scholarly journals The chemotactic response to PDGF-BB: evidence of a role for Ras.

1995 ◽  
Vol 130 (3) ◽  
pp. 725-731 ◽  
Author(s):  
V Kundra ◽  
B Anand-Apte ◽  
L A Feig ◽  
B R Zetter
Keyword(s):  
Chemotactic Response ◽  
Dominant Negative ◽  
Pdgf Receptor ◽  
Gtpase Activating Protein ◽  
Ras Gtpase ◽  
Downstream Effector ◽  
Ras Inhibition ◽  
Receptor Beta ◽  
Constitutively Active

The PDGF receptor-beta mediates both mitogenic and chemotactic responses to PDGF-BB. Although the role of Ras in tyrosine kinase-mediated mitogenesis has been characterized extensively, its role in PDGF-stimulated chemotaxis has not been defined. Using cells expressing a dominant-negative ras, we find that Ras inhibition suppresses migration toward PDGF-BB. Overexpression of either Ras-GTPase activating protein (Ras-GAP) or a Ras guanine releasing factor (GRF) also inhibited PDGF-stimulated chemotaxis. In addition, cells producing excess constitutively active Ras failed to migrate toward PDGF-BB, consistent with the observation that either excess ligand or excess signaling intermediate can suppress the chemotactic response. These results suggest that Ras can function in normal cells to support chemotaxis toward PDGF-BB and that either too little or too much Ras activity can abrogate the chemotactic response. In contrast to Ras overexpression, cells producing excess constitutively active Raf, a downstream effector of Ras, did migrate toward PDGF-BB. Cells expressing dominant-negative Ras were able to migrate toward soluble fibronectin demonstrating that these cells retained the ability to migrate. These results suggest that Ras is an intermediate in PDGF-stimulated chemotaxis but may not be required for fibronectin-stimulated cell motility.

scholarly journals Characterization of the Role of AMP-Activated Protein Kinase in the Regulation of Glucose-Activated Gene Expression Using Constitutively Active and Dominant Negative Forms of the Kinase

2000 ◽  
Vol 20 (18) ◽  
pp. 6704-6711 ◽  
Author(s):  
Angela Woods ◽  
Dalila Azzout-Marniche ◽  
Marc Foretz ◽  
Silvie C. Stein ◽  
Patricia Lemarchand ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Fatty Acid Synthase ◽  
Physiological Role ◽  
Rat Hepatocytes ◽  
Dominant Negative ◽  
Ampk Activity ◽  
Amp Activated Protein Kinase ◽  
Constitutively Active

ABSTRACT In the liver, glucose induces the expression of a number of genes involved in glucose and lipid metabolism, e.g., those encoding L-type pyruvate kinase and fatty acid synthase. Recent evidence has indicated a role for the AMP-activated protein kinase (AMPK) in the inhibition of glucose-activated gene expression in hepatocytes. It remains unclear, however, whether AMPK is involved in the glucose induction of these genes. In order to study further the role of AMPK in regulating gene expression, we have generated two mutant forms of AMPK. One of these (α1312) acts as a constitutively active kinase, while the other (α1DN) acts as a dominant negative inhibitor of endogenous AMPK. We have used adenovirus-mediated gene transfer to express these mutants in primary rat hepatocytes in culture in order to determine their effect on AMPK activity and the transcription of glucose-activated genes. Expression of α1312 increased AMPK activity in hepatocytes and blocked completely the induction of a number of glucose-activated genes in response to 25 mM glucose. This effect is similar to that observed following activation of AMPK by 5-amino-imidazolecarboxamide riboside. Expression of α1DN markedly inhibited both basal and stimulated activity of endogenous AMPK but had no effect on the transcription of glucose-activated genes. Our results suggest that AMPK is involved in the inhibition of glucose-activated gene expression but not in the induction pathway. This study demonstrates that the two mutants we have described will provide valuable tools for studying the wider physiological role of AMPK.

