Stress granules (SGs) are membrane-less organelles formed through liquid-liquid phase separation of proteins and RNAs, serving as temporary repositories for biomacromolecules to protect cells under stress conditions. Impaired SG disassembly is closely implicated in neurodegenerative diseases and aging, yet the mechanisms regulating SG dynamics are incompletely investigated. The constituents of heterogenous SGs are complicated and broadly categorized as core and shell components. In contrary to the relatively stable core components, our understanding of the diverse SG shell is deficient. By combining interactomic and proximity proteomic approaches, we reveal that the deubiquitinating enzyme OTUD6B is associated with SG-related functions. Immunofluorescence assays showed that OTUD6B localized to SGs, as well as regulated their early assembly and clearance, partially dependent on its enzymatic activity. Further proximity proteomics and interactomics results uncover the ATPase VCP/p97, a key SG disassembly factor, as an OTUD6B-associated protein. OTUD6B and VCP association is governed through their disordered regions normally participated in biomolecular condensation. VCP knockdown or pharmacological inhibition phenocopied OTUD6B silencing by leading to defects in SG dynamics. Mechanistically, SG coalescence of VCP incurred by OTUD6B in a partially enzymatic activity-dependent manner functions to accelerate not only the early assembly, but also SG clearance following stress removal. Therefore, our findings establish OTUD6B as a critical modulator of SG dynamics, linking its function to stress responses and potential disease mechanisms.

BACKGROUND:Recent advances have revealed oncogenic HER2 mutations as an alternative tumorigenic mechanism independent of HER2 overexpression. Certain HER2 mutations confer resistance to current HER2-targeted therapies. OBJECTIVE:Based on our previous finding that neratinib promotes HER2 endocytic degradation, its inhibitory effects were examined on drug-resistant oncogenic HER2 mutations. METHODS:The intracellular distribution of HER2 was observed by immunofluorescence. The expression levels of HER2, pAKT, and pMEK with or without neratinib treatment were investigated by Western blotting. Proliferation was assessed using MTT, colony formation, and wound-healing assays. The tumorigenic potential of HER2 mutations was assessed in vivo. The effects of neratinib on HER2 mutants were investigated by colony and spheroid formation assays, and HER2 ubiquitination and intracellular localization were examined by immunoprecipitation and immunofluorescence, respectively. RESULTS:HER2 mutations enhanced downstream AKT/MEK signaling and promoted tumor-igenesis in vitro and in vivo. Neratinib effectively suppressed downstream signaling, growth, and spheroid formation in cells expressing oncogenic HER2 mutants, including T733I, L755S, and the exon 16 deletion, which was accompanied by evidently enhanced ubiquitination and internalization of these mutants. DISCUSSION:Neratinib effectively induces the ubiquitination and degradation of HER2 mutants to suppress oncogenic signaling. This feature provides a mechanistic explanation of neratinib activities against therapy-resistant HER2 mutations. CONCLUSION:Drug-resistant HER2 mutations can be suppressed by neratinib-induced endocytic degradation, resulting in effective suppression of cancer cell growth.

BACKGROUND:Intracellular membraneless organelles formed by liquid-liquid phase separation (LLPS) function in diverse physiological processes and have been linked to tumor-promoting properties. The nucleolus is one of the largest membraneless organelle formed through LLPS. Deubiquitylating enzymes (DUBs) emerge as novel therapeutic targets against human cancers. However, the nucleolar phase separation of DUBs and association with lung cancer development have remained incompletely investigated till now. METHODS:GFP-USP39 fusion proteins were analyzed for LLPS properties using immunofluorescence, fluorescence recovery after photobleaching (FRAP) and in vitro LLPS assays. Intrinsically-disordered regions of USP39 were analyzed by PhaSepDB database. Transcriptomic profiling, Western blot, RT-PCR and luciferase reporter assays were conducted to identify targets regulated by USP39. The effects of USP39 depletion on tumor progression were tested using doxycycline-inducible USP39 knockdown and rescue lung adenocarcinoma cells both in vitro and in vivo by performing MTT, colony formation, EdU staining, transwell and tumor xenograft model experiments. RESULTS:USP39 phase separates into nucleoli depending upon its N-terminal disordered region with amino acid residues 1-103. Lung cancer cell growth and migration were dramatically inhibited by USP39 knockdown, which was rescued by exogenous USP39 complementation. Moreover, knockdown of USP39 reduced oncogenic transcription effector GLI1 levels. Finally, USP39 downregulation restricted the formation of lung cancer xenografts in nude mice. CONCLUSIONS:USP39 undergoes LLPS in the nucleolus and promotes tumor progression by regulating GLI1 expression. Downregulation of USP39 effectively suppressed lung cancer growth, and therefore targeting USP39 provides novel therapeutic strategy to treat lung cancer.

