Kinetic model for the desensitization of G protein-coupled receptor

GPCR desensitization is a general regulatory mechanism adopted by biological organisms against overstimulation of G protein-coupled receptors. Although the details of mechanism aren extensively studied, it is not easy to gain an overarching understanding of the process constituted by a multitude of molecular events with vastly differing time scales. To offer a semi-quantitative yet predictive understanding of the mechanism, we formulate a kinetic model for the G protein signaling and desensitization by considering essential biochemical steps from ligand binding to receptor internalization. The internalization followed by the receptor depletion from the plasma membrane attenuates the downstream signal. Together with the kinetic model, an approximated form of expression derived for the dose-response clarifies the role played by the individual biochemical processes and allows us to identify three distinct regimes for the downregulation that emerge from the balance between phosphorylation, dephosphorylation and the cellular level ofβ-arrestin.