scholarly journals The TOR Signal Transduction Cascade Controls Cellular Differentiation in Response to Nutrients

2001 ◽  
Vol 12 (12) ◽  
pp. 4103-4113 ◽  
Author(s):  
N. Shane Cutler ◽  
Xuewen Pan ◽  
Joseph Heitman ◽  
Maria E. Cardenas
Keyword(s):  
Signal Transduction ◽  
Protein Kinases ◽  
Protein Phosphatase ◽  
Nutrient Sensing ◽  
Yeast Cells ◽  
Regulatory Subunit ◽  
Growth Defect ◽  
Tor Pathway ◽  
Pseudohyphal Growth ◽  
Pseudohyphal Differentiation

Rapamycin binds and inhibits the Tor protein kinases, which function in a nutrient-sensing signal transduction pathway that has been conserved from the yeast Saccharomyces cerevisiaeto humans. In yeast cells, the Tor pathway has been implicated in regulating cellular responses to nutrients, including proliferation, translation, transcription, autophagy, and ribosome biogenesis. We report here that rapamycin inhibits pseudohyphal filamentous differentiation of S. cerevisiae in response to nitrogen limitation. Overexpression of Tap42, a protein phosphatase regulatory subunit, restored pseudohyphal growth in cells exposed to rapamycin. The tap42-11 mutation compromised pseudohyphal differentiation and rendered it resistant to rapamycin. Cells lacking the Tap42-regulated protein phosphatase Sit4 exhibited a pseudohyphal growth defect and were markedly hypersensitive to rapamycin. Mutations in other Tap42-regulated phosphatases had no effect on pseudohyphal differentiation. Our findings support a model in which pseudohyphal differentiation is controlled by a nutrient-sensing pathway involving the Tor protein kinases and the Tap42–Sit4 protein phosphatase. Activation of the MAP kinase or cAMP pathways, or mutation of the Sok2 repressor, restored filamentation in rapamycin treated cells, supporting models in which the Tor pathway acts in parallel with these known pathways. Filamentous differentiation of diverse fungi was also blocked by rapamycin, demonstrating that the Tor signaling cascade plays a conserved role in regulating filamentous differentiation in response to nutrients.

scholarly journals Yeast Ppz1 protein phosphatase toxicity involves the alteration of multiple cellular targets

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Diego Velázquez ◽  
Marcel Albacar ◽  
Chunyi Zhang ◽  
Carlos Calafí ◽  
María López-Malo ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Protein Phosphatase ◽  
Mitotic Cell ◽  
Yeast Cells ◽  
Growth Defect ◽  
Cellular Targets ◽  
Major Mechanism ◽  
Bud Emergence ◽  
Phosphorylation Pattern

Abstract Control of the protein phosphorylation status is a major mechanism for regulation of cellular processes, and its alteration often lead to functional disorders. Ppz1, a protein phosphatase only found in fungi, is the most toxic protein when overexpressed in Saccharomyces cerevisiae. To investigate the molecular basis of this phenomenon, we carried out combined genome-wide transcriptomic and phosphoproteomic analyses. We have found that Ppz1 overexpression causes major changes in gene expression, affecting ~ 20% of the genome, together with oxidative stress and increase in total adenylate pools. Concurrently, we observe changes in the phosphorylation pattern of near 400 proteins (mainly dephosphorylated), including many proteins involved in mitotic cell cycle and bud emergence, rapid dephosphorylation of Snf1 and its downstream transcription factor Mig1, and phosphorylation of Hog1 and its downstream transcription factor Sko1. Deletion of HOG1 attenuates the growth defect of Ppz1-overexpressing cells, while that of SKO1 aggravates it. Our results demonstrate that Ppz1 overexpression has a widespread impact in the yeast cells and reveals new aspects of the regulation of the cell cycle.

scholarly journals Phosphorylation Sites in Protein Kinases and Phosphatases Regulated by Formyl Peptide Receptor 2 Signaling

2020 ◽  
Vol 21 (11) ◽  
pp. 3818
Author(s):  
Maria Carmela Annunziata ◽  
Melania Parisi ◽  
Gabriella Esposito ◽  
Gabriella Fabbrocini ◽  
Rosario Ammendola ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinases ◽  
Protein Phosphatase ◽  
Intracellular Signaling ◽  
Molecular Mechanisms ◽  
Fine Tuning ◽  
Formyl Peptide Receptor ◽  
Signaling Cascades ◽  
Regulatory Subunit ◽  
Formyl Peptides

