Glycerophosphoinositols as potential markers of ras-induced transformation and novel second messengers.

Glycerophosphoinositols are metabolites formed by the sequential action of a phospholipase A2 specific for membrane phosphoinositides, and a lysolipase. Increased levels of these compounds characterize cell lines of different origin transformed by ras and other oncogenes. Thus, glycerophosphoinositols have been proposed as markers of cell transformation. These compounds are also biologically active. In particular, glycerophosphoinositol-4-phosphate (GroPIns4P) is an inhibitor of adenylyl cyclase that acts on the Gs protein. Since GroPIns4P is formed physiologically upon hormone stimulation in several cell lines including fibroblasts, thyrocytes, neuronal and leukemia cells, we propose that GroPIns4P could act as a second messenger able to mediate a cross-talk between the ras cascade and adenylyl cyclase.