Biology subjects

Kessler, B. M.

Publications and source records attributed to Kessler, B. M..

At least 19 recordsLinked to original sources

bioRxiv2026

N-terminal truncation diversifies USP18 function during early myogenesis

Ubiquitin-specific protease 18 (USP18) is primarily studied for its dual role in type-I interferon (IFN-I) signaling. At basal levels, however, USP18 also regulates muscle cell development, independently of IFN-I signaling. USP18 exists as a canonical long isoform (LF) and a short isoform (SF) generated by N-terminal truncation. Endogenous SF accumulates in the nucleus during muscle differentiation, but its cellular functions remain poorly understood. Here, we compared USP18 SF and LF in muscle cells stably overexpressing each isoform. We show that their distinct N-termini are associated with marked differences in protein stability, subcellular localization, and protein-protein interactions. SF displayed a substantially expanded interactome, with increased association with nuclear proteins, chaperones, and regulators of protein homeostasis. Functionally, SF enhanced an early stage of myogenic differentiation and was associated with changes in alternative splicing, including key sarcomere genes. Together, these findings identify the SF USP18 proteoform as a potential regulator of muscle differentiation and highlight the N-terminus as a determinant of non-canonical USP18 functions and proteoform diversity.

cell biology↗

bioRxiv2026

Spatial Tumour Tissue Distribution Dynamics of a Bicycle Peptide-MMAE Toxin Conjugate Profiled by Targeted Mass Spectrometry

A highly specific-NECTIN-4 binding bicyclic peptide covalently linked to the cytotoxin monomethyl auristatin E (MMAE) via a valine-citrulline cleavable linker (zelenectide pevedotin, BT8009) is a promising modality to treat cancer patients with solid tumours. Although the pharmacokinetics and biodistribution of zelenectide pevedotin have been well characterised, a more precise view of tumour delivery and intra-tumoural distribution of its released payload is lacking. To address this, we have developed an approach to profile the spatial tumour and healthy tissue distribution of this anti-cancer agent using laser capture microdissection coupled to targeted liquid chromatography parallel reaction monitoring (LCM-LC-PRM) mass spectrometry. This LCM-assisted spatial pharmacology workflow enables the precise isolation of specific tissue regions, followed by high-resolution analysis of MMAE distribution at sub-tissue-specific levels. By identifying and optimising MS/MS-specific fragmentation ions for accurate and sensitive detection and quantitation of MMAE released from zelenectide pevedotin within tumour tissues, we observed progressive accumulation and sustained retention of MMAE in mouse tumour tissues over a period of 24 h. Conversely, in plasma, liver and muscle tissues, MMAE levels generally declined following early exposure, although inter-animal variability was observed. LCM-based intra-tumour spatial profiling revealed heterogeneous MMAE distribution between tumour cell-rich and stroma-rich regions, with distinct temporal patterns across compartments. Together, our spatial targeted MS method provided valuable insights into zelenectide pevedotin's payload distribution dynamics in vivo, thereby enhancing our understanding of its therapeutic potential and guiding the development of next-generation Bicycle Drug Conjugate (BDC).

cancer biology↗

bioRxiv2026

Refined USP25/28 inhibitors with improved selectivity towards c-Myc driven squamous lung cancer cells

The ubiquitin specific protease 28 (USP28) is implicated in tumorigenesis by controlling the turnover of substrates including the oncogene c-MYC and the ubiquitin ligase FBW7. Here, we describe small molecule inhibitors of USP25 and USP28, leading to cancer cell cycle arrest and death. However, genetic deletion of USP25/28 does not replicate this effect. An integrated -omics approach revealed off-target effects for thienopyridine and thienopyrazine carboxamide compounds in protein translation. Chemoproteomics and biochemical analyses suggested binding of such compounds to a region near the ribosome complex polypeptide exit tunnel. Structural analysis of a USP28-inhibitor complex enabled the design of modified USP25/28 inhibitor molecules which minimized translation-related off-target effects. In distinction to earlier compounds, the optimized inhibitors were non-toxic to breast cancer cells yet retained potent anti-proliferative activity in squamous lung carcinoma cells, where USP28 is associated with disease progression. Together, our results demonstrate that refined USP25/28 inhibitors can selectively suppress tumor growth by targeting c-MYC driven pathways, offering a more precise therapeutic strategy for treating squamous lung cancers whilst minimizing undesired cytotoxicity.

