UBQLN2 and amyotrophic lateral sclerosis: Impaired protein degradation is a well-recognized potential causative effect in ALS pathogenesis, supported by the discovery of fALS-linked mutations affecting proteins that are directly involved in proteostasis such as SOD1, which account for about 20% of fALS, but also ubiquitin 2 (UBQLN2) and Optineurin (OPTN)3.