Not surprisingly, dysfunctional membrane trafficking—mediated by Rab GTPases—and defective cytoskeletal dynamics—regulated by Rho GTPases—have been implicated in neurodegenerative disorders, including PD, AD, and ALS (Stankiewicz and Linseman, 2014; Kiral et al., 2018; Zhang et al., 2019, 2021; Oguchi et al., 2020; Homma et al., 2021). This evidence concerns the gene RAB6A and Alzheimer disease.