Related Experiment Video
Updated: Dec 18, 2025
10:27
Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
Published on: March 9, 2012
11.2K
A conserved, N-terminal tyrosine signal directs Ras for inhibition by Rabex-5.
Chalita Washington1,2, Rachel Chernet1, Rewatee H Gokhale1,3,4
1Department of Oncological Sciences, The Icahn School of Medicine at Mount Sinai, New York, New York, United States of America.
Plos Genetics
|June 20, 2020
Summary
Rabex-5 inhibits Ras oncogene activation by ubiquitination, a process dependent on Ras Tyrosine 4 (Y4) phosphorylation. This discovery reveals a new mechanism for maintaining Ras pathway homeostasis and preventing cancer.
Area of Science:
- Molecular Biology
- Oncology
- Cell Signaling
Background:
- Ras oncogene dysregulation causes developmental disorders (Rasopathies) and cancer.
- Rabex-5 inhibits Ras by promoting its ubiquitination.
- Ras signaling is critical for cell growth and differentiation.
Purpose of the Study:
- To investigate the role of Ras Tyrosine 4 (Y4) in Rabex-5-mediated Ras ubiquitination.
- To elucidate the mechanism by which Rabex-5 regulates Ras activity.
- To identify potential therapeutic targets for Ras-driven diseases.
Main Methods:
- Site-directed mutagenesis to create Ras substitution mutants.
- Cellular ubiquitination assays.
- In vivo phenotypic analysis.
- Development of phospho-specific antibodies against Ras Y4.
- Kinase assays (JAK2, SRC, EGFR).
Main Results:
- Rabex-5-mediated Ras ubiquitination requires Ras Y4 phosphorylation.
- Ras mutants insensitive to Y4 phosphorylation exhibit Ras gain-of-function phenotypes.
- Phosphomimic substitution at Y4 enhances Rabex-5-mediated ubiquitination and blocks oncogenic Ras phenotypes.
- JAK2, SRC, and EGFR can phosphorylate Ras at Y4 in vitro.
- Phospho-Y4 antibodies recognize phosphorylated Ras in cellular contexts.
Conclusions:
- Ras Y4 phosphorylation is a critical signal for Rabex-5-mediated Ras inhibition.
- This mechanism contributes to Ras pathway homeostasis.
- Dysregulation of this pathway may contribute to tumorigenesis, as suggested by rare Ras Y4 variants in glioblastomas.
Related Concept Videos
01:14Rab Proteins
4.8K
Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
4.8K
02:38The Ras Gene
6.9K
The Ras-gene-encoded proteins are regulators of signaling pathways controlling cell proliferation, differentiation, or cell survival. The Ras-gene family in humans constitutes three primary members—the HRas, NRas, and KRas. These genes code for four functionally distinct yet closely related proteins—the HRas, NRas, KRas4A, and KRas4B. The involvement of mutant Ras genes in human cancer was first discovered in 1982 and is among the most common causes of human tumorigenesis.
Ras is a...
Ras is a...
6.9K
01:24Small GTPases - Ras and Rho
5.0K
Ras and Rho are small monomeric GTPases that act downstream of receptor tyrosine kinase (RTK) and regulate various cellular processes. These GTPases switch between active and inactive states by binding to guanine nucleotides.
Three regulatory proteins control their activity:
Three regulatory proteins control their activity:
5.0K
01:25Rab Cascades
3.3K
Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.
3.3K
01:26Receptor Tyrosine Kinases
17.3K
Receptor tyrosine kinases or RTKs are membrane-bound receptors that phosphorylate specific tyrosine on protein substrates. RTKs regulate cellular growth, differentiation, survival, and migration. They contain an extracellular ligand binding domain, a transmembrane domain, and a cytosolic tail with intrinsic kinase activity. Several extracellular signaling molecules activate RTKs in one or more ways and relay the signal downstream. Ligands such as platelet-derived growth factor (PDGF) or...
17.3K
01:07MAPK Signaling Cascades
7.6K
Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
7.6K