Metabotropic receptor activation, desensitization and sequestration—II: modelling the dynamics of the pleckstrin homology domain

Recent observations have been made regarding the generation of inositol 1,4,5-trisphosphate (IP3), using chimeras of green fluorescent protein and the pleckstrin homology domain of phospholipase C-δ. In this paper a model is presented giving the quantitative relations between the green fluorescent protein–pleckstrin homology domain (GFP–PHD) construct and membrane phosphatidylinositol 4,5-bisphosphate (PIP2) levels as well as the concentration of IP3, the product of hydrolysis of PIP2. The model can correctly reproduce the dependence of cytosolic GFP–PHD fluorescence on IP3 concentration. This model extends a previous one (Metabotropic receptor activation, desensitization and sequestration—I: modelling calcium and inositol 1,4,5-trisphosphate dynamics following receptor activation, in this issue) dealing with the processes governing the production of IP3 and the subsequent calcium (Ca2+) changes in cells following activation of metabotropic receptors. This model is applied to the case of purinergic P2Y2 receptor activation in Madin–Darby Canine Kidney (MDCK) cells with adenosine triphosphate (ATP) (Science 284 (1999) 1527). It is shown that it can correctly reproduce the dependence of GFP–PHD fluorescence on the concentration of P2Y2 receptor ligand, as well as the temporal changes of GFP–PHD fluorescence following application of ligand.