Phospho-GSK3伪/尾 (Ser21/9) refers to the phosphorylated forms of glycogen synthase kinase 3 alpha (GSK3伪) at serine 21 and glycogen synthase kinase 3 beta (GSK3尾) at serine 9. The phosphorylation at these sites is inhibitory, meaning it reduces the activity of these kinases. GSK3伪/尾 are serine/threonine kinases that play crucial roles in various cellular processes, including cell fate determination, glucose homeostasis, and Wnt signaling. When phosphorylated at Ser21/9, the activity of GSK3伪/尾 is suppressed, which can have significant impacts on these pathways. For example, in the Wnt signaling pathway, the inhibition of GSK3尾 by phosphorylation at Ser9 prevents the degradation of 尾-catenin, allowing it to accumulate and activate downstream gene expression. This phosphorylation is often regulated by upstream signals such as insulin or growth factors, which can induce the phosphorylation of GSK3伪/尾 at these sites through various signaling cascades.