Rabbit Anti-Human GSK3 alpha (phospho Ser21) monoclonal antibody for IHC-P, WB. Glycogen synthase kinase 3-alpha is a multifunctional protein serine kinase, homologous to Drosophila 'shaggy' (zeste-white3) and implicated in the control of several regulatory proteins including glycogen synthase and transcription factors . It also plays a role in the WNT and PI3K signaling pathways.