Fig. 1: Schematic of the phosphoinositide (PIns) cycle.

The key enzymes referred to in the article are indicated: (1) Inositol monophosphatase (IMPase), which is inhibited by lithium ions, and (2) Phosphatidylinositide synthase (PI-synthase) and the reverse phosphatidylinositol: inositol exchange reaction. The double arrows indicate the influx and efflux of inositol across the plasma membrane. Other abbreviations are: CDP-DAG cytidine diphosphate diacylglycerol, PI phosphatidylinositide, PIP phosphatidylinositide phosphate, PIP2 phosphatidylinositide-4,5-bisphosphate (this is the most abundant of the PIP2 species), DAG diacylglycerol, PA phosphatidic acid, IPs inositol phosphates with various numbers of attached phosphate groups, as indicated by the subscripts