Deterministic Limit of Intracellular Calcium Spikes

Area of Science:

• Cellular biology
• Biophysics
• Computational modeling

Background:

• Global calcium (Ca^{2+}) spikes in nonexcitable cells are crucial for various cellular functions.
• These spikes emerge from the collective behavior of calcium channel clusters coupled by diffusion.
• Existing models present conflicting stochastic and deterministic approaches, both aligning with experimental data.

Purpose of the Study:

• To reconcile the seemingly contradictory stochastic and deterministic modeling approaches for calcium (Ca^{2+}) spikes.
• To investigate the underlying mechanisms generating global Ca^{2+} spikes in nonexcitable cells.

Main Methods:

• Employed fully stochastic simulations to model calcium (Ca^{2+}) dynamics.
• Utilized mean-field analyses to complement the stochastic simulations.
• Developed a phenomenological spike nucleation mechanism.

Main Results:

• Demonstrated that stochastic and deterministic models can be reconciled.
• Showed that fully stochastic models generate spike sequences as noise-perturbed oscillations.
• Identified a phenomenological spike nucleation mechanism as the source of underlying deterministic oscillations.

Conclusions:

• The collective dynamics of calcium (Ca^{2+}) channels can be accurately described by reconciling stochastic and deterministic models.
• Global Ca^{2+} spikes represent noise-perturbed oscillations originating from a deterministic nucleation mechanism.
• This unified modeling approach provides a more comprehensive understanding of Ca^{2+} signaling in nonexcitable cells.