Phospholipase D1 mediates bFGF-induced Bcl-2 expression leading to neurite outgrowth in H19-7 cells

2011 ◽  
Vol 441 (1) ◽  
pp. 407-416 ◽  
Author(s):  
Sung Nyo Yoon ◽  
Kang Sik Kim ◽  
Ju Hwan Cho ◽  
Weina Ma ◽  
Hye-Jin Choi ◽  
...  
Keyword(s):  
Neurite Outgrowth ◽  
Dominant Negative ◽  
Signal Transducer ◽  
Downstream Effector ◽  
Phospholipase D1 ◽  
Protein Kinase Cα ◽  
Phosphoinositide 3 Kinase ◽  
Interfering Rna ◽  
Transcription 3

The purpose of the present study was to investigate the role of PLD (phospholipase D) in bFGF (basic fibroblast growth factor)-induced Bcl-2 expression and to examine whether overexpressed Bcl-2 influences neurite outgrowth in immortalized hippocampal progenitor cells (H19-7 cells). We found that Bcl-2 expression was maximally induced by bFGF within 24 h, and that this effect was reduced by inhibiting PLD1 expression with PLD1 small interfering RNA or by overexpressing DN (dominant-negative)-PLD1, whereas PLD1 overexpression markedly induced Bcl-2 expression. bFGF treatment activated Ras, Src, PI3K (phosphoinositide 3-kinase), PLCγ (phospholipase Cγ) and PKCα (protein kinase Cα). Among these molecules, Src and PKCα were not required for Bcl-2 expression. PLD activity was decreased by Ras, PI3K or PLCγ inhibitor, suggesting that PLD1 activation occurred through Ras, PI3K or PLCγ. We found that Ras was the most upstream molecule among these proteins, followed by the PI3K/PLCγ pathway, indicating that bFGF-induced PLD activation took place through the Ras/PI3K/PLCγ pathway. Furthermore, PLD1 was required for activation of JNK (c-Jun N-terminal kinase), which led to activation of STAT3 (signal transducer and activator of transcription 3) and finally Bcl-2 expression. When Bcl-2 was overexpressed, neurite outgrowth was stimulated along with induction of neurotrophic factors such as brain-derived neurotrophic factor and neurotrophin 4/5. In conclusion, PLD1 acts as a downstream effector of bFGF/Ras/PI3K/PLCγ signalling and regulates Bcl-2 expression through JNK/STAT3, which leads to neurite outgrowth in H19-7 cells.

Domain topology of human Rasal

2017 ◽  
Vol 399 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Jorge Cuellar ◽  
José María Valpuesta ◽  
Alfred Wittinghofer ◽  
Begoña Sot
Keyword(s):  
Electron Microscopy ◽  
Small Gtpase ◽  
Full Length ◽  
Gtpase Activating Protein ◽  
Ras Gtpase ◽  
Cryo Electron Microscopy ◽  
Domain Protein ◽  
Negative Staining Electron Microscopy ◽  
Resolution Structure

AbstractRasal is a modular multi-domain protein of the GTPase-activating protein 1 (GAP1) family; its four known members, GAP1m, Rasal, GAP1IP4BPand Capri, have a Ras GTPase-activating domain (RasGAP). This domain supports the intrinsically slow GTPase activity of Ras by actively participating in the catalytic reaction. In the case of Rasal, GAP1IP4BPand Capri, their remaining domains are responsible for converting the RasGAP domains into dual Ras- and Rap-GAPs, via an incompletely understood mechanism. Although Rap proteins are small GTPase homologues of Ras, their catalytic residues are distinct, which reinforces the importance of determining the structure of full-length GAP1 family proteins. To date, these proteins have not been crystallized, and their size is not adequate for nuclear magnetic resonance (NMR) or for high-resolution cryo-electron microscopy (cryoEM). Here we present the low resolution structure of full-length Rasal, obtained by negative staining electron microscopy, which allows us to propose a model of its domain topology. These results help to understand the role of the different domains in controlling the dual GAP activity of GAP1 family proteins.

scholarly journals Disruption of gastrulation and oral-aboral ectoderm differentiation in the Lytechinus pictus embryo by a dominant/negative PDGF receptor

Development ◽  
1997 ◽  
Vol 124 (12) ◽  
pp. 2355-2364 ◽  
Author(s):  
R.K. Ramachandran ◽  
A.H. Wikramanayake ◽  
J.A. Uzman ◽  
V. Govindarajan ◽  
C.R. Tomlinson
Keyword(s):  
Sea Urchin ◽  
The Body ◽  
Dominant Negative ◽  
Specific Gene ◽  
Pdgf Receptor ◽  
Lytechinus Pictus ◽  
Sea Urchin Embryo ◽  
Oral Ectoderm ◽  
Cell Commitment ◽  
Receptor Beta