cancer biology↗

bioRxiv2026

Time resolved proteomic analysis of hepatitis B virus infection

Hepatitis B virus (HBV) infection can result in progressive inflammatory liver diseases that are associated with the development of hepatocellular carcinoma. Our understanding of the HBV infection proteome is limited, and we used label-free quantitative (LFQ) proteomics to address this gap in knowledge. Kinetic sampling of mock and HBV infected human hepatoma HepG2 cells showed a time-dependent expression of the viral core (C) and Surface (S) proteins. Concomitantly, we observed altered host cell proteome dynamics, including cytoskeletal proteins, collagens, fibrinogen subunits, extracellular matrix receptor interaction and focal adhesion pathways, as well as an elevated abundance of complement proteins. Specifically, we noted evidence for elevated C5 complement protein abundance in the HBV infected cells, highlighting selective complement adaptations during infection.

microbiology↗

bioRxiv2026

Menin maintains enhancer-promoter interactions in a leukemia-specific manner

Inhibition of the protein-protein interaction between Mixed Lineage Leukemia (MLL) and Menin is a promising therapy for both high-risk MLL-rearranged and NPM1-mutant (NPM1c) acute leukemias, yet the mechanistic basis of this dependency in distinct contexts remains unclear. By comparing the transcriptional responses of MLL::AF4 and NPM1c leukemia models to Menin inhibition, we find broad, acute transcriptional dysregulation in MLL::AF4 cells, but minor transcriptional consequences in NPM1c cells, despite similarities in Menin promoter occupancy. Using high-resolution Micro Capture-C, we discover that Menin drives enhancer activity and maintains enhancer-promoter contacts in MLL::AF4 cells but not in NPM1c cells. Crucially, Menin is also essential for patient-specific enhancer function in primary MLL-rearranged leukemia samples. Proteomic analysis further demonstrates that Menin associates with distinct transcriptional and elongation complexes in MLL::AF4 compared to NPM1c cells, supporting a context-dependent mechanism of action. Together, these findings establish that Menin is not a uniform transcriptional cofactor, but a context-dependent regulator of enhancer connectivity, and identifies enhancer-promoter architecture as a selective vulnerability in MLL-rearranged leukemia.

cancer biology↗

bioRxiv2026

Urine Recirculation During Normothermic Kidney Preservation Improves Energy Balance Involving the Urea and TCA Cycles

