An integrated bioinformatics platform for investigating the human E3 ubiquitin ligase-substrate interaction network

Targeting USP47 enhances the efficacy of KRAS inhibitor in KRASG12C mutated non-small cell lung cancer by controlling deubiquitination of c-Myc

FDA-approved KRASG12C inhibitors, like Sotorasib, target G12C-mutated KRAS in NSCLC. However, issues with insensitivity and drug resistance have emerged, requiring the development of new combination therapies to overcome these limitations. USP47 has been identified as a regulator of cancer-related signaling pathways such as Wnt, Hippo, and p53. However, its role in the KRAS signaling pathway remains largely unexplored and USP47 inhibitors are less developed than those targeting its homolog, USP7. Here, we identify USP47 as a novel therapeutic target in KRASG12C-mutated NSCLC and report K-552, a selective USP47 inhibitor, as a potential treatment strategy. We demonstrate that USP47 stabilizes c-Myc by preventing its proteasomal degradation through deubiquitination, thereby promoting NSCLC cell proliferation. Additionally, the compound K-552, a USP47 inhibitor identified through virtual screening, effectively destabilizes c-Myc and inhibits KRASG12C-mutated NSCLC cell proliferation. Furthermore, USP47 inhibition-either by siRNA knockdown or K-552 treatment-enhances the efficacy of Sotorasib in vitro and in vivo. Together, our findings establish USP47 as a promising therapeutic target in KRASG12C-mutated NSCLC and introduce K-552 as a USP47 inhibitor with potential for combination therapy with KRASG12C inhibitors.

MARCH8 promotes the proteasomal degradation of foot-and-mouth disease virus VP1, VP2, and VP3 to negatively regulate viral replication

The host cell membrane-associated RING-CH8 protein (MARCH8) functions as an antiviral host factor by targeting viral envelope glycoproteins. Foot-and-mouth disease virus (FMDV) is a non-enveloped, positive-sense, single-stranded RNA virus. The potential impact of MARCH8 on FMDV replication remains uncertain. Here, we found that the overexpression of MARCH8 significantly inhibited FMDV replication in a dose-dependent manner. Conversely, the knockdown of MARCH8 facilitated FMDV replication. Specifically, MARCH8 interacted with VP1, VP2, and VP3, mediating their degradation in a proteasome-dependent manner. MARCH8 catalyzed the K33-linked polyubiquitination of VP1, VP2, and VP3. Moreover, the Lys210 residue of VP1, the Lys63 residue of VP2, and the Lys118 residue of VP3 were identified as critical target sites for MARCH8-mediated degradation. Overall, we conclude that MARCH8 is an intrinsic antiviral factor against FMDV.

Circular RNA CDYL facilitates hepatocellular carcinoma stemness and PD-L1+ exosomes-mediated immunotherapy resistance via stabilizing hornerin protein by blocking synoviolin 1-mediated ubiquitination

Despite the revolutionary progress in cancer immunotherapy, only a minority of hepatocellular carcinoma (HCC) patients respond to immune checkpoint inhibitors (ICIs). In this study, we found that the oncogenic circular RNA Circ-CDYL in HCC influences the efficacy of immunotherapy and the stemness characteristics of HCC cells by interacting with the hornerin (HRNR) protein. The degraded anti-PD-L1 immunotherapy responses induced by Circ-CDYL and HRNR were confirmed by peripheral blood mononuclear cells (PBMCs) killing assays in HCC cells, patient-derived organoids, and humanized immune system mouse models. Furthermore, Circ-CDYL interference reversed the cytotoxicity and proliferation of CD8+ T cells, resulting in ameliorated immune evasion in tumor spheroids upon anti-PD-L1 treatment. Mechanistically, Circ-CDYL upregulated HRNR expression by stabilizing the HRNR protein through the prevention of its degradation by the E3 ubiquitin ligase synoviolin 1 (SYVN1), which in sequence promoted the phosphorylation of the mTORC1 and p70S6K substrate. The abnormally activated mTORC1-p70S6K signaling increases the stemness of HCC cells and upregulates PD-L1 expression, which may attenuate anti-PD-L1 therapy efficacy via PD-L1+ exosomes. Our study revealed the mechanism by which Circ-CDYL and HRNR regulate the sensitivity of HCC to anti-PD-L1 therapy, and the findings have potential implications for patient stratification and clinical decision-making in HCC immunotherapy.

BARD1-mediated stabilization of METTL14 promotes retinal neovascularization by m6A-modifying MXD1 mRNA on a YTHDF2-dependent manner

Retinal vascular diseases are typified by the proliferation of irregular and leaky microvessels, resulting in vision impairment. Although the etiology of retinal angiogenesis is not yet fully understood, it is evident that microglia play a pivotal role in promoting angiogenesis. Methods: In vivo, the METTL14 conditional knockout (cKO) mouse was constructed to investigate the role of METTL14 in oxygen-induced retinopathy (OIR). In vitro, a combination of methylated RNA immunoprecipitation sequencing (MeRIP-seq), RNA-sequencing (RNA-seq), RNA Immunoprecipitation (RIP) assay, dual-luciferase reporter assays, and Chromatin immunoprecipitation-qPCR (ChIP-qPCR), was performed to explore the underlying mechanisms. Results: The proteomic analysis of hypoxic microglia has uncovered a pronounced enrichment in pathways related to RNA modification. Western blot has revealed that N6-methyladenosine (m6A) methyltransferase-like 14 (METTL14) exhibits the most significant increase among the RNA methylases. METTL14 cKO mice within an OIR model showed fewer neovascular formations. Additionally, in co-culture with sh-METTL14 HMC3 cells, HRMECs also exhibited reduced angiogenesis capabilities. Mechanically, E3 ubiquitin-protein ligase BARD1 can directly interact with METTL14, leading to an up-regulation of METTL14 protein level in hypoxic microglia. METTL14 could directly modifies and regulates the transcription factor MAX Dimerization Protein 1 (MXD1), which is subsequently recognized by the m6A "reader" YTH domain-containing family protein 2 (YTHDF2). Consequently, the modified MXD1 modulates the expression of VEGFA and VCAM1, promotes retinal neovascularization. Conclusion: Our study highlights the critical role of METTL14 in the OIR model and suggests a novel therapeutic target for addressing retinal vascular diseases.

Targeting METTL3 mitigates venetoclax resistance via proteasome-mediated modulation of MCL1 in acute myeloid leukemia

Venetoclax, a selective BCL2 inhibitor, is extensively utilized in clinical settings for the treatment of acute myeloid leukemia (AML). However, its efficacy is often compromised by the development of drug resistance. Hence, identification of potential venetoclax combination treatment strategies is imperative to overcome this acquired resistance. In this study, we discovered that inhibition of METTL3 can synergistically enhance the anti-leukemic efficacy of venetoclax, and is capable of overcoming venetoclax resistance in in vivo experiments and various venetoclax resistance models. Mechanistic study revealed that STM2457 augmented venetoclax activity by downregulating MCL1 and MYC, thereby increasing apoptosis in leukemia cells induced by venetoclax. Further investigation demonstrated that STM2457 promotes the ubiquitination and subsequent protein degradation of MCL1 primarily through pharmaceutically targeting METTL3. Moreover, through molecular docking-based virtual screening, we identified isoliquiritigenin as a potential novel small molecule natural product targeting METTL3, which exhibited potential effects as an anti-leukemic agent.

eIF3f promotes tumour malignancy by remodelling fatty acid biosynthesis in hepatocellular carcinoma

BACKGROUND & AIMS

Fatty acid metabolism is closely associated with hepatocellular carcinoma (HCC). Elucidating the molecules that influence fatty acid metabolism in HCC is important for developing precise therapy. However, elucidating its molecular mechanisms in tumour cells is challenging. In this study, we aimed to determine the characteristics and differences of fatty acid metabolism in HCC.

METHODS

We employed organoid models, single-cell RNA sequencing, and spatial transcriptomics to identify key genes involved in tumour fatty acid metabolism. Metabolomics, proteomics, metabolic flux analysis, and transmission electron microscopy were utilized to evaluate this metabolic process. Tumour malignancy was characterized using multi-species models. Changes in the immune microenvironment were analyzed by time-of-flight mass cytometry and multiplexed immunohistochemistry. Gene knockdown targeting the liver was achieved using lipid nanoparticles.

RESULTS

Eukaryotic translation initiation factor 3 subunit f (eIF3f) is upregulated in HCC tissues and is associated with poor prognosis. eIF3f directly interacted with and stabilised long chain acyl CoA synthetase 4 (ACSL4) through K48-linked deubiquitination, promoting fatty acid biosynthesis (FAB) and tumour malignancy. The increased fatty acid levels in the tumour microenvironment indirectly reduced CD8+ T-cell infiltration. In addition, phosphorylated eIF3f enhanced the interaction between eIF3f and ACSL4.

CONCLUSIONS

Targeting the eIF3f-ACSL4-FAB axis could decelerate HCC malignancy and enhance anti-programmed cell death-1 efficacy, suggesting that eIF3f is a potential target for precision therapy in HCC.

