Ubiquitin-specific peptidase 9, X-linked (USP9X)

Ubiquitin-specific peptidase 9, X-linked (USP9X) is a highly conserved deubiquitinating enzyme (DUB) belonging to the peptidase C19 family that plays a critical role in maintaining cellular homeostasis by removing ubiquitin chains from substrate proteins, thereby preventing their proteasomal degradation [1, 4, 10]. It is involved in a wide array of essential biological processes, including cell survival, proliferation, migration, and signal transduction pathways such as TGF-beta, Wnt, Notch, and mTOR [1, 5, 9]. USP9X acts as a significant oncogenic driver in various malignancies, including multiple myeloma and pancreatic cancer, by stabilizing key pro-survival proteins like MCL-1 and XIAP [1, 11, 19]. Beyond its role in oncology, USP9X is vital for normal neuronal development, and its dysfunction is linked to X-linked intellectual disability and neurodegenerative diseases like Alzheimer's and Parkinson's [5, 14, 16]. Pharmacological targeting of USP9X with small-molecule inhibitors such as WP1130 and G9 has shown promise in preclinical studies by inducing apoptosis and sensitizing cancer cells to treatment, although its context-dependent role as a tumor suppressor in some cancers presents a therapeutic challenge [13, 19, 22, 25].

Other names

Ubiquitin Specific Peptidase 9 X-LinkedUbiquitin Specific Protease 9, X-LinkedProbable Ubiquitin Carboxyl-Terminal Hydrolase FAF-XUbiquitin-Specific Processing Protease FAF-XDrosophila Fat Facets Related, X-LinkedFat Facets Protein Related, X-LinkedUbiquitin Thiolesterase FAF-XMRXS99FXLID99DFFRXFAFFAMMRX99

Inhibition of deubiquitinase activity through covalent or non-covalent binding to the catalytic domain, leading to the accumulation of ubiquitinated pro-survival substrates (e.g., MCL-1, XIAP, YAP) and their subsequent proteasomal degradation, which induces apoptosis or cell cycle arrest [4, 11, 15, 19, 25].