Involvement of Ataxin-3 (ATXN3) in the malignant progression of pancreatic cancer via deubiquitinating HDAC6

ATXN3 deubiquitinates ZEB1 and facilitates epithelial-mesenchymal transition in glioblastoma

The activation of epithelial-mesenchymal transition (EMT) promotes glioblastoma (GBM) invasion, thereby enhancing its malignancy. Elucidating the underlying mechanisms that regulate EMT is essential for the development of effective treatments for GBM. In this study, we found that GBM tissues and cells exhibit significantly elevated expression levels of ataxin 3 (ATXN3). Functional experiments demonstrated that ATXN3 promotes the invasion, migration, and tumor growth of GBM cells by activating EMT. Mechanistically, ATXN3 was identified as a bona fide deubiquitinase for ZEB1, a key EMT-inducing transcription factor, in GBM cells. ATXN3 interacts directly with ZEB1, cleaves ubiquitin moieties from conjugated substrates and maintains the stability of ZEB1. Ectopic expression of ZEB1 significantly mitigates the inhibitory effects of ATXN3 depletion on the invasion, migration, and tumor growth of GBM cells. Furthermore, ATXN3 exhibits a positive correlation with ZEB1 expression levels and serves as a predictor of poor prognosis in human GBM specimens. Collectively, our study elucidates a critical ATXN3-ZEB1 signaling axis in EMT and invasion, thereby providing a rationale for potential therapeutic interventions against GBM.

The deubiquitinase function of ataxin-3 and its role in the pathogenesis of Machado-Joseph disease and other diseases

Machado-Joseph disease (MJD) is a devastating and incurable neurodegenerative disease characterised by progressive ataxia, difficulty speaking and swallowing. Consequently, affected individuals ultimately become wheelchair dependent, require constant care, and face a shortened life expectancy. The monogenic cause of MJD is expansion of a trinucleotide (CAG) repeat region within the ATXN3 gene, which results in polyglutamine (polyQ) expansion within the resultant ataxin-3 protein. While it is well established that the ataxin-3 protein functions as a deubiquitinating (DUB) enzyme and is therefore critically involved in proteostasis, several unanswered questions remain regarding the impact of polyQ expansion in ataxin-3 on its DUB function. Here we review the current literature surrounding ataxin-3's DUB function, its DUB targets, and what is known regarding the impact of polyQ expansion on ataxin-3's DUB function. We also consider the potential neuroprotective effects of ataxin-3's DUB function, and the intersection of ataxin-3's role as a DUB enzyme and regulator of gene transcription. Ataxin-3 is the principal pathogenic protein in MJD and also appears to be involved in cancer. As aberrant deubiquitination has been linked to both neurodegeneration and cancer, a comprehensive understanding of ataxin-3's DUB function is important for elucidating potential therapeutic targets in these complex conditions. In this review, we aim to consolidate knowledge of ataxin-3 as a DUB and unveil areas for future research to aid therapeutic targeting of ataxin-3's DUB function for the treatment of MJD and other diseases.