CDKN2A and Alzheimer disease: Indeed, accumulating evidence suggests the functional importance of the cytohesin–Arf pathway not only in normal neuronal functions, including neuronal morphogenesis [27,28,29] and synaptic transmission [30,31,32], but also in the development of chronic pain [23] and neurotoxicity induced by proteins related to neurodegenerative disorders, such as amyotrophic lateral sclerosis (ALS) [33,34] and Alzheimer’s disease (AD) [35].