Browse
Submit Data
Databases
API
Help

Dataset Information

24 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Feedback regulation of Ras signaling by Rabex-5-mediated ubiquitination.

ABSTRACT: Ras proteins play a central role in transducing signals that control cell proliferation, differentiation, motility, and survival. The location-specific signaling activity of Ras has been previously shown to be regulated by ubiquitination [1]. However, the molecular machinery that controls Ras ubiquitination has not been defined. Here we demonstrate through biochemical and functional analyses that Rabex-5 (also known as RabGEF1) [2, 3] functions as an E3 ligase for Ras. Rabex-5-mediated Ras ubiquitination promotes Ras endosomal localization and leads to the suppression of ERK activation. Moreover, the Ras effector RIN1 [4, 5] is required for Rabex-5-dependent Ras ubiquitination, suggesting a feedback mechanism by which Ras activation can be coupled to ubiquitination. These findings define new elements in the regulatory circuitry that link Ras compartmentalization to signaling output.

SUBMITTER: Xu L

PROVIDER: S-EPMC3436604 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Feedback regulation of Ras signaling by Rabex-5-mediated ubiquitination.

Xu Lizhong L Lubkov Veronica V Taylor Laura J LJ Bar-Sagi Dafna D

Current biology : CB 20100722 15

Ras proteins play a central role in transducing signals that control cell proliferation, differentiation, motility, and survival. The location-specific signaling activity of Ras has been previously shown to be regulated by ubiquitination [1]. However, the molecular machinery that controls Ras ubiquitination has not been defined. Here we demonstrate through biochemical and functional analyses that Rabex-5 (also known as RabGEF1) [2, 3] functions as an E3 ligase for Ras. Rabex-5-mediated Ras ubiqu ...[more]

PMID: 20655225

Similar Datasets

Rabex-5 ubiquitin ligase activity restricts Ras signaling to establish pathway homeostasis in Drosophila.

Project description:The Ras signaling pathway allows cells to translate external cues into diverse biological responses. Depending on context and the threshold reached, Ras signaling can promote growth, proliferation, differentiation, or cell survival. Failure to maintain precise control of Ras can have adverse physiological consequences. Indeed, excess Ras signaling disrupts developmental patterning and causes developmental disorders [1, 2], and in mature tissues, it can lead to cancer [3-5]. We identify Rabex-5 as a new component of Ras signaling crucial for achieving proper pathway outputs in multiple contexts in vivo. We show that Drosophila Rabex-5 restricts Ras signaling to establish organism size, wing vein pattern, and eye versus antennal fate. Rabex-5 has both Rab5 guanine nucleotide exchange factor (GEF) activity that regulates endocytic trafficking [6] and ubiquitin ligase activity [7, 8]. Surprisingly, overexpression studies demonstrate that Rabex-5 ubiquitin ligase activity, not its Rab5 GEF activity, is required to restrict wing vein specification and to suppress the eye phenotypes of oncogenic Ras expression. Furthermore, genetic interaction experiments indicate that Rabex-5 acts at the step of Ras, and tissue culture studies show that Rabex-5 promotes Ras ubiquitination. Together, these findings reveal a new mechanism for attenuating Ras signaling in vivo and suggest an important role for Rabex-5-mediated Ras ubiquitination in pathway homeostasis.

| S-EPMC2938185 | biostudies-literature

LZTR1 is a regulator of RAS ubiquitination and signaling.

