Modelling of promiscuous receptor-Gi/Gs-protein coupling and effector response.

A single G-protein-coupled receptor might activate multiple G-protein species. This multiplex coupling ability can be used by tissues to regulate signalling; for the pharmacologist, such multiplex coupling might cause difficulties in the interpretation of experimental data. In this article, we present mathematical models for the activation of two separate G-protein species by a single receptor. Issues addressed concern mutual antagonism between the G proteins and the availability of an already activated receptor for interaction with a new G protein (receptor-G-protein-effector complexing versus free diffusion of G proteins) in addition to receptor-G-protein precoupling at different G-protein and receptor expression levels. The output from the receptor models uses, as readout, a new model for adenylyl cyclase regulation by two allosteric regulators (i.e. G(s) and G(i)).