Stochastic Aspects of Kinase Cascade Pathways in Cellular Signaling

Simplified kinase cascade pathways in cellular signaling are analyzed from the viewpoint of the stochastic fluctuations of each activated constituent kinases. The analytical representations of the kinetics of the kinases are obtained by approximation for the two extreme cases of far-from-saturation with the substrate and of the saturation in enzymes. These stochastic models predict the attenuations of the stochastic fluctuations along downward in the cascade tiers for the case of far-from-saturation and the accumulations of the fluctuations for the case of the saturation. These predictions are further confirmed by the Gillespie simulations. Hence, kinase cascade pathways could work as both of the stochastic fluctuation attenuator and the accumulator, depending on the kinase saturation levels with the substrates.