scholarly journals The Role of the Cell Integrity Pathway in Septum Assembly in Yeast

2021 ◽  
Vol 7 (9) ◽  
pp. 729
Author(s):  
Cesar Roncero ◽  
Rubén Celador ◽  
Noelia Sánchez ◽  
Patricia García ◽  
Yolanda Sánchez
Keyword(s):  
Cell Wall ◽  
Map Kinases ◽  
Signalling Pathways ◽  
Cell Integrity ◽  
Animal Cells ◽  
Yeast Saccharomyces Cerevisiae ◽  
Downstream Effectors ◽  
Cell Wall Integrity Pathway ◽  
Extracellular Matrix Remodelling ◽  
Relationship Of

Cytokinesis divides a mother cell into two daughter cells at the end of each cell cycle and proceeds via the assembly and constriction of a contractile actomyosin ring (CAR). Ring constriction promotes division furrow ingression, after sister chromatids are segregated to opposing sides of the cleavage plane. Cytokinesis contributes to genome integrity because the cells that fail to complete cytokinesis often reduplicate their chromosomes. While in animal cells, the last steps of cytokinesis involve extracellular matrix remodelling and mid-body abscission, in yeast, CAR constriction is coupled to the synthesis of a polysaccharide septum. To preserve cell integrity during cytokinesis, fungal cells remodel their cell wall through signalling pathways that connect receptors to downstream effectors, initiating a cascade of biological signals. One of the best-studied signalling pathways is the cell wall integrity pathway (CWI) of the budding yeast Saccharomyces cerevisiae and its counterpart in the fission yeast Schizosaccharomyces pombe, the cell integrity pathway (CIP). Both are signal transduction pathways relying upon a cascade of MAP kinases. However, despite strong similarities in the assembly of the septa in both yeasts, there are significant mechanistic differences, including the relationship of this process with the cell integrity signalling pathways.

scholarly journals The MAP kinase signal transduction network in Candida albicans

Microbiology ◽  
2006 ◽  
Vol 152 (4) ◽  
pp. 905-912 ◽  
Author(s):  
R. Alonso Monge ◽  
E. Román ◽  
C. Nombela ◽  
J. Pla
Keyword(s):  
Signal Transduction ◽  
Cell Wall ◽  
Candida Albicans ◽  
Map Kinases ◽  
Mitogen Activated Protein Kinase ◽  
Phenotypic Characterization ◽  
Cell Integrity ◽  
Hog Pathway ◽  
Chlamydospore Formation ◽  
Mitogen Activated Protein

MAP (mitogen-activated protein) kinase-mediated pathways are key elements in sensing and transmitting the response of cells to environmental conditions by the sequential action of phosphorylation events. In the fungal pathogen Candida albicans, different routes have been identified by genetic analysis, and especially by the phenotypic characterization of mutants altered in the Mkc1, Cek1/2 and Hog1 MAP kinases. The cell integrity (or MKC1-mediated) pathway is primarily involved in the biogenesis of the cell wall. The HOG pathway participates in the response to osmotic stress while the Cek1 pathway mediates mating and filamentation. Their actual functions are, however, much broader and Mkc1 senses several types of stress, while Hog1 is also responsive to other stress conditions and participates in two morphogenetic programmes: filamentation and chlamydospore formation. Furthermore, it has been recently shown that Cek1 participates in a putative pathway involved in the construction of the cell wall and which seems to be operative under basal conditions. As these stimuli are frequently encountered in the human host, they provide a reasonable explanation for the significant reduction in pathogenicity that several signal transduction mutants show in certain animal models of virulence. MAPK pathways therefore represent an attractive multienzymic system for which novel antifungal therapy could be designed.

scholarly journals Toll-like receptor signalling pathways as key targets for mediating the anti-inflammatory and immunosuppressive effects of glucocorticoids

2003 ◽  
Vol 179 (2) ◽  
pp. 139-144 ◽  
Author(s):  
PN Moynagh
Keyword(s):  
Transcription Factors ◽  
Map Kinases ◽  
Adaptor Protein ◽  
The Body ◽  
Signalling Pathways ◽  
Type I ◽  
Toll Like Receptor ◽  
Receptor Signalling ◽  
Downstream Effectors ◽  
Anti Inflammatory

