The protein kinase inhibitor, staurosporine, does not inhibit phosphoinositide kinases

The effects of the protein kinase inhibitor staurosporine on phosphatidylinositol (PI) kinase and phosphatidylinositol 4-phosphate (PIP) kinase activities in brain membranes, and the synthesis of polyphosphoinositides in cultured NIH 3T3 fibroblasts were examined. Staurosporine, at concentrations up to 1 uM did not significantly modulate either PI kinase or PIP kinase activity in brain membranes. DNA synthesis was dose-dependently inhibited by sub-nanomolar concentrations of staurosporine; however, cells treated with up to 1 uM staurosporine contained levels of PIP and phosphatidylinositol 4,5-bisphosphate (PIP₂) similar to those observed in untreated cells. Therefore, phosphoinositide kinases do not appear to be either directly or indirectly affected by staurosporine.