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Signal response sensitivity in the yeast mitogen-activated protein kinase cascade.

Thalhauser CJ, Komarova NL - PLoS ONE (2010)

Bottom Line: At the basis of our theory is an analytical result that weak interactions make the response biphasic while tight interactions lead to a graded response.We then show via an analysis of the kinetic binding rate constants how the results of experimental manipulations, modeled as changes to certain of these binding constants, lead to predictions of pathway output consistent with experimental observations.We demonstrate how the results of these experimental manipulations are consistent within the framework of our theoretical treatment of this scaffold-dependent MAPK cascades, and how future efforts in this style of systems biology can be used to interpret the results of other signal transduction observations.

View Article: PubMed Central - PubMed

Affiliation: Department of Mathematics, University of California Irvine, Irvine, California, United States of America.

ABSTRACT
The yeast pheromone response pathway is a canonical three-step mitogen activated protein kinase (MAPK) cascade which requires a scaffold protein for proper signal transduction. Recent experimental studies into the role the scaffold plays in modulating the character of the transduced signal, show that the presence of the scaffold increases the biphasic nature of the signal response. This runs contrary to prior theoretical investigations into how scaffolds function. We describe a mathematical model of the yeast MAPK cascade specifically designed to capture the experimental conditions and results of these empirical studies. We demonstrate how the system can exhibit either graded or ultrasensitive (biphasic) response dynamics based on the binding kinetics of enzymes to the scaffold. At the basis of our theory is an analytical result that weak interactions make the response biphasic while tight interactions lead to a graded response. We then show via an analysis of the kinetic binding rate constants how the results of experimental manipulations, modeled as changes to certain of these binding constants, lead to predictions of pathway output consistent with experimental observations. We demonstrate how the results of these experimental manipulations are consistent within the framework of our theoretical treatment of this scaffold-dependent MAPK cascades, and how future efforts in this style of systems biology can be used to interpret the results of other signal transduction observations.

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Related in: MedlinePlus

Signal response of the scaffold-MAPK complex in the presence () or absence () of constitutive  binding.Plots represent slow (, left panel) or fast (, right panel) scaffold-membrane association rates.
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pone-0011568-g006: Signal response of the scaffold-MAPK complex in the presence () or absence () of constitutive binding.Plots represent slow (, left panel) or fast (, right panel) scaffold-membrane association rates.

Mentions: With the results from the mammalian system in mind, we next explore what role the selective activation hypothesis plays in shaping the response curve. We modify the model by allowing scaffold realignment, the reaction in model 2, to occur in the absence of signal with a flag parameter . Here corresponds to the yeast wild type configuration, and allows for signal-competent scaffold to always exist in the cell, which is more representative of mammalian scaffolds. As seen in figure 6, loss of the selective activation component of scaffold activation results in the loss of ultrasensitive behavior in the response, in accordance with the theoretical investigations of Levchenko.


Signal response sensitivity in the yeast mitogen-activated protein kinase cascade.

Thalhauser CJ, Komarova NL - PLoS ONE (2010)

Signal response of the scaffold-MAPK complex in the presence () or absence () of constitutive  binding.Plots represent slow (, left panel) or fast (, right panel) scaffold-membrane association rates.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2909145&req=5

pone-0011568-g006: Signal response of the scaffold-MAPK complex in the presence () or absence () of constitutive binding.Plots represent slow (, left panel) or fast (, right panel) scaffold-membrane association rates.
Mentions: With the results from the mammalian system in mind, we next explore what role the selective activation hypothesis plays in shaping the response curve. We modify the model by allowing scaffold realignment, the reaction in model 2, to occur in the absence of signal with a flag parameter . Here corresponds to the yeast wild type configuration, and allows for signal-competent scaffold to always exist in the cell, which is more representative of mammalian scaffolds. As seen in figure 6, loss of the selective activation component of scaffold activation results in the loss of ultrasensitive behavior in the response, in accordance with the theoretical investigations of Levchenko.

Bottom Line: At the basis of our theory is an analytical result that weak interactions make the response biphasic while tight interactions lead to a graded response.We then show via an analysis of the kinetic binding rate constants how the results of experimental manipulations, modeled as changes to certain of these binding constants, lead to predictions of pathway output consistent with experimental observations.We demonstrate how the results of these experimental manipulations are consistent within the framework of our theoretical treatment of this scaffold-dependent MAPK cascades, and how future efforts in this style of systems biology can be used to interpret the results of other signal transduction observations.

View Article: PubMed Central - PubMed

Affiliation: Department of Mathematics, University of California Irvine, Irvine, California, United States of America.

ABSTRACT
The yeast pheromone response pathway is a canonical three-step mitogen activated protein kinase (MAPK) cascade which requires a scaffold protein for proper signal transduction. Recent experimental studies into the role the scaffold plays in modulating the character of the transduced signal, show that the presence of the scaffold increases the biphasic nature of the signal response. This runs contrary to prior theoretical investigations into how scaffolds function. We describe a mathematical model of the yeast MAPK cascade specifically designed to capture the experimental conditions and results of these empirical studies. We demonstrate how the system can exhibit either graded or ultrasensitive (biphasic) response dynamics based on the binding kinetics of enzymes to the scaffold. At the basis of our theory is an analytical result that weak interactions make the response biphasic while tight interactions lead to a graded response. We then show via an analysis of the kinetic binding rate constants how the results of experimental manipulations, modeled as changes to certain of these binding constants, lead to predictions of pathway output consistent with experimental observations. We demonstrate how the results of these experimental manipulations are consistent within the framework of our theoretical treatment of this scaffold-dependent MAPK cascades, and how future efforts in this style of systems biology can be used to interpret the results of other signal transduction observations.

Show MeSH
Related in: MedlinePlus