UBR5 HECT domain mutations identified in mantle cell lymphoma control maturation of B cells

UBR5 in Tumor Biology: Exploring Mechanisms of Immune Regulation and Possible Therapeutic Implications in MPNST

Malignant peripheral nerve sheath tumor (MPNST) is a rare but aggressive soft-tissue sarcoma characterized by poor response to therapy. The primary treatment remains surgical resection with negative margins. Nonetheless, in the setting of neurofibromatosis type 1 (NF1), the five-year survival rate is at 20-50%, with recurrence occurring in up to 50% of individuals. For patients with metastatic and unresectable disease, current treatment options include cytotoxic chemotherapy, which offers minimal benefit, and most patients die within five years of diagnosis. Despite advances in targeted therapy focusing on inhibiting Ras signaling and its downstream effectors, clinical trials report minimal clinical benefit, highlighting the need to explore alternative pathways in MPNST pathogenesis. Here, we discuss the role of the E3 ubiquitin ligase, UBR5, in cancer progression and immune modulation across various malignancies, including breast, lung, and ovarian cancer. We focus on mechanisms by which UBR5 contributes to tumorigenesis, focusing on its influence on tumor microenvironment and immune modulation. Additionally, we explore UBR5's roles in normal tissue function, DNA damage response, metastasis, and therapeutic resistance, illustrating its multifaceted contribution to cancer biology. We discuss evidence implicating UBR5 in immune evasion and highlight its potential as a therapeutic target to enhance the efficacy of immune checkpoint blockade (ICB) therapy in MPNST, a tumor typically characterized by an immune cold microenvironment. We outline current immune-based strategies and challenges in MPNST management, ongoing efforts to shift the immune landscape in MPNST, and ultimately, we suggest that targeting UBR5 could be a novel strategy to potentiate ICB therapy-mediated anti-tumor immune response and clinical outcomes, particularly in MPNST patients with inoperable or metastatic disease.

A review: targeting UBR5 domains to mediate emerging roles and mechanisms - chance or necessity?

Ubiquitinases are known to catalyze ubiquitin chains on target proteins to regulate various physiological functions like cell proliferation, autophagy, apoptosis, and cell cycle progression. As a member of E3 ligase, ubiquitin protein ligase E3 component n-recognin 5 (UBR5) belongs to the HECT E3 ligase and has been reported to be correlated with various pathophysiological processes. In this review, the authors give a comprehensive insight into the structure and function of UBR5. The authors discuss the specific domains of UBR5 and explore their biological functions separately. Furthermore, the authors describe the involvement of UBR5 in different pathophysiological conditions, including immune response, virus infection, DNA damage response, and protein quality control. Moreover, the authors provide a thorough summary of the important roles and regulatory mechanisms of UBR5 in cancers and other diseases. On the whole, investigating the domains and functions of UBR5, elucidating the underlying mechanisms of UBR5 with various substrates in detail may provide new theoretical basis for the treatment of diseases, including cancers, which could improve future studies to construct novel UBR5-targeted therapy strategies.

Targeting the ubiquitin pathway in lymphoid malignancies

Ubiquitination and related cellular processes control a variety of aspects in human cell biology, and defects in these processes contribute to multiple illnesses. In recent decades, our knowledge about the pathological role of ubiquitination in lymphoid cancers and therapeutic strategies to target the modified ubiquitination system has evolved tremendously. Here we review the altered signalling mechanisms mediated by the aberrant expression of cancer-associated E2s/E3s and deubiquitinating enzymes (DUBs), which result in the hyperactivation of oncoproteins or the frequently allied downregulation of tumour suppressors. We discuss recent highlights pertaining to the several different therapeutic interventions which are currently being evaluated to effectively block abnormal ubiquitin-proteasome pathway and the use of heterobifunctional molecules which recruit the ubiquitination system to degrade or stabilize non-cognate substrates. This review aids in comprehension of ubiquitination aberrance in lymphoid cancers and current targeting strategies and elicits further investigations to deeply understand the link between cellular ubiquitination and lymphoid pathogenesis as well as to ameliorate corresponding treatment interventions.