Bioengineered Extracellular Vesicles Delivering siMDM2 Sensitize Oxaliplatin Therapy Efficacy in Colorectal Cancer

Oxaliplatin (OXA) is the first-line drug for the treatment of colorectal cancer (CRC), and susceptibility to drug resistance affects patient prognosis. However, the exact underlying mechanisms remain unclear. Platinum-acquired resistance in CRC is a continuous transition process; though, current research has mainly focused on the end state of drug resistance, and the early events of drug resistance have been ignored. In this study, single-cell transcriptome sequencing is combined with a dynamic network biomarker (DNB), and found that the functional inhibition of the mitochondrial electron transport chain complex I occur early in the development of attained resistance to OXA in CRC cells, as evidenced by a decrease in the levels of subunit proteins, primarily NDUFB8. Specifically, the mouse double minute 2 homologue (MDM2) mediates the ubiquitination and degradation of NDUFB8, reducing intracellular reactive oxygen species (ROS) generation under chemotherapeutic stress, consequently contributing to drug resistance. Based on this, the study constructs engineered extracellular vesicles carrying siMDM2 by electroporation and validates the application of EV-siMDM2 to improve the efficacy of OXA-based chemotherapy by inhibiting the MDM2/NDUFB8/ROS signaling axis in patient-derived xenograft (PDX) and hepatic and pulmonary metastasis mouse models, thus providing new ideas and an experimental basis for the platinum-resistant treatment of CRC.

Lactylation-driven transcriptional activation of FBXO33 promotes gallbladder cancer metastasis by regulating p53 polyubiquitination

Gallbladder cancer (GBC) is the most common malignant tumor of the biliary tract and is often prone to early distant metastasis. However, the mechanisms underlying GBC's invasive metastasis remain unclear. This study identified that F-box only protein 33 (FBXO33) expression is significantly elevated in GBC and is negatively associated with patient prognosis. In vivo and in vitro experiments demonstrated that knockdown of FBXO33 inhibits epithelial-mesenchymal transition (EMT) progression in GBC, while overexpression of FBXO33 promotes EMT progression. Mechanistically, FBXO33 regulates EMT progression by modulating the polyubiquitination of p53 at K291 and K292. Moreover, the upregulation of FBXO33 in GBC is driven by transcriptional regulation mediated by Yin Yang-1 (YY1). The lactylation modification of YY1 at K183 was found to be essential for the transcriptional activation of FBXO33. These findings underscore the role of the lactylation-driven FBXO33-p53 axis in promoting the invasive metastasis of GBC.

MTOR Promotes Astrocyte Activation and Participates in Neuropathic Pain through an Upregulation of RIP3

Neuropathic pain (NP), a chronic pain condition, is the result of abnormalities in both central and peripheral pain conduction pathways. Here, we investigated the underlying mechanisms associated with this effect. We found that following chronic constriction injury (CCI) surgery, there was an increase of mTOR in astrocytes and an activation of astrocytes within the spinal cord. Pharmacological inhibition of mTOR reversed CCI-induced hyperalgesia and neuroinflammation. Moreover, knockdown of astrocytic mTOR rescued the downregulation of spinal glutamate metabolism-related protein expression, underscoring the pivotal role of mTOR in modulating this pathway. Intriguingly, we observed that overexpression of mTOR, achieved via intrathecal administration of TSC2-shRNA, led to an upregulation of RIP3. Notably, pharmacological inhibition of RIP3, while ineffective in modulating mTOR activation, effectively eliminated the mTOR-induced astrocyte activation. Mechanistically, we found that mTOR controlled the expression of RIP3 in astrocytes through ITCH-mediated ubiquitination and an autophagy-dependent degradation. Taken together, our results reveal an unanticipated link between mTOR and RIP3 in promoting astrocyte activation, providing new avenues of investigation directed toward the management and treatment of NP.

VANGL2 alleviates inflammatory bowel disease by recruiting the ubiquitin ligase MARCH8 to limit NLRP3 inflammasome activation through OPTN-mediated selective autophagy

Inflammatory bowel disease (IBD) is a chronic and potentially life-threatening inflammatory disease of gastroenteric tissue characterized by episodes of intestinal inflammation, but the underlying mechanisms remain elusive. Here, we explore the role and precise mechanism of Van-Gogh-like 2 (VANGL2) during the pathogenesis of IBD. VANGL2 decreases in IBD patients and dextran sulfate sodium (DSS)-induced colitis in mice. Myeloid VANGL2 deficiency exacerbates the progression of DSS-induced colitis in mice and specifically enhances the activation of NLRP3 inflammasome in macrophages. NLRP3-specific inhibitor MCC950 effectively alleviates DSS-induced colitis in VANGL2 deficient mice. Mechanistically, VANGL2 interacts with NLRP3 and promotes the autophagic degradation of NLRP3 through enhancing the K27-linked polyubiquitination at lysine 823 of NLRP3 by recruiting E3 ligase MARCH8, leading to optineurin (OPTN)-mediated selective autophagy. Notably, decreased VANGL2 in the peripheral blood mononuclear cells from IBD patients results in overt NLRP3 inflammasome activation and sustained inflammation. Taken together, this study demonstrates that VANGL2 acts as a repressor of IBD progression by inhibiting NLRP3 inflammasome activation and provides insights into the crosstalk between inflammation and autophagy in preventing IBD.

Nuclear farnesoid X receptor protects against bone loss by driving osteoblast differentiation through stabilizing RUNX2

The delicate balance between bone formation by osteoblasts and bone resorption by osteoclasts maintains bone homeostasis. Nuclear receptors (NRs) are now understood to be crucial in bone physiology and pathology. However, the function of the Farnesoid X receptor (FXR), a member of the NR family, in regulating bone homeostasis remains incompletely understood. In this study, in vitro and in vivo models revealed delayed bone development and an osteoporosis phenotype in mice lacking FXR in bone marrow mesenchymal stem cells (BMSCs) and osteoblasts due to impaired osteoblast differentiation. Mechanistically, FXR could stabilize RUNX2 by inhibiting Thoc6-mediated ubiquitination, thereby promoting osteogenic activity in BMSCs. Moreover, activated FXR could directly bind to the Thoc6 promoter, suppressing its expression. The interaction between RUNX2 and Thoc6 was mediated by the Runt domain of RUNX2 and the WD repeat of Thoc6. Additionally, Obeticholic acid (OCA), an orally available FXR agonist, could ameliorate bone loss in an ovariectomy (OVX)-induced osteoporotic mouse model. Taken together, our findings suggest that FXR plays pivotal roles in osteoblast differentiation by regulating RUNX2 stability and that targeting FXR may be a promising therapeutic approach for osteoporosis.

A computational tool to infer enzyme activity using post-translational modification profiling data

Enzymes play a pivotal role in orchestrating complex cellular responses to external stimuli and environmental changes through signal transduction pathways. Despite their crucial roles, measuring enzyme activities is typically indirect and performed on a smaller scale, unlike protein abundance measured by high-throughput proteomics. Moreover, it is challenging to derive the activity of enzymes from proteome-wide post-translational modification (PTM) profiling data. To address this challenge, we introduce enzyme activity inference with structural equation modeling under the JUMP umbrella (JUMPsem), a novel computational tool designed to infer enzyme activity using PTM profiling data. We demonstrate that the JUMPsem program enables estimating kinase activities using phosphoproteome data, ubiquitin E3 ligase activities from the ubiquitinome, and histone acetyltransferase (HAT) activities based on the acetylome. In addition, JUMPsem is capable of establishing novel enzyme-substrate relationships through searching motif sequences. JUMPsem outperforms widely used kinase activity tools, such as IKAP and KSEA, in terms of the number of kinases and the computational speed. The JUMPsem program is scalable and publicly available as an open-source R package and user-friendly web-based R/Shiny app. Collectively, JUMPsem provides an improved tool for inferring protein enzyme activities, potentially facilitating targeted drug development.

PCDH17 induces colorectal cancer metastasis by destroying the vascular endothelial barrier

Compromised vascular integrity facilitates the cancer cells extravasation and metastasis. However, the mechanisms leading to a disruption in vascular integrity in colorectal cancer (CRC) remain unclear. In this study, PCDH17 expression was higher in the vascular endothelial cells of colon cancer with distant metastasis, and the rates of PCDH17+ endothelial cells (ECs) was associated with the M stage in clinical pathological characteristics analysis and correlated with a poor survival prognosis. The liver and lung metastatic dissemination of MC-38 was significantly decreased in PCDH17-/-mice. The ubiquitination and degradation of VEGFR2 was prevented by the interaction between PCDH17 and the E3 ubiquitin ligase MARCH5, which causing the separation of internalized VE-cadherin, and increased the vascular permeability and metastasis of CRC. These results highlight the importance of PCDH17 in maintaining vascular integrity, which has emphasis for endothelial barrier function in metastatic cancer. PCDH17 has the potential to be a marker for predicting tumor metastasis as well as a viable treatment target for CRC.

STAMBPL1/TRIM21 Balances AXL Stability Impacting Mesenchymal Phenotype and Immune Response in KIRC

Kidney renal clear cell carcinoma (KIRC) is recognized as an immunogenic tumor, and immunotherapy is incorporated into its treatment landscape for decades. The acquisition of a tumor mesenchymal phenotype through epithelial-to-mesenchymal transition (EMT) is associated with immune evasion and can contribute to immunotherapy resistance. Here, the involvement of STAM Binding Protein Like 1 (STAMBPL1) is reported in the development of mesenchymal and immune evasion phenotypes in KIRC cells. Mechanistically, STAMBPL1 elevated protein abundance and surface accumulation of TAM Receptor AXL through diminishing the TRIM21-mediated K63-linked ubiquitination and subsequent lysosomal degradation of AXL, thereby enhancing the expression of mesenchymal genes while suppressing chemokines CXCL9/10 and HLA/B/C. In addition, STAMBPL1 enhanced PD-L1 transcription via facilitating nuclear translocation of p65, and knockdown (KD) of STAMBPL1 augmented antitumor effects of PD-1 blockade. Furthermore, STAMBPL1 silencing and the tyrosine kinase inhibitor (TKI) sunitinib also exhibited a synergistic effect on the suppression of KIRC. Collectively, targeting the STAMBPL1/TRIM21/AXL axis can decrease mesenchymal phenotype and potentiate anti-tumor efficacy of cancer therapy.

