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Peer reviewed: True, Funder: European Regional Development Fund, Funder: Scottish Funding Council, Funder: Highlands and Islands Enterprise, CBL is rapidly phosphorylated upon insulin receptor activation. Mice whole body CBL depletion improved insulin sensitivity and glucose clearance; however, the precise mechanisms remain unknown. We depleted either CBL or its associated protein SORBS1/CAP independently in myocytes and assessed mitochondrial function and metabolism compared to control cells. CBL- and CAP-depleted cells showed increased mitochondrial mass with greater proton leak. Mitochondrial respiratory complex I activity and assembly into respirasomes were reduced. Proteome profiling revealed alterations in proteins involved in glycolysis and fatty acid degradation. Our findings demonstrate CBL/CAP pathway couples insulin signaling to efficient mitochondrial respiratory function and metabolism in muscle.

Recent evidence revealed an inhibitory effect of circ-ITCH on the progression of papillary thyroid cancer via affecting the circ-ITCH/miR-22-3p/CBL axis. Rs4911154, an SNP located in circ-ITHC, was previously reported to be significantly associated with an increased risk of hepatocellular carcinoma. Ultrasound testing was used to evaluate the doubling time of thyroid nodules. 202 patients diagnosed with thyroid nodule disorders were divided into three groups according to their genotypes at rs4911154. We found that the A allele was correlated with a shortening doubling time of thyroid nodules. Moreover, the A allele contributed to reduced expression of circ-ITCH/CBL and increased expression of miR-22-3p. Besides, decreased tissue apoptosis was linked to the A allele. Luciferase assays indicated that miR-22-3p could effectively suppress the luciferase activities of CBL and circ-ITCH. Furthermore, manual up-regulation of miR-22-3p effectively suppressed the expression of CBL, while CBL siRNA apparently abolished circ-ITCH induced CBL upregulation, reduced proliferation and increased apoptosis of K1 and TPC-1 cells. A signaling pathway of circ-ITCH/miR-22-3p/CBL axis was established to explain the effect of SNP of circ-ITCH in thyroid tumor malignancy. Compared with the G allele, the A allele in rs4911154 contributed to the malignancy of thyroid nodules with decreased doubling time and down-regulated CBL expression.

BackgroundCBL syndrome is a RASopathy caused by heterozygous germline mutations of the Casitas B-lineage lymphoma (CBL) gene. It is characterized by heterogeneous clinical phenotype, including developmental delay, facial dysmorphisms, cardiovascular malformations and an increased risk of cancer development, particularly juvenile myelomonocytic leukemia (JMML). Although the clinical phenotype has been progressively defined in recent years, immunological manifestations have not been well elucidated to date.MethodsWe studied the genetic, immunological, coagulative, and clinical profile of a family with CBL syndrome that came to our observation after the diagnosis of JMML, with homozygous CBL mutation, in one of the members.ResultsVariant analysis revealed the co-occurrence of CBL heterozygous mutation (c.1141 T > C) andSH2B3mutation (c.1697G > A) in two other members. Patients carrying both mutations showed an ALPS-like phenotype characterized by lymphoproliferation, cytopenia, increased double-negative T-cells, impaired Fas-mediated lymphocyte apoptosis, altered cell death in PBMC and low TRECs expression. A coagulative work-up was also performed and showed the presence of subclinical coagulative alterations in patients carrying both mutations.ConclusionIn the reported family, we described immune dysregulation, as part of the clinical spectrum of CBL mutation with the co-occurrence of SH2B3.

