Excitability in a stochastic differential equation model for calcium puffs

Area of Science:

• Cellular Biology
• Biophysics
• Mathematical Modeling

Background:

• Calcium dynamics are crucial for cellular functions.
• Localized calcium releases (calcium puffs) are fundamental to cellular signaling.
• Previous models faced challenges due to high noise in small calcium release clusters.

Purpose of the Study:

• To re-evaluate and validate mathematical models for local calcium release.
• To investigate the role of noise and multiple scales in calcium signaling.
• To develop accurate stochastic differential equations for calcium puff dynamics.

Main Methods:

• Revisiting master equations for local calcium release.
• Analyzing multi-scale calcium concentrations within channel clusters.
• Deriving and adapting stochastic differential equations.
• Comparing discrete and continuous trajectories using Langevin equations.

Main Results:

• Langevin equations were reconciled with master equations, even for minimal channel numbers.
• The model demonstrated that excitability underlies calcium puff generation.
• A bifurcation predicting a transition from transient to sustained calcium release was identified.

Conclusions:

• The developed stochastic models accurately represent calcium puff dynamics, addressing previous noise concerns.
• Excitability is confirmed as a core mechanism for calcium puffs.
• The findings suggest a potential mechanism linking local and global cellular calcium signals through release dynamics.