SKP2 inhibition activates tumor cell-intrinsic immunity by inducing DNA replication stress and genomic instability

BACKGROUND

S-phase kinase-associated protein 2 (SKP2) is a typical oncogene aberrantly overexpressing in a variety of cancer types, but it remains elusive whether SKP2 regulates the antitumor immunity of triple-negative breast cancer.

METHODS

The efficacy of anti-PD-1 was evaluated in the orthotopic xenografts of immunocompetent mice models. The infiltration of cytotoxic T cells in tumor microenvironment(TME) were assessed by immunofluorescence staining. The levels of pro-inflammatory chemokines were analyzed by ELISA. The protein interaction was analyzed by co-immunoprecipitation and GST pull-down. The genomic instability was analyzed by fluorescent microscopy.

RESULTS

SKP2 inhibition significantly improved the antitumor efficacy of immune checkpoint blockade (ICB). Furthermore, SKP2 inhibition activated the cGAS/STING signal pathway and induced the secretion of pro-inflammatory chemokines, thereby promoting cytotoxic T cell infiltration. Additionally, we identified CDC6, a DNA replication licensing factor as a novel substrate of SKP2 in addition to CDT1. SKP2 induced protein degradation of CDC6 and CDT1 through the ubiquitin-proteasome pathway. Conversely, SKP2 inhibition elevated CDC6 and CDT1 protein levels, which caused DNA aberrant replication, DNA damage and genomic instability, thereby resulting in the accumulation of cytosolic DNA, activating cGAS/STING signaling pathway and improving antitumor immunity.

CONCLUSION

SKP2 may be used as an effective therapeutic target to enable ICB antitumor immunotherapy.

SOCIAL MEDIA

Peng et al. found that SKP2 inhibition improved the antitumor immunotherapy by activating tumor cell-intrinsic immunity, thereby providing evidences that SKP2 may be used as an effective therapeutic target to enable ICB antitumor immunotherapy.

Sox2 interacts with Atoh1 and Huwe1 loci to regulate Atoh1 transcription and stability during hair cell differentiation

Stem cell pluripotency gene Sox2 stimulates expression of proneural basic-helix-loop-helix transcription factor Atoh1. Sox2 is necessary for the development of cochlear hair cells and binds to the Atoh1 3' enhancer to stimulate Atoh1 expression. We show here that Sox2 deletion in late embryogenesis results in the formation of extra hair cells, in contrast to the absence of hair cell development obtained after Sox2 knockout early in gestation. Sox2 overexpression decreased the level of Atoh1 protein despite an increase in Atoh1 mRNA. Sox2 upregulated E3 ubiquitin ligase, Huwe1, by direct binding to the Huwe1 gene. By upregulating its cognate E3 ligase, Sox2 disrupts the positive feedback loop through which Atoh1 protein increases the expression of Atoh1. We conclude that Sox2 initiates expression, while also limiting continued activity of bHLH transcription factor, Atoh1, and this inhibition represents a new mechanism for regulating the activity of this powerful initiator of hair cell development.

Immune-related diagnostic markers for benign prostatic hyperplasia and their potential as drug targets

Background

Benign prostatic hyperplasia (BPH) is a common issue among older men. Diagnosis of BPH currently relies on imaging tests and assessment of urinary flow rate due to the absence of definitive diagnostic markers. Developing more accurate markers is crucial to improve BPH diagnosis.

Method

The BPH dataset utilized in this study was sourced from the Gene Expression Omnibus (GEO). Initially, differential expression and functional analyses were conducted, followed by the application of multiple machine learning techniques to identify key diagnostic markers. Subsequent investigations have focused on elucidating the functions and mechanisms associated with these markers. The ssGSEA method was employed to evaluate immune cell scores in BPH samples, facilitating the exploration of the relationship between key diagnostic markers and immune cells. Additionally, molecular docking was performed to assess the binding affinity of these key markers to therapeutic drugs for BPH. Tissue samples from BPH patients were collected for experimental validation of the expression differences of the aforementioned genes.

Result

A total of 185 differential genes were identified, comprising 67 up-regulated and 118 down-regulated genes. These genes are implicated in pathways that regulate extracellular matrix tissue composition and cellular responses to transforming growth factor beta stimulation, as well as critical signaling pathways such as AMPK and mTOR. Through the application of various machine learning techniques, DACH1, CACNA1D, STARD13, and RUNDC3B were identified as key diagnostic markers. The ssGSEA algorithm further corroborated the association of these diagnostic genes with diverse immune cells. Moreover, molecular docking analysis revealed strong binding affinities of these markers to tamsulosin and finasteride, suggesting their potential as drug targets. Finally, experimental validation confirmed the expression differences of DACH1, CACNA1D, STARD13, and RUNDC3B in BPH tissues.

Conclusion

This study introduces novel immune-related diagnostic markers for BPH and highlights their promise as new drug targets, providing a valuable approach for predictive diagnosis and targeted therapy of BPH.

Nitric oxide facilitates the S-nitrosylation and deubiquitination of Notch1 protein to maintain cancer stem cells in human NSCLC

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality, with tumour heterogeneity, fueled by cancer stem cells (CSCs), intricately linked to treatment resistance. Therefore, it is imperative to advance therapeutic strategies targeting CSCs in NSCLC. In this study, we utilized RNA sequencing to investigate metabolic pathway alterations in NSCLC CSCs and identified a crucial role of nitric oxide (NO) metabolism in governing CSC stemness, primarily through modulation of the Notch1 protein. Mechanistically, NO-induced S-nitrosylation of Notch1 facilitated its interaction with the deubiquitylase UCHL1, leading to increased Notch1 protein stability and enhanced CSC stemness. By inhibiting NO synthesis and downregulating UCHL1 expression, we validated the impact of NO on the Notch signalling pathway and CSC stemness. Importantly, targeting NO effectively reduced CSC populations within patient-derived organoids (PDOs) during radiotherapy. This mechanism presents a promising therapeutic target to surmount radiotherapy resistance in NSCLC treatment.

TMEM209 promotes hepatocellular carcinoma progression by activating the Wnt/β-catenin signaling pathway through KPNB1 stabilization

Hepatocellular carcinoma (HCC) is the most common malignancy in the liver, with a poor prognosis. Transmembrane protein 209 (TMEM209) involves multiple biological processes, such as substance transportation and signal transduction, and is abundantly expressed in tumor tissues. However, the relationship between TMEM209 and HCC has not been comprehensively elucidated. In this study, we aimed to illustrate this issue by in vitro and in vivo experiments. Bioinformatic analysis and clinical sample validation revealed that TMEM209 was upregulated in HCC and correlated with reduced survival duration. Functionally, TMEM209 promoted the proliferation, migration, invasion, and EMT of HCC cells in vitro and facilitated tumor growth and metastasis in xenograft models. Mechanistically, TMEM209 promoted the proliferation and metastasis of HCC in a KPNB1-dependent manner. Specifically, TMEM209 could bind to KPNB1, thereby competitively blocking the interaction between KPNB1 and the E3 ubiquitin ligase RING finger and CHY zinc finger domain-containing protein 1 (RCHY1) and preventing K48-associated ubiquitination degradation of KPNB1. Ultimately, the Wnt/β-catenin signaling pathway was activated, contributing to the progression of the malignant phenotype of HCC. In conclusion, the molecular mechanism underlying the TMEM209/KPNB1/Wnt/β-catenin axis in HCC progression was elucidated. TMEM209 is a potential biomarker and therapeutic target for HCC.

The NEDD4/FLRT2 axis regulates NSCLC cell stemness

INTRODUCTION

Lung cancer is the leading cause of cancer-related death worldwide. The treatment for lung cancer, particularly for non-small cell lung cancer (NSCLC), remains a clinical challenge. Cancer stem cells are vital for lung cancer development. This study aimed to determine the influence of the neuronally expressed developmentally downregulated 4-fibronectin leucine-rich transmembrane 2 (NEDD4-FLRT2) axis on cancer cell stemness in NSCLC.

METHODS

FLRT2 expression in NSCLC tissues and stem cells was investigated using western blot and RT-qPCR. The sphere formation assay and the abundance of stemness markers were employed to confirm the stemness of NSCLC stem cells. The CCK-8, colony formation, and Trans-well assays, as well as flow cytometry, were used to determine NSCLC stem cell growth, metastasis, and apoptosis, respectively. The Co-IP assay was used to confirm the binding between NEDD4 and FLRT2. Xenograft tumor mouse models were used to investigate tumorigenesis in vivo.

RESULTS

Here, we reported that FLRT2 expression was reduced in NSCLC tissues, cells, and NSCLC stem cells. FLRT2 upregulation inhibited NSCLC stem cell proliferation, sphere formation, and drug resistance and promoted drug-resistant cell apoptosis. Furthermore, FLRT2 overexpression demonstrated antitumor effects in a xenograft tumor mouse model. Mechanically, FLRT2 was ubiquitinated and degraded by E3 ligase NEDD4. NEDD4 overexpression significantly abolished the inhibitory effects of FLRT2 on NSCLC stemness, as evidenced by in vitro and in vivo experiments.

