scholarly journals The Ustilago maydis ubc4 and ubc5 Genes Encode Members of a MAP Kinase Cascade Required for Filamentous Growth

2000 ◽  
Vol 13 (7) ◽  
pp. 781-786 ◽  
Author(s):  
David L. Andrews ◽  
John D. Egan ◽  
María E. Mayorga ◽  
Scott E. Gold
Keyword(s):  
Map Kinase ◽  
Ustilago Maydis ◽  
Filamentous Growth ◽  
Mitogen Activated Protein Kinase ◽  
Genetic Determinants ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
Suppressor Mutants ◽  
Corn Smut

Ustilago maydis, the causal agent of corn smut disease, displays dimorphic growth in which it alternates between a budding haploid saprophyte and a filamentous dikaryotic pathogen. We are interested in identifying the genetic determinants of filamentous growth and pathogenicity in U. maydis. To do this we have taken a forward genetic approach. Earlier, we showed that haploid adenylate cyclase (uac1) mutants display a constitutively filamentous phenotype. Mutagenesis of a uac1 disruption strain allowed the isolation of a large number of budding suppressor mutants. These mutants are named ubc, for Ustilago bypass of cyclase, as they no longer require the production of cyclic AMP (cAMP) to grow in the budding morphology. Complementation of a subset of these suppressor mutants led to the identification of the ubc4 and ubc5 genes, which are required for filamentous growth and encode a MAP (mitogen-activated protein) kinase kinase kinase and a MAP kinase kinase, respectively. Evidence suggests that they are important in the pheromone response pathway and in pathogenicity. These results further support an important interplay of the cAMP and MAP kinase signal transduction pathways in the control of morphogenesis and pathogenicity in U. maydis.

scholarly journals Interaction of Rac Exchange Factors Tiam1 and Ras-GRF1 with a Scaffold for the p38 Mitogen-Activated Protein Kinase Cascade

2002 ◽  
Vol 22 (12) ◽  
pp. 4073-4085 ◽  
Author(s):  
Rachel J. Buchsbaum ◽  
Beth A. Connolly ◽  
Larry A. Feig
Keyword(s):  
Map Kinase ◽  
P38 Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Nucleotide Exchange ◽  
Rac Gtpase ◽  
Signaling Specificity ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
In Cells

ABSTRACT Tiam1 and Ras-GRF1 are guanine nucleotide exchange factors (GEFs) that activate the Rac GTPase. The two GEFs have similar N-terminal regions containing pleckstrin homology domains followed by coiled-coils and additional sequences that function together to allow regulated GEF activity. Here we show that this N-terminal region of both proteins binds to the scaffold protein IB2/JIP2. IB2/JIP2 is a scaffold for the p38 mitogen-activated protein (MAP) kinase cascade because it binds to the Rac target MLK3, the MAP kinase kinase MKK3, and the p38 MAP kinase. Expression of IB2/JIP2 in cells potentiates the ability of Tiam1 or Ras-GRF1 to activate the p38 MAP kinase cascade but not the Jnk MAP kinase cascade. In addition, Tiam1 or Ras-GRF1 binding to IB2/JIP2 increases the association of the components of the p38 MAP kinase signaling cassette with IB2/JIP2 in cells and activates scaffold-associated p38. These findings imply that Tiam1 and Ras-GRF1 can contribute to Rac signaling specificity by their ability to form a complex with a scaffold that binds components of one of the many known Rac effector pathways.

scholarly journals Legionella pneumophila Suppresses Macrophage Interleukin-12 Production by Activating the p42/44 Mitogen-Activated Protein Kinase Cascade

2003 ◽  
Vol 71 (11) ◽  
pp. 6672-6675 ◽  
Author(s):  
Kazuto Matsunaga ◽  
Hiroyuki Yamaguchi ◽  
Thomas W. Klein ◽  
Herman Friedman ◽  
Yoshimasa Yamamoto
Keyword(s):  
Map Kinase ◽  
Legionella Pneumophila ◽  
Kinase Inhibitors ◽  
Selective Inhibition ◽  
P38 Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Interleukin 12 ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

ABSTRACT A possible involvement of the mitogen-activated protein (MAP) kinase cascade in the inhibition of macrophage interleukin-12 (IL-12) production by Legionella pneumophila infection was examined. The results of MAP kinase inhibition by p42/44 and p38 MAP kinase inhibitors and of p42/44 MAP kinase activity assays indicate that L. pneumophila infection of macrophages causes a selective inhibition of lipopolysaccharide-induced IL-12 production by activating the p42/44 MAP kinase cascade. In addition, it was also revealed that the p38 MAP kinase may be important for the production of IL-12 but not for the inhibition caused by L. pneumophila infection.

