Transforming growth factor beta stimulates phosphoinositol metabolism and translocation of protein kinase C in cultured astrocytes

Transforming growth factor beta (TGF-β) is a regulatory peptide found in many normal and neoplastic tissues, including brain, with a diverse range of cellular effects. The transmembrane biochemical signals by which TGF-β exerts these effects and the second messenger systems that may amplify them are unknown. We investigated the effects of TGF-β upon membrane phosphoinositol metabolism and protein kinase C activity in cultured astrocytes. We found that exposure of astrocyte enriched cultures to TGF-β resulted in the stimulation of phosphoinositol lipid turnover to inositol phosphates and in the apparent redistribution of protein kinase C from cytosol to membrane.