SKM 2023 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 11: Poster Session I
BP 11.62: Poster
Dienstag, 28. März 2023, 12:30–15:30, P1
Cumulative refractoriness in Calcium signaling — •Lukas Ramlow1, Martin Falcke1,2, and Benjamin Lindner1 — 1Physics Department of Humboldt University, Berlin, Germany — 2Max Delbrück Center for Molecular Medicine, Berlin, Germany
Stochastic spiking and adaptation are two essential feature of calcium signaling. The stochasticty stems from the punctate calcium release from the ER into the cytosol by IP3R channel clusters. The adaptation is due to the depletion and slow replenishment of the ER. To capture calcium spike generation, we adopt the popular stochastic adaptive integral-and-fire (IF) model from neuroscience. Our model describes i) activity of IP3R clusters and ii) dynamics of the global calcium concentrations in the cytosol and ER. Cluster activity is modeled by a Markov chain, capturing the puff. The calcium concentrations are described by a two-variable IF model driven by the puff current. While it has been known for decades that the activity of IP3R clusters is random, a method to derive the noise acting on the cytosolic calcium is lacking. We close this gap using a time scale separation to approximate the puffing current by a white Gaussian noise with analytically accessible intensity. This results in a nonlinear IF model with and multiplicative noise. Assuming fast replenishment the IF model generates a renewal spike train and we can derive analytical expressions for the mean and coefficient of variation of the interspike interval (ISI). Taking into account ER depletion, the model displays cumulative refractoriness and can be used to infer otherwise inaccesible parameters from experimental data.