The mitogen-activated protein kinase cascade is activated by B-Raf in response to nerve growth factor through interaction with p21ras

1994 ◽  
Vol 14 (10) ◽  
pp. 6944-6953
Author(s):  
R K Jaiswal ◽  
S A Moodie ◽  
A Wolfman ◽  
G E Landreth
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Map Kinase ◽  
Pc12 Cells ◽  
Mitogen Activated Protein Kinase ◽  
Stable Complex ◽  
Nerve Growth ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

Nerve growth factor (NGF) activates the mitogen-activated protein (MAP) kinase cascade through a p21ras-dependent signal transduction pathway in PC12 cells. The linkage between p21ras and MEK1 was investigated to identify those elements which participate in the regulation of MEK1 activity. We have screened for MEK activators using a coupled assay in which the MAP kinase cascade has been reconstituted in vitro. We report that we have detected a single NGF-stimulated MEK-activating activity which has been identified as B-Raf. PC12 cells express both B-Raf and c-Raf1; however, the MEK-activating activity was found only in fractions containing B-Raf. c-Raf1-containing fractions did not exhibit a MEK-activating activity. Gel filtration analysis revealed that the B-Raf eluted with an apparent M(r) of 250,000 to 300,000, indicating that it is present within a stable complex with other unidentified proteins. Immunoprecipitation with B-Raf-specific antisera quantitatively precipitated all MEK activator activity from these fractions. We also demonstrate that B-Raf, as well as c-Raf1, directly interacted with activated p21ras immobilized on silica beads. NGF treatment of the cells had no effect on the ability of B-Raf or c-Raf1 to bind to activated p21ras. These data indicate that this interaction was not dependent upon the activation state of these enzymes; however, MEK kinase activity was found to be associated with p21ras following incubation with NGF-treated samples at levels higher than those obtained from unstimulated cells. These data provide direct evidence that NGF-stimulated B-Raf is responsible for the activation of the MAP kinase cascade in PC12 cells, whereas c-Raf1 activity was not found to function within this pathway.

scholarly journals The Stress-activated Mitogen-activated Protein Kinase Signaling Cascade Promotes Exit from Mitosis

2006 ◽  
Vol 17 (7) ◽  
pp. 3136-3146 ◽  
Author(s):  
Vladimír Reiser ◽  
Katharine E. D’Aquino ◽  
Ly-Sha Ee ◽  
Angelika Amon
Keyword(s):  
Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Hog Pathway ◽  
Hypertonic Stress ◽  
Map Kinase Cascade ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Early Anaphase ◽  
Kinase Cascade ◽  
Protein Kinase Signaling

In budding yeast, a signaling network known as the mitotic exit network (MEN) triggers exit from mitosis. We find that hypertonic stress allows MEN mutants to exit from mitosis in a manner dependent on the high osmolarity glycerol (HOG) mitogen-activated protein (MAP) kinase cascade. The HOG pathway drives exit from mitosis in MEN mutants by promoting the activation of the MEN effector, the protein phosphatase Cdc14. Activation of Cdc14 depends on the Cdc14 early anaphase release network, a group of proteins that functions in parallel to the MEN to promote Cdc14 function. Notably, exit from mitosis is promoted by the signaling branch defined by the Sho1 osmosensing system, but not by the Sln1 osmosensor of the HOG pathway. Our results suggest that the stress MAP kinase pathway mobilizes programs to promote completion of the cell cycle and entry into G1 under unfavorable conditions.

scholarly journals ras2 Controls Morphogenesis, Pheromone Response, and Pathogenicity in the Fungal Pathogen Ustilago maydis

2002 ◽  
Vol 1 (6) ◽  
pp. 954-966 ◽  
Author(s):  
Nancy Lee ◽  
James W. Kronstad
Keyword(s):  
Protein Kinase ◽  
Map Kinase ◽  
Ustilago Maydis ◽  
Mitogen Activated Protein Kinase ◽  
Gene Encoding ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
Map Kinase Pathway ◽  
Altered Cell ◽  
Kinase Pathway