Members from the RAS GTPase superfamily have been closely implicated in the tumorigenesis of various human cancers. Recent sequencing analysis of lung adenocarcinoma has revealed the prevalence of alterations in the RIT1 gene that is a close RAS paralog. However, relative to RAS subfamily members KRAS, NRAS, and HRAS, our characterization of RIT1 oncogenic properties remains incomplete. Therefore, further investigation on RIT1 will facilitate future development of targeted therapies. Our bioinformatic analysis revealed that RIT1 alterations in lung cancer predicted poor survivals but differed from its RAS paralogs by showing largely amplification and mutation. Through biochemical characterization of RIT1 hotspot mutations, we propose that RIT1 alterations were associated with increased protein abundance that promoted cell growth. Transcriptomic profiling indicated that oncogenic RIT1 mutant expression influenced common tumorigenic RAS/MAPK, PI3K/AKT, and E2F1 pathways, in addition to altered NFE2L2 target expression. Importantly, RIT1 mutants markedly sensitized cells to ferroptosis induction, and RIT1 knockdown suppressed ferroptotic cell death. Lung adenocarcinoma NCI-H2110 cells containing endogenous RIT1 M90I mutation were susceptible to ferroptosis induction both in vitro and in vivo within xenograft models. Hence, our study unravels a novel aspect of RIT1 mutations in lung cancer and suggests ferroptosis induction as a potential therapeutic strategy to treat lung cancer patients carrying RIT1 mutations.

The continued rise in recurrence and mortality rates of cervical cancer suggests the need to find novel therapeutic targets. Previous studies suggest that TRIP4 acts as a transcription factor to regulate cervical carcinogenesis and progression. Our aim was to explore whether the key downstream genes of TRIP4 functions same as TRIP4 in promoting cervical cancer development. We analyzed and confirmed the downstream targets of TRIP4 by RNA sequencing in cervical cancer cells with TRIP4 knockdown. The expression correlation between TRIP4 and GATA2 and the effect of GATA2 on cervical cancer cell growth were determined respectively by Western Blot, Scratch, Spheroid, and MTT analyses. Pulldown and ChIP experiments were performed to analyze the binding of TRIP4 to the promoter of GATA2. The clinical significance of GATA2 and TRIP4 expression in cervical cancer patients was analyzed by tissue microarray staining. GATA2 was highly expressed in cervical cancer tissues. Knockdown of GATA2 inhibited the growth, metastasis and stemness of cervical cancer cells and sensitized cervical cancer cells to radiation therapy. The inhibitory effect of TRIP4 knockdown on cervical cancer cells was rescued by GATA2 overexpression. Furthermore, TRIP4 could bind to the specific GATA2 promoter region, thereby activating its transcription. Clinical tissue microarray analysis indicated that the expression of TRIP4 and GATA2 was positively correlated, and high expression of both predicted a poor prognosis in cervical cancer patients. Our study demonstrated that GATA2 functions as the key downstream target of TRIP4 to promote cervical cancer progression and effective intervention of TRIP4/GATA2 signaling is expected to be developed as potential cervical cancer therapeutic strategy.

Non-small cell lung cancer represents the main histological subtype of lung cancer. Periplocin is a major cardiac glycoside found in the traditional Chinese medicine Cortex periplocae administered in cardiovascular and autoimmune diseases. Inspired by recent findings reporting the anticancer activities of periplocin, this study investigates its potential effects against lung cancer. The influence of periplocin on non-small cell lung cancer cells was examined by CCK-8, colony formation, and EdU staining assays, followed by transcriptomic profiling with RNA sequencing. Gene set enrichment analysis was conducted to identify pathways affected by periplocin. Nrf2 expression was assessed by Western blotting and turnover was investigated by cycloheximide chase assays. Cellular ferroptosis was induced by the GPX4 inhibitor with or without periplocin treatment. The in vivo effects of periplocin were assessed using lung cancer xenograft mouse models. Periplocin inhibited lung cancer cell growth in vitro. Transcriptomic analysis showed significant downregulation of Nrf2 downstream targets. Biochemical characterization revealed that periplocin increased Nrf2 turnover by promoting proteasomal degradation, leading to decreased levels of downstream transcripts. Functionally, Nrf2 reduction imposed by periplocin treatment rendered lung cancer cells increased susceptibility to ferroptosis induction. Finally, periplocin treatment demonstrated similar inhibition to restrict lung cancer xenograft growth as compared to the ferroptosis inducer imidazole ketone erastin, with both compounds leading to elevated expression of the ferroptosis marker COX2 in xenograft tumor tissues. Our investigation suggests periplocin as a potential agent in the development of ferroptosis-inducing therapies against non-small cell lung cancer.

