Related Experiment Video

Updated: Jul 5, 2026

RhoC GTPase Activation Assay
09:58

RhoC GTPase Activation Assay

Published on: August 22, 2010

Galectin-3 regulates RasGRP4-mediated activation of N-Ras and H-Ras

Ruby Shalom-Feuerstein1, Ran Levy, Victoria Makovski

  • 1Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel.

Biochimica Et Biophysica Acta
|April 17, 2008
PubMed

Insights

Galectin-3 (Gal-3) protein inhibits Ras guanine nucleotide releasing protein 4 (RasGRP4) to control Ras activation in cancer. This Gal-3 mechanism impacts N-Ras and H-Ras, offering new therapeutic targets.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • Galectin-3 (Gal-3) is a beta-galactoside-binding protein found in human neoplasms.
  • Gal-3 binds K-Ras, stabilizing its active GTP-bound state.
  • Gal-3's effect on N-Ras-GTP levels in cancer cells was previously unknown.

Purpose of the Study:

  • To elucidate the mechanism by which Galectin-3 influences N-Ras-GTP levels.
  • To investigate the interaction between Gal-3 and Ras guanine nucleotide releasing proteins (RasGRPs).
  • To determine the role of the Gal-3 N-terminal domain in regulating Ras protein activation.

Main Methods:

  • Comparative analysis of Ras-GTP levels and Gal-3 expression across various cancer cell lines.
  • Stimulation of Ras-GTP loading using epidermal growth factor and phorbol 12-myristate 13-acetate (PMA).
  • Downregulation of Gal-3 using Gal-3 shRNA and assessment of N-Ras-GTP levels.
  • Investigation of the interaction between the Gal-3 N-terminal domain and RasGRP4.

Main Results:

  • A positive correlation was observed between high Gal-3 expression and a low N-Ras-GTP/high K-Ras-GTP phenotype.
  • High Gal-3 levels blocked epidermal growth factor-stimulated N-Ras GTP loading.
  • Gal-3 downregulation or RasGRP activation increased N-Ras-GTP levels in Gal-3 expressing cells.
  • The Gal-3 N-terminal domain directly interacted with and inhibited RasGRP4-mediated GTP loading on N-Ras and H-Ras.

Conclusions:

  • Galectin-3's N-terminal domain inhibits RasGRP4, thereby controlling N-Ras and H-Ras activation.
  • This interaction represents a novel regulatory mechanism for Ras signaling in cancer.
  • Targeting the Gal-3 N-terminal domain may offer a therapeutic strategy for cancers driven by Ras pathway dysregulation.

More Related Videos

Visualization of G3BP Stress Granules Dynamics in Live Primary Cells10:12

Visualization of G3BP Stress Granules Dynamics in Live Primary Cells

Published on: May 21, 2014

Related Concept Videos

Small GTPases - Ras and Rho01:24

Small GTPases - Ras and Rho

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:
The Ras Gene02:38

The Ras Gene

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 superfamily...
Activation and Inactivation of G Proteins01:22

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

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...
GPCRs Regulate Adenylyl Cylase Activity01:09

GPCRs Regulate Adenylyl Cylase Activity

Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
GTPases and their Regulation02:14

GTPases and their Regulation

Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒  small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...