Brain protein kinase PK40erk converts TAU into a PHF-like form as found in Alzheimer's disease.

The novel protein kinase PK40 (1) was characterized by its ability to phosphorylate Lys-Ser-Pro sites in neurofilament and TAU proteins. PK40 is now recognized to be a member of the family of External-stimulus Regulated Kinases (ERKs) by its reactivity with ERK-specific antibodies and will therefore be called PK40erk. Bovine TAU or recombinant human TAU proteins can be hyperphosphorylated by PK40erk to produce the electrophoretic mobility shifts and certain immunochemical properties characteristic of PHF-TAU isolated from Alzheimer's disease brain tissue. PK40erk may play a crucial role in the etiology of this disease.