PHOSPHOINOSITIDE SIGNAL-TRANSDUCTION PATHWAY IN RAT-LIVER MITOCHONDRIA

Phosphorylation of endogeneous phosholipids of rat liver mitochondrial fractions with gamma[P-32]ATP revealed formation of all the known ino sitol phospholipids, such as phosphatidy linositol, phosphatidylinosit ol phosphate and phosphatidylinositol bisphosphate. Additionally, a ne w inositol phospholipid was detected. Incorporation of [H-3]-labelled insositol followed a similar profile. Enzymatic experiments indicated that the new lipid could possibly be phosphatidylinositol trisphosphat e. The presence of phosphoinositides-generated second messengers such as diacylglgcerol and inositol trisphosphate was also confirmed. Prote in kinase C, which acts as mediator between second messengers and nucl ear factors, was also found to be present in mitochondria in significa nt amount, These results suggest that phosphoinositide signal transduc tion pathway is operative in rat liver mitochondria.