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Related Concept Videos

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,...
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...
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:
cAMP-dependent Protein Kinase Pathways01:25

cAMP-dependent Protein Kinase Pathways

Cyclic Adenosine Monophosphate (cAMP) is an essential second messenger that activates protein kinase A (PKA) and regulates various biological processes. A single epinephrine molecule binds to GPCR and activates several heterotrimeric G proteins, each stimulating multiple adenylyl cyclase, amplifying the signal, and synthesizing large numbers of cAMP molecules. Small changes in cAMP concentration affect PKA activity. The binding of four cAMP molecules induces a conformational change in PKA,...
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...

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Related Experiment Video

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Characterize Disease-related Mutants of RAF Family Kinases by Using a Set of Practical and Feasible Methods
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Calmodulin modulates H-Ras mediated Raf-1 activation.

Jemina Moretó1, Anna Lladó, Maite Vidal-Quadras

  • 1Departament de Biologia Cel.lular, Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036-Barcelona, Spain.

Cellular Signalling
|March 22, 2008
PubMed
Summary

Calmodulin regulates MAPK signaling by controlling Raf-1 activation through PI3K and H-Ras in COS-1 cells. This pathway is crucial for downstream signaling events.

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Published on: June 15, 2017

Area of Science:

  • Cellular signaling pathways
  • Molecular biology
  • Signal transduction

Background:

  • Calmodulin (CaM) influences Ras-GTP levels, Raf-1 activity, and MAPK signaling in COS-1 cells.
  • Previous studies indicated an inverse relationship between CaM inhibition and MAPK activity.

Purpose of the Study:

  • To elucidate the precise role of calmodulin in the regulation of Raf-1 activation.
  • To investigate the involvement of phosphatidylinositol 3-kinase (PI3K) and H-Ras in CaM-mediated signaling.

Main Methods:

  • Förster resonance energy transfer (FRET) microscopy to assess protein interactions.
  • Analysis of Raf-1 phosphorylation states, specifically at Ser338.
  • Utilizing dominant-negative PI3K mutants and specific inhibitors for CaM and PI3K.
  • Employing H-Ras depleted cells to evaluate pathway dependency.

Main Results:

  • Calmodulin inhibition does not decrease H-Ras and Raf-1 interaction.
  • Calmodulin, via PI3K, is essential for the phosphorylation of Ser338-Raf-1, a key activation step.
  • Inhibition of PI3K or CaM reduces phospho-Ser338 and Raf-1 activity, dependent on endocytosis.
  • Calmodulin's modulation of MAPK activation is abolished in H-Ras depleted cells.

Conclusions:

  • Calmodulin regulation of MAPK signaling in COS-1 cells is dependent on H-Ras.
  • The pathway involves H-Ras controlling Raf-1 activity, with PI3K playing a critical role in CaM-mediated activation.