Synthetic lipid products of PI3-kinase which are added to culture medium prevent low K+-induced apoptosis of cerebellar granule neurons via Akt kinase activation.

To examine which lipid product of phosphatidylinositol 3-kinase (PI3-K) is essential for the survival-promoting pathway in cultured cerebellar granule neurons, three synthetic derivatives of lipid products of PI3-K were added to culture medium containing a low concentration (5 mM) of potassium (LK+) which induces apoptotic cell death. We found that dipalmitoylphosphatidylinositol 3,4-bisphosphate and dipalmitoylphosphatidylinositol 3,4,5-trisphosphate, but not dipalmitoylphosphatidylinositol 3-monophosphate, effectively blocked the LK+-induced apoptosis. These two synthetic phospholipids increased Akt activity but not that of PI3-K. These findings demonstrated that specific lipid products of PI3-K which are added to culture medium activate Akt/PKB without modulating PI3-K itself, and as a result prevent neuronal cell death in cerebellar granule neurons.