DISCUSSION

This study revealed that FLRT2 acted as a tumor suppressor by inhibiting cancer cell stemness in NSCLC. NEDD4 promoted ubiquitination degradation of FLRT2 protein. NEDD4 counteracted the inhibitory effects of FLRT2 on NSCLC stem cell tumorigenesis.

Iron-(Fe3+)-Dependent Reactivation of Telomerase Drives Colorectal Cancers

Over-consumption of iron-rich red meat and hereditary or genetic iron overload are associated with an increased risk of colorectal carcinogenesis, yet the mechanistic basis of how metal-mediated signaling leads to oncogenesis remains enigmatic. Using fresh colorectal cancer samples we identify Pirin, an iron sensor, that overcomes a rate-limiting step in oncogenesis, by reactivating the dormant human telomerase reverse transcriptase (hTERT) subunit of the telomerase holoenzyme in an iron-(Fe3+)-dependent manner and thereby drives colorectal cancers. Chemical genetic screens combined with isothermal dose-response fingerprinting and mass spectrometry identified a small molecule SP2509 that specifically inhibits Pirin-mediated hTERT reactivation in colorectal cancers by competing with iron-(Fe3+) binding. Our findings, first to document how metal ions reactivate telomerase, provide a molecular mechanism for the well-known association between red meat and increased incidence of colorectal cancers. Small molecules like SP2509 represent a novel modality to target telomerase that acts as a driver of 90% of human cancers and is yet to be targeted in clinic. Significance: We show how iron-(Fe3+) in collusion with genetic factors reactivates telomerase, providing a molecular mechanism for the association between iron overload and increased incidence of colorectal cancers. Although no enzymatic inhibitors of telomerase have entered the clinic, we identify SP2509, a small molecule that targets telomerase reactivation and function in colorectal cancers.

Computational methods and key considerations for in silico design of proteolysis targeting chimera (PROTACs)

Proteolysis-targeting chimeras (PROTACs), as heterobifunctional molecules, have garnered significant attention for their ability to target previously undruggable proteins. Due to the challenges in obtaining crystal structures of PROTAC molecules in the ternary complex, a plethora of computational tools have been developed to aid in PROTAC design. These computational tools can be broadly classified into artificial intelligence (AI)-based or non-AI-based methods. This review aims to provide a comprehensive overview of the latest computational methods for the PROTAC design process, covering both AI and non-AI approaches, from protein selection to ternary complex modeling and prediction. Key considerations for in silico PROTAC design are discussed, along with additional considerations for deploying AI-based models. These considerations are intended to guide subsequent model development in the PROTAC design process. Finally, future directions and recommendations are provided.

Inhibition of GLUD1 mediated by LASP1 and SYVN1 contributes to hepatitis B virus X protein-induced hepatocarcinogenesis

Glutamate dehydrogenase 1 (GLUD1) is implicated in oncogenesis. However, little is known about the relationship between GLUD1 and hepatocellular carcinoma (HCC). In the present study, we demonstrated that the expression levels of GLUD1 significantly decreased in tumors, which was relevant to the poor prognosis of HCC. Functionally, GLUD1 silencing enhanced the growth and migration of HCC cells. Mechanistically, the upregulation of interleukin-32 through AKT activation contributes to GLUD1 silencing-facilitated hepatocarcinogenesis. The interaction between GLUD1 and AKT, as well as α-ketoglutarate regulated by GLUD1, can suppress AKT activation. In addition, LIM and SH3 protein 1 (LASP1) interacts with GLUD1 and induces GLUD1 degradation via the ubiquitin-proteasome pathway, which relies on the E3 ubiquitin ligase synoviolin (SYVN1), whose interaction with GLUD1 is enhanced by LASP1. In hepatitis B virus (HBV)-related HCC, the HBV X protein (HBX) can suppress GLUD1 with the participation of LASP1 and SYVN1. Collectively, our data suggest that GLUD1 silencing is significantly associated with HCC development, and LASP1 and SYVN1 mediate the inhibition of GLUD1 in HCC, especially in HBV-related tumors.

Proteome and ubiquitinome analyses of the brain cortex in K18-hACE2 mice infected with SARS-CoV-2

Clinical research indicates that SARS-CoV-2 infection is linked to several neurological consequences, and the virus is still spreading despite the availability of vaccinations and antiviral medications. To determine how hosts respond to SARS-CoV-2 infection, we employed LC-MS/MS to perform ubiquitinome and proteome analyses of the brain cortexes from K18-hACE2 mice in the presence and absence of SARS-CoV-2 infection. A total of 8,024 quantifiable proteins and 5,220 quantifiable lysine ubiquitination (Kub) sites in 2023 proteins were found. Glutamatergic synapse, calcium signaling pathway, and long-term potentiation may all play roles in the neurological consequences of SARS-CoV-2 infection. Then, we observed possible interactions between 26 SARS-CoV-2 proteins/E3 ubiquitin-protein ligases/deubiquitinases and several differentially expressed mouse proteins or Kub sites. We present the first description of the brain cortex ubiquitinome in K18-hACE2 mice, laying the groundwork for further investigation into the pathogenic processes and treatment options for neurological dysfunction following SARS-CoV-2 infection.

NDR1/FBXO11 promotes phosphorylation-mediated ubiquitination of β-catenin to suppress metastasis in prostate cancer

Background: Prostate cancer progression hinges on β-catenin's stability and activity, a key factor in epithelial-mesenchymal transition (EMT) and metastasis. This study delves into NDR1-dependent phosphorylation's impact on β-catenin via FBXO11, an E3 ubiquitin ligase, in prostate cancer cells. Methods: Human prostate cancer cell lines underwent various in vitro assays, including real-time PCR, Western blotting, immunoprecipitation, immunofluorescence, and protein stability assays, to explore β-catenin's interactions and post-translational modifications. NDR1 modulation's in vivo efficacy was assessed using a nude mice lung metastasis model. Small-molecule screening identified a potential NDR1 activator, aNDR1, tested for its effects on metastasis via in vitro and in vivo assays. Results: NDR1 phosphorylated β-catenin at Ser33/37, facilitating its interaction with FBXO11. This led to FBXO11-mediated ubiquitination and cytoplasmic degradation of β-catenin, while the NDR1-FBXO11 complex impeded β-catenin nuclear translocation by inducing JNK2 ubiquitination. Thus, NDR1 and FBXO11 jointly regulate β-catenin activity in prostate cancer cells through dual phosphorylation-driven ubiquitination, potentially suppressing EMT. Reduced NDR1 expression inhibited FBXO11 and β-catenin phosphorylation, diminishing β-catenin and JNK2 ubiquitination, promoting EMT and enhancing prostate cancer cell metastasis. The inhibitory effects of aNDR1 on prostate cancer metastasis were validated. Conclusion: The NDR1/FBXO11 axis outlines a non-canonical β-catenin degradation pathway crucial in regulating EMT and prostate cancer cell metastasis. NDR1 activation, particularly with aNDR1, could offer a promising therapeutic avenue against prostate cancer metastasis.

A machine learning approach to differentiate wide QRS tachycardia: distinguishing ventricular tachycardia from supraventricular tachycardia

BACKGROUND

Differential diagnosis of wide QRS tachycardia (WQCT) has been a challenging issue. Published algorithms to distinguish ventricular tachycardia (VT) and supraventricular tachycardia (SVT) have limited diagnostic capabilities.

METHODS

A total of 278 patients with WQCT from January 2010 to March 2022 were enrolled. The electrophysiological study confirmed SVT in 154 patients and VT in 65 ones. Two hundred nineteen WQCT 12-lead ECGs were randomly divided into development cohort (n = 165) and testing cohort (n = 54) data sets. The development cohort was split into a training group (n = 115) and an internal validation group (n = 50). Forty ECG features extracted from the 219 WQCT ECGs are fed into 9 iteratively trained ML algorithms. This novel ML algorithm was also compared with four published algorithms.

RESULTS

In the development cohort, the Gradient Boosting Machine (GBM) model displayed the maximum area under curve (AUC) (0.91, 95% confidence interval (CI) 0.81-1.00). In the testing cohort, the GBM model had a higher AUC of 0.97 compared to 4 validated ECG algorithms, namely, Brugada (0.68), avR (0.62), RWPTII (0.72), and LLA algorithms (0.70). Accuracy, sensitivity, specificity, negative predictive value, and positive predictive value of the GBM model were 0.94, 0.97, 0.90, 0.94, and 0.95, respectively.

CONCLUSIONS

A GBM ML model contributes to distinguishing SVT from VT based on surface ECG features. In addition, we were able to identify important indicators for distinguishing WQCT.

Gut microbiota-derived indole-3-propionic acid alleviates diabetic kidney disease through its mitochondrial protective effect via reducing ubiquitination mediated-degradation of SIRT1

INTRODUCTION

Gut microbes and their metabolites play crucial roles in the pathogenesis of diabetic kidney disease (DKD). However, which one and how specific gut-derived metabolites affect the progression of DKD remain largely unknown.

OBJECTIVES

This study aimed to investigate the potential roles of indole-3-propionic acid (IPA), a microbial metabolite of tryptophan, in DKD.

METHODS

Metagenomic sequencing was performed to analyze the microbiome structure in DKD. Metabolomics screening and validation were conducted to identify characteristic metabolites associated with DKD. The protective effect of IPA on DKD glomerular endothelial cells (GECs) was assessed through in vivo and in vitro experiments. Further validation via western blot, immunoprecipitation, gene knockout, and site-directed mutation elucidated the mechanism of IPA on mitochondrial injury.

