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Updated: Jun 16, 2026
08:54
Imaging Spatial Reorganization of a MAPK Signaling Pathway Using the Tobacco Transient Expression System
Published on: March 20, 2016
Spatio-temporal correlations can drastically change the response of a MAPK pathway
Koichi Takahashi1, Sorin Tanase-Nicola, Pieter Rein ten Wolde
1Advanced Sciences Institute, RIKEN, 1-7-22 Suehirocho, Tsurumi, Yokohama 230-0045, Japan. ktakahashi@riken.jp
Summary
Enzyme action in dual phosphorylation cycles can be processive or distributive. Rapid enzyme-substrate rebindings can unexpectedly convert distributive mechanisms into processive ones, altering cellular responses.
Area of Science:
- Biochemistry
- Systems Biology
- Biophysics
Background:
- Multisite protein modification is crucial in eukaryotic cells, exemplified by mitogen-activated protein kinase (MAPK) cascades.
- Enzyme mechanism (processive vs. distributive) significantly impacts MAPK pathway response, with distributive mechanisms potentially causing ultrasensitivity, hysteresis, and bistability.
Purpose of the Study:
- To investigate the stochastic dynamics of a dual phosphorylation cycle with distributive enzyme mechanisms using Green's Function Reaction Dynamics (GFRD).
- To compare particle-level simulations with mean-field predictions for understanding ultrasensitivity and bistability in these systems.
Main Methods:
- Utilized Green's Function Reaction Dynamics (GFRD), a particle-level stochastic simulation scheme.
- Analyzed a dual phosphorylation cycle model where enzymes operate distributively.
Main Results:
- GFRD simulations revealed that the network's response can deviate significantly from mean-field predictions.
- Rapid enzyme-substrate rebindings after initial modification can accelerate the response, diminishing ultrasensitivity and bistability.
- These rapid rebindings effectively transform a distributive mechanism into a processive one.
Conclusions:
- Stochastic effects, particularly rapid rebindings, are critical in determining the behavior of distributive enzyme mechanisms in dual phosphorylation cycles.
- Slow ADP release by enzymes may be a regulatory mechanism to prevent rapid rebindings, thereby preserving ultrasensitivity and bistability.
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