BackgroundDeceased donor kidneys experience cellular stress before undergoing transplantation. To alleviate this, preservation techniques were developed including normothermic machine perfusion (NMP). MethodsHere, we performed kidney NMP on discarded human kidneys for up to 24 hours. Volume management was regulated either by urine recirculation (UR) or urine replacement (NUR) with Ringers lactate. Notably, UR led to longer perfusion times compared to NUR. To investigate kidney NMP metabolic traits with or without UR over time, we performed longitudinal metabolomics analyses of perfusates of eight NMP kidneys by 2D-gas chromatography mass spectrometry (GCxGC-MS). ResultsOver 600 metabolic features were profiled, from which 74 were identified and 54 consistently quantified across 26 perfusate samples. Most notably, elevated levels of disaccharides (different isomers), hydroxy-purines, urea, glutamate and amino acids associated with the perfusion factor UR. Moreover, donor estimated glomerular filtration rate (eGFR) correlated significantly with the accumulation of lactate and gluconate. Most strikingly, lactate levels seemed to be more balanced in UR NMP perfusate, which otherwise accumulated rapidly within the first six hours. ConclusionsKidney preservation by NMP was previously limited to hours. UR-NMP affected kidney energy homeostasis, carbohydrate & purine metabolism and the Urea and TCA cycles. These insights add value to explain how urine-driven adaptations contribute to prolonged kidney function under NMP. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSDeceased donors provide kidneys that experience cellular stress during retrieval and during transplantation. To attenuate tissue damage, preservation techniques were optimised to offer the most optimal environment for kidney organs retrieved from donation after circulatory death and brain death patients. Normothermic machine perfusion (NMP) of donor kidneys has been considered feasible, safe, offers viability assessment and contributes to favourable outcomes. However, there has been a limit in the length of time that this preservation method could be applied to kidney organs, thereby potentially restricting functional recovery of the kidney before organ transplantation. Added value of this studyBefore urine recirculation (UR) was introduced, NMP time was limited to a few hours. Remarkably, NMP with UR led to longer perfusion times and more stable kidney organ function as compared to no urine recirculation (NUR). In order to find out why, we compared urine recirculation with Ringers lactate solution for volume management during NMP on discarded human kidneys for up to 24 hours. Kidney NMP metabolic traits with or without UR over time were measured. More than 600 metabolic features were profiled, Most strikingly, lactate levels seemed to be more balanced in UR NMP perfusate of the course of 24 hours, which otherwise accumulated rapidly within the first six hours. Taken together, UR-NMP affected kidney energy metabolic pathways and rendering these more balanced. Ultimately, these urine-driven adaptations contribute to prolonged kidney function under NMP. Implications of all the available evidenceNMP as a procedure to preserve kidney organs including urine recirculation is now becoming standard in many transplantation units around the world. Our study provided a molecular snapshot of why kidney organs preserved in this way are maintained longer with a functionally active metabolism. This provides the basis for additional improvements leading to better kidney organ preservation, ultimately resulting in benefits for kidney transplant recipients.

pathology↗

bioRxiv2025

obABPP-HT*: A Precision-Engineered Activity Proteomics Pipeline for the Streamlined Discovery of Deubiquitinase Inhibitors

Deubiquitinases (DUBs), and the dysregulation thereof, are implicated in human disease. The recent inclusion of selective DUB inhibitors in clinical trials has heightened interest in DUB-focused drug discovery. Current DUB screening methods remain constrained, however, as they often rely on recombinant proteins that are truncated or derived from non-human sources, typically necessitating extensive optimisation of initial hits. We introduce a high-throughput, endogenous human DUB-focused activity proteomics workflow designed for the simultaneous screening and profiling of small, targeted libraries of catalytic group-reactive compounds. In a proof-of-concept screen, this innovative platform expanded the repertoire of electrophilic groups targeting DUBs, leading to the discovery of potent and selective inhibitors for USP47, OTUD7B, and USP5. Remarkably, these inhibitors required minimal or no optimisation to confirm the previously reported biological roles of the three DUBs, underscoring the advantages of this methodology for drug discovery applications.

biochemistry↗

bioRxiv2025

Pervasive phenotypic effects of Fbxo42 controlled by regulation of PP4 phosphatase

F-box proteins are the substrate recognition modules of the SCF (SKP1-Cullin- F-box) E3 ubiquitin ligase complex. FBXO42, an understudied member of this family, has recently emerged as a modulator of key cellular processes, including cell cycle progression, DNA damage response and glioma stem cell survival. In this study, we define the function of FBXO42 as a major regulator of the protein phosphatase PP4. Phosphoprotein phosphatases (PPPs) have a broad array of substrates, hence necessitating tight regulation. We observe that FBXO42 ubiquitinates the PP4 complex to govern the assembly of regulatory and catalytic subunits with the net effect of restraining the latters phosphatase activity. FBXO42 depletion unleashes PP4 activity with broad cellular effects highlighting FBXO42 as a novel regulatory node in ubiquitin-mediated signalling for future therapeutic exploitation. Impact StatementFBXO42 is a major regulator of PP4 phosphatase impacting multiple cellular phenotypes.