RESULTS

Alterations in gut microbial community structure and dysregulated tryptophan metabolism were evident in DKD mice. Serum IPA levels were significantly reduced in DKD patients and correlated with fasting blood glucose, HbA1c, urine albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR). IPA supplementation ameliorated albuminuria, bolstered the integrity of the glomerular filtration barrier, and mitigated mitochondrial impairments in GECs. Mechanistically, IPA hindered SIRT1 phosphorylation-mediated ubiquitin-proteasome degradation, restoring SIRT1's role in promoting PGC-1α deacetylation and nuclear translocation, thereby upregulating genes associated with mitochondrial biosynthesis and antioxidant defense.

CONCLUSION

Our findings underscore the potential of the microbial metabolite IPA to attenuate DKD progression, offering novel insights and potential therapeutic strategies for its management.

A ubiquitin-specific, proximity-based labeling approach for the identification of ubiquitin ligase substrates

Over 600 E3 ligases in humans execute ubiquitination of specific target proteins in a spatiotemporal manner to elicit desired signaling effects. Here, we developed a ubiquitin-specific proximity-based labeling method to selectively biotinylate substrates of a given ubiquitin ligase. By fusing the biotin ligase BirA and an Avi-tag variant to the candidate E3 ligase and ubiquitin, respectively, we were able to specifically enrich bona fide substrates of a ligase using a one-step streptavidin pulldown under denaturing conditions. We applied our method, which we named Ub-POD, to the really interesting new gene (RING) E3 ligase RAD18 and identified proliferating cell nuclear antigen and several other critical players in the DNA damage repair pathway. Furthermore, we successfully applied Ub-POD to the RING ubiquitin ligase tumor necrosis factor receptor-associated factor 6 and a U-box-type E3 ubiquitin ligase carboxyl terminus of Hsc70-interacting protein. We anticipate that our method could be widely adapted to all classes of ubiquitin ligases to identify substrates.

Insect ribosome-rescuer Pelo-Hbs1 complex on sperm surface mediates paternal arbovirus transmission

Arboviruses can be paternally transmitted by male insects to offspring for long-term persistence, but the mechanism remains largely unknown. Here, we use a model system of a destructive rice reovirus and its leafhopper vector to find that insect ribosome-rescuer Pelo-Hbs1 complex expressed on the sperm surface mediates paternal arbovirus transmission. This occurs through targeting virus-containing tubules constituted by viral nonstructural protein Pns11 to sperm surface via Pns11-Pelo interaction. Tubule assembly is dependent on Hsp70 activity, while Pelo-Hbs1 complex inhibits tubule assembly via suppressing Hsp70 activity. However, virus-activated ubiquitin ligase E3 mediates Pelo ubiquitinated degradation, synergistically causing Hbs1 degradation. Importantly, Pns11 effectively competes with Pelo for binding to E3, thus antagonizing E3-mediated Pelo-Hbs1 degradation. These processes cause a slight reduction of Pelo-Hbs1 complex in infected testes, promoting effective tubule assembly. Our findings provide insight into how insect sperm-specific Pelo-Hbs1 complex is modulated to promote paternal virus transmission without disrupting sperm function.

Angiotensin-Converting Enzyme 2 Posttranslational Modifications and Implications for Hypertension and SARS-CoV-2: 2023 Lewis K. Dahl Memorial Lecture

ACE2 (angiotensin-converting enzyme 2), a multifunctional transmembrane protein, is well recognized as an important member of the (RAS) renin-angiotensin system with important roles in the regulation of cardiovascular function by opposing the harmful effects of Ang-II (angiotensin II) and AT1R (Ang-II type 1 receptor) activation. More recently, ACE2 was found to be the entry point for the SARS-CoV-2 virus into cells, causing COVID-19. This finding has led to an exponential rise in the number of publications focused on ACE2, albeit these studies often have opposite objectives to the preservation of ACE2 in cardiovascular regulation. However, notwithstanding accumulating data of the role of ACE2 in the generation of angiotensin-(1-7) and SARS-CoV-2 internalization, numerous other putative roles of this enzyme remain less investigated and not yet characterized. Currently, no drug modulating ACE2 function or expression is available in the clinic, and the development of new pharmacological tools should attempt targeting each step of the lifespan of the protein from synthesis to degradation. The present review expands on our presentation during the 2023 Lewis K. Dahl Memorial Lecture Sponsored by the American Heart Association Council on Hypertension. We provide a critical summary of the current knowledge of the mechanisms controlling ACE2 internalization and intracellular trafficking, the mutual regulation with GPCRs (G-protein-coupled receptors) and other proteins, and posttranslational modifications. A major focus is on ubiquitination which has become a critical step in the modulation of ACE2 cellular levels.

LncRNA HOXC-AS3 accelerates malignant proliferation of cervical cancer cells via stabilizing KDM5B

BACKGROUND

Cervical cancer (CC) is a common malignancy amongst women globally. Ubiquitination plays a dual role in the occurrence and development of cancers. This study analyzed the mechanism of long noncoding RNA HOXC cluster antisense RNA 3 (lncRNA HOXC-AS3) in malignant proliferation of CC cells via mediating ubiquitination of lysine demethylase 5B (KDM5B/JARID1B).

METHODS

The expression patterns of lncRNA HOXC-AS3 and KDM5B were measured by real-time quantitative polymerase chain reaction or Western blot analysis. After transfection with lncRNA HOXC-AS3 siRNA and pcDNA3.1-KDM5B, proliferation of CC cells was assessed by the cell counting kit-8, colony formation, and 5-Ethynyl-2'-deoxyuridine staining assays. The xenograft tumor model was established to confirm the impact of lncRNA HOXC-AS3 on CC cell proliferation in vivo by measuring tumor size and weight and the immunohistochemistry assay. The subcellular location of lncRNA HOXC-AS3 and the binding of lncRNA HOXC-AS3 to KDM5B were analyzed. After treatment of lncRNA HOXC-AS3 siRNA or MG132, the protein and ubiquitination levels of KDM5B were determined. Thereafter, the interaction and the subcellular co-location of tripartite motif-containing 37 (TRIM37) and KDM5B were analyzed by the co-immunoprecipitation and immunofluorescence assays.

RESULTS

LncRNA HOXC-AS3 and KDM5B were upregulated in CC tissues and cells. Depletion of lncRNA HOXC-AS3 repressed CC cell proliferation and in vivo tumor growth. Mechanically, lncRNA HOXC-AS3 located in the nucleus directly bound to KDM5B, inhibited TRIM37-mediated ubiquitination of KDM5B, and upregulated the protein levels of KDM5B. KDM5B overexpression attenuated the inhibitory role of silencing lncRNA HOXC-AS3 in CC cell proliferation in vivo and in vitro.

CONCLUSION

Nucleus-located lncRNA HOXC-AS3 facilitated malignant proliferation of CC cells via stabilization of KDM5B protein levels.

SUB1 promotes colorectal cancer metastasis by activating NF-κB signaling via UBR5-mediated ubiquitination of UBXN1

Metastasis accounts for the major cause of colorectal cancer (CRC) related mortality due to the lack of effective treatments. In this study, we integrated the single-cell RNA-seq (scRNA-seq) and bulk RNA-seq data and identified the transcriptional coactivator SUB1 homolog (Sac-Saccharomyces cerevisiae)/PC4 (positive cofactor 4) associated with CRC metastasis. Elevated SUB1 expression was correlated with advanced tumor stage and poor survival in CRC. In vivo and vitro assays showed that SUB1 depletion could inhibit the invasive and metastatic abilities of CRC cells. SUB1 activated NF-κB signaling and its transcriptional target genes CXCL1 and CXCL3 to drive CRC metastasis. Mechanistically, SUB1 integrated with the E3 ubiquitin-protein ligase UBR5 and increased its protein level in CRC cells. Subsequently, the increased UBR5 mainly mediated Lys11-linked polyubiquitination and degradation of NF-κB negative regulator UBXN1, thus to activate the NF-κB signaling. Overall, our study demonstrated that SUB1 promoted CRC progression by modulating UBR5/UBXN1 and activating NF-κB signaling, providing a new therapeutic strategy for treating metastatic CRC through targeting SUB1.

Diagnostic implications of ubiquitination-related gene signatures in Alzheimer's disease

The purpose of this study was to explore the diagnostic implications of ubiquitination-related gene signatures in Alzheimer's disease. In this study, we first collected 161 samples from the GEO database (including 87 in the AD group and 74 in the normal group). Subsequently, through differential expression analysis and the iUUCD 2.0 database, we obtained 3450 Differentially Expressed Genes (DEGs) and 806 Ubiquitin-related genes (UbRGs). After taking the intersection, we obtained 128 UbR-DEGs. Secondly, by conducting GO and KEGG enrichment analysis on these 128 UbR-DEGs, we identified the main molecular functions and biological pathways related to AD. Furthermore, through the utilization of GSEA analysis, we have gained insight into the enrichment of functions and pathways within both the AD and normal groups. Further, using lasso regression analysis and cross-validation techniques, we identified 22 characteristic genes associated with AD. Subsequently, we constructed a logistic regression model and optimized it, resulting in the identification of 6 RUbR-DEGs: KLHL21, WDR82, DTX3L, UBTD2, CISH, and ATXN3L. In addition, the ROC result showed that the diagnostic model we built has excellent accuracy and reliability in identifying AD patients. Finally, we constructed a lncRNA-miRNA-mRNA (competing endogenous RNA, ceRNA) regulatory network for AD based on six RUbR-DEGs, further elucidating the interaction between UbRGs and lncRNA, miRNA. In conclusion, our findings will contribute to further understanding of the molecular pathogenesis of AD and provide a new perspective for AD risk prediction, early diagnosis and targeted therapy in the population.

