scholarly journals Direct Binding of the Signal-transducing Adaptor Grb2 Facilitates Down-regulation of the Cyclin-dependent Kinase Inhibitor p27Kip1

2001 ◽  
Vol 276 (15) ◽  
pp. 12084-12090 ◽  
Author(s):  
Yoriko Sugiyama ◽  
Kiichiro Tomoda ◽  
Toshiaki Tanaka ◽  
Yukinobu Arata ◽  
Noriko Yoneda-Kato ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Kinase Inhibitor ◽  
Signal Sequence ◽  
Ectopic Expression ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Cyclin Dependent Kinase ◽  
Down Regulation ◽  
Cytoplasmic Transport ◽  
Subsequent Degradation

Ectopic expression of Jab1/CSN5 induces specific down-regulation of the cyclin-dependent kinase (Cdk) inhibitor p27 (p27Kip1) in a manner dependent upon transportation from the nucleus to the cytoplasm. Here we show that Grb2 and Grb3-3, the molecules functioning as an adaptor in the signal transduction pathway, specifically and directly bind to p27 in the cytoplasm and participate in the regulation of p27. The interaction requires the C-terminal SH3-domain of Grb2/3-3 and the proline-rich sequence contained in p27 immediately downstream of the Cdk binding domain. In living cells, enforcement of the cytoplasmic localization of p27, either by artificial manipulation of the nuclear/cytoplasmic transport signal sequence or by coexpression of ectopic Jab1/CSN5, markedly enhances the stable interaction between p27 and Grb2. Overexpression of Grb2 accelerates Jab1/CSN5-mediated degradation of p27, while Grb3-3 expression suppresses it. A p27 mutant unable to bind to Grb2 is transported into the cytoplasm in cells ectopically expressing Jab1/CSN5 but is refractory to the subsequent degradation. These findings indicate that Grb2 participates in a negative regulation of p27 and may directly link the signal transduction pathway with the cell cycle regulatory machinery.

scholarly journals Functional Analysis of the Cyclin-Dependent Kinase Inhibitor Pho81 Identifies a Novel Inhibitory Domain

2001 ◽  
Vol 21 (19) ◽  
pp. 6695-6705 ◽  
Author(s):  
Sidong Huang ◽  
Douglas A. Jeffery ◽  
Malcolm D. Anthony ◽  
Erin K. O'Shea
Keyword(s):  
Signal Transduction ◽  
Tandem Repeats ◽  
Kinase Inhibitor ◽  
Signal Transduction Pathway ◽  
Eukaryotic Cell ◽  
Phosphate Limitation ◽  
Stable Complex ◽  
Transduction Pathway ◽  
Cyclin Dependent Kinase ◽  
Ankyrin Repeats

ABSTRACT In response to phosphate limitation, Saccharomyces cerevisiae induces transcription of a set of genes important for survival. A phosphate-responsive signal transduction pathway mediates this response by controlling the activity of the transcription factor Pho4. Three components of this signal transduction pathway resemble those used to regulate the eukaryotic cell cycle: a cyclin-dependent kinase (CDK), Pho85; a cyclin, Pho80; and a CDK inhibitor (CKI), Pho81. Pho81 forms a stable complex with Pho80-Pho85 under both high- and low-phosphate conditions, but it only inhibits the kinase when cells are starved for phosphate. Pho81 contains six tandem repeats of the ankyrin consensus domain homologous to the INK4 family of mammalian CKIs. INK4 proteins inhibit kinase activity through an interaction of the ankyrin repeats and the CDK subunits. Surprisingly, we find that a region of Pho81 containing 80 amino acids C terminal to the ankyrin repeats is necessary and sufficient for Pho81's CKI function. The ankyrin repeats of Pho81 appear to have no significant role in Pho81 inhibition. Our results suggest that Pho81 inhibits Pho80-Pho85 with a novel motif.