biochemistry↗

bioRxiv2025

Huib32: A Potent and Selective USP32 Inhibitor Modulating Endosomal Processes and Advancing Cell-Permeable USP32 Probes

Deubiquitinating enzymes (DUBs) are pivotal regulators of ubiquitination, a vital post-translational modification essential for cellular processes. Dysregulated DUB activity disrupts cellular homeostasis, driving diseases like cancer and neurodegeneration. Ubiquitin-specific protease 32 (USP32) has emerged as a promising therapeutic target due to its role in endosomal and autophagosomal dynamics and its association with breast, ovarian, and lung cancers. Here, we describe Huib32 (Human deUbiquitinase Inhibitor 32) as a USP32 inhibitor. Cyanimide-containing Huib32 potently and selectively inhibits USP32 by covalently binding to the active site Cys743 in vitro and in cells, enhancing substrate ubiquitination, altering endosomal morphology, and mimicking USP32 depletion. Additionally, we present two activity-based probes (ABPs), Huib32*1 and Huib32*2, which enable precise detection of USP32 activity and confirm probe selectivity via mass spectrometry. Together, Huib32 and its probes represent a unique approach for targeting USP32, offering new research tools and potential therapeutic avenues for cancer and disorders involving endocytic trafficking.

biochemistry↗

bioRxiv2025

The ubiquitin E3 ligase Huwe1 facilitates viral and self RNA sensing by RIG-I-like receptors

RIG-I-like receptors (RLRs) are cytoplasmic RNA sensors that promote type I and type III interferon (IFN) production in response to RNA ligands of viral or endogenous origin. The RLR pathway is tightly regulated by dynamic post-translational modifications, including ubiquitination. Huwe1 is a HECT domain-containing giant ubiquitin E3 ligase that has not been implicated in the RLR or IFN pathway. Here, we investigated whether Huwe1 is required for type I IFN induction downstream of RLRs. We demonstrate that loss of Huwe1 severely attenuates the expression of IFN-{beta}, IFN-{lambda}1 and IFN-stimulated genes (ISGs) in ADAR1-deficient human cells and primary murine bone-marrow derived macrophages, in which unedited self RNAs that serve as RLR ligands accumulate. In addition, depletion of Huwe1 reduces the induction of type I and III IFNs upon transfection with synthetic viral RNA mimetics or infection with a picornavirus. Using proteomics, we identified several putative Huwe1 substrates, which include key components of the RLR pathway (MAVS, TRAFs). We demonstrate that these substrates interact with Huwe1 and that Huwe1 is essential for the activity of TRAF5 in type I IFN induction. Collectively, our results put Huwe1 on the map as an important ubiquitin E3 ligase in the RLR pathway and provide new insights into ubiquitin-dependent regulation of cell-intrinsic antiviral immune pathways.

immunology↗

bioRxiv2025

Bisphosphonates Trigger Anti-Ageing Effects Across Multiple Cell Types and Protect Against Senescence

Bisphosphonates (BPs) have been the major class of medicines used to treat disorders of excessive bone loss for over five decades. Recently it has been recognized that BPs may also have additional significant beneficial extra-skeletal effects. These include a reduction of all-cause mortality and of conditions commonly linked to ageing, such as cancer and cardiovascular disease. Here we show that bisphosphonates co-localize with lysosomal and endosomal organelles in non-skeletal cells and stimulate cell growth at low doses. In vivo spatial transcriptomic analysis revealed differentially expressed senescence markers in multiple organs of aged BP-treated mice, and a shift in cellular composition toward those of young counterparts. Similarly, a 5000-plex plasma proteome analysis from osteopenic patients before and after BP-treatment showed significant alterations in [~]400 proteins including GTPase regulators and markers of senescence, autophagy, apoptosis, and inflammatory responses. Furthermore, treatment with BPs protected against the onset of senescence in vitro. Proteome-wide target deconvolution using 2D thermal profiling revealed novel BP-binding targets (PHB2, ASAH1), and combined with RNA- and ATAC-seq of BP-treated cells and patient data, suggests downstream regulation of the MEF2A transcription factor within the heart. Collectively, these results indicate how BPs may beneficially modify the human plasma proteome, and directly impact multiple non-skeletal cell types through previously unidentified proteins, thereby influencing a range of pathways related to senescence and ageing.