FBXO21 mediated degradation of p85α regulates proliferation and survival of acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by clonal expansion of myeloid blasts in the bone marrow (BM). Despite advances in therapy, the prognosis for AML patients remains poor, and there is a need to identify novel molecular pathways regulating tumor cell survival and proliferation. F-box ubiquitin E3 ligase, FBXO21, has low expression in AML, but expression correlates with survival in AML patients and patients with higher expression have poorer outcomes. Silencing FBXO21 in human-derived AML cell lines and primary patient samples leads to differentiation, inhibition of tumor progression, and sensitization to chemotherapy agents. Additionally, knockdown of FBXO21 leads to up-regulation of cytokine signaling pathways. Through a mass spectrometry-based proteomic analysis of FBXO21 in AML, we identified that FBXO21 ubiquitylates p85α, a regulatory subunit of the phosphoinositide 3-kinase (PI3K) pathway, for degradation resulting in decreased PI3K signaling, dimerization of free p85α and ERK activation. These findings reveal the ubiquitin E3 ligase, FBXO21, plays a critical role in regulating AML pathogenesis, specifically through alterations in PI3K via regulation of p85α protein stability.

In-organoid single-cell CRISPR screening reveals determinants of hepatocyte differentiation and maturation

BACKGROUND

Harnessing hepatocytes for basic research and regenerative medicine demands a complete understanding of the genetic determinants underlying hepatocyte differentiation and maturation. Single-cell CRISPR screens in organoids could link genetic perturbations with parallel transcriptomic readout in single cells, providing a powerful method to delineate roles of cell fate regulators. However, a big challenge for identifying key regulators during data analysis is the low expression levels of transcription factors (TFs), which are difficult to accurately estimate due to noise and dropouts in single-cell sequencing. Also, it is often the changes in TF activities in the transcriptional cascade rather than the expression levels of TFs that are relevant to the cell fate transition.

RESULTS

Here, we develop Organoid-based Single-cell CRISPR screening Analyzed with Regulons (OSCAR), a framework using regulon activities as readouts to dissect gene knockout effects in organoids. In adult-stem-cell-derived liver organoids, we map transcriptomes in 80,576 cells upon 246 perturbations associated with transcriptional regulation of hepatocyte formation. Using OSCAR, we identify known and novel positive and negative regulators, among which Fos and Ubr5 are the top-ranked ones. Further single-gene loss-of-function assays demonstrate that Fos depletion in mouse and human liver organoids promote hepatocyte differentiation by specific upregulation of liver metabolic genes and pathways, and conditional knockout of Ubr5 in mouse liver delays hepatocyte maturation.

CONCLUSIONS

Altogether, we provide a framework to explore lineage specifiers in a rapid and systematic manner, and identify hepatocyte determinators with potential clinical applications.

Regulatory role of E3 ubiquitin ligases in normal B lymphopoiesis and B-cell malignancies

E3 ubiquitin ligases play an essential role in protein ubiquitination, which is involved in the regulation of protein degradation, protein-protein interactions and signal transduction. Increasing evidences have shed light on the emerging roles of E3 ubiquitin ligases in B-cell development and related malignances. This comprehensive review summarizes the current understanding of E3 ubiquitin ligases in B-cell development and their contribution to B-cell malignances, which could help explore the molecular mechanism of normal B-cell development and provide potential therapeutic targets of the related diseases.

UBR5 forms ligand-dependent complexes on chromatin to regulate nuclear hormone receptor stability

Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are widely targeted therapeutically. Agonist binding triggers NR activation and subsequent degradation by unknown ligand-dependent ubiquitin ligase machinery. NR degradation is critical for therapeutic efficacy in malignancies that are driven by retinoic acid and estrogen receptors. Here, we demonstrate the ubiquitin ligase UBR5 drives degradation of multiple agonist-bound NRs, including the retinoic acid receptor alpha (RARA), retinoid x receptor alpha (RXRA), glucocorticoid, estrogen, liver-X, progesterone, and vitamin D receptors. We present the high-resolution cryo-EMstructure of full-length human UBR5 and a negative stain model representing its interaction with RARA/RXRA. Agonist ligands induce sequential, mutually exclusive recruitment of nuclear coactivators (NCOAs) and UBR5 to chromatin to regulate transcriptional networks. Other pharmacological ligands such as selective estrogen receptor degraders (SERDs) degrade their receptors through differential recruitment of UBR5 or RNF111. We establish the UBR5 transcriptional regulatory hub as a common mediator and regulator of NR-induced transcription.

