CDK5 and early-onset autosomal dominant Alzheimer disease: Conversely, Cdk5 activity also serves as a principle feature in excitotoxic signaling and has been implicated in Alzheimer’s disease (AD), Parkinson’s disease (PD), ischemia, and brain injury (Patrick et al., 1999; Meyer et al., 2014; Binukumar et al., 2015; Yousuf et al., 2016).