Toll-like receptors (TLRs) play crucial roles in the induction of innate immune responses by recognising pathogen-associated molecular patterns. The engagement of TLRs by pathogens results in induction of co-stimulatory molecules that facilitate a specific immune response and also in the induction of pro-inflammatory proteins that will promote the elimination of pathogens from the body. TLRs employ many of the same signalling components as the type I interleukin (IL)-1 receptor (IL-1R). This is hardly surprising since the intracellular regions of TLRs and the IL-1R share a conserved Toll/IL-1R homology domain (TIR) that allows the receptors to recruit the intracellular TIR-containing adaptor protein Myd88. The latter then activates IL-1R-associated kinases that in turn recruit well-characterised downstream effectors culminating in activation of MAP kinases and transcription factors such as NFkappaB and AP-1. Since glucocorticoids are known to target the latter transcription factors and the MAP kinase cascades, this commentary highlights the likely crucial importance of Toll-like receptor signalling pathways as key targets for mediating the anti-inflammatory and immunosuppressive effects of steroids.

scholarly journals Yeast Protein Kinases and the RHO1 Exchange Factor TUS1 Are Novel Components of the Cell Integrity Pathway in Yeast

2002 ◽  
Vol 22 (5) ◽  
pp. 1329-1339 ◽  
Author(s):  
Tobias Schmelzle ◽  
Stephen B. Helliwell ◽  
Michael N. Hall
Keyword(s):  
Cell Wall ◽  
Actin Cytoskeleton ◽  
Map Kinase ◽  
Cell Integrity ◽  
Exchange Factor ◽  
Downstream Effectors ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
Map Kinase Pathway ◽  
Kinase Pathway

ABSTRACT The PKC1-associated mitogen-activated protein (MAP) kinase pathway of Saccharomyces cerevisiae regulates cell integrity by controlling the actin cytoskeleton and cell wall synthesis. Activation of PKC1 occurs via the GTPase RHO1 and the kinase pair PKH1 and PKH2. Here we report that YPK1 and YPK2, an essential pair of homologous kinases and proposed downstream effectors of PKH and sphingolipids, are also regulators of the PKC1-controlled MAP kinase cascade. ypk mutants display random distribution of the actin cytoskeleton and severely reduced activation of the MAP kinase MPK1. Upregulation of the RHO1 GTPase switch or the PKC1 effector MAP kinase pathway suppresses the growth and actin defects of ypk cells. ypk lethality is also suppressed by overexpression of an uncharacterized gene termed TUS1. TUS1 is a novel RHO1 exchange factor that contributes to cell wall integrity-mediated modulation of RHO1 activity. Thus, TUS1 and the YPKs add to the growing complexity of RHO1 and PKC1 regulation in the cell integrity signaling pathway. Furthermore, our findings suggest that the YPKs are a missing link between sphingolipid signaling and the cell integrity pathway.

scholarly journals Rho GTPases: regulation of cell polarity and growth in yeasts

2010 ◽  
Vol 426 (3) ◽  
pp. 243-253 ◽  
Author(s):  
Pilar Perez ◽  
Sergio A. Rincón
Keyword(s):  
Cell Wall ◽  
Cell Polarity ◽  
Rho Gtpases ◽  
Molecular Mechanisms ◽  
Eukaryotic Cells ◽  
Signalling Pathways ◽  
Polarized Growth ◽  
Cell Integrity ◽  
Actin Organization ◽  
Wide Range

Eukaryotic cells display a wide range of morphologies important for cellular function and development. A particular cell shape is made via the generation of asymmetry in the organization of cytoskeletal elements, usually leading to actin localization at sites of growth. The Rho family of GTPases is present in all eukaryotic cells, from yeast to mammals, and their role as key regulators in the signalling pathways that control actin organization and morphogenetic processes is well known. In the present review we will discuss the role of Rho GTPases as regulators of yeasts' polarized growth, their mechanism of activation and signalling pathways in Saccharomyces cerevisiae and Schizosaccharomyces pombe. These two model yeasts have been very useful in the study of the molecular mechanisms responsible for cell polarity. As in other organisms with cell walls, yeast's polarized growth is closely related to cell-wall biosynthesis, and Rho GTPases are critical modulators of this process. They provide the co-ordinated regulation of cell-wall biosynthetic enzymes and actin organization required to maintain cell integrity during vegetative growth.

