scholarly journals EGFRAP encodes a new negative regulator of the EGFR acting in both normal and oncogenic EGFR/Ras-driven tissue morphogenesis

PLoS Genetics ◽  
2021 ◽  
Vol 17 (8) ◽  
pp. e1009738
Author(s):  
Jennifer Soler Beatty ◽  
Cristina Molnar ◽  
Carlos M. Luque ◽  
Jose F. de Celis ◽  
María D. Martín-Bermudo
Keyword(s):  
Imaginal Disc ◽  
Feedback Loop ◽  
Notch Pathway ◽  
Sh2 Domain ◽  
Negative Regulator ◽  
Ras Signaling ◽  
Ras Pathway ◽  
Phosphorylated Form ◽  
Ras Activation ◽  
Surveillance Mechanism

Activation of Ras signaling occurs in ~30% of human cancers. However, activated Ras alone is insufficient to produce malignancy. Thus, it is imperative to identify those genes cooperating with activated Ras in driving tumoral growth. In this work, we have identified a novel EGFR inhibitor, which we have named EGFRAP, for EGFR adaptor protein. Elimination of EGFRAP potentiates activated Ras-induced overgrowth in the Drosophila wing imaginal disc. We show that EGFRAP interacts physically with the phosphorylated form of EGFR via its SH2 domain. EGFRAP is expressed at high levels in regions of maximal EGFR/Ras pathway activity, such as at the presumptive wing margin. In addition, EGFRAP expression is up-regulated in conditions of oncogenic EGFR/Ras activation. Normal and oncogenic EGFR/Ras-mediated upregulation of EGRAP levels depend on the Notch pathway. We also find that elimination of EGFRAP does not affect overall organogenesis or viability. However, simultaneous downregulation of EGFRAP and its ortholog PVRAP results in defects associated with increased EGFR function. Based on these results, we propose that EGFRAP is a new negative regulator of the EGFR/Ras pathway, which, while being required redundantly for normal morphogenesis, behaves as an important modulator of EGFR/Ras-driven tissue hyperplasia. We suggest that the ability of EGFRAP to functionally inhibit the EGFR pathway in oncogenic cells results from the activation of a feedback loop leading to increase EGFRAP expression. This could act as a surveillance mechanism to prevent excessive EGFR activity and uncontrolled cell growth.

scholarly journals Hematopoietic Cell Fate and the Initiation of Leukemic Properties in Primitive Primary Human Cells Are Influenced by Ras Activity and Farnesyltransferase Inhibition

2004 ◽  
Vol 24 (16) ◽  
pp. 6993-7002 ◽  
Author(s):  
Craig Dorrell ◽  
Katsuto Takenaka ◽  
Mark D. Minden ◽  
Robert G. Hawley ◽  
John E. Dick
Keyword(s):  
Cell Fate ◽  
Myeloid Cell ◽  
Early Event ◽  
Ras Signaling ◽  
Human Leukemia ◽  
Ras Pathway ◽  
Hematopoietic Malignancies ◽  
Ras Activation ◽  
Elevated Frequency ◽  
High Level

ABSTRACT The Ras pathway transduces divergent signals determining normal cell fate and is frequently activated in hematopoietic malignancies, but the manner in which activation contributes to human leukemia is poorly understood. We report that a high level of activated H-Ras signaling in transduced primary human hematopoietic progenitors reduced their proliferation and enhanced monocyte/macrophage differentiation. However, the exposure of these cells to a farnesyltransferase inhibitor and establishment of a moderate level of Ras activity showed increased proliferation, an elevated frequency of primitive blast-like cells, and progenitors with enhanced self-renewal capacity. These results suggest that the amplitude of Ras pathway signaling is a determinant of myeloid cell fate and that moderate Ras activation in primitive hematopoietic cells can be an early event in leukemogenesis.

