scholarly journals Ral Signals through a MAP4 Kinase-p38 MAP Kinase Cascade in C. elegans Cell Fate Patterning

Cell Reports ◽  
2018 ◽  
Vol 24 (10) ◽  
pp. 2669-2681.e5 ◽  
Author(s):  
Hanna Shin ◽  
Rebecca E.W. Kaplan ◽  
Tam Duong ◽  
Razan Fakieh ◽  
David J. Reiner
2018 ◽  
Author(s):  
Hanna Shin ◽  
Rebecca E.W. Kaplan ◽  
Tam Duong ◽  
Razan Fakieh ◽  
David J. Reiner

SummaryC. elegans vulval precursor cell (VPC) fates are patterned by an EGF gradient. High dose EGF induces 1° VPC fate, while lower dose EGF contributes to 2° fate in support of LIN-12/Notch. We previously showed that the EGF 2°-promoting signal is mediated by LET-60/Ras switching effectors, from the canonical Raf-MEK-ERK MAP kinase cascade that promotes 1° fate to the non-canonical RalGEF-Ral that promotes 2° fate. Of oncogenic Ras effectors, RalGEF-Ral is by far the least well-understood. We use genetic analysis to identify an effector cascade downstream of C. elegans RAL-1/Ral, starting with an established Ral binding partner, Exo84 of the exocyst complex. Additionally, RAL-1 signals through GCK-2, a CNH domain-containing MAP4 kinase, and PMK-1/p38 MAP kinase cascade to promote 2° fate. Our study delineates a Ral-dependent developmental signaling cascade in vivo, thus providing the mechanism by which lower EGF dose is transduced.


2005 ◽  
Vol 206 (2) ◽  
pp. 363-370 ◽  
Author(s):  
Kenji Mizumura ◽  
Kohsuke Takeda ◽  
Shu Hashimoto ◽  
Takashi Horie ◽  
Hidenori Ichijo

2002 ◽  
Vol 22 (12) ◽  
pp. 4073-4085 ◽  
Author(s):  
Rachel J. Buchsbaum ◽  
Beth A. Connolly ◽  
Larry A. Feig

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.


2003 ◽  
Vol 71 (11) ◽  
pp. 6672-6675 ◽  
Author(s):  
Kazuto Matsunaga ◽  
Hiroyuki Yamaguchi ◽  
Thomas W. Klein ◽  
Herman Friedman ◽  
Yoshimasa Yamamoto

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.


1997 ◽  
Vol 8 (12) ◽  
pp. 2539-2551 ◽  
Author(s):  
Csilla Csank ◽  
Constantin Makris ◽  
Sylvain Meloche ◽  
Klaus Schröppel ◽  
Martin Röllinghoff ◽  
...  

Mitogen-activated protein (MAP) kinases are pivotal components of eukaryotic signaling cascades. Phosphorylation of tyrosine and threonine residues activates MAP kinases, but either dual-specificity or monospecificity phosphatases can inactivate them. The Candida albicans CPP1 gene, a structural member of the VH1 family of dual- specificity phosphatases, was previously cloned by its ability to block the pheromone response MAP kinase cascade in Saccharomyces cerevisiae. Cpp1p inactivated mammalian MAP kinases in vitro and acted as a tyrosine-specific enzyme. In C. albicansa MAP kinase cascade can trigger the transition from the budding yeast form to a more invasive filamentous form. Disruption of theCPP1 gene in C. albicans derepressed the yeast to hyphal transition at ambient temperatures, on solid surfaces. A hyphal growth rate defect under physiological conditions in vitro was also observed and could explain a reduction in virulence associated with reduced fungal burden in the kidneys seen in a systemic mouse model. A hyper-hyphal pathway may thus have some detrimental effects onC. albicans cells. Disruption of the MAP kinase homologue CEK1 suppressed the morphological effects of the CPP1 disruption in C. albicans. The results presented here demonstrate the biological importance of a tyrosine phosphatase in cell-fate decisions and virulence in C. albicans.


Physiology ◽  
1997 ◽  
Vol 12 (3) ◽  
pp. 117-121
Author(s):  
JA Williams ◽  
A Dabrowski ◽  
CD Logsdon

Pancreatic secretagogues that activate digestive enzyme secretion through classic intracellular mediators such as Ca2+ also activate novel signaling kinase cascades. The best defined of these is the MAP kinase cascade, but cholecystokinin also activates jun kinase, p38 MAP kinase, and S6 kinase. These novel pathways are likely involved with pancreatic growth and gene expression.


2003 ◽  
Vol 23 (14) ◽  
pp. 4778-4787 ◽  
Author(s):  
Louis-François Bélanger ◽  
Sophie Roy ◽  
Michel Tremblay ◽  
Barbara Brott ◽  
Ann-Muriel Steff ◽  
...  

ABSTRACT MEK is a dual-specificity kinase that activates the extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase upon agonist binding to receptors. The ERK/MAP kinase cascade is involved in cell fate determination in many organisms. In mammals, this pathway is proposed to regulate cell growth and differentiation. Genetic studies have shown that although a single Mek gene is present in Caenorhabditis elegans, Drosophila melanogaster, and Xenopus laevis, two Mek homologs, Mek1 and Mek2, are present in the mammalian cascade. The inactivation of the Mek1 gene leads to embryonic lethality and has revealed the unique role played by Mek1 during embryogenesis. To investigate the biological function of the second homolog, we have generated mice deficient in Mek2 function. Mek2 mutant mice are viable and fertile, and they do not present flagrant morphological alteration. Although several components of the ERK/MAP kinase cascade have been implicated in thymocyte development, no such involvement was observed for MEK2, which appears to be nonessential for thymocyte differentiation and T-cell-receptor-induced proliferation and apoptosis. Altogether, our findings demonstrate that MEK2 is not necessary for the normal development of the embryo and T-cell lineages, suggesting that the loss of MEK2 can be compensated for by MEK1.


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