Related Experiment Video

Updated: Jul 5, 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

p21 activated kinase 5 activates Raf-1 and targets it to mitochondria

Xiaochong Wu1, Heather S Carr, Ippeita Dan

  • 1Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, Texas 77030, USA.

Journal of Cellular Biochemistry
|May 10, 2008
PubMed

Insights

Group II PAK kinases, including PAK5, phosphorylate Raf-1 at serine 338, a key site for ERK/MAPK pathway activation. PAK5 specifically binds Raf-1, potentially regulating its activity at mitochondria.

Area of Science:

  • Cellular signaling
  • Molecular biology
  • Kinase regulation

Background:

  • Raf-1 is a key effector in Ras-mediated signaling and a critical regulator of the ERK/MAPK pathway.
  • Raf-1 activation depends on phosphorylation at multiple sites, including serine 338, with PAK1 and casein kinase II previously implicated as kinases for this residue.

Purpose of the Study:

  • To identify novel kinases responsible for phosphorylating Raf-1 at serine 338.
  • To investigate the role of group II PAKs (PAKs 4-6) in regulating Raf-1 activity and localization.

Main Methods:

  • In vitro kinase assays to assess serine 338 phosphorylation by group II PAKs.
  • Co-immunoprecipitation assays to determine complex formation between PAKs and Raf-1 isoforms.
  • Cellular localization studies to track Raf-1 in the presence of PAK5.

Main Results:

  • All group II PAKs (PAKs 4-6) efficiently phosphorylated Raf-1 at serine 338.
  • PAK1 and PAK5 significantly stimulated Raf-1 kinase activity.
  • PAK5 formed a stable complex with Raf-1, but not A-Raf or B-Raf.
  • PAK5 binding targeted a subpopulation of Raf-1 to mitochondria.

Conclusions:

  • PAK5 is identified as a potent regulator of Raf-1 activity.
  • PAK5-mediated phosphorylation and mitochondrial localization suggest a role in controlling Raf-1 dependent signaling at the mitochondria.

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

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

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