Lyn Is an Important Component of the Signal Transduction Pathway Specific to FLT3/ITD and Can Be a Therapeutic Target in the Treatment of AML with FLT3/ITD.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1908-1908
Author(s):  
Fumihiko Hayakawa ◽  
Mitsunori Okamoto ◽  
Akihiro Abe ◽  
Hitoshi Kiyoi ◽  
Tomoki Naoe
Keyword(s):  
Signal Transduction ◽  
Cell Growth ◽  
Therapeutic Target ◽  
Kinase Inhibitor ◽  
Critical Role ◽  
Signal Transduction Pathway ◽  
Sh2 Domain ◽  
Transduction Pathway ◽  
Mice Model ◽  
Juxtamembrane Domain

Abstract Fms-like tyrosine kinase 3 (FLT3) is expressed in hematopoietic progenitor cells. An internal tandem duplication (ITD) of the FLT3 juxtamembrane domain (FLT3/ITD) is the most frequent mutation in human adult acute myeloid leukemia (AML). Being transfected into IL-3 dependent cell line, 32D, FLT3/ITD causes constitutive activation of FLT3 itself and its downstream signal components, which leads to IL-3 independent cell growth. In particular, STAT5 activation is thought to be a key signaling event since it is induced only by FLT3/ITD not by wild type FLT3. However the signal component which mediates FLT3/ITD to STAT5 is yet to be clarified. In the present study, we showed the mutant- specific association of FLT3/ITD with Lyn, which led to the phosphorylation of Lyn in vivo. We also demonstrated that Lyn directly bound to FLT3 through its SH2 domain in vitro and that the association depended on tyrosyl-phosphorylation at juxtamembrane domain of FLT3. We revealed the critical role of Lyn for STAT5 activation and the autonomous cell growth in FLT3/ITD transfectant of 32D by using anti-Lyn siRNA and the Src family kinase inhibitor PP2. More importantly, we demonstrated successful treatment of FLT3/ITD induced tumors with PP2 in the mice model. These results demonstrate that Lyn is a critical component of the signal transduction pathway specific to FLT3/ITD and can be a therapeutic target in the treatment of AML with FLT3/ITD.

scholarly journals Lactosylceramide-enriched glycosphingolipid signaling domain mediates superoxide generation from human neutrophils

Blood ◽  
2002 ◽  
Vol 100 (4) ◽  
pp. 1454-1464 ◽  
Author(s):  
Kazuhisa Iwabuchi ◽  
Isao Nagaoka
Keyword(s):  
Signal Transduction ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Phosphatidylinositol 3 Kinase ◽  
Superoxide Generation ◽  
Kinase C ◽  
Signaling Domain

This study is focused on the functional significance of neutrophil lactosylceramide (LacCer)–enriched microdomains, which are involved in the initiation of a signal transduction pathway leading to superoxide generation. Treatment of neutrophils with anti-LacCer antibody, T5A7 or Huly-m13, induced superoxide generation from the cells, which was blocked by PP1, a Src kinase inhibitor; wortmannin, a phosphatidylinositol-3 kinase inhibitor; SB203580, a p38 mitogen-activated protein kinase (MAPK) inhibitor; and H7, an inhibitor for protein kinase C. When promyelocytic leukemia HL-60 cells were differentiated into neutrophilic lineage by dimethyl sulfoxide (DMSO) treatment, they acquired superoxide-generating activity but did not respond to anti-LacCer antibodies. Density gradient centrifugation revealed that LacCer and Lyn were recovered in detergent-insoluble membrane (DIM) of neutrophils and DMSO-treated HL-60 cells. However, immunoprecipitation experiments indicated that LacCer was associated with Lyn in neutrophils but not in DMSO-treated HL-60 cells. Interestingly, T5A7 induced the phosphorylation of Lyn in neutrophils but not in DMSO-treated HL-60 cells. Moreover, T5A7 induced the phosphorylation of p38 MAPK in neutrophils. T5A7-induced Lyn phosphorylation in neutrophil DIM fraction was significantly enhanced by cholesterol depletion or sequestration with methyl-β-cyclodextrin or nystatin. Collectively, these data suggest that neutrophils are characterized by the presence of cell surface LacCer-enriched glycosphingolipid signaling domain coupled with Lyn and that the ligand binding to LacCer induces the activation of Lyn, which may be suppressibly regulated by cholesterol, leading to superoxide generation through the phosphatidylinositol-3 kinase–, p38 MAPK–, and protein kinase C–dependent signal transduction pathway.

scholarly journals Modulation of β-Catenin Phosphorylation/Degradation by Cyclin-dependent Kinase 2

2004 ◽  
Vol 279 (19) ◽  
pp. 19592-19599 ◽  
Author(s):  
Chun Shik Park ◽  
Sung Il Kim ◽  
Mi Su Lee ◽  
Cho-ya Youn ◽  
Dae Joong Kim ◽  
...  
Keyword(s):  
Cyclin E ◽  
Signal Transduction Pathway ◽  
Transduction Pathway ◽  
Cyclin Dependent Kinase ◽  
Rapid Degradation ◽  
Subsequent Degradation ◽  
Proteasome Pathway ◽  
Fine Tune

