Related Experiment Video

Updated: Aug 11, 2026

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
09:32

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

Published on: June 15, 2017

PB1 domain-dependent signaling complex is required for extracellular signal-regulated kinase 5 activation

Kazuhiro Nakamura1, Mark T Uhlik, Nancy L Johnson

  • 1Department of Pharmacology, CB#7365, 1108 Mary Ellen Jones Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA.

Molecular and Cellular Biology
|March 2, 2006
PubMed

Insights

The MEK5 PB1 domain acts as a scaffold, binding both MEKK2 and ERK5 to form a signaling complex. This interaction is crucial for activating the ERK5 pathway and demonstrates specific kinase regulation.

Area of Science:

  • Cellular signaling pathways
  • Protein-protein interactions
  • MAPK signaling cascades

Background:

  • Mitogen-activated protein kinase kinase kinase 2 (MEKK2), MEK5, and extracellular signal-regulated kinase 5 (ERK5) form a three-kinase cascade.
  • MEK5 is unique among MAP2Ks for possessing a PB1 domain, which mediates heterodimerization with MEKK2.

Purpose of the Study:

  • To investigate the role of the MEK5 PB1 domain in forming a functional MEKK2-MEK5-ERK5 complex.
  • To define the binding sites and critical residues within the MEK5 PB1 domain for MEKK2 and ERK5 interactions.
  • To understand how this complex formation regulates ERK5 pathway activation.

Main Methods:

  • Reconstitution assays to study protein interactions.
  • Förster resonance energy transfer (FRET) using CFP/YFP imaging to measure MEKK2/MEK5 and MEK5/ERK5 interactions in living cells.
  • Mutational analysis to identify critical residues in the MEK5 PB1 domain.

Main Results:

  • The MEK5 PB1 domain acts as a scaffold, binding both MEKK2 and ERK5.
  • Distinct binding sites for MEKK2 and ERK5 exist within the MEK5 PB1 domain, with its C-terminal extension involved in ERK5 binding.
  • Specific MEK5 PB1 domain residues are essential for MEKK2/MEK5 and MEK5/ERK5 interactions, enabling ERK5 pathway activation.
  • Fusion of the MEK5 PB1 domain to MEK1 enabled ERK5 pathway regulation.

Conclusions:

  • The MEK5 PB1 domain is a critical scaffold organizing the MEKK2-MEK5-ERK5 signaling complex.
  • This scaffold mechanism ensures stringent MAP3K regulation of ERK5, contrasting with broader regulation of other MAPK pathways.
  • The findings provide insights into the specific mechanisms governing ERK5 pathway activation.

More Related Videos

Assaying Protein Kinase Activity with Radiolabeled ATP08:05

Assaying Protein Kinase Activity with Radiolabeled ATP

Published on: May 26, 2017

A Guide to Production, Crystallization, and Structure Determination of Human IKK1/α11:27

A Guide to Production, Crystallization, and Structure Determination of Human IKK1/α

Published on: November 2, 2018

Related Concept Videos

The JAK-STAT Signaling Pathway01:20

The JAK-STAT Signaling Pathway

Several cytokine receptors have tightly bound Janus kinase or JAK proteins attached at their cytosolic tail. Small signaling molecules such as cytokines, growth hormones, or prolactins bind to the cytokine receptors and initiate their dimerization. The dimerization brings the cytosolic JAKs together that trans-phosphorylate and activates each other. The activated JAKs now phosphorylate cytosolic tails of the cytokine receptors, which serve as binding sites for adaptor proteins such as  SH2...
Assembly of Signaling Complexes01:30

Assembly of Signaling Complexes

Multiprotein signaling complexes are formed in a dynamic process involving protein-protein interactions at the cytoplasmic domain of transmembrane receptors or enzymatic and non-enzymatic proteins associated with the receptor. These complexes ensure the activation and propagation of intracellular signals that regulate cell functions.
Interaction domains in cell signaling
Interaction domains recognize exposed features of their binding partners containing post-translationally modified sequences,...
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...
Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze 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...
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...