Structural and Functional Basis of JAMM Deubiquitinating Enzymes in Disease

Identification of STAM-binding protein as a target for the treatment of gemcitabine resistance pancreatic cancer in a nutrient-poor microenvironment

Pancreatic cancer (PC) is a highly malignant solid tumor whose resistance to gemcitabine (GEM) chemotherapy is a major cause of poor patient prognosis. Although PC is known to thrive on malnutrition, the mechanism underlying its chemotherapy resistance remains unclear. The current study analyzed clinical tissue sample databases using bioinformatics tools and observed significantly upregulated expression of the deubiquitinase STAMBP in PC tissues. Functional experiments revealed that STAMBP knockdown remarkably increases GEM sensitivity in PC cells. Multiple omics analyses suggested that STAMBP enhances aerobic glycolysis and suppresses mitochondrial respiration to increase GEM resistance in PC both in vitro and in vivo. STAMBP knockdown decreased PDK1 levels, an essential regulator of the aerobic glycolytic process, in several cancers. Mechanistically, STAMBP promoted the PDK1-mediated Warburg effect and chemotherapy resistance by modulating E2F1 via direct binding to E2F1 and suppressing its degradation and ubiquitination. High-throughput compound library screening using three-dimensional protein structure analysis and drug screening identified the FDA drug entrectinib as a potent GEM sensitizer and STAMBP inhibitor, augmenting the antitumor effect of GEM in a patient-derived xenograft (PDX) model. Overall, we established a novel mechanism, via the STAMBP-E2F1-PDK1 axis, by which PC cells become chemoresistant in a nutrient-poor tumor microenvironment.

BRCC3 mediates inflammation and pyroptosis in cerebral ischemia/reperfusion injury by activating the NLRP6 inflammasome

AIMS

Neuroinflammation and pyroptosis are key mediators of cerebral ischemia/reperfusion (I/R) injury-induced pathogenic cascades. BRCC3, the human homolog of BRCC36, is implicated in neurological disorders and plays a crucial role in neuroinflammation and pyroptosis. However, its effects and potential mechanisms in cerebral I/R injury in mice are unclear.

METHODS

Cellular localization of BRCC3 and the interaction between BRCC3 and NLRP6 were assessed. Middle cerebral artery occlusion/reperfusion (MCAO) and oxygen-glucose deprivation/reoxygenation (OGD/R) models were established in mice and HT22 cells, respectively, to simulate cerebral I/R injury in vivo and in vitro.

RESULTS

BRCC3 protein expression peaked 24 h after MCAO and OGD/R. BRCC3 knockdown reduced the inflammation and pyroptosis caused by cerebral I/R injury and ameliorated neurological deficits in mice after MCAO. The effects of BRCC3 on inflammation and pyroptosis may be mediated by NLRP6 inflammasome activation. Moreover, both BRCC3 and its N- and C-terminals interacted with NLRP6, and both BRCC3 and its terminals reduced NLRP6 ubiquitination. Additionally, BRCC3 affected the interaction between NLRP6 and ASC, which may be related to inflammasome activation.

CONCLUSION

BRCC3 shows promise as a novel target to enhance neurological recovery and attenuate the inflammatory responses and pyroptosis caused by NLRP6 activation in cerebral I/R injury.

Deubiquitinating enzyme PSMD7 promotes bladder cancer development: Involvement of RAB1A stabilization

BACKGROUND

Proteasome 26S subunit, non-ATPase 7 (PSMD7) is a deubiquitinating enzyme that is involved in the stability of ubiquitinated proteins and participates in the development of multiple types of cancer. The roles of PSMD7 and its potential mechanisms in bladder cancer (BC) remain elusive.

METHODS

In this study, we identified that PSMD7 was overexpressed in BC tissues based on gene expression omnibus (GEO) database and TNMplot web. To investigate the functional role of PSMD7, two BC cell lines, T24 and 5637, were selected. The cells were transfected with vectors containing short hairpin RNAs against PSMD7 or plasmids containing full-length PSMD7 to knockdown or overexpress PSMD7.

RESULTS

Our results revealed that silencing PSMD7 inhibited cell proliferation, cycle progression, migration, invasion, and promoted cell apoptosis, whereas PSMD7 overexpression led to the opposite effects in the BC cells. Mechanically, PSMD7 influenced the protein expression but not the mRNA expression of the Ras-related protein Rab-1 A (RAB1A). PSMD7 combined with RAB1A and negatively regulated its ubiquitination, indicating that PSMD7 enhanced the stability of RAB1A through post-transcriptional modification. Moreover, the rescue experiment demonstrated that RAB1A was an important downstream effector molecule of PSMD7. Besides, the negative regulation of silencing PSMD7 on tumor growth was confirmed in mice.

CONCLUSIONS

Our study substantiated a novel mechanism by which PSMD7 stabilized RAB1A to accelerate the progression of BC.

