Related Experiment Video

Updated: Aug 21, 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

A novel role for mixed lineage kinase 3 (MLK3) in B-Raf activation and cell proliferation

Deborah N Chadee1, John M Kyriakis

  • 1The Molecular Cardiology Research Institute, Tufts-New England Medical Center, Boston, Massachusetts 02111, USA. dchadee@tufts-nemc.org

Cell Cycle (Georgetown, Tex.)
|October 7, 2004
PubMed

Insights

Mixed lineage kinase-3 (MLK3) unexpectedly regulates ERK and p38 signaling pathways, crucial for cell proliferation. Targeting MLK3 may offer new treatments for cancers with specific mutations.

Area of Science:

  • Cellular signaling pathways
  • Mitogen-activated protein kinases (MAPKs)
  • Cancer biology

Background:

  • Extracellular signal-regulated kinase (ERK) pathways are vital for cell proliferation.
  • Raf kinases, particularly B-Raf, are key activators of ERK signaling.
  • Mixed lineage kinase-3 (MLK3) was previously considered a selective regulator of JNK pathways.

Purpose of the Study:

  • To investigate the role of MLK3 in mitogen and cytokine signaling.
  • To determine MLK3's involvement in ERK and p38 activation.
  • To assess MLK3's impact on cell proliferation, especially in cancer contexts.

Main Methods:

  • RNA interference (RNAi) was used to silence MLK3 expression.
  • Analysis of MAPK pathway activation (JNK, ERK, p38) following MLK3 silencing.
  • Assessment of B-Raf phosphorylation at specific sites (Thr598, Ser601).
  • Evaluation of cell proliferation in response to serum stimulation and in tumor cells with specific mutations (Ras, NF1, NF2, B-Raf, Raf-1).

Main Results:

  • MLK3 silencing suppressed activation of JNK, ERK, and p38 pathways.
  • MLK3 depletion blocked mitogen-stimulated B-Raf phosphorylation, a critical activation step.
  • MLK3 silencing inhibited serum-stimulated cell proliferation and proliferation of tumor cells with oncogenic Ki-Ras or NF1/NF2 mutations.
  • Tumor cell proliferation driven by activating B-Raf or Raf-1 mutations was unaffected by MLK3 silencing.

Conclusions:

  • MLK3 plays a novel and significant role in activating B-Raf, thereby influencing ERK signaling and cell proliferation.
  • MLK3 is a key regulator of both JNK and non-JNK MAPK pathways.
  • Targeting MLK3 presents a potential therapeutic strategy for tumors driven by activated receptor tyrosine kinases, Ras mutations, or NF1/NF2 deficiencies.

More Related Videos

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development09:32

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

Published on: June 15, 2017

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

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...
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...
Mitogens and the Cell Cycle02:38

Mitogens and the Cell Cycle

Mitogens and their receptors play a crucial role in controlling the progression of the cell cycle. However, the loss of mitogenic control over cell division leads to tumor formation. Therefore, mitogens and mitogen receptors play an important role in cancer research. For instance, the epidermal growth factor (EGF) - a type of mitogen and its transmembrane receptor (EGFR), decides the fate of the cell's proliferation. When EGF binds to EGFR, a member of the ErbB family of tyrosine kinase...
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...
Abnormal Proliferation02:23

Abnormal Proliferation

Under normal conditions, most adult cells remain in a non-proliferative state unless stimulated by internal or external factors to replace lost cells. Abnormal cell proliferation is a condition in which the cell's growth exceeds and is uncoordinated with normal cells. In such situations, cell division persists in the same excessive manner even after cessation of the stimuli, leading to persistent tumors. The tumor arises from the damaged cells that replicate to pass the damage to the daughter...