CDK5 and Alzheimer disease: Specific PP2A inhibition has been proven to lead to in vivo deregulation of many major brain Ser/Thr kinases implicated in AD, including GSK3β (Wang et al., 2010; Louis et al., 2011), cdk5 (Louis et al., 2011; Kimura et al., 2013), extracellular signal-regulated kinase (ERK) and JNK (Kins et al., 2003).