Glycogen synthase kinase 3 beta is identical to tau protein kinase I generating several epitopes of paired helical filaments.

We previously reported that tau protein kinase I (TPKI) induced normal tau protein into a state of paired helical filaments (PHF); this is further confirmed here by immunoblot analysis using several antibodies. We also present the amino acid sequence of TPKI, which is identical to glycogen synthase kinase 3 beta (GSK3 beta). Moreover, we found that TPKI activity was inseparable from GSK3 activity throughout the purification procedure. These results indicate that TPKI is identical to GSK3 beta.