Project description:In genetic screens aimed at understanding drug resistance mechanisms in chronic myeloid leukemia cells, inactivation of the cullin 3 adapter protein-encoding leucine zipper-like transcription regulator 1 (LZTR1) gene led to enhanced mitogen-activated protein kinase (MAPK) pathway activity and reduced sensitivity to tyrosine kinase inhibitors. Knockdown of the Drosophila LZTR1 ortholog CG3711 resulted in a Ras-dependent gain-of-function phenotype. Endogenous human LZTR1 associates with the main RAS isoforms. Inactivation of LZTR1 led to decreased ubiquitination and enhanced plasma membrane localization of endogenous KRAS (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog). We propose that LZTR1 acts as a conserved regulator of RAS ubiquitination and MAPK pathway activation. Because LZTR1 disease mutations failed to revert loss-of-function phenotypes, our findings provide a molecular rationale for LZTR1 involvement in a variety of inherited and acquired human disorders.

| S-EPMC6794158 | biostudies-literature

Dynamic regulation of RAS and RAS signaling.

Project description:RAS proteins regulate most aspects of cellular physiology. They are mutated in 30% of human cancers and 4% of developmental disorders termed Rasopathies. They cycle between active GTP-bound and inactive GDP-bound states. When active, they can interact with a wide range of effectors that control fundamental biochemical and biological processes. Emerging evidence suggests that RAS proteins are not simple on/off switches but sophisticated information processing devices that compute cell fate decisions by integrating external and internal cues. A critical component of this compute function is the dynamic regulation of RAS activation and downstream signaling that allows RAS to produce a rich and nuanced spectrum of biological outputs. We discuss recent findings how the dynamics of RAS and its downstream signaling is regulated. Starting from the structural and biochemical properties of wild-type and mutant RAS proteins and their activation cycle, we examine higher molecular assemblies, effector interactions and downstream signaling outputs, all under the aspect of dynamic regulation. We also consider how computational and mathematical modeling approaches contribute to analyze and understand the pleiotropic functions of RAS in health and disease.

| S-EPMC9988006 | biostudies-literature

Cooperative loss of RAS feedback regulation drives myeloid leukemogenesis.

Project description:RAS network activation is common in human cancers, and in acute myeloid leukemia (AML) this activation is achieved mainly through gain-of-function mutations in KRAS, NRAS or the receptor tyrosine kinase FLT3. We show that in mice, premalignant myeloid cells harboring a Kras(G12D) allele retained low levels of Ras signaling owing to negative feedback involving Spry4 that prevented transformation. In humans, SPRY4 is located on chromosome 5q, a region affected by large heterozygous deletions that are associated with aggressive disease in which gain-of-function mutations in the RAS pathway are rare. These 5q deletions often co-occur with chromosome 17 alterations involving the deletion of NF1 (another RAS negative regulator) and TP53. Accordingly, combined suppression of Spry4, Nf1 and p53 produces high levels of Ras signaling and drives AML in mice. Thus, SPRY4 is a tumor suppressor at 5q whose disruption contributes to a lethal AML subtype that appears to acquire RAS pathway activation through a loss of negative regulators.

| S-EPMC4414804 | biostudies-literature

Negative feedback regulation of Wnt signaling by Gbetagamma-mediated reduction of Dishevelled.

Project description:Wnt signaling is known to be important for diverse embryonic and post-natal cellular events and be regulated by the proteins Dishevelled and Axin. Although Dishevelled is activated by Wnt and involved in signal transduction, it is not clear how Dishevelled-mediated signaling is turned off. We report that guanine nucleotide binding protein beta 2 (Gnb2; Gbeta2) bound to Axin and Gbeta2 inhibited Wnt mediated reporter activity. The inhibition involved reduction of the level of Dishevelled, and the Gbeta2gamma2 mediated reduction of Dishevelled was countered by increased expression of Axin. Consistent with these effects in HEK293T cells, injection of Gbeta2gamma2 into Xenopus embryos inhibited the formation of secondary axes induced either by XWnt8 or Dishevelled, but not by beta-catenin. The DEP domain of Dishevelled is necessary for both interaction with Gbeta2gamma2 and subsequent degradation of Dishevelled via the lysosomal pathway. Signaling induced by Gbeta2gamma2 is required because a mutant of Gbeta2, Gbeta2 (W332A) with lower signaling activity, had reduced ability to downregulate the level of Dishevelled. Activation of Wnt signaling by either of two methods, increased Frizzled signaling or transient transfection of Wnt, also led to increased degradation of Dishevelled and the induced Dishevelled loss is dependent on Gbeta1 and Gbeta2. Other studies with agents that interfere with PLC action and calcium signaling suggested that loss of Dishevelled is mediated through the following pathway: Wnt/Frizzled-->Gbetagamma-->PLC-->Ca(+2)/PKC signaling. Together the evidence suggests a novel negative feedback mechanism in which Gbeta2gamma2 inhibits Wnt signaling by degradation of Dishevelled.