FPR1, FPR2, and FPR3 are members of Formyl Peptides Receptors (FPRs) family belonging to the GPCR superfamily. FPR2 is a low affinity receptor for formyl peptides and it is considered the most promiscuous member of this family. Intracellular signaling cascades triggered by FPRs include the activation of different protein kinases and phosphatase, as well as tyrosine kinase receptors transactivation. Protein kinases and phosphatases act coordinately and any impairment of their activation or regulation represents one of the most common causes of several human diseases. Several phospho-sites has been identified in protein kinases and phosphatases, whose role may be to expand the repertoire of molecular mechanisms of regulation or may be necessary for fine-tuning of switch properties. We previously performed a phospho-proteomic analysis in FPR2-stimulated cells that revealed, among other things, not yet identified phospho-sites on six protein kinases and one protein phosphatase. Herein, we discuss on the selective phosphorylation of Serine/Threonine-protein kinase N2, Serine/Threonine-protein kinase PRP4 homolog, Serine/Threonine-protein kinase MARK2, Serine/Threonine-protein kinase PAK4, Serine/Threonine-protein kinase 10, Dual specificity mitogen-activated protein kinase kinase 2, and Protein phosphatase 1 regulatory subunit 14A, triggered by FPR2 stimulation. We also describe the putative FPR2-dependent signaling cascades upstream to these specific phospho-sites.

Regulation of dimorphism in Saccharomyces cerevisiae: involvement of the novel protein kinase homolog Elm1p and protein phosphatase 2A

1993 ◽  
Vol 13 (9) ◽  
pp. 5567-5581
Author(s):  
M J Blacketer ◽  
C M Koehler ◽  
S G Coats ◽  
A M Myers ◽  
P Madaule
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Protein Phosphatase ◽  
Nitrogen Starvation ◽  
Gene Dosage ◽  
Protein Phosphatase 2A ◽  
Pseudohyphal Growth ◽  
Phosphatase 2A ◽  
Pseudohyphal Differentiation ◽  
Novel Protein

The Saccharomyces cerevisiae genes ELM1, ELM2, and ELM3 were identified on the basis of the phenotype of constitutive cell elongation. Mutations in any of these genes cause a dimorphic transition to a pseudohyphal growth state characterized by formation of expanded, branched chains of elongated cells. Furthermore, elm1, elm2, and elm3 mutations cause cells to grow invasively under the surface of agar medium. S. cerevisiae is known to be a dimorphic organism that grows either as a unicellular yeast or as filamentous cells termed pseudohyphae; although the yeast-like form usually prevails, pseudohyphal growth may occur during conditions of nitrogen starvation. The morphologic and physiological properties caused by elm1, elm2, and elm3 mutations closely mimic pseudohyphal growth occurring in conditions of nitrogen starvation. Therefore, we propose that absence of ELM1, ELM2, or ELM3 function causes constitutive execution of the pseudohyphal differentiation pathway that occurs normally in conditions of nitrogen starvation. Supporting this hypothesis, heterozygosity at the ELM2 or ELM3 locus significantly stimulated the ability to form pseudohyphae in response to nitrogen starvation. ELM1 was isolated and shown to code for a novel protein kinase homolog. Gene dosage experiments also showed that pseudohyphal differentiation in response to nitrogen starvation is dependent on the product of CDC55, a putative B regulatory subunit of protein phosphatase 2A, and a synthetic phenotype was observed in elm1 cdc55 double mutants. Thus, protein phosphorylation is likely to regulate differentiation into the pseudohyphal state.

scholarly journals Regulation of dimorphism in Saccharomyces cerevisiae: involvement of the novel protein kinase homolog Elm1p and protein phosphatase 2A.

1993 ◽  
Vol 13 (9) ◽  
pp. 5567-5581 ◽  
Author(s):  
M J Blacketer ◽  
C M Koehler ◽  
S G Coats ◽  
A M Myers ◽  
P Madaule
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Protein Phosphatase ◽  
Nitrogen Starvation ◽  
Gene Dosage ◽  
Protein Phosphatase 2A ◽  
Pseudohyphal Growth ◽  
Phosphatase 2A ◽  
Pseudohyphal Differentiation ◽  
Novel Protein

The Saccharomyces cerevisiae genes ELM1, ELM2, and ELM3 were identified on the basis of the phenotype of constitutive cell elongation. Mutations in any of these genes cause a dimorphic transition to a pseudohyphal growth state characterized by formation of expanded, branched chains of elongated cells. Furthermore, elm1, elm2, and elm3 mutations cause cells to grow invasively under the surface of agar medium. S. cerevisiae is known to be a dimorphic organism that grows either as a unicellular yeast or as filamentous cells termed pseudohyphae; although the yeast-like form usually prevails, pseudohyphal growth may occur during conditions of nitrogen starvation. The morphologic and physiological properties caused by elm1, elm2, and elm3 mutations closely mimic pseudohyphal growth occurring in conditions of nitrogen starvation. Therefore, we propose that absence of ELM1, ELM2, or ELM3 function causes constitutive execution of the pseudohyphal differentiation pathway that occurs normally in conditions of nitrogen starvation. Supporting this hypothesis, heterozygosity at the ELM2 or ELM3 locus significantly stimulated the ability to form pseudohyphae in response to nitrogen starvation. ELM1 was isolated and shown to code for a novel protein kinase homolog. Gene dosage experiments also showed that pseudohyphal differentiation in response to nitrogen starvation is dependent on the product of CDC55, a putative B regulatory subunit of protein phosphatase 2A, and a synthetic phenotype was observed in elm1 cdc55 double mutants. Thus, protein phosphorylation is likely to regulate differentiation into the pseudohyphal state.