cell biology↗

bioRxiv2025

Distinct mechanisms are employed by T-cell-instructed myeloid cells for IL-1β production in humans and mice.

Interleukin-1 beta (IL-1{beta}) is known as an inflammasome-dependent pro-inflammatory cytokine that has been implicated in T-cell-driven autoimmune diseases. In mice, T-cells were reported to instruct myeloid cells to produce IL-1{beta} via an inflammasome-independent mechanism, that engages TNFR and Fas-caspase-8-dependent signalling pathways. In this study, we explored T-cell-driven myeloid IL-1{beta} production in humans. Co-culturing of autologous primary T-cells (memory CD4+ and CD8+) with myeloid cells (monocyte, macrophage and dendritic cells) revealed that both memory CD4+ and CD8+ T cells induce IL-1{beta} secretion. Also, caspase-1 rather than caspase-8 cleaves pro-IL-1{beta} in human myeloid cells. This process depends on TNF-, CD40L and IFN-{gamma} together rather than TNF- alone, leading to upregulated pro-IL-1{beta} expression in human myeloid cells. We additionally show that TNF-, CD40L and IFN-{gamma} independently enhance IL-1{beta} secretion. Together, our study highlights that, despite the shared biology in T-cell-instructed IL-1{beta} production between humans and mice, different underlying molecular pathways are implicated. SummaryLike murine cells, human T-cells stimulate IL-1{beta} secretion from myeloid cells. However, the underlying mechanisms differ, with IL-1{beta} production in humans being driven by TNF-, CD40L, IFN-{gamma}, and Caspase-1, whereas in mice, it is primarily regulated by TNF- and Caspase-8.

immunology↗

bioRxiv2025

USP30 inhibition improves mitochondrial health through both PINK1-dependent and independent mechanisms

Mitochondrial dysfunction is a key feature of many pathologies, including Parkinsons disease. The selective vulnerability of dopaminergic neurons is thought to be influenced by mitochondrial dysfunction and mutations in the mitophagy regulating proteins PINK1 and Parkin that are known to cause early-onset Parkinsonism in an autosomal recessive manner. Augmentation of mitophagy through inhibition of USP30 may be a viable therapeutic strategy for a number of diseases including Parkinsons. USP30 inhibition has been demonstrated to augment PINK1/PRKN mitophagy but also potentiate basal mitophagy to support the removal of dysfunctional mitochondria. Therefore, long-term de-regulation of mitophagy has been proposed to lead to mitochondrial depletion. We have used an integrated approach across cell lines, primary neurons and iPSC-derived dopaminergic neuronal cultures to assess the short and long-term effects of USP30 inhibition on mitochondrial health and neuronal activity. We investigated the dependence of USP30 inhibition phenotypes on the PINK1/Parkin pathway using genetic ablation and in iPSC-derived neurons from Parkinsons patients with PINK1 or PRKN mutations. Loss of USP30 through CRISPR/Cas9-mediated knockout resulted in increased basal and depolarisation-induced mitophagy in SH-SY5Y cells. Loss of USP30 or pharmacological inhibition altered mitochondrial morphology and led to increases in membrane potential and ATP levels with decreased oxygen consumption, suggesting that USP30 loss results in a more efficient mitochondrial network. These changes in morphology were found to be independent of PINK1 or Parkin. Chronic pharmacological inhibition of USP30 or CRISPRi-mediated knockdown of USP30 did not impact dopaminergic neuronal activity, as assessed by electrophysiological profiling, but did potentiate depolarisation-induced mitophagy in primary and iPSC-derived neuronal cultures. We observed minimal changes in mitophagy levels in iPSC-derived dopaminergic neurons from Parkinsons patients with PINK1 or PRKN mutations that were independent of the ability to produce p65Ub. Importantly, within this experimental paradigm, pharmacological USP30 inhibition increased depolarisation-induced mitophagy in both PINK1 and PRKN patients to the same extent as control neurons. These results support a role for USP30 in modulating the trigger threshold for mitophagy and suggest that USP30 inhibitors may be beneficial in patients with impairments in PINK1/Parkin-mediated mitophagy.

