GSK3B and Alzheimer disease: In vitro studies (Takashima et al., 1996b) and transgenic animal models of AD (Terwel et al., 2008) indicate that Aβ activates GSK-3β signaling (Takashima et al., 1996a, b) by preventing inhibitory phosphorylation of this enzyme in the case of in vitro studies and by an independent mechanism in the case of animal studies.