The phosphorylated PPPSPXS peptide inhibits phosphorylation of glycogen synthase and Tau by GSK3.

<p><i>A</i>. Recombinant GST-tagged mouse glycogen synthase carboxyl-terminal domain (mGS-CTD) was expressed in bacteria, and purified by glutathione agarose resin. <i>B</i>. In vitro reconstitution of GS phosphorylation by CK2 and GSK3. The phosphorylation reaction products were analyzed using an anti-phospho-Ser641 GS antibody. <i>C</i>. GS phosphorylation at Ser641 was inhibited by Phos-A, but not by A-mut. The phosphorylation reaction products were analyzed using an anti-phospho-Ser641 GS antibody. <i>D</i>. In vitro reconstitution of Tau phosphorylation by GSK3. The phosphorylation reaction products were analyzed using an anti-phospho-Tau antibody (PHF1). <i>E</i>. Tau phosphorylation was inhibited by Phos-A, but not A-mut. The phosphorylation reaction products were analyzed using an anti-phospho-Tau antibody (PHF1). <i>F</i> and <i>G</i>. Different concentrations of Phos-A inhibited β-catenin and Tau phosphorylation by GSK3 in a similar manner. A four-fold dilution of Phos-A was employed. The graph represents the average of three independent experiments.