Role of inositol phospholipids metabolism in the signal transduction of erbB gene product

We have observed the enhanced metabolism of inositol phospholipids in erbB transformed chicken fibroblasts. This increased metabolism seemed to be due to the activation of PI-kinase, DPI-kinase and DG-kinase activities in these cells. And also, C-kinase activity in the transformed cells was observed to be sustained as an active form. These results suggest the signal transduction system through the enhanced metabolism of inositol phospholipids was activated in the transformed cells. When the normal cells were treated with the combination of TPA, which is an activator of C-kinase, and Ca2+-ionophore A23187, the stimulation of DNA synthesis was detected. However, such treatment caused the only inhibitory effect on the cell growth of the transformed cells. On the other hand, the erbB gene product by itself dose not have significant activity of PI-kinase, DPI-kinase and DG-kinase. Therefore, erbB gene product may indirectly enhance inositol-phospholipids metabolism and induce abnormal growth of transformed cells.