| S-EPMC2772972 | biostudies-literature

Feedback regulation of ubiquitination and phase separation of HECT E3 ligases.

Project description:Lipid homeostasis is essential for normal cellular functions and dysregulation of lipid metabolism is highly correlated with human diseases including neurodegenerative diseases. In the ubiquitin-dependent autophagic degradation pathway, Troyer syndrome-related protein Spartin activates and recruits HECT-type E3 Itch to lipid droplets (LDs) to regulate their turnover. In this study, we find that Spartin promotes the formation of Itch condensates independent of LDs. Spartin activates Itch through its multiple PPAY-motif platform generated by self-oligomerization, which targets the WW12 domains of Itch and releases the autoinhibition of the ligase. Spartin-induced activation and subsequent autoubiquitination of Itch lead to liquid-liquid phase separation (LLPS) of the poly-, but not oligo-, ubiquitinated Itch together with Spartin and E2 both in vitro and in living cells. LLPS-mediated condensation of the reaction components further accelerates the generation of polyubiquitin chains, thus forming a positive feedback loop. Such Itch-Spartin condensates actively promote the autophagy-dependent turnover of LDs. Moreover, we show that the catalytic HECT domain of Itch is sufficient to interact and phase separate with poly-, but not oligo-ubiquitin chains. HECT domains from other HECT E3 ligases also exhibit LLPS-mediated the promotion of ligase activity. Therefore, LLPS and ubiquitination are mutually interdependent and LLPS promotes the ligase activity of the HECT family E3 ligases.

| S-EPMC10438380 | biostudies-literature

A conserved, N-terminal tyrosine signal directs Ras for inhibition by Rabex-5.

Project description:Dysregulation of the Ras oncogene in development causes developmental disorders, "Rasopathies," whereas mutational activation or amplification of Ras in differentiated tissues causes cancer. Rabex-5 (also called RabGEF1) inhibits Ras by promoting Ras mono- and di-ubiquitination. We report here that Rabex-5-mediated Ras ubiquitination requires Ras Tyrosine 4 (Y4), a site of known phosphorylation. Ras substitution mutants insensitive to Y4 phosphorylation did not undergo Rabex-5-mediated ubiquitination in cells and exhibited Ras gain-of-function phenotypes in vivo. Ras Y4 phosphomimic substitution increased Rabex-5-mediated ubiquitination in cells. Y4 phosphomimic substitution in oncogenic Ras blocked the morphological phenotypes associated with oncogenic Ras in vivo dependent on the presence of Rabex-5. We developed polyclonal antibodies raised against an N-terminal Ras peptide phosphorylated at Y4. These anti-phospho-Y4 antibodies showed dramatic recognition of recombinant wild-type Ras and RasG12V proteins when incubated with JAK2 or SRC kinases but not of RasY4F or RasY4F,G12V recombinant proteins suggesting that JAK2 and SRC could promote phosphorylation of Ras proteins at Y4 in vitro. Anti-phospho-Y4 antibodies also showed recognition of RasG12V protein, but not wild-type Ras, when incubated with EGFR. A role for JAK2, SRC, and EGFR (kinases with well-known roles to activate signaling through Ras), to promote Ras Y4 phosphorylation could represent a feedback mechanism to limit Ras activation and thus establish Ras homeostasis. Notably, rare variants of Ras at Y4 have been found in cerebellar glioblastomas. Therefore, our work identifies a physiologically relevant Ras ubiquitination signal and highlights a requirement for Y4 for Ras inhibition by Rabex-5 to maintain Ras pathway homeostasis and to prevent tissue transformation.

| S-EPMC7329146 | biostudies-literature

Regulation of PD-L1 expression in K-ras-driven cancers through ROS-mediated FGFR1 signaling.