Little is known about the cell signaling involved in forming the body plan of the sea urchin embryo. Previous work suggested that PDGF-like and EGF-like receptor-mediated signaling pathways are involved in gastrulation and spiculogenesis in the Lytechinus pictus embryo. Here we show that expression of the human PDGF receptor-beta lacking the cytoplasmic domain disrupted development in a manner consistent with a dominant/negative mechanism. The truncated PDGF receptor-beta inhibited gut and spicule formation and differentiation along the oral-aboral axis. The most severely affected embryos arrested at a developmental stage resembling mesenchyme blastula. Coinjection into eggs of RNA encoding the entire human PDGF receptor-beta rescued development. The truncated PDGF receptor-beta caused the aboral ectoderm-specific genes LpS1 and LpC2 to be repressed while an oral ectoderm-specific gene, Ecto-V, was expressed in all ectoderm cells. The results support the hypothesis that a PDGF-like signaling pathway plays a key role in the intercellular communication required for gastrulation and spiculogenesis, and in cell commitment and differentiation along the oral-aboral axis.

The Role of ras GTPase Activating Protein in Human Tumorigenesis

Pathobiology ◽  
1995 ◽  
Vol 63 (6) ◽  
pp. 348-350 ◽  
Author(s):  
Eitan Friedman
Keyword(s):  
Gtpase Activating Protein ◽  
Ras Gtpase

scholarly journals Identification of a GTPase-activating protein homolog in Schizosaccharomyces pombe.

1991 ◽  
Vol 11 (6) ◽  
pp. 3088-3094 ◽  
Author(s):  
Y Imai ◽  
S Miyake ◽  
D A Hughes ◽  
M Yamamoto
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Gene Product ◽  
Protein A ◽  
Negative Regulator ◽  
Loss Of Function ◽  
Gtpase Activating Protein ◽  
Ras Gtpase ◽  
Downstream Effector ◽  
Gtpase Cycle ◽  
Conserved Core

Loss of function of the Schizosaccharomyces pombe gap1 gene results in the same phenotypes as those caused by an activated ras1 mutation, i.e., hypersensitivity to the mating factor and inability to perform efficient mating. Sequence analysis of gap1 indicates that it encodes a homolog of the mammalian Ras GTPase-activating protein (GAP). The predicted gap1 gene product has 766 amino acids with relatively short N- and C-terminal regions flanking the conserved core sequence of GAP. Genetic analysis suggests that S. pombe Gap1 functions primarily as a negative regulator of Ras1, like S. cerevisiae GAP homologs encoded by IRA1 and IRA2, but is unlikely to be a downstream effector of the Ras protein, a role proposed for mammalian GAP. Thus, Gap1 and Ste6, a putative GDP-GTP-exchanging protein for Ras1 previously identified, appear to play antagonistic roles in the Ras-GTPase cycle in S. pombe. Furthermore, we suggest that this Ras-GTPase cycle involves the ra12 gene product, another positive regulator of Ras1 whose homologs have not been identified in other organisms, which could function either as a second GDP-GTP-exchanging protein or as a factor that negatively regulates Gap1 activity.

scholarly journals Reciprocal Role of ERK and Nf-κb Pathways in Survival and Activation of Osteoclasts

2000 ◽  
Vol 148 (2) ◽  
pp. 333-342 ◽  
Author(s):  
Tsuyoshi Miyazaki ◽  
Hideki Katagiri ◽  
Yumi Kanegae ◽  
Hiroshi Takayanagi ◽  
Yasuhiro Sawada ◽  
...  
Keyword(s):  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Erk Activation ◽  
Iκb Kinase ◽  
Mitogen Activated Protein ◽  
Osteoclast Activation ◽  
Osteoclast Survival ◽  
Constitutively Active

To examine the role of mitogen-activated protein kinase and nuclear factor kappa B (NF-κB) pathways on osteoclast survival and activation, we constructed adenovirus vectors carrying various mutants of signaling molecules: dominant negative Ras (RasDN), constitutively active MEK1 (MEKCA), dominant negative IκB kinase 2 (IKKDN), and constitutively active IKK2 (IKKCA). Inhibiting ERK activity by RasDN overexpression rapidly induced the apoptosis of osteoclast-like cells (OCLs) formed in vitro, whereas ERK activation after the introduction of MEKCA remarkably lengthened their survival by preventing spontaneous apoptosis. Neither inhibition nor activation of ERK affected the bone-resorbing activity of OCLs. Inhibition of NF-κB pathway with IKKDN virus suppressed the pit-forming activity of OCLs and NF-κB activation by IKKCA expression upregulated it without affecting their survival. Interleukin 1α (IL-1α) strongly induced ERK activation as well as NF-κB activation. RasDN virus partially inhibited ERK activation, and OCL survival promoted by IL-1α. Inhibiting NF-κB activation by IKKDN virus significantly suppressed the pit-forming activity enhanced by IL-1α. These results indicate that ERK and NF-κB regulate different aspects of osteoclast activation: ERK is responsible for osteoclast survival, whereas NF-κB regulates osteoclast activation for bone resorption.