Stress granules (SGs), transient nonmembranous cytoplasmic condensates that formed in response to cellular stresses, require precise characterization to unravel their cell-type and stress-specific protein compositions. This study introduced a G3BP1 antibody-guided proximity labeling (Ab-PL) method to explore the composition and diversity of SGs, overcoming the challenges of traditional enzyme-mediated proximity labeling techniques across various cell types, especially for the immune cells. Application of Ab-PL to HeLa and RAW264.7 cells under heat shock (HS), sodium arsenate (AS), and sodium chloride stress (SS) revealed two categories of SG proteins: "SG-core" and "SG-shell," characterized by their different abilities to undergo phase separation. The core proteins form the SG scaffold with strong self-segregation, while shell proteins are dynamically recruited based on the type of stress. Cell- and stress-specific SG proteins were also identified, highlighting compositional heterogeneity. Intriguingly, unique nuclear-cytoplasmic shuttling behaviors of SG components were observed under varying conditions, uncovering over 10 novel SG proteins, including REXO4, RBM28, and OGFR. This study provides a versatile tool for SG analysis across diverse cell types and offers insights into SG heterogeneity, which has potential implications for human diseases, paving the way for future studies on RNA metabolism, ribosome assembly, and immune regulation.

Ovarian cancer is a frequently observed type of gynaecologic malignancy generally associated with poor prognosis around the world. Ubiquitin-specific proteases (USPs) form the largest subfamily of deubiquitylating enzymes and have emerged as potential therapeutic targets against human cancers. Through a systematic analysis of the prognostic significance of USP expression, USP2 was found to be inversely correlated with patient survival in ovarian cancer. Accordingly, we investigated the effects of pharmacological inhibition of USP2 on ovarian cancer by exploiting its small molecule inhibitor ML364. Our findings show that ML364 effectively hindered ovarian cancer growth and migration using a series of in vitro assays. In addition to apoptosis induction, ML364 also sensitized ovarian cancer cells to ferroptosis. Mechanistically, ML364 treatment resulted in cyclin D1 downregulation, increased poly (ADP-ribose) polymerase (PARP) cleavage, and elevated ROS levels in ovarian cancer cells. Collectively, our findings suggest USP2 as a potential therapeutic target in ovarian cancer, and hence, its pharmacological inhibition warrants further investigation.

The ubiquitin-proteasome system governs a wide spectrum of cellular events and offers therapeutic opportunities for pharmacological intervention in cancer treatment. Renal clear cell carcinoma represents the predominant histological subtype and accounts for the majority of cancer death related to kidney malignancies. Through a systematic survey in the association of human ubiquitin-specific proteases with patient prognosis of renal clear cell carcinoma and subsequent phenotypic validation, we uncovered the tumor-promoting role of USP35. Biochemical characterizations confirmed the stabilizing effects of USP35 towards multiple members of the IAP family in an enzymatic activity-dependent manner. USP35 silencing led to reduced expression levels of IAP proteins, which were accompanied with increased cellular apoptosis. Further transcriptomic analysis revealed that USP35 knockdown affected the expression levels of NRF2 downstream transcripts, which were conferred by compromised NRF2 abundance. USP35 functions to maintain NRF2 levels by catalyzing its deubiquitylation and thus antagonizing degradation. NRF2 reduction imposed by USP35 silencing rendered renal clear cell carcinoma cells increased sensitivity to ferroptosis induction. Finally, induced USP35 knockdown markedly attenuated xenograft formation of renal clear cell carcinoma in nude mice. Hence, our findings reveal a number of USP35 substrates and uncover the protecting roles of USP35 against both apoptosis and ferroptosis in renal clear cell carcinoma.

Glioblastoma (GBM) is a malignant brain tumor. The purpose of this study is to estimate the potential effects and underlying mechanisms of a ubiquitin-specific protease 8 (USP8) small-molecule inhibitor on the phenotypic characteristics of GBM cells. The growth, migration, invasion, and stemness of GBM LN229 and T98G cells were evaluated by conducting cell proliferation, colony formation, wound healing, transwell, Ki-67 staining, spheroid formation, and ionizing radiation assays, and the results collectively showed the suppressive effects of USP8 inhibition on GBM cells. Furthermore, transcriptomic profiling of GBM cells treated with the USP8 inhibitor deubiquitinase (DUB)-IN-1 revealed significantly altered mRNA expression induced by pharmacological USP8 inhibition, from which we confirmed downregulated Aurora kinase A (AURKA) protein levels using immunoblotting assays. Our findings indicated that the proliferation, invasion, and stemness of LN229 and T98G cells were markedly suppressed by USP8 inhibition. Pharmacological USP8 suppression elicits multiple tumor-inhibitory effects, likely through dysregulating various mRNA expression events, including that of the key cell cycle regulator and oncogenic protein AURKA. Therefore, our observations corroborate the GBM-supportive roles of USP8 and suggest pharmacological USP8 inhibition is a viable therapeutic approach to target GBM. The purpose of this study was to investigate the effect and mechanism of action of the USP8 inhibitor DUB-IN-1 on GBM.

