AUTHOR=Givré Alan , Ponce Dawson Silvina 

TITLE=Information Content in Stochastic Pulse Sequences of Intracellular Messengers

JOURNAL=Frontiers in Physics

VOLUME=6

YEAR=2018

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2018.00074

DOI=10.3389/fphy.2018.00074

ISSN=2296-424X

ABSTRACT=<p>Many cell signaling pathways rely on oscillatory messenger concentrations even to transduce aperiodic environmental changes. The universal second messenger calcium, Ca<sup>2+</sup> often exhibits pulsatile behavior in the presence of constant concentrations of external ligands such as hormones or neurotransmitters. The analysis of intracellular Ca<sup>2+</sup> pulses that involve Ca<sup>2+</sup> release through inositol 1,4,5-trisphosphate (IP<sub>3</sub>) receptors led to a model with stochastic pulse firing at rate, λ and deterministic inhibition with recovery at rate, ρ. Here we combine this model with recent observations that established an exponential relationship between λ and the external ligand concentration, <italic>C</italic>. We compute analytically the mutual information between <italic>C</italic> and the interpulse time, <italic>t</italic>, or the number of pulses, <italic>N</italic>, in the λ/ρ ≪ 1 and λ/ρ ≫ 1 limits. We obtain that both <italic>I</italic>(<italic>C, t</italic>) and <italic>I</italic>(<italic>C, N</italic>) are largest in the second limit with a difference of at most ~1<italic>bit</italic>. Thus, the resolution with which the values of <italic>C</italic> can be discriminated at most doubles in one limit with respect to the other. The components of the model and the exponential dependence of the firing rate with <italic>C</italic> are features common to noise-driven excitable systems. Our results thus hold in this more general setting that applies widely in biology.</p>