β-Catenin functions as a downstream component of the Wnt/Wingless signal transduction pathway, and inappropriate control of cytosolic β-catenin is a crucial step in the genesis of several human cancers. Here we demonstrate that cyclin-dependent kinase 2 (CDK2) in association with cyclin A or cyclin E directly binds to β-catenin.In vivoandin vitrokinase assays with cyclin-CDK2 demonstrate β-catenin phosphorylation on residues Ser33, Ser37, Thr41, and Ser45. This phosphorylation promotes rapid degradation of cytosolic β-catenin via the β-TrCP-mediated proteasome pathway. Moreover, cyclin E-CDK2 contributes to rapid degradation of cytosolic β-catenin levels during G1phase by regulating β-catenin phosphorylation and subsequent degradation. In this way, CDK2 may “fine tune” β-catenin levels over the course of the cell cycle.

scholarly journals Riboflavin Induces Disease Resistance in Plants by Activating a Novel Signal Transduction Pathway

2000 ◽  
Vol 90 (8) ◽  
pp. 801-811 ◽  
Author(s):  
H. Dong ◽  
S. V. Beer
Keyword(s):  
Signal Transduction ◽  
Protein Kinase ◽  
Induced Resistance ◽  
Pseudomonas Syringae ◽  
Kinase Inhibitor ◽  
Signal Transduction Pathway ◽  
Systemic Resistance ◽  
Transduction Pathway ◽  
Pr Genes ◽  
Npr1 Gene

The role of riboflavin as an elicitor of systemic resistance and an activator of a novel signaling process in plants was demonstrated. Following treatment with riboflavin, Arabidopsis thaliana developed systemic resistance to Peronospora parasitica and Pseudomonas syringae pv. Tomato, and tobacco developed systemic resistance to Tobacco mosaic virus (TMV) and Alternaria alternata. Riboflavin, at concentrations necessary for resistance induction, did not cause cell death in plants or directly affect growth of the culturable pathogens. Riboflavin induced expression of pathogenesis-related (PR) genes in the plants, suggesting its ability to trigger a signal transduction pathway that leads to systemic resistance. Both the protein kinase inhibitor K252a and mutation in the NIM1/NPR1 gene which controls transcription of defense genes, impaired responsiveness to riboflavin. In contrast, riboflavin induced resistance and PR gene expression in NahG plants, which fail to accumulate salicylic acid (SA). Thus, riboflavin-induced resistance requires protein kinase signaling mechanisms and a functional NIM1/NPR1 gene, but not accumulation of SA. Riboflavin is an elicitor of systemic resistance, and it triggers resistance signal transduction in a distinct manner.

scholarly journals Gastrin activates tyrosine kinase and phospholipase C in isolated rat colonocytes.

1996 ◽  
Vol 43 (3) ◽  
pp. 539-546 ◽  
Author(s):  
E Małecka-Panas ◽  
J Tureaud ◽  
A P Majumdar
Keyword(s):  
Signal Transduction ◽  
Tyrosine Kinase ◽  
Phospholipase C ◽  
Kinase Inhibitor ◽  
Signal Transduction Pathway ◽  
Distal Colon ◽  
Cellular Growth ◽  
Transduction Pathway ◽  
Buffer Control ◽  
Trophic Action

Postreceptor regulation of the trophic action of gastrin is not fully elucidated. Tyrosine kinase (Tyr-kinase) has been associated with receptors of a number of growth factors and plays an important role in regulation of cellular growth within the gastrointestinal tract. The aim of this study was to determine, whether Tyr-kinase plays a role in mediating the growth promoting action of gastrin and whether phospholipase C (PLC) is involved in the signal transduction pathway. Colonocytes isolated from Fischer 344 rats were incubated for 2 min with gastrin (10(-8) M) and assayed for Tyr-kinase and PLC activities. Incubations with gastrin resulted in 60%-70% rise in Tyr-kinase and 150%-200% rise in PLC activities over the corresponding basal levels. When processed separately, in proximal colon Tyr-kinase activation by gastrin was 15%-20%, while in distal colon 70%-80% as compared to the buffer control. Gastrin activation of both Tyr-kinase and PLC was abolished by Tyr-kinase inhibitor, tyrphostin-25 (3.2 microM) and was not affected by staurosporine (20 ng/ml). We conclude that Tyr-kinase is involved in the mechanism of trophic action of gastrin, and PLC activation appears to be the next step in the signal transduction pathway.

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