DUBing Primary Tumors of the Central Nervous System: Regulatory Roles of Deubiquitinases

The ubiquitin proteasome system (UPS) utilizes an orchestrated enzymatic cascade of E1, E2, and E3 ligases to add single or multiple ubiquitin-like molecules as post-translational modification (PTM) to proteins. Ubiquitination can alter protein functions and/or mark ubiquitinated proteins for proteasomal degradation but deubiquitinases (DUBs) can reverse protein ubiquitination. While the importance of DUBs as regulatory factors in the UPS is undisputed, many questions remain on DUB selectivity for protein targeting, their mechanism of action, and the impact of DUBs on the regulation of diverse biological processes. Furthermore, little is known about the expression and role of DUBs in tumors of the human central nervous system (CNS). In this comprehensive review, we have used publicly available transcriptional datasets to determine the gene expression profiles of 99 deubiquitinases (DUBs) from five major DUB families in seven primary pediatric and adult CNS tumor entities. Our analysis identified selected DUBs as potential new functional players and biomarkers with prognostic value in specific subtypes of primary CNS tumors. Collectively, our analysis highlights an emerging role for DUBs in regulating CNS tumor cell biology and offers a rationale for future therapeutic targeting of DUBs in CNS tumors.

Deubiquitinase OTUD3: a double-edged sword in immunity and disease

Deubiquitination is an important form of post-translational modification that regulates protein homeostasis. Ovarian tumor domain-containing proteins (OTUDs) subfamily member OTUD3 was identified as a deubiquitinating enzyme involved in the regulation of various physiological processes such as immunity and inflammation. Disturbances in these physiological processes trigger diseases in humans and animals, such as cancer, neurodegenerative diseases, diabetes, mastitis, etc. OTUD3 is aberrantly expressed in tumors and is a double-edged sword, exerting tumor-promoting or anti-tumor effects in different types of tumors affecting cancer cell proliferation, metastasis, and metabolism. OTUD3 is regulated at the transcriptional level by a number of MicroRNAs, such as miR-520h, miR-32, and miR101-3p. In addition, OTUD3 is regulated by a number of post-translational modifications, such as acetylation and ubiquitination. Therefore, understanding the regulatory mechanisms of OTUD3 expression can help provide insight into its function in human immunity and disease, offering the possibility of its use as a therapeutic target to diagnose or treat disease.

Ubiquitin Engineering for Interrogating the Ubiquitin-Proteasome System and Novel Therapeutic Strategies

Protein turnover, a highly regulated process governed by the ubiquitin-proteasome system (UPS), is essential for maintaining cellular homeostasis. Dysregulation of the UPS has been implicated in various diseases, including viral infections and cancer, making the proteins in the UPS attractive targets for therapeutic intervention. However, the functional and structural redundancies of UPS enzymes present challenges in identifying precise drug targets and achieving target selectivity. Consequently, only 26S proteasome inhibitors have successfully advanced to clinical use thus far. To overcome these obstacles, engineered peptides and proteins, particularly engineered ubiquitin, have emerged as promising alternatives. In this review, we examine the impact of engineered ubiquitin on UPS and non-UPS proteins, as well as on viral enzymes. Furthermore, we explore their potential to guide the development of small molecules targeting novel surfaces, thereby expanding the range of druggable targets.

Regulatory mechanisms and therapeutic potential of JAB1 in neurological development and disorders

c-Jun activation domain binding protein-1 (JAB1) is a multifunctional regulator that plays vital roles in diverse cellular processes. It regulates AP-1 transcriptional activity and also acts as the fifth component of the COP9 signalosome complex. While JAB1 is considered an oncoprotein that triggers tumor development, recent studies have shown that it also functions in neurological development and disorders. In this review, we summarize the general features of the JAB1 gene and protein, and present recent updates on the regulation of JAB1 expression. Moreover, we also highlight the functional roles and regulatory mechanisms of JAB1 in neurodevelopmental processes such as neuronal differentiation, synaptic morphogenesis, myelination, and hair cell development and in the pathogenesis of some neurological disorders such as Alzheimer's disease, multiple sclerosis, neuropathic pain, and peripheral nerve injury. Furthermore, current challenges and prospects are discussed, including updates on drug development targeting JAB1.

The expression and clinical significance of STAMBP in breast cancer

BACKGROUND

Breast cancer is the leading cause of death from cancer in women worldwide. STAMBP functions as a JAMM family deubiquitinating enzyme that modulates the stability of substrate proteins in cells by cleaving ubiquitin moieties. The expression of STAMBP and its clinical significance in breast cancer remain unclear.

METHODS AND RESULTS

The level of the STAMBP protein in noncancerous and tumor tissues of breast cancer patients was examined by immunohistochemical staining. The expression of STAMBP mRNA in tissues based on healthy individual and breast cancer patient data in the TCGA database was evaluated. The association between the expression of STAMBP mRNA and clinical features and prognosis was evaluated using TCGA database. Cell growth was assessed by Cell Counting Kit-8 (CCK-8) assay, and cell migration and invasion were assessed by wound healing and Transwell assays. Activation of the ERK signaling was detected by Western blotting. The expression of STAMBP was markedly upregulated in the cytoplasm of tumor cells from breast cancer patients. The level of STAMBP was closely associated with the tumor subtype and size and the TNM stage of the breast cancer patients. Importantly, high expression of STAMBP predicted poor overall survival (OS) for breast cancer patients. Furthermore, knockdown of STAMBP expression reduced cell mobility and invasion of breast cancer cells. Notably, the phosphorylation of EGFR and ERK was markedly reduced in STAMBP-knockdown cells.

CONCLUSION

STAMBP plays a critical role in the progression of breast cancer and may serve as a biomarker to monitor the progression of the disease.