Hepatitis B virus core protein stabilizes RANGAP1 to upregulate KDM2A and facilitate hepatocarcinogenesis

PURPOSE

As a vital component of the hepatitis B virus (HBV) nucleocapsid, HBV core protein (HBC) contributes to hepatocarcinogenesis. Here, we aimed to assess the effects of RANGAP1 and KDM2A on tumorigenesis induced by HBC.

METHODS

Co-immunoprecipitation (Co-IP) combined with mass spectrometry were utilized to identify the proteins with the capacity to interact with HBC. The gene and protein levels of RANGAP1 and KDM2A in hepatocellular carcinoma (HCC) and HBV-positive HCC tissues were evaluated using different cohorts. The roles of RANGAP1 and KDM2A in HCC cells mediated by HBC were investigated in vitro and in vivo. Co-IP and western blot were used to estimate the interaction of HBC with RANGAP1 and KDM2A and assess RANGAP1 stabilization regulated by HBC.

RESULTS

We discovered that HBC could interact with RANGAP1 and KDM2A, the levels of which were markedly elevated in HCC tissues. Relying on RANGAP1 and KDM2A, HBC facilitated HCC cell growth and migration. The increased stabilization of RANGAP1 mediated by HBC was relevant to the disruption of the interaction between RANGAP1 and an E3 ligase SYVN1. RANGAP1 interacted with KDM2A, and it further promoted KDM2A stabilization by disturbing the interaction between KDM2A and SYVN1. HBC enhanced the interaction of KDM2A with RANGAP1 and upregulated the expression of KDM2A via RANGAP1 in HCC cells.

CONCLUSIONS

These findings demonstrate a novel mechanism by which HBC facilitates hepatocarcinogenesis. RANGAP1 and KDM2A could act as potential molecular targets for treating HBV-associated malignancy.

Membrane-associated RING-CH 7 inhibits stem-like capacities of bladder cancer cells by interacting with nucleotide-binding oligomerization domain containing 1

BACKGROUND

Cancer stem-like capacities are major factors contributing to unfavorable prognosis. However, the associated molecular mechanisms underlying cancer stem-like cells (CSCs) maintain remain unclear. This study aimed to investigate the role of the ubiquitin E3 ligase membrane-associated RING-CH 7 (MARCH7) in bladder cancer cell CSCs.

METHODS

Male BALB/c nude mice aged 4-5 weeks were utilized to generate bladder xenograft model. The expression levels of MARCHs were checked in online databases and our collected bladder tumors by quantitative real-time PCR (q-PCR) and immunohistochemistry (IHC). Next, we evaluated the stem-like capacities of bladder cancer cells with knockdown or overexpression of MARCH7 by assessing their spheroid-forming ability and spheroid size. Additionally, we conducted proliferation, colony formation, and transwell assays to validate the effects of MARCH7 on bladder cancer CSCs. The detailed molecular mechanism of MARCH7/NOD1 was validated by immunoprecipitation, dual luciferase, and in vitro ubiquitination assays. Co-immunoprecipitation experiments revealed that nucleotide-binding oligomerization domain-containing 1 (NOD1) is a substrate of MARCH7.

RESULTS

We found that MARCH7 interacts with NOD1, leading to the ubiquitin-proteasome degradation of NOD1. Furthermore, our data suggest that NOD1 significantly enhances stem-like capacities such as proliferation and invasion abilities. The overexpressed MARCH7 counteracts the effects of NOD1 on bladder cancer CSCs in both in vivo and in vitro models.

CONCLUSION

Our findings indicate that MARCH7 functions as a tumor suppressor and inhibits the stem-like capacities of bladder tumor cells by promoting the ubiquitin-proteasome degradation of NOD1. Targeting the MARCH7/NOD1 pathway could be a promising therapeutic strategy for bladder cancer patients.

E3 ubiquitin ligase rififylin has yin and yang effects on rabbit cardiac transient outward potassium currents (Ito) and corresponding channel proteins

Genome-wide association studies have reported a correlation between a SNP of the RING finger E3 ubiquitin protein ligase rififylin (RFFL) and QT interval variability in humans (Newton-Cheh et al., 2009). Previously, we have shown that RFFL downregulates expression and function of the human-like ether-a-go-go-related gene potassium channel and corresponding rapidly activating delayed rectifier potassium current (IKr) in adult rabbit ventricular cardiomyocytes. Here, we report that RFFL also affects the transient outward current (Ito), but in a peculiar way. RFFL overexpression in adult rabbit ventricular cardiomyocytes significantly decreases the contribution of its fast component (Ito,f) from 35% to 21% and increases the contribution of its slow component (Ito,s) from 65% to 79%. Since Ito,f in rabbits is mainly conducted by Kv4.3, we investigated the effect of RFFL on Kv4.3 expressed in HEK293A cells. We found that RFFL overexpression reduced Kv4.3 expression and corresponding Ito,f in a RING domain-dependent manner in the presence or absence of its accessory subunit Kv channel-interacting protein 2. On the other hand, RFFL overexpression in Kv1.4-expressing HEK cells leads to an increase in both Kv1.4 expression level and Ito,s, similarly in a RING domain-dependent manner. Our physiologically detailed rabbit ventricular myocyte computational model shows that these yin and yang effects of RFFL overexpression on Ito,f, and Ito,s affect phase 1 of the action potential waveform and slightly decrease its duration in addition to suppressing IKr. Thus, RFFL modifies cardiac repolarization reserve via ubiquitination of multiple proteins that differently affect various potassium channels and cardiac action potential duration.

Lysine acetylation of histone acetyltransferase adaptor protein ADA2 is a mechanism of metabolic control of chromatin modification in plants

Histone acetylation is a predominant active chromatin mark deposited by histone acetyltransferases (HATs) that transfer the acetyl group from acetyl coenzyme A (acetyl-CoA) to lysine ε-amino groups in histones. GENERAL CONTROL NON-REPRESSED PROTEIN 5 (GCN5) is one of the best-characterized HATs and functions in association with several adaptor proteins such as ADA2 within multiprotein HAT complexes. ADA2-GCN5 interaction increases GCN5 binding to acetyl-CoA and stimulates its HAT activity. It remains unclear whether the HAT activity of GCN5 (which acetylates not only histones but also cellular proteins) is regulated by acetyl-CoA levels, which vary greatly in cells under different metabolic and nutrition conditions. Here we show that the ADA2 protein itself is acetylated by GCN5 in rice cells. Lysine acetylation exposes ADA2 to a specific E3 ubiquitin ligase and reduces its protein stability. In rice plants, ADA2 protein accumulation reversely parallels its lysine acetylation and acetyl-CoA levels, both of which are dynamically regulated under varying growth conditions. Stress-induced ADA2 accumulation could stimulate GCN5 HAT activity to compensate for the reduced acetyl-CoA levels for histone acetylation. These results indicate that ADA2 lysine acetylation that senses cellular acetyl-CoA variations is a mechanism to regulate HAT activity and histone acetylation homeostasis in plants under changing environments.

METTL3-mediated m6A modification of lncRNA TSPAN12 promotes metastasis of hepatocellular carcinoma through SENP1-depentent deSUMOylation of EIF3I

In a previous study, we discovered that the level of lnc-TSPAN12 was significantly elevated in hepatocellular carcinoma (HCC) and correlated with a low survival rate. However, the function and mechanism of lnc-TSPAN12 in modulating epithelial-mesenchymal transition (EMT) and metastasis in HCC remains poorly understood. This study demonstrates that lnc-TSPAN12 positively influences migration, invasion, and EMT of HCC cells in vitro and promotes hepatic metastasis in vivo. The modification of N6-methyladenosine, driven by METTL3, is essential for the stability of lnc-TSPAN12, which may partially contribute to the upregulation of lnc-TSPAN12. Mechanistically, lnc-TSPAN12 exhibits direct interactions with EIF3I and SENP1, acting as a scaffold to enhance the SENP1-EIF3I interaction. As a result, the SUMOylation of EIF3I is inhibited, preventing its ubiquitin-mediated degradation. Ultimately, this activates the Wnt/β-catenin signaling pathway, stimulating EMT and metastasis in HCC. Our findings shed light on the regulatory mechanism of lnc-TSPAN12 in HCC metastasis and identify the lnc-TSPAN12-EIF3I/SENP1 axis as a novel therapeutic target for HCC.

HRD1-induced TMEM2 ubiquitination promotes ER stress-mediated apoptosis through a non-canonical pathway in intestinal ischemia/reperfusion

Intestinal ischemia/reperfusion (I/R) injury is a typical pathological course in the clinic with a high morbidity rate. Recent research has pointed out the critical role of ubiquitination during the occurrence and development of intestinal I/R by precisely mediating protein quality control and function. Here, we conducted an integrated multiomic analysis to identify critical ubiquitination-associated molecules in intestinal I/R and identified endoplasmic reticulum-located HRD1 as a candidate molecule. During intestinal I/R, excessive ER stress plays a central role by causing apoptotic pathway activation. In particular, we found that ER stress-mediated apoptosis was mitigated by HRD1 knockdown in intestinal I/R mice. Mechanistically, TMEM2 was identified as a new substrate of HRD1 in intestinal I/R by mass spectrometry analysis, which has a crucial role in attenuating apoptosis and promoting non-canonical ER stress resistance. A strong negative correlation was found between the protein levels of HRD1 and TMEM2 in human intestinal ischemia samples. Specifically, HRD1 interacted with the lysine 42 residue of TMEM2 and reduced its stabilization by K48-linked polyubiquitination. Furthermore, KEGG pathway analysis revealed that TMEM2 regulated ER stress-mediated apoptosis in association with the PI3k/Akt signaling pathway rather than canonical ER stress pathways. In summary, HRD1 regulates ER stress-mediated apoptosis through a non-canonical pathway by ubiquitinating TMEM2 and inhibiting PI3k/Akt activation during intestinal I/R. The current study shows that HRD1 is an intestinal I/R critical regulator and that targeting the HRD1/TMEM2 axis may be a promising therapeutic approach.

