Information propagation from IP3 to target protein: A combined model for encoding and decoding of Ca2+ signal

It is well known that information is encoded in the frequency or amplitude of Ca2+ signal and then decoded by target protein. However, few models considered both the encoding and decoding procedures of Ca2+ signal. In this work, a minimal Li-Rinzel model is coupled with a phosphorylation-dephosphorylation cycle model, which is used to investigate information transmissions from inositol 1,4,5-trisphosphate (IP3) to target proteins and their relations. We found that the mean target protein activity increases with the IP3 concentration, and at a low level of stimulation, the target protein can be more efficiently activated by an oscillatory signal than a constant signal of the same average calcium if Ca2+ acts cooperatively on the kinase. The internal noise resulting from the finite system size is also taken into account in the combined model.