scholarly journals Pheromone-induced signal transduction in Saccharomyces cerevisiae requires the sequential function of three protein kinases.

1993 ◽  
Vol 13 (4) ◽  
pp. 2069-2080 ◽  
Author(s):  
Z Zhou ◽  
A Gartner ◽  
R Cade ◽  
G Ammerer ◽  
B Errede
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Signal Transduction ◽  
Protein Kinases ◽  
Signal Transmission ◽  
Yeast Cells ◽  
In Vitro Assays ◽  
Induced Signal ◽  
Hyperphosphorylated Form ◽  
Dependent Mechanism

Protein phosphorylation plays an important role in pheromone-induced differentiation processes of haploid yeast cells. Among the components necessary for signal transduction are the STE7 and STE11 kinases and either one of the redundant FUS3 and KSS1 kinases. FUS3 and presumably KSS1 are phosphorylated and activated during pheromone induction by a STE7-dependent mechanism. Pheromone also induces the accumulation of STE7 in a hyperphosphorylated form. This modification of STE7 requires the STE11 kinase, which is proposed to act before STE7 during signal transmission. Surprisingly, STE7 hyperphosphorylation also requires a functional FUS3 (or KSS1) kinase. Using in vitro assays for FUS3 phosphorylation, we show that pheromone activates STE7 even in the absence of FUS3 and KSS1. Therefore, STE7 activation must precede modification of FUS3 (and KSS1). These findings suggest that STE7 hyperphosphorylation is a consequence of its activation but not the determining event.

scholarly journals The budding yeast PP2ACdc55 protein phosphatase prevents the onset of anaphase in response to morphogenetic defects

2007 ◽  
Vol 177 (4) ◽  
pp. 599-611 ◽  
Author(s):  
Elena Chiroli ◽  
Valentina Rossio ◽  
Giovanna Lucchini ◽  
Simonetta Piatti
Keyword(s):  
Protein Phosphatase ◽  
Budding Yeast ◽  
S Phase ◽  
Yeast Cells ◽  
Regulatory Subunit ◽  
Chromosome Transmission ◽  
Anaphase Onset ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Noncanonical Pathway

Faithful chromosome transmission requires establishment of sister chromatid cohesion during S phase, followed by its removal at anaphase onset. Sister chromatids are tethered together by cohesin, which is displaced from chromosomes through cleavage of its Mcd1 subunit by the separase protease. Separase is in turn inhibited, up to this moment, by securin. Budding yeast cells respond to morphogenetic defects by a transient arrest in G2 with high securin levels and unseparated chromatids. We show that neither securin elimination nor forced cohesin cleavage is sufficient for anaphase in these conditions, suggesting that other factors contribute to cohesion maintainance in G2. We find that the protein phosphatase PP2A bound to its regulatory subunit Cdc55 plays a key role in this process, uncovering a new function for PP2ACdc55 in controlling a noncanonical pathway of chromatid cohesion removal.

scholarly journals NPK1, a tobacco gene that encodes a protein with a domain homologous to yeast BCK1, STE11, and Byr2 protein kinases

1993 ◽  
Vol 13 (8) ◽  
pp. 4745-4752
Author(s):  
H Banno ◽  
K Hirano ◽  
T Nakamura ◽  
K Irie ◽  
S Nomoto ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Protein Kinase ◽  
Stationary Phase ◽  
Protein Kinases ◽  
Catalytic Domain ◽  
Signal Transduction Pathway ◽  
Yeast Cells ◽  
Transduction Pathway ◽  
Pheromone Response ◽  
Tobacco Cells

