Protein kinases involved in the phosphorylation of human tau protein in transfected COS-1 cells.

Human tau phosphorylation has been studied in transfected COS-1 cells. Treatment with okadaic acid alters the electrophoretic mobility of human tau protein transiently expressed in transfected cells, due to an increase in the level of phosphorylation. Treatment with okadaic acid also results in an increased phosphorylation of Alzheimer's disease-type phosphoepitopes. Tau phosphorylation within COS-1 cells is partially inhibited by in vivo treatment with DRB, a protein kinase inhibitor. Double treatment of transfected cells with okadaic acid and DRB reveals that phosphorylation of tau protein at the AT8 epitope is achieved by a DRB-resistant protein kinase which is different from that responsible for tau phosphorylation at the SMI-31 epitope, which appears to be sensitive to DRB.