Project description:K-ras mutations are major genetic events that drive cancer development associated with aggressive malignant phenotypes, while expression of the immune checkpoint molecule PD-L1 plays a key role in cancer evasion of the immune surveillance that also profoundly affects the patient outcome. However, the relationship between K-ras oncogenic signal and PD-L1 expressions as an important area that requires further investigation. Using both in vitro and in vivo experimental models of K-ras-driven cancer, we found that oncogenic K-ras significantly enhanced PD-L1 expression through a redox-mediated mechanism. Activation of K-rasG12V promoted ROS generation and induced FGFR1 expression, leading to a significant upregulation of PD-L1. We further showed that exogenous ROS such as hydrogen peroxide alone was sufficient to activate FGFR1 and induce PD-L1, while antioxidants could largely abrogate PD-L1 expression in K-ras mutant cells, indicating a critical role of redox regulation. Importantly, genetic knockout of FGFR1 led to a decrease in PD-L1 expression, and impaired tumor growth in vivo due to a significant increase of T cell infiltration in the tumor tissues and thus enhanced T-cell-mediated tumor suppression. Our study has identified a novel mechanism by which K-ras promotes PD-L1 expression, and suggests that modulation of ROS or inhibition of the FGFR1 pathway could be a novel strategy to abrogate PD-L1-mediated immunosuppression and thus potentially improve the efficacy of immunotherapy in K-ras-driven cancers.

| S-EPMC7658718 | biostudies-literature

IAP-Mediated Protein Ubiquitination in Regulating Cell Signaling.

Project description:Over the last decade, the E3-ubiquitine ligases from IAP (Inhibitor of Apoptosis) family have emerged as potent regulators of immune response. In immune cells, they control signaling pathways driving differentiation and inflammation in response to stimulation of tumor necrosis factor receptor (TNFR) family, pattern-recognition receptors (PRRs), and some cytokine receptors. They are able to control the activity, the cellular fate, or the stability of actors of signaling pathways, acting at different levels from components of receptor-associated multiprotein complexes to signaling effectors and transcription factors, as well as cytoskeleton regulators. Much less is known about ubiquitination substrates involved in non-immune signaling pathways. This review aimed to present IAP ubiquitination substrates and the role of IAP-mediated ubiquitination in regulating signaling pathways.

| S-EPMC7290580 | biostudies-literature

Feedback regulation of RTK signaling in development.

Project description:Precise regulation of the amplitude and duration of receptor tyrosine kinase (RTK) signaling is critical for the execution of cellular programs and behaviors. Understanding these control mechanisms has important implications for the field of developmental biology, and in recent years, the question of how augmentation or attenuation of RTK signaling via feedback loops modulates development has become of increasing interest. RTK feedback regulation is also important for human disease research; for example, germline mutations in genes that encode RTK signaling pathway components cause numerous human congenital syndromes, and somatic alterations contribute to the pathogenesis of diseases such as cancers. In this review, we survey regulators of RTK signaling that tune receptor activity and intracellular transduction cascades, with a focus on the roles of these genes in the developing embryo. We detail the diverse inhibitory mechanisms utilized by negative feedback regulators that, when lost or perturbed, lead to aberrant increases in RTK signaling. We also discuss recent biochemical and genetic insights into positive regulators of RTK signaling and how these proteins function in tandem with negative regulators to guide embryonic development.

| S-EPMC5920792 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data