QUASI-STEADY STATE DYNAMICS OF IFN-γ INDUCED JAK-STAT SIGNAL TRANSDUCTION PATHWAY

A Quasi-Steady-State Approximation (QSSA) theorem is applied to a simplified mathematical model of IFN-gamma induced JAK-STAT signal transduction pathway. On the basis of previously published parameter values, the system of ten ordinary differential equations is rewritten in a form suitable for model reduction. In accordance with the terminology of the QSSA theorem, it is established that five of the protein concentrations are 'fast varying', such that the corresponding kinetic equations form an attached system. Another concentration is medium varying and the corresponding equation is degenerate with respect to the five fast ones. The other two concentrations are 'slow varying', and form a degenerate system. The rest two variables appear to be constants. Analytical relations between stationary values of all variables of the model and initial values of slow components are derived and interpreted as restrictions on concentrations of the considered cell signalling process.