The Src family of protein tyrosine kinases: regulation and functions

Development ◽  
1993 ◽  
Vol 119 (Supplement) ◽  
pp. 57-64
Author(s):  
Sara A. Courtneidge ◽  
Stefano Fumagalli ◽  
Manfred Koegl ◽  
Giulio Superti-Furga ◽  
Geraldine M. Twamley-Stein
Keyword(s):  
Tyrosine Kinases ◽  
Sh3 Domain ◽  
Sh2 Domain ◽  
Dominant Negative ◽  
Pdgf Receptor ◽  
Intramolecular Association ◽  
Src Family Tyrosine Kinases ◽  
Carboxy Terminal ◽  
Mitogenic Signal

Most of the nine members of the Src family of tyrosine kinases arc restricted in their expression, often to cells of the haematopoietic lineage, while some, particularly Src, Fyn and Yes, are more unbiquitously expressed. We have been studying the functions of Src, Fyn and Yes in fibroblasts. We have shown that stimulation of quiescent fibroblasts with platelet-derived growth factor (PDGF) causes Src, Fyn and Yes to become activated, and to associate transiently with the PDGF receptor. To address the role of Src, Fyn and Yes in the response to PDGF, we have used a dominant negative approach, in which cells were engineered to express catalytically inactive forms of Src kinases. These cells were unable to enter S phase in response to PDGF, and we therefore conclude that Src family tyrosine kinases are required in order for the PDGF receptor to transmit a mitogenic signal. It has previously been shown that the kinase activity of Src is negatively regulated by phosphorylation of tyr 527 in its carboxy-terminal tail. A kinase, Csk, that phosphorylates tyr 527 has recently been identified. We expressed Src in yeast to test the model that phosphorylation of tyr 527 represses activity by promoting intramolecular association between the tail and the SH2 domain. Inducible expression of Src in S. pombe caused cell death. Co-expression of Csk counteracted this effect. Src proteins mutated in the SH2 domain were as lethal as wild-type Src, but were insensitive to Csk. We interpret these results in favour of an SH2 domain : phosphorylated tail interaction repressing Src activity. However, we have also found that Src molecules containing mutations in the SH3 domain are not regulated by Csk, suggesting that the SH3 domain also functions in the intramolecular regulation of Src activity.

scholarly journals Class IA Phosphoinositide 3-Kinase Regulates Heart Size and Physiological Cardiac Hypertrophy

2005 ◽  
Vol 25 (21) ◽  
pp. 9491-9502 ◽  
Author(s):  
Ji Luo ◽  
Julie R. McMullen ◽  
Cassandra L. Sobkiw ◽  
Li Zhang ◽  
Adam L. Dorfman ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Dominant Negative ◽  
Class I ◽  
Regulatory Subunit ◽  
Developmental Growth ◽  
Physiological Cardiac Hypertrophy ◽  
Heart Size ◽  
Physiological Hypertrophy ◽  
Constitutively Active

ABSTRACT Class IA phosphoinositide 3-kinases (PI3Ks) are activated by growth factor receptors, and they regulate, among other processes, cell growth and organ size. Studies using transgenic mice overexpressing constitutively active and dominant negative forms of the p110α catalytic subunit of class IA PI3K have implicated the role of this enzyme in regulating heart size and physiological cardiac hypertrophy. To further understand the role of class IA PI3K in controlling heart growth and to circumvent potential complications from the overexpression of dominant negative and constitutively active proteins, we generated mice with muscle-specific deletion of the p85α regulatory subunit and germ line deletion of the p85β regulatory subunit of class IA PI3K. Here we show that mice with cardiac deletion of both p85 subunits exhibit attenuated Akt signaling in the heart, reduced heart size, and altered cardiac gene expression. Furthermore, exercise-induced cardiac hypertrophy is also attenuated in the p85 knockout hearts. Despite such defects in postnatal developmental growth and physiological hypertrophy, the p85 knockout hearts exhibit normal contractility and myocardial histology. Our results therefore provide strong genetic evidence that class IA PI3Ks are critical regulators for the developmental growth and physiological hypertrophy of the heart.

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