ABSTRACT Ustilago maydis, a pathogen of maize, is a useful model for the analysis of mating, pathogenicity, and the morphological transition between budding and filamentous growth in fungi. As in other fungi, these processes are regulated by conserved signaling mechanisms, including the cyclic AMP (cAMP)/protein kinase A (PKA) pathway and at least one mitogen-activated protein kinase (MAP kinase) pathway. A current challenge is to identify additional factors that lie downstream of the cAMP pathway and that influence morphogenesis in U. maydis. In this study, we identified suppressor mutations that restored budding growth to a constitutively filamentous mutant with a defect in the gene encoding a catalytic subunit of PKA. Complementation of one suppressor mutation unexpectedly identified the ras2 gene, which is predicted to encode a member of the well-conserved ras family of small GTP-binding proteins. Deletion of the ras2 gene in haploid cells altered cell morphology, eliminated pathogenicity on maize seedlings, and revealed a role in the production of aerial hyphae during mating. We also used an activated ras2 allele to demonstrate that Ras2 promotes pseudohyphal growth via a MAP kinase cascade involving the MAP kinase kinase Fuz7 and the MAP kinase Ubc3. Overall, our results reveal an additional level of crosstalk between the cAMP signaling pathway and a MAP kinase pathway influenced by Ras2.

scholarly journals Role of a Mitogen-Activated Protein Kinase Cascade in Ion Flux-Mediated Turgor Regulation in Fungi

2006 ◽  
Vol 5 (3) ◽  
pp. 480-487 ◽  
Author(s):  
Roger R. Lew ◽  
Natalia N. Levina ◽  
Lana Shabala ◽  
Marinela I. Anderca ◽  
Sergey N. Shabala
Keyword(s):  
Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Wild Type ◽  
Turgor Regulation ◽  
Map Kinase Cascade ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
Protein Kinase Cascade

ABSTRACT Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca2+ influx and the sustained hyperpolarization is due to H+ efflux by activation of the plasma membrane H+-ATPase. Protein synthesis is not required for H+-ATPase activation. Net K+ and Cl− uptake occurs at the same time as turgor recovery. The magnitude of the ion uptake is more than sufficient to account for the osmotic gradients required for turgor to return to its original level. Two osmotic mutants, os-1 and os-2, homologs of a two-component histidine kinase sensor and the yeast high osmotic glycerol mitogen-activated protein (MAP) kinase, respectively, have lower turgor than the wild type and do not exhibit the sustained hyperpolarization after hyperosmotic treatment. The os-1 mutant does not exhibit all of the wild-type turgor-adaptive ion fluxes (Cl− uptake increases, but net K+ flux barely changes and net H+ efflux declines) (os-2 was not examined). Both os mutants are able to regulate turgor but at a lower level than the wild type. Our results demonstrate that a MAP kinase cascade regulates ion transport, activation of the H+-ATPase, and net K+ and Cl− uptake during turgor regulation. Other pathways regulating turgor must also exist.

Genetic Analysis of rolled, Which Encodes a Drosophila Mitogen-Activated Protein Kinase

Genetics ◽  
1999 ◽  
Vol 153 (2) ◽  
pp. 763-771 ◽  
Author(s):  
Young-Mi Lim ◽  
Kimiko Nishizawa ◽  
Yoshimi Nishi ◽  
Leo Tsuda ◽  
Yoshihiro H Inoue ◽  
...  
Keyword(s):  
Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Female Sterility ◽  
Tor Signaling ◽  
Map Kinase Cascade ◽  
Dominant Female ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

Abstract Genetic and molecular characterization of the dominant suppressors of D-rafC110 on the second chromosome identified two gain-of-function alleles of rolled (rl), which encodes a mitogen-activated protein (MAP) kinase in Drosophila. One of the alleles, rlSu23, was found to bear the same molecular lesion as rlSem, which has been reported to be dominant female sterile. However, rlSu23 and the current stock of rlSem showed only a weak dominant female sterility. Detailed analyses of the rl mutations demonstrated moderate dominant activities of these alleles in the Torso (Tor) signaling pathway, which explains the weak dominant female sterility observed in this study. The dominant rl mutations failed to suppress the terminal class maternal-effect mutations, suggesting that activation of Rl is essential, but not sufficient, for Tor signaling. Involvement of rl in cell proliferation was also demonstrated by clonal analysis. Branching and integration of signals in the MAP kinase cascade is discussed.