Clinicopathological Features and Prognostic Evaluation of UBR5 in Liver Cancer Patients

Background: Typically, liver cancer patients are diagnosed at an advanced stage and have a poor prognosis. N-recognin 5 (UBR5), a component of the ubiquitin protein ligase E3, is involved in the genesis and progression of several types of cancer. As of yet, it is unknown what the exact biological function of UBR5 is in liver cancer. Methods: A Kaplan-Meier survival curve (OS) was used to examine the effect of UBR5 expression on overall survival based on the TCGA database. To determine the molecular functions of UBR5 in liver cancer, we used the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. A protein-protein interaction (PPI) network was established for the screening of UBR5-related proteins in liver cancer. Western blot analysis was used to determine the expression levels of UBR5 and YWHAZ (tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta), and in order to detect cell proliferation, an MTT assay was used. Results: The expression of UBR5 in liver cancer patient samples is significantly higher than in adjacent normal tissues. A high level of UBR5 expression was associated with older patients, a higher tumor grade, lymph node metastasis, and poor survival. We discovered YWHAZ with high connectivity, and UBR5 expression correlated positively with YWHAZ expression (r = 0.83, p < 0.05). Furthermore, we found that elevated UBR5 levels directly correlated with YWHAZ overexpression, and that UBR5 promoted cell proliferation by affecting YWHAZ expression. Additionally, the TCGA databases confirmed that patients with liver cancer who expressed higher levels of YWHAZ had poorer outcomes. Conclusion: This suggests that UBR5 associated with YWHAZ may influence prognosis in patients with liver cancer, and that UBR5 may be a candidate treatment target for liver cancer. Therefore, UBR5 associated with YWHAZ may influence prognosis in patients with liver cancer, and UBR5 could serve as a potential target for liver cancer treatment.

Targeting UBR5 in hepatocellular carcinoma cells and precise treatment via echinacoside nanodelivery

Background

Hepatocellular carcinoma (HCC) is among the most common and malignant cancers with no effective therapeutic approaches. Echinacoside (ECH), a phenylethanoid glycoside isolated from Chinese herbal medicine, Cistanche salsa, can inhibit HCC progression; however, poor absorption and low bioavailability limit its biological applications.

Methods

To improve ECH sensitivity to HepG2 cells, we developed a mesoporous silica nanoparticle (MSN)-based drug delivery system to deliver ECH to HepG2 cells via galactose (GAL) and poly(ethylene glycol) diglycidyl ether (PEGDE) conjugation (ECH@Au@MSN-PEGDE-GAL, or ECH@AMPG). Gain- and loss-of-function assays were conducted to assess the effects of UBR5 on HCC cell apoptosis and glycolysis. Moreover, the interactions among intermediate products were also investigated to elucidate the mechanisms by which UBR5 functions.

Results

The present study showed that ubiquitin protein ligase E3 component N-recognin 5 (UBR5) acted as an oncogene in HCC tissues and that its expression was inhibited by ECH. AMPG showed a high drug loading property and a slow and sustained release pattern over time. Moreover, owing to the valid drug accumulation, ECH@AMPG promoted apoptosis and inhibited glycolysis of HepG2 cells in vitro. In vivo experiments demonstrated that AMPG also enhanced the antitumor effects of ECH in HepG2 cell-bearing mice.

Conclusions

Our results indicated the clinical significance of UBR5 as a therapeutic target. On the basis of the nontoxic and high drug-loading capabilities of AMPG, ECH@AMPG presented better effects on HCC cells compared with free ECH, indicating its potential for the chemotherapy of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00394-w.

