Related Experiment Video

Updated: Aug 7, 2026

Assaying Protein Kinase Activity with Radiolabeled ATP
08:05

Assaying Protein Kinase Activity with Radiolabeled ATP

Published on: May 26, 2017

Regulation of mitogen-activated protein kinase activation by protein kinases A and C in a cell-free system

B VanRenterghem1, M D Browning, J L Maller

  • 1Department of Pharmacology, University of Colorado School of Medicine, Denver 80262.

The Journal of Biological Chemistry
|October 7, 1994
PubMed

Insights

Protein kinase C (PKC) stimulates mitogen-activated protein kinase (MAPK) via Ras. cAMP-dependent protein kinase (PKA) inhibits MAPK activation by multiple signals, suggesting a convergence point for signaling pathways in Xenopus oocytes.

Area of Science:

  • Cellular signaling pathways
  • Molecular biology
  • Xenopus oocyte maturation

Background:

  • Mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK) are activated by various factors including pp60v-src, cyclin A, p39mos, and maturation-promoting factor in Xenopus oocytes.
  • The pp60v-src pathway requires a functional Ras signal, while the cyclin/maturation-promoting factor pathway does not.

Purpose of the Study:

  • To investigate the role of protein kinase C (PKC) in MAPK activation.
  • To elucidate the regulatory mechanisms of MAPK activation by cAMP-dependent protein kinase (PKA).

Main Methods:

  • Utilized cell-free extracts of Xenopus oocytes.
  • Investigated the effects of PKC, Ras, pp60v-src, and PKA on MAPK and MEK activation.
  • Employed heat-stable PKA inhibitor to assess endogenous PKA activity.

Main Results:

  • PKC stimulates MAPK in a Ras-dependent manner, independent of pp60v-src signaling.
  • PKA inhibits MAPK activation stimulated by cyclin, p21V12ras, PKC, and pp60v-src.
  • Inhibition of endogenous PKA stimulates MAPK activity independently of Ras and protein synthesis.
  • c-Mos-induced MAPK activation is unaffected by PKA preincubation.

Conclusions:

  • Independent pp60v-src and PKC signaling pathways converge at Ras.
  • PKA acts as a negative regulator, blocking MAPK activation through both Ras-dependent and -independent pathways.

More Related Videos

An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation11:20

An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation

Published on: August 30, 2017

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

Inhibition of Cdk Activity02:34

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...
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...
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 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...
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...
Calmodulin-dependent Signaling01:16

Calmodulin-dependent Signaling

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...