scholarly journals Receptor Internalization in Yeast Requires the Tor2-Rho1 Signaling Pathway

2003 ◽  
Vol 14 (11) ◽  
pp. 4676-4684 ◽  
Author(s):  
Amy K.A. deHart ◽  
Joshua D. Schnell ◽  
Damian A. Allen ◽  
Ju-Yun Tsai ◽  
Linda Hicke
Keyword(s):  
Cell Wall ◽  
Cell Cycle Progression ◽  
Structural Integrity ◽  
Nutrient Sensing ◽  
Receptor Internalization ◽  
Cell Integrity ◽  
Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Similar Phenotype ◽  
Cell Growth And Differentiation

Efficient internalization of proteins from the cell surface is essential for regulating cell growth and differentiation. In a screen for yeast mutants defective in ligand-stimulated internalization of the α-factor receptor, we identified a mutant allele of TOR2, tor2G2128R. Tor proteins are known to function in translation initiation and nutrient sensing and are required for cell cycle progression through G1. Yeast Tor2 has an additional role in regulating the integrity of the cell wall by activating the Rho1 guanine nucleotide exchange factor Rom2. The endocytic defect in tor2G2128Rcells is due to disruption of this Tor2 unique function. Other proteins important for cell integrity, Rom2 and the cell integrity sensor Wsc1, are also required for efficient endocytosis. A rho1 mutant specifically defective in activation of the glucan synthase Fks1/2 does not internalize α-factor efficiently, and fks1Δ cells exhibit a similar phenotype. Removal of the cell wall does not inhibit internalization, suggesting that the function of Rho1 and Fks1 in endocytosis is not through cell wall synthesis or structural integrity. These findings reveal a novel function for the Tor2-Rho1 pathway in controlling endocytosis in yeast, a function that is mediated in part through the plasma membrane protein Fks1.

Pneumocystis carinii BCK1 Complements the Saccharomyces cerevisiae Cell Wall Integrity Pathway

2003 ◽  
Vol 50 (s1) ◽  
pp. 676-677 ◽  
Author(s):  
PAWAN K. VOHRA ◽  
THEODORE J. KOTTOM ◽  
ANDREW H. LIMPER ◽  
CHARLES F. THOMAS
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Pneumocystis Carinii ◽  
Cell Wall Integrity ◽  
Cell Wall Integrity Pathway

scholarly journals Cell Wall Perturbation Sensitizes Fungi to the Antimalarial Drug Chloroquine

2013 ◽  
Vol 57 (8) ◽  
pp. 3889-3896 ◽  
Author(s):  
Farida Islahudin ◽  
Combiz Khozoie ◽  
Steven Bates ◽  
Kang-Nee Ting ◽  
Richard J. Pleass ◽  
...  
Keyword(s):  
Cell Wall ◽  
Antimalarial Drug ◽  
Content Type ◽  
Combination Treatments ◽  
Fungal Inhibition ◽  
Cell Wall Integrity Pathway ◽  
Strain Collection ◽  
Induced Changes ◽  
Wild Type Yeast ◽  
Wall Perturbation