neuroscience↗

bioRxiv2025

The developmental environment mediates adult seminal proteome allocation in male Drosophila melanogaster

Early life conditions can have long-lasting fitness effects on organisms. In insects, crowding during larval stages impose a significant constraint on adult phenotypes due to increased intraspecific competition for resources, which can modulate males success in pre- and post-mating competition in adulthood. Evidence for larval crowding effects on male seminal fluid allocation exists but is limited to a small subset of well-known seminal fluid proteins (Sfps), and often overlooks the interactions between male and female phenotypes. We currently lack a comprehensive understanding of how male and female larval crowding interact to affect production, composition, and transfer of the wider seminal proteome. Here, we manipulated Drosophila melanogaster larval crowding (low versus high) of males and females to generate individuals with large and small body size, respectively. We mated individuals in a fully factorial design, and measured the abundance, composition, and transfer of Sfps. Large males produced Sfps in significantly higher abundances, yet this difference was marginal and not detected when Sfps were analysed individually. Conversely, small males transferred greater quantities of much of their seminal proteome to females than did large males. When analysing proteins individually, 10 Sfps were transferred in significantly higher abundances by small males than large males. Our results suggest that small males invest more on each mating opportunity, potentially as a response of overall fewer mating opportunities due to their reduced size, or due to the larval cues of high population density. This work provides an insight into early life effects on ejaculate allocation in D. melanogaster and sheds light on the physiological and behavioural responses to developmental conditions in insects.

evolutionary biology↗

bioRxiv2024

Altered Hormone and Bioactive Lipid Plasma Profile in Rodent Models of Polycystic Ovarian Syndrome Revealed by Targeted Mass Spectrometry

Polycystic ovarian syndrome (PCOS) symptoms include excessive body or facial hair, irregular periods, reduced fertility, and reoccurring pregnancy loss. Hyperandrogenism and chronic inflammation are hallmarks of PCOS, which is diagnosed by analysing steroid hormones in the blood. Studies suggest that bioactive lipids are contributing to chronic inflammation. To research PCOS, animal models, such as letrozole- and dihydrotestosterone-treated rats, are used. They display similar ovarian and metabolic characteristics, although plasma lipid profiles have not been determined. Therefore, in order to validate the use of these models for PCOS, we have optimised a mass spectrometry based targeted lipidomics workflow which increases the sensitivity of measuring these lipids in rat plasma. Our analysis shows that letrozole caused a significant elevation of 5-androstene-3,17-dione and testosterone. Dihydrotestosterone treatment resulted in increased dehydroepiandrosterone-sulphate and allopregnanolone but a reduction in testosterone, progesterone, pregnenolone, and D-sphingosine. In both models 25-hydroxycholesterol and leukotriene C4 were significantly diminished and 4-cholesten-3-one was significantly increased, and these particular metabolites are not known to be changed in human PCOS. These results suggest that the plasma lipids of these rodent models have some changes akin to human PCOS and other changes that are not.