The Hox gene lin-39 is required during C. elegans vulval induction to select the outcome of Ras signaling

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 181-190 ◽  
Author(s):  
J.N. Maloof ◽  
C. Kenyon
Keyword(s):  
Body Region ◽  
Ras Signaling ◽  
Cell Fates ◽  
Vulval Development ◽  
Ras Pathway ◽  
Hox Gene ◽  
C Elegans ◽  
Cell Divisions ◽  
Ras Activation ◽  
Vulval Precursor Cells

The Ras signaling pathway specifies a variety of cell fates in many organisms. However, little is known about the genes that function downstream of the conserved signaling cassette, or what imparts the specificity necessary to cause Ras activation to trigger different responses in different tissues. In C. elegans, activation of the Ras pathway induces cells in the central body region to generate the vulva. Vulval induction takes place in the domain of the Hox gene lin-39. We have found that lin-39 is absolutely required for Ras signaling to induce vulval development. During vulval induction, the Ras pathway, together with basal lin-39 activity, up-regulates lin-39 expression in vulval precursor cells. We find that if lin-39 function is absent at this time, no vulval cell divisions occur. Furthermore, if lin-39 is replaced with the posterior Hox gene mab-5, then posterior structures are induced instead of a vulva. Our findings suggest that in addition to permitting vulval cell divisions to occur, lin-39 is also required to specify the outcome of Ras signaling by selectively activating vulva-specific genes.

scholarly journals The RASSF1A Tumor Suppressor Binds the RasGAP DAB2IP and Modulates RAS Activation in Lung Cancer

Cancers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3807
Author(s):  
Desmond R. Harrell Stewart ◽  
M. Lee Schmidt ◽  
Howard Donninger ◽  
Geoffrey J. Clark
Keyword(s):  
Lung Cancer ◽  
Tumor Suppressor ◽  
Promoter Hypermethylation ◽  
Negative Regulator ◽  
Ras Signaling ◽  
Mitogenic Signaling ◽  
Protein Levels ◽  
Ras Activation

Lung cancer is the leading cause of cancer-related death worldwide. Lung cancer is commonly driven by mutations in the RAS oncogenes, the most frequently activated oncogene family in human disease. RAS-induced tumorigenesis is inhibited by the tumor suppressor RASSF1A, which induces apoptosis in response to hyperactivation of RAS. RASSF1A expression is suppressed in cancer at high rates, primarily owing to promoter hypermethylation. Recent reports have shown that loss of RASSF1A expression uncouples RAS from apoptotic signaling in vivo, thereby enhancing tumor aggressiveness. Moreover, a concomitant upregulation of RAS mitogenic signaling upon RASSF1A loss has been observed, suggesting RASSF1A may directly regulate RAS activation. Here, we present the first mechanistic evidence for control of RAS activation by RASSF1A. We present a novel interaction between RASSF1A and the Ras GTPase Activating Protein (RasGAP) DAB2IP, an important negative regulator of RAS. Using shRNA-mediated knockdown and stable overexpression approaches, we demonstrate that RASSF1A upregulates DAB2IP protein levels in NSCLC cells. Suppression of RASSF1A and subsequent downregulation of DAB2IP enhances GTP loading onto RAS, thus increasing RAS mitogenic signaling in both mutant- and wildtype-RAS cells. Moreover, co-suppression of RASSF1A and DAB2IP significantly enhances in vitro and in vivo growth of wildtype-RAS cells. Tumors expressing wildtype RAS, therefore, may still suffer from hyperactive RAS signaling when RASSF1A is downregulated. This may render them susceptible to the targeted RAS inhibitors currently in development.

scholarly journals Unusual Interplay of Two Types of Ras Activators, RasGRP and SOS, Establishes Sensitive and Robust Ras Activation in Lymphocytes

2007 ◽  
Vol 27 (7) ◽  
pp. 2732-2745 ◽  
Author(s):  
Jeroen P. Roose ◽  
Marianne Mollenauer ◽  
Mary Ho ◽  
Tomohiro Kurosaki ◽  
Arthur Weiss
Keyword(s):  
B Lymphocytes ◽  
Feedback Loop ◽  
Binding Pocket ◽  
Lymphocyte Development ◽  
Ras Signaling ◽  
Receptor Stimulation ◽  
Gtp Binding ◽  
Ras Activation ◽  
Low Levels

