This report was presented at The Journal of Physiology Symposium on Regulation of ion channels and transporters by phosphatidylinositol 4,5-bisphosphate (PIP2), Baltimore, MD, USA, 2 March 2007. It was commissioned by the Editorial Board and reflects the views of the author.
Where does all the PIP2 come from?
Article first published online: 21 JUL 2007
The Journal of Physiology
Volume 582, Issue 3, pages 945–951, August 2007
How to Cite
Loew, L. M. (2007), Where does all the PIP2 come from?. The Journal of Physiology, 582: 945–951. doi: 10.1113/jphysiol.2007.132860
- Issue published online: 21 JUL 2007
- Article first published online: 21 JUL 2007
- (Received 20 March 2007; accepted 28 March 2007; first published online 29 March 2007)
Despite its very low concentration in the plasma membrane, PIP2 is the precursor for the important second messenger InsP3 and, independently, is a key modulator of membrane signalling molecules such as ion channels. However, it has been difficult to determine the spatial and temporal characteristics of PIP2 and InsP3 during a cell signalling event. Our laboratory used bradykinin stimulation of N1E-115 neuroblastoma cells to infer the InsP3 dynamics from calcium imaging studies, biochemical analysis and InsP3 uncaging. We have used computational modelling with Virtual Cell to help analyse and interpret experimental data on the details of the calcium release process as well as to build a comprehensive image-based model of agonist-induced calcium release in a neuronal cell. These data provided a constraint for the further investigation of how low levels of cellular PIP2 could provide sufficient InsP3 for calcium release. Using biochemical assays, quantitative imaging of GFP-based probe translocation and computational analysis, it was shown that PIP2 synthesis is stimulated concomitant with its hydrolysis. This mechanism should be important not just for consideration of PIP2 as a precursor of InsP3, but for any pathway that can be directly or indirectly modulated by PIP2.