biochemistry↗

bioRxiv2024

Integrative Proximal-Ubiquitomics Profiling for Deubiquitinase and E3 Ligase Substrate Discovery Applied to USP30

Increasing interest in deubiquitinases (DUBs) and ubiquitin E3 ligases as drug targets to modulate critical molecular pathways in disease is driven by the discovery of specific cellular roles of these enzymes. Key to this is the identification of DUB or E3 ligase substrates. While global cellular ubiquitination changes upon perturbation of DUB/E3 ligase activity can be studied using mass spectrometry-based proteomic methods, these datasets include indirect and downstream ubiquitination events. To enrich for direct substrates of DUB/E3 ligase enzymes, we have combined proximity-labelling methodology (APEX2) and subsequent ubiquitination enrichment (based on the K-{varepsilon}-GG motif) to form a proximal-ubiquitome workflow. We have applied this technology to identify altered ubiquitination events in the proximity of the DUB ubiquitin specific protease 30 (USP30) upon its inhibition. We show ubiquitination events previously linked to USP30 on TOMM20 and FKBP8 and the previously undescribed candidate substrate LETM1, which is deubiquitinated in a USP30-dependent manner.

molecular biology↗

bioRxiv2024

Identification of a new Plasmodium falciparum E2 ubiquitin conjugating enzyme

The ubiquitin-proteasome system (UPS) is essential for Plasmodium falciparum survival and represents a potential target for antimalarial therapies. We utilised a ubiquitin-activity based probe (Ub-Dha) to capture active components of the ubiquitin conjugating machinery during asexual blood-stage development. Several E2 ubiquitin-conjugating enzymes, the E1 activating enzyme, and the HECT E3 ligase PfHEUL were identified and validated through in vitro ubiquitination assays. We also demonstrate selective functional interactions between PfHEUL and a subset of both human and P. falciparum E2s. Additionally, the Ub-Dha probe captured an uncharacterized protein, PF3D7_0811400 (C0H4U0) with no known homology to ubiquitin-pathway enzymes in other organisms. Through structural and biochemical analysis, we validate it as a novel E2 enzyme, capable of binding ubiquitin in a cysteine-specific manner. These findings contribute to our understanding of the P. falciparum UPS, identifying promising novel drug targets and highlighting the evolutionary uniqueness of the Ub-proteasome system in this parasite.

cell biology↗

bioRxiv2024

USP24 is an ISG15 cross-reactive deubiquitinasethat mediates IFN-I production by de-ISGylatingthe RNA helicase MOV10

The interferon-stimulated gene 15 (ISG15) is a ubiquitin-like modifier induced by type I Interferon (IFN-I) and plays a crucial role in the innate immune response against viral infections. ISG15 is conjugated to target proteins by an enzymatic cascade through a process called ISGylation. While ubiquitin-specific protease 18 (USP18) is a well-defined deISGylase counteracting ISG15 conjugation, ISG15 cross-reactive deubiquitylating enzymes (DUBs) have also been reported. Our study reports USP24 as a novel ISG15 cross-reactive DUB identified through activity-based protein profiling (ABPP). We demonstrate that recombinant USP24 processed pro-ISG15 and ISG15-linked synthetic substrates in vitro. Moreover, the depletion of USP24 significantly increased the accumulation of ISG15 conjugates upon IFN-{beta} stimulation. An extensive proteomic analysis of the USP24-dependent ISGylome, integrating total proteome, GG-peptidome, and ISG15 interactome data, identified the helicase Moloney leukemia virus 10 (MOV10) as a specific target of USP24 for deISGylation. Further validation in cells revealed that ISGylated MOV10 enhances IFN-{beta} production/secretion, whereas USP24 deISGylates MOV10 to negatively regulate the innate immune response. This study showcases USP24s novel roles in modulating ISGylation and modulation of the IFN-I-dependent immune responses, with potential therapeutic implications in infectious diseases, cancer, autoimmunity, and neuroinflammation.

biochemistry↗