical for this regulation by promoting the translation of both key components of TORC2 and repressors of TORC1. We further identified the TORC2 pathway as an activator of Elongator by down-regulating a Gsk3 (glycogen synthase kinase 3)–dependent inhibitory phosphorylation of Elongator. Therefore, a feedback control is operating between TOR complex (TORC) signaling and tRNA modification by Elongator to enforce the advancement of mitosis that precedes cell differentiation.

scholarly journals Assessment and Imaging of Intracellular Magnesium in SaOS-2 Osteosarcoma Cells and Its Role in Proliferation

Nutrients ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 1376
Author(s):  
Concettina Cappadone ◽  
Emil Malucelli ◽  
Maddalena Zini ◽  
Giovanna Farruggia ◽  
Giovanna Picone ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Growth ◽  
Magnesium Deficiency ◽  
Acid Synthesis ◽  
Osteosarcoma Cell ◽  
Osteosarcoma Cells ◽  
High Concentration ◽  
Proliferating Cells ◽  
Intracellular Magnesium ◽  
In Cells

Magnesium is an essential nutrient involved in many important processes in living organisms, including protein synthesis, cellular energy production and storage, cell growth and nucleic acid synthesis. In this study, we analysed the effect of magnesium deficiency on the proliferation of SaOS-2 osteosarcoma cells. When quiescent magnesium-starved cells were induced to proliferate by serum addition, the magnesium content was 2–3 times lower in cells maintained in a medium without magnesium compared with cells growing in the presence of the ion. Magnesium depletion inhibited cell cycle progression and caused the inhibition of cell proliferation, which was associated with mTOR hypophosphorylation at Serine 2448. In order to map the intracellular magnesium distribution, an analytical approach using synchrotron-based X-ray techniques was applied. When cell growth was stimulated, magnesium was mainly localized near the plasma membrane in cells maintained in a medium without magnesium. In non-proliferating cells growing in the presence of the ion, high concentration areas inside the cell were observed. These results support the role of magnesium in the control of cell proliferation, suggesting that mTOR may represent an important target for the antiproliferative effect of magnesium. Selective control of magnesium availability could be a useful strategy for inhibiting osteosarcoma cell growth.

The nine amino-terminal residues of delta-aminolevulinate synthase direct beta-galactosidase into the mitochondrial matrix

1986 ◽  
Vol 6 (2) ◽  
pp. 355-364
Author(s):  
T Keng ◽  
E Alani ◽  
L Guarente
Keyword(s):  
Amino Acid ◽  
Fusion Proteins ◽  
Specific Activity ◽  
Nuclear Gene ◽  
Yeast Cells ◽  
Mitochondrial Matrix ◽  
Aminolevulinate Synthase ◽  
Amino Terminal ◽  
Activity Measurements ◽  
Beta Galactosidase

delta-Aminolevulinate synthase, the first enzyme in the heme biosynthetic pathway, is encoded by the nuclear gene HEM1. The enzyme is synthesized as a precursor in the cytoplasm and imported into the matrix of the mitochondria, where it is processed to its mature form. Fusions of beta-galactosidase to various lengths of amino-terminal fragments of delta-aminolevulinate synthase were constructed and transformed into yeast cells. The subcellular location of the fusion proteins was determined by organelle fractionation. Fusion proteins were found to be associated with the mitochondria. Protease protection experiments involving the use of intact mitochondria or mitoplasts localized the fusion proteins to the mitochondrial matrix. This observation was confirmed by fractionation of the mitochondrial compartments and specific activity measurements of beta-galactosidase activity. The shortest fusion protein contains nine amino acid residues of delta-aminolevulinate synthase, indicating that nine amino-terminal residues are sufficient to localize beta-galactosidase to the mitochondrial matrix. The amino acid sequence deduced from the DNA sequence of HEM1 showed that the amino-terminal region of delta-aminolevulinate synthase was largely hydrophobic, with a few basic residues interspersed.

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