UCHL1

UCHL1 (ubiquitin C-terminal hydrolase L1) is a neuronal deubiquitinase belonging to the peptidase C12 family that hydrolyzes ubiquitin C-terminal adducts and contributes to monoubiquitin homeostasis within the ubiquitin-proteasome system (UPS)^[1][2]. UCHL1 is highly enriched in neurons and neuroendocrine cells, where it participates in ubiquitin processing and protein quality control, linking its activity to cellular proteostasis and neuronal function^[1][2]. Mechanistically, UCHL1 regulates the stability and turnover of specific protein substrates through its deubiquitinating activity, thereby influencing signaling pathways associated with cell survival, protein degradation, and stress responses^[1]. Dysregulation of UCHL1 has been implicated in neurodegenerative disorders, including Parkinson’s disease, and pathogenic variants can lead to progressive neurodegenerative phenotypes characterized by motor and neurological dysfunction^[2][3]. In addition to nervous system disorders, aberrant UCHL1 expression has been reported in several cancers and fibrotic diseases, supporting a broader role for UCHL1 in pathological tissue remodeling and cell signaling regulation^[2][4]. Compared with the closely related isoform UCHL3, UCHL1 exhibits a more restricted neuronal and neuroendocrine expression pattern and is widely used as a marker of neuronal identity and neurodegeneration-related processes^[2]. For experimental applications, the small-molecule inhibitor LDN57444 has been used to suppress UCHL1 activity and has demonstrated efficacy in reducing UCHL1-dependent fibrotic responses in disease models, providing a useful pharmacological tool for mechanistic studies of UCHL1 signaling^[4].