MAPT and Alzheimer disease: Substantial evidences revealed that functioning as a downstream target of the phosphatidylinositol-3-kinase (PI3K)/threonine/serine protein kinase B (Akt) signaling pathway and a major Tau kinase, GSK-3β regulated both Tau phosphorylation and Aβ production in PI3K/Akt-dependent pathway in AD [18].