Nuclear localization and signalling activity of inositol lipids.

It has been recently shown that also the nucleus is a site for both synthesis and hydrolysis of the phosphorylated forms of phosphatidylinositol. Among the enzymes of the cycle we and others have demonstrated that phospholipase C specific for inositol lipids (PLC) is one of the main steps of the inositol lipid cycle. The PLC family and namely the type raised a noticeable interest since, because of their common COOH-terminus, it has been shown a nuclear localisation in addition to that at the plasma membrane. The autonomous intranuclear inositide cycle is endowed, besides the PLC, with conventional lipid kinases and phosphatidylinositol 3 kinase (PI 3-kinase) which plays an important role in granulocytic differentiation. The combination of morphology and molecular biology gave us the opportunity to localise the sites inside the nucleus where the cycle takes place and to understand the physiological significance of such a subcellular compartmentalisation both during cell growth and differentiation.