ABSTRACTChloroquine (CQ) has been a mainstay of antimalarial drug treatment for several decades. Additional therapeutic actions of CQ have been described, including some reports of fungal inhibition. Here we investigated the action of CQ in fungi, including the yeast modelSaccharomyces cerevisiae. A genomewide yeast deletion strain collection was screened against CQ, revealing thatbck1Δ andslt2Δ mutants of the cell wall integrity pathway are CQ hypersensitive. This phenotype was rescued with sorbitol, consistent with cell wall involvement. The cell wall-targeting agent caffeine caused hypersensitivity to CQ, as did cell wall perturbation by sonication. The phenotypes were not caused by CQ-induced changes to cell wall components. Instead, CQ accumulated to higher levels in cells with perturbed cell walls: CQ uptake was 2- to 3-fold greater inbck1Δ andslt2Δ mutants than in wild-type yeast. CQ toxicity was synergistic with that of the major cell wall-targeting antifungal drug, caspofungin. The MIC of caspofungin against the yeast pathogenCandida albicanswas decreased 2-fold by 250 μM CQ and up to 8-fold at higher CQ concentrations. Similar effects were seen inCandida glabrataandAspergillus fumigatus. The results show that the cell wall is critical for CQ resistance in fungi and suggest that combination treatments with cell wall-targeting drugs could have potential for antifungal treatment.

scholarly journals The Cek1 and Hog1 Mitogen-Activated Protein Kinases Play Complementary Roles in Cell Wall Biogenesis and Chlamydospore Formation in the Fungal Pathogen Candida albicans

2006 ◽  
Vol 5 (2) ◽  
pp. 347-358 ◽  
Author(s):  
B. Eisman ◽  
R. Alonso-Monge ◽  
E. Román ◽  
D. Arana ◽  
C. Nombela ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Map Kinase ◽  
Fungal Pathogen ◽  
Hog Pathway ◽  
Cell Wall Biogenesis ◽  
Chlamydospore Formation ◽  
Mitogen Activated Protein ◽  
Morphological Transitions ◽  
Relationship Of

ABSTRACT The Hog1 mitogen-activated protein (MAP) kinase mediates an adaptive response to both osmotic and oxidative stress in the fungal pathogen Candida albicans. This protein also participates in two distinct morphogenetic processes, namely the yeast-to-hypha transition (as a repressor) and chlamydospore formation (as an inducer). We show here that repression of filamentous growth occurs both under serum limitation and under other partially inducing conditions, such as low temperature, low pH, or nitrogen starvation. To understand the relationship of the HOG pathway to other MAP kinase cascades that also play a role in morphological transitions, we have constructed and characterized a set of double mutants in which we deleted both the HOG1 gene and other signaling elements (the CST20, CLA4, and HST7 kinases, the CPH1 and EFG1 transcription factors, and the CPP1 protein phosphatase). We also show that Hog1 prevents the yeast-to-hypha switch independent of all the elements analyzed and that the inability of the hog1 mutants to form chlamydospores is suppressed when additional elements of the CEK1 pathway (CST20 or HST7) are altered. Finally, we report that Hog1 represses the activation of the Cek1 MAP kinase under basal conditions and that Cek1 activation correlates with resistance to certain cell wall inhibitors (such as Congo red), demonstrating a role for this pathway in cell wall biogenesis.

scholarly journals The Endoplasmic Reticulum and the Golgi Structures in Maize Root Cells

1959 ◽  
Vol 5 (3) ◽  
pp. 501-506 ◽  
Author(s):  
W. Gordon Whaley ◽  
Hilton H. Mollenhauer ◽  
Joyce E. Kephart
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Electron Microscope ◽  
Nuclear Envelope ◽  
Epoxy Resin ◽  
Maize Root ◽  
Root Tips ◽  
Animal Cells ◽  
Root Cells ◽  
Vesicular Structure

Maize root tips were fixed in potassium permanganate, embedded in epoxy resin, sectioned to show silver interference color, and studied with the electron microscope. All the cells were seen to contain an endoplasmic reticulum and apparently independent Golgi structures. The endoplasmic reticulum is demonstrated as a membrane-bounded, vesicular structure comparable in many aspects to that of several types of animal cells. With the treatment used here the membranes appear smooth surfaced. The endoplasmic reticulum is continuous with the nuclear envelope and, by contact at least, with structures passing through the cell wall. The nuclear envelope is characterized by discontinuities, as previously reported for animal cells. The reticula of adjacent cells seem to be in contact at or through the plasmodesmata. Because of these contacts the endoplasmic reticulum of a given cell appears to be part of an intercellular system. The Golgi structures appear as stacks of platelet-vesicles which apparently may, under certain conditions, produce small vesicles around their edges. Their form changes markedly with development of the cell.

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