Inositol lipids in cellular signalling mechanisms

At the opening of the 1980s, two camps vigorously contested whether receptor-stimulated inositol lipid hydrolysis was a transmembrane signalling reaction that brought about an elevation of cytosolic [Ca²⁺] or simply a frequent, but unexplained, response of many stimulated cells to a stimulated elevation of cytosolic [Ca²⁺]. Since 1984, this discussion has been replaced by intensive work that is well on the way to providing a detailed description of the complex set of signalling pathways initiated by phosphatidylinositol 4,5-biphosphate hydrolysis to form the second messengers inositol 1,4,5-triphosphate and 1,2-diacylglycerol. In addition, it has been realized that cells closely regulate their levels both of a novel family of 3-phosphorylated inositol lipids and of a large number of water-soluble inositol polyphosphates; the definition of the functions of these molecules will be a job for the 1990s.