E3 ubiquitin ligases in neurodegenerative diseases.

Neurodegenerative diseases (NDs) are characterized by progressive neuronal loss and proteostatic failure, driven by impaired clearance of misfolded proteins via the ubiquitin-proteasome system (UPS) and autophagy. In UPS, E3 ubiquitin ligases are crucial for regulating protein ubiquitination and degradation. Mutations in E3 ligases, along with dysfunctions of specific ligases such as Parkin, the C-terminus of HSC70-interacting protein (CHIP), and tripartite motif-containing proteins, have been identified as key factors in the buildup of amyloid-β, α-synuclein, tau, trans-active response DNA-binding protein 43, and mutant huntingtin. These accumulations are associated with NDs like Parkinson's disease, Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis. Therapeutic strategies targeting E3 ligases, particularly proteolysis-targeting chimeras (PROTACs), are being developed for ND treatment and are currently in clinical trials. These approaches aim to enhance E3 ligase activity and promote selective protein degradation. Here, we examine how individual E3 ligases influence cell-fate decisions in NDs, showing that their substrate selection determines whether neurons survive or die. Building on this knowledge, we present an innovative therapeutic pipeline that includes ligase activators, PROTAC degraders, and miRNA switches, which are molecules designed to transition from research to clinical application.