ABSTRACT Ras activation is crucial for lymphocyte development and effector function. Both T and B lymphocytes contain two types of Ras activators: ubiquitously expressed SOS and specifically expressed Ras guanyl nucleotide-releasing protein (RasGRP). The need for two activators is enigmatic since both are activated following antigen receptor stimulation. In addition, RasGRP1 appears to be dominant over SOS in an unknown manner. The crystal structure of SOS provides a clue: an unusual allosteric Ras-GTP binding pocket. Here, we demonstrate that RasGRP orchestrates Ras signaling in two ways: (i) by activating Ras directly and (ii) by facilitating priming of SOS with RasGTP that binds the allosteric pocket. Priming enhances SOS' in vivo activity and creates a positive RasGTP-SOS feedback loop that functions as a rheostat for Ras activity. Without RasGRP1, initiation of this loop is impaired because SOS' catalyst is its own product (RasGTP)—hence the dominance of RasGRP1. Introduction of an active Ras-like molecule (RasV12C40) in T- and B-cell lines can substitute for RasGRP function and enhance SOS' activity via its allosteric pocket. The unusual RasGRP-SOS interplay results in sensitive and robust Ras activation that cannot be achieved with either activator alone. We hypothesize that this mechanism enables lymphocytes to maximally respond to physiologically low levels of stimulation.

scholarly journals A quantitative systems pharmacology analysis of KRAS G12C covalent inhibitors

2017 ◽  
Author(s):  
Edward C. Stites ◽  
Andrey S. Shaw
Keyword(s):  
Human Cancer ◽  
Conventional Wisdom ◽  
Ras Signaling ◽  
Systems Pharmacology ◽  
Ras Pathway ◽  
Ras Protein ◽  
Oncogenic Mutation ◽  
Ras Activation ◽  
Covalent Inhibitors ◽  
Computational Systems

AbstractThe KRAS oncogene is the most common, activating, oncogenic mutation in human cancer. KRAS has proven difficult to target effectively. Two different strategies have recently been described for covalently targeting the most common activating KRAS mutant in lung cancer, KRAS G12C. Previously, we have developed a computational model of the processes that regulate Ras activation and this model has proven useful for understanding the complex behaviors of Ras signaling. Here, we use this model to perform a computational systems pharmacology analysis of KRAS G12C targeted covalent inhibitors. After updating our model to include Ras protein turnover, we verified the validity of our model for problems in this domain by comparing model behaviors with experimental behaviors. The model naturally reproduces previous experimental data, including several experimental observations that were interpreted as being contrary to conventional wisdom. Overall, this suggests that our model describes the Ras system well, including those areas where conventional wisdom struggles. We then used the model to investigate possible strategies to improve the ability of KRAS G12C inhibitors to inhibit Ras pathway signaling. We identify one, as of yet unexplored mechanism, that, if optimized, could improve the effectiveness of one class of KRAS inhibitor. We also simulated resistance to targeted therapies and found that resistance promoting mutations may reverse which class of KRAS G12C inhibitor inhibits the system better, suggesting that there may be value to pursuing both types of KRAS G12C inhibitors. Overall, this work demonstrates that systems biology approaches can provide insights that inform the drug development process.

scholarly journals GPCR-controlled membrane recruitment of negative regulator C2GAP1 locally inhibits Ras signaling for adaptation and long-range chemotaxis

2017 ◽  
Vol 114 (47) ◽  
pp. E10092-E10101 ◽  
Author(s):  
Xuehua Xu ◽  
Xi Wen ◽  
Douwe M. Veltman ◽  
Ineke Keizer-Gunnink ◽  
Henderikus Pots ◽  
...  
Keyword(s):  
Long Range ◽  
Molecular Mechanisms ◽  
Leading Edge ◽  
Negative Regulator ◽  
Ras Signaling ◽  
Gradient Sensing ◽  
Membrane Recruitment ◽  
Inhibitory Processes ◽  
Ras Activation ◽  
Wide Range

Eukaryotic cells chemotax in a wide range of chemoattractant concentration gradients, and thus need inhibitory processes that terminate cell responses to reach adaptation while maintaining sensitivity to higher-concentration stimuli. However, the molecular mechanisms underlying inhibitory processes are still poorly understood. Here, we reveal a locally controlled inhibitory process in a GPCR-mediated signaling network for chemotaxis inDictyostelium discoideum. We identified a negative regulator of Ras signaling, C2GAP1, which localizes at the leading edge of chemotaxing cells and is activated by and essential for GPCR-mediated Ras signaling. We show that both C2 and GAP domains are required for the membrane targeting of C2GAP1, and that GPCR-triggered Ras activation is necessary to recruit C2GAP1 from the cytosol and retains it on the membrane to locally inhibit Ras signaling. C2GAP1-deficientc2gapA−cells have altered Ras activation that results in impaired gradient sensing, excessive polymerization of F actin, and subsequent defective chemotaxis. Remarkably, these cellular defects ofc2gapA−cells are chemoattractant concentration dependent. Thus, we have uncovered an inhibitory mechanism required for adaptation and long-range chemotaxis.

scholarly journals Interaction of Shc with Grb2 regulates association of Grb2 with mSOS.

