Related Experiment Video

Updated: Jun 18, 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

Impact of feedback phosphorylation and Raf heterodimerization on normal and mutant B-Raf signaling

Daniel A Ritt1, Daniel M Monson, Suzanne I Specht

  • 1Laboratory of Cell and Developmental Signaling, NCI-Frederick, Building 560, Frederick, MD 21702, USA.

Molecular and Cellular Biology
|November 26, 2009
PubMed

Insights

Normal and cancerous B-Raf proteins undergo a regulatory cycle involving extracellular signal-regulated kinase (ERK) phosphorylation and dephosphorylation. This feedback loop impacts Ras binding and C-Raf heterodimerization, influencing cancer development.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Oncology

Background:

  • B-Raf kinase is a key effector in the Ras pathway, frequently mutated in cancers and developmental disorders.
  • Understanding B-Raf regulation is crucial for targeted cancer therapies and comprehending disease mechanisms.

Purpose of the Study:

  • To elucidate the regulatory feedback mechanism of B-Raf kinase.
  • To investigate the role of ERK-dependent phosphorylation and subsequent dephosphorylation in B-Raf function.
  • To determine how these regulatory events affect B-Raf's interaction with Ras and C-Raf, and its oncogenic potential.

Main Methods:

  • Identification of B-Raf phosphorylation sites targeted by ERK.
  • Analysis of B-Raf binding to Ras and heterodimerization with C-Raf under various conditions.
  • Assessment of transformation potential upon mutation of feedback sites or manipulation of PP2A/Pin1 activity.
  • Investigation of B-Raf/C-Raf heterodimerization in developmental disorder-associated mutants.

Main Results:

  • Four S/TP sites on B-Raf are phosphorylated by ERK, inhibiting Ras binding and C-Raf heterodimerization.
  • Feedback phosphorylation modulates the transforming potential of certain oncogenic B-Raf variants.
  • Mutations in feedback sites or Pin1 overexpression increase transformation, while S729 site mutation or dominant-negative Pin1 reduces it.
  • Developmental disorder-associated B-Raf/C-Raf mutants constitutively heterodimerize, with activity modulated by feedback phosphorylation.

Conclusions:

  • B-Raf activity is tightly regulated by a feedback phosphorylation/dephosphorylation cycle involving ERK, PP2A, and Pin1.
  • This regulatory cycle plays a significant role in modulating B-Raf's oncogenic potential and interaction dynamics.
  • Understanding this cycle offers potential therapeutic targets for B-Raf-driven cancers and related disorders.

More Related Videos

Bioluminescence Resonance Energy Transfer (BRET)-Based Assay for Measuring Interactions of CRAF with 14-3-3 Proteins in Live Cells06:44

Bioluminescence Resonance Energy Transfer (BRET)-Based Assay for Measuring Interactions of CRAF with 14-3-3 Proteins in Live Cells

Published on: March 1, 2024

Deciphering the Structural Effects of Activating EGFR Somatic Mutations with Molecular Dynamics Simulation15:05

Deciphering the Structural Effects of Activating EGFR Somatic Mutations with Molecular Dynamics Simulation

Published on: May 20, 2020

Related Concept Videos

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...
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...
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:
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...
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...