Steady state analysis of signal response in receptor trafficking networks.

Receptor trafficking is used to describe the internalization and recycling processes of receptors in the cell. Considerable efforts of quantitative modeling have been made so far in the study of receptor trafficking networks. For the reason of simple mathematical analysis, the canonical receptor trafficking models either ignored the recycling step of receptors or didn't consider the trafficking of empty receptors. Here, we revisit the canonical receptor trafficking models and implement steady state analysis for a general model of receptor trafficking networks, which is composed of the de novo appearance of surface receptor, ligand-receptor interaction, internalization, recycling and degradation of both empty and occupied receptors. We present the analytical solution of the two steady states of the receptor trafficking networks before and after the network is exposed to the signal. The results indicate that the distribution of the empty receptor at the cell surface and inside of the cell, before signal is added, is mainly determined by the ratio of internalization rate and recycling rate of empty receptor. Furthermore, the steady state analysis demonstrates that classic Scatchard plot analysis is still valid for the steady state of the complicated receptor trafficking network.