MARCH5-mediated downregulation of ACC2 promotes fatty acid oxidation and tumor progression in ovarian cancer

Lipid metabolic reprogramming has been recognized as a hallmark of human cancer. Acetyl-CoA Carboxylases (ACCs) are key rate-limiting enzymes involved in fatty acid metabolism regulation by catalyzing the carboxylation of acetyl-CoA to malonyl-CoA. Previously, most studies focused on the role of ACC1 in fatty acid metabolism in cancer, while the function of ACC2 remains largely uncharacterized in human cancers, especially in ovarian cancer (OC). Here, we show that ACC2 was significantly downregulated in cancerous tissue of OC, and the downregulation of ACC2 is closely associated with lager tumor size, metastases and worse prognosis in OC patients. Downregulation of ACC2 promoted proliferation and metastasis of OC both in vitro and in vivo by enhancing FAO. Notably, mitochondria-associated ubiquitin ligase (MARCH5) was identified to interact with and downregulate ACC2 by ubiquitination and degradation in OC. Moreover, ACC2 downregulation-enhanced FAO contributed to the progression of OC promoted by MARCH5. In conclusion, our findings demonstrate that MARCH5-mediated downregulation of ACC2 promotes FAO and tumorigenesis in OC, suggesting MARCH5-ACC2 axis as a potent candidate for the treatment and prevention of OC.

BCLAF1 binds SPOP to stabilize PD-L1 and promotes the development and immune escape of hepatocellular carcinoma

Interaction between programmed death-1 (PD-1) ligand 1 (PD-L1) on tumor cells and PD-1 on T cells allows tumor cells to evade T cell-mediated immune surveillance. Strategies targeting PD-1/PD-L1 have shown clinical benefits in a variety of cancers. However, limited response rates in hepatocellular carcinoma (HCC) have prompted us to investigate the molecular regulation of PD-L1. Here, we identify B cell lymphoma-2-associated transcription factor 1 (BCLAF1) as a key PD-L1 regulator in HCC. Specifically, BCLAF1 interacts with SPOP, an E3 ligase that mediates the ubiquitination and degradation of PD-L1, thereby competitively inhibiting SPOP-PD-L1 interaction and subsequent ubiquitination and degradation of PD-L1. Furthermore, we determined an SPOP-binding consensus (SBC) motif mediating the BCLAF1-SPOP interaction on BCLAF1 protein and mutation of BCLAF1-SBC motif disrupts the regulation of the SPOP-PD-L1 axis. In addition, BCLAF1 expression was positively correlated with PD-L1 expression and negatively correlated with biomarkers of T cell activation, including CD3 and CD8, as well as with the level of immune cell infiltration in HCC tissues. Besides, BCLAF1 depletion leads to a significant reduction of PD-L1 expression in vitro, and this reduction of PD-L1 promoted T cell-mediated cytotoxicity. Notably, overexpression of BCLAF1 sensitized tumor cells to checkpoint therapy in an in vitro HCC cells-Jurkat cells co-culture model, whereas BCLAF1-SBC mutant decreased tumor cell sensitivity to checkpoint therapy, suggesting that BCLAF1 and its SBC motif serve as a novel therapeutic target for enhancing anti-tumor immunity in HCC.

SRSF1 inhibits ferroptosis and reduces cisplatin chemosensitivity of triple-negative breast cancer cells through the circSEPT9/GCH1 axis

Cisplatin (DDP) is a commonly used chemotherapeutic agent for triple negative breast cancer (TNBC), but its efficacy can be limited by chemoresistance. This study aimed to explore the functional mechanism of SR-rich splicing factor 1 (SRSF1) in DDP chemosensitivity of TNBC cells. Levels of SRSF1, circular RNA septin 9 (circSEPT9), and GTP cyclohydrolase-1 (GCH1) in TNBC cells, DDP-resistant cells, and normal cells were determined. Cell viability, half-maximal inhibitory concentration (IC50) value, and proliferation were evaluated. Ferroptosis was determined by assay kits (ferric ion/ROS/MDA/GSH) and Western blot assay (SLC7A11/ACSL4). The genetic binding was analyzed by RNA immunoprecipitation and RNA pull-down assays. SRSF1, circSEPT9, and GCH1 were upregulated in TNBC cells. SRSF1 downregulation reduced IC50 to DDP of parent and drug-resistant TNBC cells and inhibited cell viability and proliferation, meanwhile, the downregulation reduced GSH/SLC7A11 levels while elevated ferric ion/ROS/MDA/ACSL4 levels, promoting ferroptosis. SRSF1 bound to and upregulated circSEPT9 and circSEPT9 blocked the ubiquitination of GCH1, thereby increasing GCH1 protein level. Overexpression of circSEPT9 and GCH1 attenuated the DDP chemosensitivity of TNBC cells by inhibiting ferroptosis. This study is the first to report the role of SRSF1 inhibitors combined with chemotherapy in TNBC, which provides a promising strategy for the treatment of TNBC. SIGNIFICANCE: Cisplatin (DDP) is a commonly used chemotherapeutic agent for triple negative breast cancer (TNBC), but its efficacy can be limited by chemoresistance. This study aimed to unravel the molecular mechanism of SR-rich splicing factor 1 (SRSF1) in DDP chemosensitivity of TNBC cells.

METTL3 regulates TFRC ubiquitination and ferroptosis through stabilizing NEDD4L mRNA to impact stroke

BACKGROUND

Stroke is a major medical problem, and novel therapeutic targets are urgently needed. This study investigates the protective role and potential mechanisms of the N6-methyladenosine (m6A) RNA methyltransferase METTL3 against cerebral injury resulting from insufficient cerebral blood flow.

METHODS

In this study, we constructed mouse MCAO models and HT-22 cell OGD/R models to mimic ischemic stroke-induced brain injury and neuronal damage. We generated NEDD4L knockout and METTL3 overexpression models and validated therapeutic effects using infarct volume, brain edema, and neurologic scoring. We performed qRT-PCR, western blotting, and co-immunoprecipitation to assess the influence of NEDD4L on ferroptosis markers and TFRC expression. We verified the effect of NEDD4L on TFRC ubiquitination by detecting half-life and ubiquitination. Finally, we validated the impact of METTL3 on NEDD4L mRNA stability and MCAO outcomes in both in vitro and in vivo experimental models.

RESULT

We find NEDD4L expression is downregulated in MCAO models. Overexpressing METTL3 inhibits the iron carrier protein TFRC by upregulating the E3 ubiquitin ligase NEDD4L, thereby alleviating oxidative damage and ferroptosis to protect the brain from ischemic injury. Mechanistic studies show METTL3 can methylate and stabilize NEDD4L mRNA, enhancing NEDD4L expression. As a downstream effector, NEDD4L ubiquitinates and degrades TFRC, reducing iron accumulation and neuronal ferroptosis.

CONCLUSION

In summary, we uncover the METTL3-NEDD4L-TFRC axis is critical for inhibiting post-ischemic brain injury. Enhancing this pathway may serve as an effective strategy for stroke therapy. This study lays the theoretical foundation for developing m6A-related therapies against ischemic brain damage.

Quercetin-induced degradation of RhoC suppresses hepatocellular carcinoma invasion and metastasis

BACKGROUND

Tumor metastasis and recurrence are major causes of mortality in patients with hepatocellular carcinoma (HCC) that is still lack of effective therapeutic targets and drugs. Previous reports implied that ras homolog family member C (RhoC) plays a toxic role on metastasis and proliferation of cancer.

METHODS

In this research, the correlation between RhoC and metastasis ability was confirmed by in vitro experiments and TCGA database. We explored whether quercetin could inhibit cell migration or invasion by transwell assay. Real-time PCR, overexpression and ubiquitination assay, etc. were applied in mechanism study. Primary HCC cells and animal models including patient-derived xenografts (PDXs) were employed to evaluate the anti-metastasis effects of quercetin.

RESULTS

Clinical relevance and in vitro experiments further confirmed the level of RhoC was positively correlated with invasion and metastasis ability of HCC. Then we uncovered that quercetin could attenuate invasion and metastasis of HCC by downregulating RhoC's level in vitro, in vivo and PDXs. Furthermore, mechanistic investigations displayed quercetin hindered the E3 ligase expression of SMAD specific E3 ubiquitin protein ligase 2 (SMURF2) leading to enhancement of RhoC's ubiquitination and proteasomal degradation.

CONCLUSIONS

Our research has revealed the novel mechanisms quercetin regulates degradation of RhoC level by targeting SMURF2 and identified quercetin may be a potential compound for HCC therapy.

Systematic pan-cancer analysis of RNF186 with potential implications in progression and prognosis in human cancer

AIMS

Cancer remains a significant global public health issue. There is growing proof that Ring Finger Protein 186 (RNF186) may play a function in pan-cancer, however, this has not yet been thoroughly determined. This study aims to analyze RNF186 with potential implications in progression and prognosis in human cancer.

MATERIALS AND METHODS

A comprehensive bioinformatics approaches combined with experimental verification were used across 33 types of cancers in this study to conduct a pan-cancer investigation of RNF186 from the perspectives of gene expression, prognosis, genomic alterations, immunological markers, gene set, and function.

