GSK3B and Alzheimer disease: To examine whether increased expression of GSK3β in AD [33] is connected to SGK1, we treated CT1 and AD1 neurons with the selective GSK3β inhibitor CHIR 99021 (1 μM for 48 h), which significantly inhibited the activated phospho-GSK3 (pGSK) α and β isoforms, and reduced the expression level of GSK3β in AD neurons (Fig. 9b).