1995 ◽  
Vol 15 (2) ◽  
pp. 593-600 ◽  
Author(s):  
K S Ravichandran ◽  
U Lorenz ◽  
S E Shoelson ◽  
S J Burakoff
Keyword(s):  
T Cell ◽  
Interleukin 2 ◽  
Antigen Receptor ◽  
Sh2 Domain ◽  
T Antigen ◽  
Ras Signaling ◽  
Adapter Protein ◽  
Cell Antigen Receptor ◽  
Cell Antigen ◽  
Ras Activation

The adapter protein Shc has been implicated in Ras signaling via many receptors, including the T-cell antigen receptor (TCR), B-cell antigen receptor, interleukin-2 receptor, interleukin-3 receptor, erythropoietin receptor, and insulin receptor. Moreover, transformation via polyomavirus middle T antigen is dependent on its interaction with Shc and Shc tyrosine phosphorylation. One of the mechanisms of TCR-mediated, tyrosine kinase-dependent Ras activation involves the simultaneous interaction of phosphorylated Shc with the TCR zeta chain and with a second adapter protein, Grb2. Grb2, in turn, interacts with the Ras guanine nucleotide exchange factor mSOS, thereby leading to Ras activation. Although it has been reported that in fibroblasts Grb2 and mSOS constitutively associate with each other and that growth factor stimulation does not alter the levels of Grb2:mSOS association, we show here that TCR stimulation leads to a significant increase in the levels of Grb2 associated with mSOS. This enhanced Grb2:mSOS association, which occurs through an SH3-proline-rich sequence interaction, is regulated through the SH2 domain of Grb2. The following observations support a role for Shc in regulating the Grb2:mSOS association: (i) a phosphopeptide corresponding to the sequence surrounding Tyr-317 of Shc, which displaces Shc from Grb2, abolished the enhanced association between Grb2 and mSOS; and (ii) addition of phosphorylated Shc to unactivated T cell lysates was sufficient to enhance the interaction of Grb2 with mSOS. Furthermore, using fusion proteins encoding different domains of Shc, we show that the collagen homology domain of Shc (which includes the Tyr-317 site) can mediate this effect. Thus, the Shc-mediated regulation of Grb2:mSOS association may provide a means for controlling the extent of Ras activation following receptor stimulation.

A novel negative regulatory function of the phosphoprotein associated with glycosphingolipid-enriched microdomains: blocking Ras activation

Blood ◽  
2007 ◽  
Vol 110 (2) ◽  
pp. 596-625 ◽  
Author(s):  
Michal Smida ◽  
Anita Posevitz-Fejfar ◽  
Vaclav Horejsi ◽  
Burkhart Schraven ◽  
Jonathan A. Lindquist
Keyword(s):  
T Cells ◽  
T Cell Activation ◽  
Cell Activation ◽  
Kinase Activity ◽  
Src Kinase ◽  
Sh2 Domain ◽  
Negative Regulator ◽  
Regulatory Function ◽  
Ras Activation ◽  
Anergic T Cells

Abstract In primary human T cells, anergy induction results in enhanced p59Fyn activity. Because Fyn is the kinase primarily responsible for the phosphorylation of PAG (the phosphoprotein associated with glycosphingolipid-enriched microdomains), which negatively regulates Src-kinase activity by recruiting Csk (the C-terminal Src kinase) to the membrane, we investigated whether anergy induction also affects PAG. Analysis of anergic T cells revealed that PAG is hyperphosphorylated at the Csk binding site, leading to enhanced Csk recruitment and inhibitory tyrosine phosphorylation within Fyn. This together with enhanced phosphorylation of a tyrosine within the SH2 domain of Fyn leads to the formation of a hyperactive conformation, thus explaining the enhanced Fyn kinase activity. In addition, we have also identified the formation of a multiprotein complex containing PAG, Fyn, Sam68, and RasGAP in stimulated T cells. We demonstrate that PAG-Fyn overexpression is sufficient to suppress Ras activation in Jurkat T cells and show that this activity is independent of Csk binding. Thus, in addition to negatively regulating Src family kinases by recruiting Csk, PAG also negatively regulates Ras by recruiting RasGAP to the membrane. Finally, by knocking down PAG, we demonstrate both enhanced Src kinase activity and Ras activation, thereby establishing PAG as an important negative regulator of T-cell activation.