Introduction: The human genome encodes two melatonin receptors (MT1 and MT2) that relay melatonin signals to cellular interior. Accumulating evidence has linked melatonin to multiple health benefits, among which its anticancer effects have become well-established. However, the implications of its receptors in lung adenocarcinoma have so far remained incompletely understood. Objectives: This study aims to investigate the response of the MT1 receptor to melatonin treatment and its dynamic regulation by ubiquitin-specific protease 8 (USP8) in lung adenocarcinoma. Methods: The mRNA levels of MT1 and MT2 receptors were analyzed with sequencing data. The expression and localization of the MT1 receptor with melatonin treatment were investigated by immunoblotting, immunofluorescence and confocal microscopy assays. Endocytic deubiquitylases were screened to identify MT1 association. The effects of USP8 were assessed with shRNA-mediated knockdown and small molecule inhibitor. The combined efficacy of melatonin and USP8 suppression was also evaluated using xenograft animal models. Results: Bioinformatic analysis revealed increased expression of the MT1 receptor in lung adenocarcinoma tissues. Melatonin treatment leads to the downregulation of the MT1 receptor in lung adenocarcinoma cells, which is attributed to receptor endocytosis and lysosomal degradation via the canonical endo-lysosomal route. USP8 negatively regulates the endocytic degradation of the MT1 receptor incurred by melatonin exposure and thus protects lung adenocarcinoma cell growth. USP8 suppression by knockdown or pharmacological inhibition effectively deters cancer cell proliferation and sensitizes lung adenocarcinoma cells to melatonin in vitro. Furthermore, USP8 silencing significantly potentiates the anticancer effects of melatonin in xenograft tumor models. Conclusion: The MT1 receptor responds to melatonin treatment and is endocytosed for lysosomal degradation that is counteracted by USP8. The inhibition of USP8 demonstrates tumor-suppressive effects and thus can be exploited as potential therapeutic strategy either as monotherapy or combined therapy with melatonin.

Purpose The epidermal growth factor receptor (EGFR) represents a top therapeutic target in the treatment of non-small cell lung cancer. EGFR expression is intricately modulated by receptor endocytosis, during which EGFR ubiquitylation and deubiquitylation play fundamental roles to govern receptor fate. This study aims to uncover novel aspects of the endocytic regulation of EGFR trafficking by deubiquitylases. Methods The expression and ubiquitylation of EGFR in non-small cell lung cancer cells treated with deubiquitylase inhibitors were assessed by immunoblotting, immunoprecipitation and mass spectrometry analyses. The intracellular EGFR distribution was investigated using immunofluorescence and confocal microscopy assays, and colocalizations with endocytic compartments were examined using GFP-tagged Rab proteins as markers. The influence of the proteasomal deubiquitylase inhibitor b-AP15 on EGF- and HSP90 inhibitor-induced EGFR downregulation was evaluated by immunoblotting. The anticancer effects of b-AP15 were assessed by cell proliferation, colony formation and flow cytometry assays, as well as xenograft animal models. Results We found that b-AP15 caused a dramatically enhanced ubiquitylation of EGFR in lung cancer cells. Treatment with b-AP15 decreased cell surface EGFR levels and accumulated EGFR on recycling endosomes marked with Rab4A and Rab11A. b-AP15 effectively repressed EGF- and HSP90 inhibitor-induced EGFR degradation. Lung cancer cells exposed to b-AP15 showed markedly reduced cell propagation and significantly increased cell apoptosis. Furthermore, b-AP15 effectively inhibited tumor xenograft growth in nude mice. Conclusion Proteasomal USP14 and UCHL5 act collectively to promote cell surface recovery of EGFR. Inhibition of proteasomal deubiquitylase activity induces increased EGFR ubiquitylation and retention on recycling endosomes. The USP14 and UCHL5 dual inhibitor b-AP15 elicits potent tumor-suppressive effects to deter cell proliferation and induce apoptotic cell death in lung cancer.