scholarly journals Requirement for phosphoinositide 3-OH kinase in growth hormone signalling to the mitogen-activated protein kinase and p70s6k pathways

1996 ◽  
Vol 315 (2) ◽  
pp. 517-522 ◽  
Author(s):  
Elaine KILGOUR ◽  
Ivan GOUT ◽  
Neil G. ANDERSON
Keyword(s):  
Growth Hormone ◽  
Map Kinase ◽  
Map Kinases ◽  
Specific Inhibitor ◽  
Mitogen Activated Protein Kinase ◽  
Regulatory Subunit ◽  
Glutathione S Transferase ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

Pituitary growth hormone (GH) co-ordinately stimulates three distinct signalling pathways in 3T3-F442A preadipocytes, the STAT (signal transducer and activator of transcription) pathway, the mitogen-activated protein (MAP) kinase cascade and p70s6k. The mechanisms linking the GH receptor to these signals have not been fully identified. In this study we have examined the role of phosphoinositide 3-OH kinase (PI 3-kinase). Pretreatment of cells with wortmannin, a specific inhibitor of PI 3-kinase, prevented the activation of p70s6k and partially inhibited the activation of p42 and p44 MAP kinases by GH. In contrast, wortmannin failed to appreciably affect the GH-stimulated tyrosyl phosphorylation of JAK-2 or STAT-1. GH transiently increased the activity of PI 3-kinase recovered in anti-phosphotyrosine immunoprecipitates. In addition, several tyrosyl-phosphorylated proteins were specifically adsorbed from lysates of cells exposed to GH by a glutathione S-transferase fusion protein containing the 85 kDa regulatory subunit of PI 3-kinase. GH also induced an increase in the PI 3-kinase activity associated with both JAK-2 and insulin receptor substrate-1 (IRS-1) immunoprecipitates. These results establish PI 3-kinase as an important mediator of GH signalling to the MAP kinase and p70s6k pathways and suggest that PI 3-kinase is activated by a mechanism involving JAK-2 and IRS-1.

scholarly journals Transforming growth factor β 1 inhibits mitogen-activated protein kinase induced by basic fibroblast growth factor in smooth muscle cells

1996 ◽  
Vol 316 (1) ◽  
pp. 167-173 ◽  
Author(s):  
Eliane BERROU ◽  
Michaëla FONTENAY-ROUPIE ◽  
Rozenn QUARCK ◽  
Fergus R. McKENZIE ◽  
Sylviane LÉVY-TOLEDANO ◽  
...  
Keyword(s):  
Growth Factor ◽  
Map Kinase ◽  
Kinase Activity ◽  
Transforming Growth Factor ◽  
Mitogen Activated Protein Kinase ◽  
Map Kinase Cascade ◽  
Mitogen Activated Protein ◽  
Kinase Cascade ◽  
Tgf Β1

Stimulation of smooth muscle cells with basic fibroblast growth factor (bFGF) results in the activation of the mitogen-activated protein kinase (MAP kinase) cascade and leads to cell proliferation. We show that transforming growth factor β1 (TGF-β1), at concentrations that completely inhibited bFGF-induced mitogenic activity, decreased bFGF-induced MAP kinase activity. Under these conditions, tyrosine and threonine phosphorylations of MAP kinase were differentially affected depending on the time period of TGF-β1 pretreatment. After a short (30 min) TGF-β1 pretreatment, the bFGF-mediated increase in phosphorylation of p42mapk on threonine was inhibited, with no effect on the level of phosphotyrosine or decrease in the electrophoretic mobility of p42mapk. This suggests that TGF-β1 inhibited MAP kinase activity through the action of a serine/threonine phosphatase. In contrast, a longer TGF-β1 pretreatment (4 h) partly inhibited the bFGF-induced MAP kinase mobility shift and correlated with the inhibition of phosphorylation on both threonine and tyrosine, suggesting that long-term TGF-β1 treatment prevented activation of the MAP kinase cascade or directly blocked MAP kinase. The ability of long-term (4 h) but not short-term (30 min) TGF-β1 pretreatment to inhibit MAP kinase activity was completely dependent on protein synthesis and suggests that TGF-β1 inhibits MAP kinase activity by two distinct mechanisms. These findings provide a molecular basis for the growth-inhibitory action of TGF-β1 on bFGF-induced mitogenic activity.

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