scholarly journals Requirements of Multiple Domains of SLI-1, aCaenorhabditis elegansHomologue of c-Cbl, and an Inhibitory Tyrosine in LET-23 in Regulating Vulval Differentiation

2000 ◽  
Vol 11 (11) ◽  
pp. 4019-4031 ◽  
Author(s):  
Charles H. Yoon ◽  
Chieh Chang ◽  
Neil A. Hopper ◽  
Giovanni M. Lesa ◽  
Paul W. Sternberg
Keyword(s):  
Calcium Binding ◽  
Ring Finger ◽  
Growth Factor Receptor ◽  
Chimeric Protein ◽  
Sh2 Domain ◽  
Negative Regulator ◽  
Functional Assay ◽  
Ring Finger Domain ◽  
C Terminus ◽  
Ras Activation

SLI-1, a Caenorhabditis elegans homologue of the proto-oncogene product c-Cbl, is a negative regulator of LET-23-mediated vulval differentiation. Lack of SLI-1 activity can compensate for decreased function of the LET-23 epidermal growth factor receptor, the SEM-5 adaptor, but not the LET-60 RAS, suggesting that SLI-1 acts before RAS activation. SLI-1 and c-Cbl comprise an N-terminal region (termed SLI-1:N/Cbl-N, containing a four-helix bundle, an EF hand calcium-binding domain, and a divergent SH2 domain) followed by a RING finger domain and a proline-rich C-terminus. In a transgenic functional assay, the proline-rich C-terminal domain is not essential for sli-1(+) function. A protein lacking the SH2 and RING finger domains has no activity, but a chimeric protein with the SH2 and RING finger domains of SLI-1 replaced by the equivalent domains of c-Cbl has activity. The RING finger domain of c-Cbl has been shown recently to enhance ubiquitination of active RTKs by acting as an E3 ubiquitin–protein ligase. We find that the RING finger domain of SLI-1 is partially dispensable. Further, we identify an inhibitory tyrosine of LET-23 requiring sli-1(+) for its effects: removal of this tyrosine closely mimics the loss ofsli-1 but not of another negative regulator,ark-1. Thus, we suggest that this inhibitory tyrosine mediates its effects through SLI-1, which in turn inhibits signaling upstream of LET-60 RAS in a manner not wholly dependent on the ubiquitin–ligase domain.

scholarly journals A Systems Mechanism for KRAS Mutant Allele Specific Responses to Targeted Therapy

2018 ◽  
Author(s):  
Thomas McFall ◽  
Jolene K Diedrich ◽  
Meron Mengistu ◽  
Stacy L Littlechild ◽  
Kendra V Paskvan ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Genomic Medicine ◽  
Interaction Strength ◽  
Ras Signaling ◽  
Wild Type ◽  
Kras Mutations ◽  
Ras Pathway ◽  
Egfr Inhibition ◽  
Ras Activation ◽  
Allele Specific

A well-established genotype to phenotype relationship in genomic medicine is that activating KRAS mutations indicate resistance to anti-EGFR agents. We used a computational model of Ras signaling to investigate a confusing exception to this relationship whereby colorectal cancers with one specific, constitutively-active, mutant, KRAS G13D, respond to anti-EGFR agents. Our computational simulations of the biochemical processes that regulate Ras suggest EGFR inhibition reduces wild-type Ras activation in KRAS G13D mutant cancer cells more than in other KRAS mutant cancer cells. The model also reveals a non-intuitive, mutant-specific, dependency of wild-type Ras activation on EGFR. This dependency is determined by the interaction strength between a KRAS mutant and tumor suppressor neurofibromin. Our prospective experiments confirm this mechanism that arises from the systems-level regulation of Ras pathway signaling. Overall, our work demonstrates how systems approaches enable mechanism-based inference in genomic medicine.

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