KEY FINDINGS

RNF186 is a valuable prognostic biomarker in several cancer types, especially breast invasive carcinoma (BRCA) and uterine corpus endometrial carcinoma (UCEC). The levels of RNF186 promoter methylation and genetic alterations may be responsible for some cancers' abnormal expression. Furthermore, RNF186 expression was determined to be associated with immune checkpoint genes. Analysis of RNF186-related genes revealed that proteasome and PI3K-AKT signaling pathway were primarily involved in the cellular function of RNF186. Additionally, our research first confirmed that RNF186 may function as an oncogene and contribute to cancer proliferation, migration and invasion in UCEC. In contrast, RNF186 may play an inhibitory role in BRCA progression. This function depends on the ligase activity of RNF186.

SIGNIFICANCE

This study suggests that RNF186 is a novel critical target for tumor progression in BRCA and UCEC. It reveals that RNF186 may be associated with tumor immunotherapy, which may provide an effective predictive evaluation of the prognosis of immunotherapy.

The long noncoding RNA HNF1A-AS1 with dual functions in the regulation of cytochrome P450 3A4

Cytochrome P450 3A4 (CYP3A4) is the most important and abundant drug-metabolizing enzyme in the human liver. Inter-individual differences in the expression and activity of CYP3A4 affect clinical and precision medicine. Increasing evidence indicates that long noncoding RNAs (lncRNAs) play crucial roles in the regulation of CYP3A4 expression. Here, we showed that lncRNA hepatocyte nuclear factor 1 alpha-antisense 1 (HNF1A-AS1) exerted dual functions in regulating CYP3A4 expression in Huh7 and HepG2 cells. Mechanistically, HNF1A-AS1 served as an RNA scaffold to interact with both protein arginine methyltransferase 1 and pregnane X receptor (PXR), thereby facilitating their protein interactions and resulting in the transactivation of PXR and transcriptional alteration of CYP3A4 via histone modifications. Furthermore, HNF1A-AS1 bound to the HNF1A protein, a liver-specific transcription factor, thereby blocking its interaction with the E3 ubiquitin ligase tripartite motif containing 25, ultimately preventing HNF1A ubiquitination and protein degradation, further regulating the expression of CYP3A4. In summary, these results reveal the novel functions of HNF1A-AS1 as the transcriptional and post-translational regulator of CYP3A4; thus, HNF1A-AS1 may serve as a new indicator for establishing or predicting individual differences in CYP3A4 expression.

DCAF13 inhibits the p53 signaling pathway by promoting p53 ubiquitination modification in lung adenocarcinoma

BACKGROUND

Lung cancer is a malignant tumor with the highest mortality worldwide. Abnormalities in the ubiquitin proteasome system are considered to be contributed to lung cancer progression with deleterious effects. DDB1 and CUL4 associated factor 13 (DCAF13) is a substrate receptor of the E3 ubiquitin ligase CRL4, but its role in lung cancer remains unknown. In this study, we aimed to investigate the regulatory mechanisms of DCAF13 in lung adenocarcinoma (LUAD).

METHODS

So as to investigate the effect of DCAF13 on lung adenocarcinoma cell function using in vivo and in vitro. Mechanistically, we have identified the downstream targets of DCAF13 by using RNA-sequencing, as well as ubiquitination assays, co-immunoprecipitation, immunofluorescence, immunohistochemistry and chromatin immunoprecipitation - qPCR experiments.

RESULTS

Our findings reveal that DCAF13 is a carcinogenic factor in LUAD, as it is highly expressed and negatively correlated with clinical outcomes in LUAD patients. Through RNA-sequencing, it has been shown that DCAF13 negatively regulates the p53 signaling pathway and inhibits p53 downstream targets including p21, BAX, FAS, and PIDD1. We also demonstrate that DCAF13 can bind to p53 protein, leading to K48-linked ubiquitination and degradation of p53. Functionally, we have shown that DCAF13 knockdown inhibits cell proliferation and migration. Our results highlight the significant role of DCAF13 in promoting LUAD progression by inhibiting p53 protein stabilization and the p53 signaling pathway. Furthermore, our findings suggest that high DCAF13 expression is a poor prognostic indicator in LUAD, and DCAF13 may be a potential therapeutic target for treating with this aggressive cancer.

CONCLUSIONS

The DCAF13 as a novel negative regulator of p53 to promote LUAD progression via facilitating p53 ubiquitination and degradation, suggesting that DCAF13 might be a novel biomarker and therapeutical target for LUAD.

Neuronal-specific TNFAIP1 ablation attenuates postoperative cognitive dysfunction via targeting SNAP25 for K48-linked ubiquitination

BACKGROUND

Synaptosomal-associated protein 25 (SNAP25) exerts protective effects against postoperative cognitive dysfunction (POCD) by promoting PTEN-induced kinase 1 (PINK1)/Parkin-mediated mitophagy and repressing caspase-3/gasdermin E (GSDME)-mediated pyroptosis. However, the regulatory mechanisms of SNAP25 protein remain unclear.

METHODS

We employed recombinant adeno-associated virus 9 (AAV9)-hSyn to knockdown tumor necrosis factor α-induced protein 1 (TNFAIP1) or SNAP25 and investigate the role of TNFAIP1 in POCD. Cognitive performance, hippocampal injury, mitophagy, and pyroptosis were assessed. Co-immunoprecipitation (co-IP) and ubiquitination assays were conducted to elucidate the mechanisms by which TNFAIP1 stabilizes SNAP25.

RESULTS

Our results demonstrated that the ubiquitin ligase TNFAIP1 was upregulated in the hippocampus of mice following isoflurane (Iso) anesthesia and laparotomy. The N-terminal region (residues 1-96) of TNFAIP1 formed a conjugate with SNAP25, leading to lysine (K) 48-linked polyubiquitination of SNAP25 at K69. Silencing TNFAIP1 enhanced SH-SY5Y cell viability and conferred antioxidant, pro-mitophagy, and anti-pyroptosis properties in response to Iso and lipopolysaccharide (LPS) challenges. Conversely, TNFAIP1 overexpression reduced HT22 cell viability, increased reactive oxygen species (ROS) accumulation, impaired PINK1/Parkin-dependent mitophagy, and induced caspase-3/GSDME-dependent pyroptosis by suppressing SNAP25 expression. Neuron-specific knockdown of TNFAIP1 ameliorated POCD, restored mitophagy, and reduced pyroptosis, which was reversed by SNAP25 depletion.

CONCLUSIONS

In summary, our findings demonstrated that inhibiting TNFAIP1-mediated degradation of SNAP25 might be a promising therapeutic approach for mitigating postoperative cognitive decline. Video Abstract.

TRIM69 suppressed the anoikis resistance and metastasis of gastric cancer through ubiquitin‒proteasome-mediated degradation of PRKCD

The tripartite motif (TRIM) protein family has been investigated in multiple human cancers, including gastric cancer (GC). However, the role of TRIM69 in the anoikis resistance and metastasis of GC cells remains to be elucidated. We identified the differentially expressed genes in anoikis-resistant GC cells using RNA-sequencing analysis. The interaction between TRIM69 and PRKCD was analyzed by coimmunoprecipitation and mass spectrometry. Our results have shown that TRIM69 was significantly downregulated in anoikis-resistant GC cells. TRIM69 overexpression markedly suppressed the anoikis resistance and metastasis of GC cells in vitro and in vivo. TRIM69 knockdown had the opposite effects. Mechanistically, TRIM69 interacted with PRKCD through its B-box domain and catalyzed the K48-linked polyubiquitination of PRKCD. Moreover, TRIM69 inhibited BDNF production in a PRKCD-dependent manner. Importantly, overexpression of PRKCD or BDNF blocked the effects of TRIM69 on the anoikis resistance and metastasis of GC cells. Interestingly, a TRIM69-PRKCD+BDNF+ cell subset was positively associated with metastasis in GC patients. TRIM69-mediated suppression of the anoikis resistance and metastasis of GC cells via modulation of the PRKCD/BDNF axis, with potential implications for novel therapeutic approaches for metastatic GC.

Spatial Mechano-Signaling Regulation of GTPases through Non-Degradative Ubiquitination

Blood flow produces shear stress exerted on the endothelial layer of the vessels. Spatial characterization of the endothelial proteome is required to uncover the mechanisms of endothelial activation by shear stress, as blood flow varies in the vasculature. An integrative ubiquitinome and proteome analysis of shear-stressed endothelial cells demonstrated that the non-degradative ubiquitination of several GTPases is regulated by mechano-signaling. Spatial analysis reveals increased ubiquitination of the small GTPase RAP1 in the descending aorta, a region exposed to laminar shear stress. The ubiquitin ligase WWP2 is identified as a novel regulator of RAP1 ubiquitination during shear stress response. Non-degradative ubiquitination fine-tunes the function of GTPases by modifying their interacting network. Specifically, WWP2-mediated RAP1 ubiquitination at lysine 31 switches the balance from the RAP1/ Talin 1 (TLN1) toward RAP1/ Afadin (AFDN) or RAP1/ RAS Interacting Protein 1 (RASIP1) complex formation, which is essential to suppress shear stress-induced reactive oxygen species (ROS) production and maintain endothelial barrier integrity. Increased ROS production in endothelial cells in the descending aorta of endothelial-specific Wwp2-knockout mice leads to increased levels of oxidized lipids and inflammation. These results highlight the importance of the spatially regulated non-degradative ubiquitination of GTPases in endothelial mechano-activation.