CDK5 and Parkinson disease: Previous studies have reported the dysregulation of Cdk5 and increased p25/p35 ratio in the animal model of PD as well as in the brains of PD patients (Smith et al., 2003; Alvira et al., 2008; He et al., 2018), along with enhanced neuroinflammation (Surendranathan et al., 2015; Kouli et al., 2020).