We have isolated a cDNA (cNPK1) that encodes a predicted protein kinase of 690 amino acids from suspension cultures of tobacco cells. The deduced sequence is closely related to those of the protein kinases encoded by the STE11 and BCK1 genes of Saccharomyces cerevisiae and the byr2 gene of Schizosaccharomyces pombe. STE11 and Byr2 function in the yeast mating pheromone response pathways, and BCK1 acts downstream of the yeast protein kinase C homolog encoded by the PKC1 gene, which is essential for normal growth and division of yeast cells. Overexpression in yeast cells of a truncated form of cNPK1, which encodes only the putative catalytic domain, replaced the growth control functions of BCK1 and PKC1 but not the mating pheromone response function of STE11. Thus, the catalytic domain of NPK1 specifically activates the signal transduction pathway mediated by BCK1 in yeast. In tobacco cells in suspension culture, the NPK1 gene is transcribed during logarithmic phase and early stationary phase but not during late stationary phase. In a tobacco plant, it is also transcribed in stems and roots but not in mature leaves, which rarely contain growing cells. The present results suggest that a signal transduction pathway mediated by this BCK1- and STE11-related protein kinase is also conserved in plants and that a function of NPK1 is controlled at least in part at a transcriptional level.

scholarly journals Developmental Expression of Protein Phosphatase 2A in the Kidney

1999 ◽  
Vol 10 (8) ◽  
pp. 1737-1745
Author(s):  
ALLEN D. EVERETT ◽  
CHUN XUE ◽  
TAMARA STOOPS
Keyword(s):  
Signal Transduction ◽  
Protein Phosphatase ◽  
Kidney Development ◽  
Developmental Regulation ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Developmental Expression ◽  
Regulatory Subunit ◽  
Northern Analysis ◽  
Phosphatase 2A

Abstract. Although a number of growth and transcription factors are known to regulate renal growth and development, the signal transduction molecules necessary to mediate these developmental signals are relatively unknown. Therefore, the activity and mRNA and protein expression of the signal transduction molecule protein phosphatase 2A (PP2A) were examined during rat kidney development. Northern analysis of total kidney RNA or Western analysis of kidney protein homogenates from embryonic day 15 to 90-d-old adults demonstrated developmental regulation of the catalytic, major 55-kD B regulatory subunit and A structural subunit with the highest levels of expression in late embryonic and newborn kidneys. Similarly, okadaic acid-inhibitable phosphatase enzyme activity was highest in the embryonic and newborn kidney. To map cell-specific expression of PP2A in the developing kidney, in situ hybridization with a catalytic subunit digoxigenin-labeled cRNA was performed on embryonic day 20 and newborn kidneys. PP2A was found predominately in the nephrogenic cortex and particularly in the developing glomeruli and nonbrush border tubules in the embryonic day 20 and newborn kidneys. Similarly, immunocytochemistry with a specific PP2A catalytic subunit polyclonal anti-peptide antibody demonstrated catalytic subunit protein particularly concentrated in the podocytes of glomeruli in the newborn kidney. In the adult kidney, PP2A protein was no longer detectable except in the nuclei of distal tubular cells. Therefore, the developmental regulation of PP2A activity and protein during kidney development and its mapping to the nephrogenic cortex, developing glomeruli, and tubules suggests a role for PP2A in the regulation of nephron growth and differentiation.

scholarly journals Adenovirus Protein E4orf4 Induces Premature APCCdc20 Activation in Saccharomyces cerevisiae by a Protein Phosphatase 2A-Dependent Mechanism

2010 ◽  
Vol 84 (9) ◽  
pp. 4798-4809 ◽  
Author(s):  
Melissa Z. Mui ◽  
Diana E. Roopchand ◽  
Matthew S. Gentry ◽  
Richard L. Hallberg ◽  
Jackie Vogel ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Functional Characterization ◽  
Specific Inhibitor ◽  
Human Adenovirus ◽  
Yeast Cells ◽  
Regulatory Subunit ◽  
Phosphatase 2A

ABSTRACT Protein phosphatase 2A (PP2A) has been implicated in cell cycle progression and mitosis; however, the complexity of PP2A regulation via multiple B subunits makes its functional characterization a significant challenge. The human adenovirus protein E4orf4 has been found to induce both high Cdk1 activity and the accumulation of cells in G2/M in both mammalian and yeast cells, effects which are largely dependent on the B55/Cdc55 regulatory subunit of PP2A. Thus, E4orf4 represents a unique means by which the function of a specific form of PP2A can be delineated in vivo. In Saccharomyces cerevisiae, only two PP2A regulatory subunits exist, Cdc55 and Rts1. Here, we show that E4orf4-induced toxicity depends on a functional interaction with Cdc55. E4orf4 expression correlates with the inappropriate reduction of Pds1 and Scc1 in S-phase-arrested cells. The unscheduled loss of these proteins suggests the involvement of PP2ACdc55 in the regulation of the Cdc20 form of the anaphase-promoting complex (APC). Contrastingly, activity of the Hct1 form of the APC is not induced by E4orf4, as demonstrated by the observed stability of its substrates. We propose that E4orf4, being a Cdc55-specific inhibitor of PP2A, demonstrates the role of PP2ACdc55 in regulating APCCdc20 activity.

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