Multi-omics reveals mitochondrial metabolism proteins susceptible for drug discovery in AML

Acute myeloid leukemia (AML) is a devastating cancer affecting the hematopoietic system. Previous research has relied on RNA sequencing and microarray techniques to study the downstream effects of genomic alterations. While these studies have proven efficacious, they fail to capture the changes that occur at the proteomic level. To interrogate the effect of protein expression alterations in AML, we performed a quantitative mass spectrometry in parallel with RNAseq analysis using AML mouse models. These combined results identified 34 proteins whose expression was upregulated in AML tumors, but strikingly, were unaltered at the transcriptional level. Here we focus on mitochondrial electron transfer proteins ETFA and ETFB. Silencing of ETFA and ETFB led to increased mitochondrial activity, mitochondrial stress, and apoptosis in AML cells, but had little to no effect on normal human CD34+ cells. These studies identify a set of proteins that have not previously been associated with leukemia and may ultimately serve as potential targets for therapeutic manipulation to hinder AML progression and help contribute to our understanding of the disease.

Mantle cell lymphoma in 2022-A comprehensive update on molecular pathogenesis, risk stratification, clinical approach, and current and novel treatments

The field of mantle cell lymphoma (MCL) has witnessed remarkable progress due to relentless advances in molecular pathogenesis, prognostication, and newer treatments. MCL consists of a spectrum of clinical subtypes. Rarely, atypical cyclin D1-negative MCL and in situ MCL neoplasia are identified. Prognostication of MCL is further refined by identifying somatic mutations (such as TP53, NSD2, KMT2D), methylation status, chromatin organization pattern, SOX-11 expression, minimal residual disease (MRD), and genomic clusters. Lymphoid tissue microenvironment studies demonstrated the role of B-cell receptor signaling, nuclear factor kappa B (NF-kB), colony-stimulating factor (CSF)-1, the CD70-SOX-11 axis. Molecular mechanism of resistance, mutation dynamics, and pathogenic pathways (B-cell receptor (BCR), oxidative phosphorylation, and MYC) were identified in mediating resistance to various treatments (bruton tyrosine kinase (BTK) inhibitors [ibrutinib, acalabrutinib]. Treatment options range from conventional chemoimmunotherapy and stem cell transplantation (SCT) to targeted therapies against BTK (covalent and noncovalent), Bcl2, ROR1, cellular therapy such as anti-CD19 chimeric antigen receptor therapy (CAR-T), and most recently bispecific antibodies against CD19 and CD20. MCL patients frequently relapse. Complex pathogenesis and the management of patients with progression after treatment with BTK/Bcl2 inhibitors and CAR-T (triple-resistant MCL) remain a challenge. Next-generation clinical trials incorporating newer agents and concurrent translational and molecular investigations are ongoing.

Epigenetic, Metabolic, and Immune Crosstalk in Germinal-Center-Derived B-Cell Lymphomas: Unveiling New Vulnerabilities for Rational Combination Therapies

B-cell non-Hodgkin lymphomas (B-NHLs) are highly heterogenous by genetic, phenotypic, and clinical appearance. Next-generation sequencing technologies and multi-dimensional data analyses have further refined the way these diseases can be more precisely classified by specific genomic, epigenomic, and transcriptomic characteristics. The molecular and genetic heterogeneity of B-NHLs may contribute to the poor outcome of some of these diseases, suggesting that more personalized precision-medicine approaches are needed for improved therapeutic efficacy. The germinal center (GC) B-cell like diffuse large B-cell lymphomas (GCB-DLBCLs) and follicular lymphomas (FLs) share specific epigenetic programs. These diseases often remain difficult to treat and surprisingly do not respond advanced immunotherapies, despite arising in secondary lymphoid organs at sites of antigen recognition. Epigenetic dysregulation is a hallmark of GCB-DLBCLs and FLs, with gain-of-function (GOF) mutations in the histone methyltransferase EZH2, loss-of-function (LOF) mutations in histone acetyl transferases CREBBP and EP300, and the histone methyltransferase KMT2D representing the most prevalent genetic lesions driving these diseases. These mutations have the common effect to disrupt the interactions between lymphoma cells and the immune microenvironment, via decreased antigen presentation and responsiveness to IFN-γ and CD40 signaling pathways. This indicates that immune evasion is a key step in GC B-cell lymphomagenesis. EZH2 inhibitors are now approved for the treatment of FL and selective HDAC3 inhibitors counteracting the effects of CREBBP LOF mutations are under development. These treatments can help restore the immune control of GCB lymphomas, and may represent optimal candidate agents for more effective combination with immunotherapies. Here, we review recent progress in understanding the impact of mutant chromatin modifiers on immune evasion in GCB lymphomas. We provide new insights on how the epigenetic program of these diseases may be regulated at the level of metabolism, discussing the role of metabolic intermediates as cofactors of epigenetic enzymes. In addition, lymphoma metabolic adaptation can negatively influence the immune microenvironment, further contributing to the development of immune cold tumors, poorly infiltrated by effector immune cells. Based on these findings, we discuss relevant candidate epigenetic/metabolic/immune targets for rational combination therapies to investigate as more effective precision-medicine approaches for GCB lymphomas.

