Related Experiment Video

Updated: Aug 8, 2026

Characterize Disease-related Mutants of RAF Family Kinases by Using a Set of Practical and Feasible Methods
07:49

Characterize Disease-related Mutants of RAF Family Kinases by Using a Set of Practical and Feasible Methods

Published on: July 17, 2019

Pathway- and expression level-dependent effects of oncogenic N-Ras: p27(Kip1) mislocalization by the Ral-GEF pathway

Shiri Kfir1, Marcelo Ehrlich, Ayelet Goldshmid

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

Molecular and Cellular Biology
|September 2, 2005
PubMed

Insights

Constitutively active N-Ras disrupts cell cycle regulation by mislocalizing p27 (CDK inhibitor) and blocks TGF-beta signaling, promoting oncogenesis and metastasis in epithelial cells.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • Ras pathway overactivation is implicated in cancer development and metastasis.
  • Ras interferes with cell cycle regulation (p27) and transforming growth factor beta (TGF-beta) anti-proliferative activity.

Purpose of the Study:

  • To investigate how activated N-Ras affects p27 localization and TGF-beta signaling.
  • To elucidate the specific pathways involved in N-Ras-mediated disruption of these cellular processes.

Main Methods:

  • Expression of activated N-Ras in murine and human cells.
  • Analysis of p27 (CDK inhibitor) localization using immunofluorescence.
  • Assessment of Smad nuclear translocation via Western blotting and microscopy.
  • Investigation of the roles of Ral-GEF, Mek/Erk, and PI3K/Akt pathways.

Main Results:

  • High N-Ras levels induce cytoplasmic mislocalization of p27 via Ral-GEF and disrupt Smad nuclear translocation through Mek/Erk activation.
  • Human p27 mislocalization is also mediated by PI3K/Akt, unlike murine p27.
  • Disruption of p27 nuclear localization or Smad translocation inhibits TGF-beta growth suppression.
  • Lower levels of activated N-Ras primarily affect p27 localization, not Smad translocation.

Conclusions:

  • The Ral-GEF pathway plays a novel role in regulating p27 localization.
  • Activated Ras contributes to oncogenesis by interfering with cell cycle control and TGF-beta signaling.
  • Ras activation can convert TGF-beta from an inhibitory to a pro-metastatic factor in epithelial tumors.

More Related Videos

Identification of EGFR and RAS Inhibitors using Caenorhabditis elegans08:12

Identification of EGFR and RAS Inhibitors using Caenorhabditis elegans

Published on: October 5, 2020

Intracellular Phosphoflow Cytometry of Acute Myeloid Leukemia Patient-Derived Xenotransplants07:38

Intracellular Phosphoflow Cytometry of Acute Myeloid Leukemia Patient-Derived Xenotransplants

Published on: June 6, 2025

Related Concept Videos

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...
mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

The mammalian target of rapamycin or mTOR protein was discovered in 1994 due to its direct interaction with rapamycin. The protein gets its name from a yeast homolog called TOR. The mTOR protein complex in mammalian cells plays a major role in balancing anabolic processes such as the synthesis of proteins, lipids, and nucleotides and catabolic processes, such as autophagy in response to environmental cues, such as availability of nutrients and growth factors.
The mTOR pathway or the...
Interactions Between Signaling Pathways01:19

Interactions Between Signaling Pathways

Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
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:
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...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...