Impaired proteostasis in rare neurological and nervous system diseases

Rare diseases are classified as such when their prevalence is 1:2,000 or lower, but even if each of them is so infrequent, altogether more than 300 million people in the world suffer one of the ~7,000 diseases considered as rare. Over 1,200 of these disorders are known to affect the brain or other parts of our nervous system, and their symptoms can affect cognition, motor function and/or social interaction of the patients; we refer collectively to them as rare neurological disorders or RNDs. We have focused this review on RNDs known to have compromised protein homeostasis pathways. Proteostasis can be regulated and/or altered by a chain of cellular mechanisms, from protein synthesis and folding, to aggregation and degradation. Here we provide a compilation of 170 proteostasis-related RNDs, deepening on some representative diseases, including as well a clinical view of how those diseases are diagnosed and dealt with. Additionally, we review existing methodologies for diagnosis and treatment, discussing the potential of specific deubiquitinating enzyme inhibition as a future therapeutic avenue for RNDs.