Maternal Iron Deficiency Modulates Placental Transcriptome and Proteome in Mid-Gestation of Mouse Pregnancy

BACKGROUND

Maternal iron deficiency (ID) is associated with poor pregnancy and fetal outcomes. The effect is thought to be mediated by the placenta but there is no comprehensive assessment of placental responses to maternal ID. Additionally, whether the influence of maternal ID on the placenta differs by fetal sex is unknown.

OBJECTIVES

To identify gene and protein signatures of ID mouse placentas at mid-gestation. A secondary objective was to profile the expression of iron genes in mouse placentas across gestation.

METHODS

We used a real-time PCR-based array to determine the mRNA expression of all known iron genes in mouse placentas at embryonic day (E) 12.5, E14.5, E16.5, and E19.5 (n = 3 placentas/time point). To determine the effect of maternal ID, we performed RNA sequencing and proteomics in male and female placentas from ID and iron-adequate mice at E12.5 (n = 8 dams/diet).

RESULTS

In female placentas, 6 genes, including transferrin receptor (Tfrc) and solute carrier family 11 member 2, were significantly changed by maternal ID. An additional 154 genes were altered in male ID placentas. A proteomic analysis quantified 7662 proteins in the placenta. Proteins translated from iron-responsive element (IRE)-containing mRNA were altered in abundance; ferritin and ferroportin 1 decreased, while TFRC increased in ID placentas. Less than 4% of the significantly altered genes in ID placentas occurred both at the transcriptional and translational levels.

CONCLUSIONS

Our data demonstrate that the impact of maternal ID on placental gene expression in mice is limited in scope and magnitude at mid-gestation. We provide strong evidence for IRE-based transcriptional and translational coordination of iron gene expression in the mouse placenta. Finally, we discover sexually dimorphic effects of maternal ID on placental gene expression, with more genes and pathways altered in male compared with female mouse placentas.

Exploring the "Other" subfamily of HECT E3-ligases for therapeutic intervention

The HECT E3 ligase family regulates key cellular signaling pathways, with its 28 members divided into three subfamilies: NEDD4 subfamily (9 members), HERC subfamily (6 members) and "Other" subfamily (13 members). Here, we focus on the less-explored "Other" subfamily and discuss the recent findings pertaining to their biological roles. The N-terminal regions preceding the conserved HECT domains are significantly diverse in length and sequence composition, and are mostly unstructured, except for short regions that incorporate known substrate-binding domains. In some of the better-characterized "Other" members (e.g., HUWE1, AREL1 and UBE3C), structure analysis shows that the extended region (~ aa 50) adjacent to the HECT domain affects the stability and activity of the protein. The enzymatic activity is also influenced by interactions with different adaptor proteins and inter/intramolecular interactions. Primarily, the "Other" subfamily members assemble atypical ubiquitin linkages, with some cooperating with E3 ligases from the other subfamilies to form branched ubiquitin chains on substrates. Viruses and pathogenic bacteria target and hijack the activities of "Other" subfamily members to evade host immune responses and cause diseases. As such, these HECT E3 ligases have emerged as potential candidates for therapeutic drug development.