The present invention relates to a DNA sequence encoding a novel neuronal protein kinase (NPK) which phosphorylates tau proteins as well as other microtubule associated proteins (MAPs) in positions crucial for the binding to microtubules. The invention further relates to Serine or Theorine residues and epitopes comprising said residues phosphorylated by said NPK on said MAPs, to antibodies specifically binding to said protein kinase, pharmaceutical compositions comprising inhibitors to said protein kinase, in particular for the treatment of Alzheimer's disease and cancer, to diagnostic kits and to in vitro diagnostic methods for the detection of Alzheimer's disease and cancer.