First-line therapy with interferon beta (IFN-β), involved in gene expression modulation in immune response, is widely used for multiple sclerosis. However, 30-50% of patients do not respond optimally. Variants in CBLB, CTSS, GRIA3, OAS1 and TNFRSF10A genes have been proposed to contribute to the variation in the individual response. The purpose of this study was to evaluate the influence of gene polymorphisms on the IFN-β response in relapsing-remitting multiple sclerosis (RRMS) patients. CBLB (rs12487066), GRIA3 (rs12557782), CTSS (rs1136774), OAS1 (rs10774671) and TNFRSF10A (rs20576) polymorphisms were analysed by Taqman in 137 RRMS patients. Response to IFN-β and change in the Expanded Disability Status Scale (EDSS) after 24 months were evaluated using multivariable logistic regression analysis. Carriers of at least one copy of the C allele of CTSS-rs1136774 had a better response to IFN-β (p = 0.0423; OR = 2.94; CI95% = 1.03, 8.40). Carriers of TT genotype of TNFRSF10A-rs20576 had a higher probability of maintaining their EDSS stable after 24 months of IFN-β treatment (p = 0.0251; OR = 5.71; CI95% = 1.39, 31.75). No influence of CBLB (rs12487066), OAS1 (rs10774671) and GRIA3 (rs12557782) gene polymorphisms in the variation of the individual response to IFN-β was shown. Our results suggest that the TNFRSF10A-rs20576 and CTSS-rs1136774 gene polymorphisms influence the response to IFN-β after 24 months, while the CBLB (rs12487066), OAS1 (rs10774671) or GRIA3 (rs12557782) gene polymorphisms had no effect on the variation of the individual response to IFN-β.

CBL is a mammalian gene encoding the protein CBL, which is an E3 ubiquitin-protein ligase involved in cell signaling and protein ubiquitination. Pathogenic variants in this gene have been implicated in a number of human cancers, particularly acute myeloid leukemia (AML). Here, we present a 5-year-old male patient with a history of AML, diffuse midline glioma, and left brain lesion with histiocytic features. A variant of uncertain significance (VUS): p.L493F was detected in his CBL gene via clinical evaluation. Protein modeling predicts this variant to be pathogenic. Details of the clinical evaluation and modeling assay are discussed.

An extract of a Sinularia sp. soft coral showed inhibitory activity against the E3-ubiquitin ligase casitas B-lineage lymphoma proto-oncogene B (Cbl-b). Subsequent bioassay-guided separation of the extract provided a series of terpenoid-derived spermidine and spermine amides that were named sinularamides A–G (1–7). Compounds 1–7 represent new natural products; however, sinularamide A (1) was previously reported as a synthetic end product. The structures of sinularamides A–G (1–7) were elucidated by analysis of spectroscopic and spectrometric data from NMR, IR, and HRESIMS experiments and by comparison with literature data. All of the isolated compounds showed Cbl-b inhibitory activities with IC(50) values that ranged from approximately 6.5 to 33 μM.

Casitas B-lineage lymphoma (CBL) encodes an E3 ubiquitin ligase and signaling adaptor that regulates receptor and nonreceptor tyrosine kinases. Recurrent CBL mutations occur in myeloid neoplasms, including 10% to 20% of chronic myelomonocytic leukemia (CMML) cases, and selectively disrupt the protein’s E3 ubiquitin ligase activity. CBL mutations have been associated with poor prognosis, but the oncogenic mechanisms and therapeutic implications of CBL mutations remain incompletely understood. We combined functional assays and global mass spectrometry to define the phosphoproteome, CBL interactome, and mechanism of signaling activation in a panel of cell lines expressing an allelic series of CBL mutations. Our analyses revealed that increased LYN activation and interaction with mutant CBL are key drivers of enhanced CBL phosphorylation, phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) recruitment, and downstream phosphatidylinositol 3-kinase (PI3K)/AKT signaling in CBL-mutant cells. Signaling adaptor domains of CBL, including the tyrosine kinase–binding domain, proline-rich region, and C-terminal phosphotyrosine sites, were all required for the oncogenic function of CBL mutants. Genetic ablation or dasatinib-mediated inhibition of LYN reduced CBL phosphorylation, CBL-PIK3R1 interaction, and PI3K/AKT signaling. Furthermore, we demonstrated in vitro and in vivo antiproliferative efficacy of dasatinib in CBL-mutant cell lines and primary CMML. Overall, these mechanistic insights into the molecular function of CBL mutations provide rationale to explore the therapeutic potential of LYN inhibition in CBL-mutant myeloid malignancies.

Ubiquitin ligase Casitas B-lineage lymphoma-b (Cbl-b) play a critical role in nonloading-mediated skeletal muscle atrophy: Cbl-b ubiquitinates insulin receptor substrate-1 (IRS-1), leading to its degradation and a resulting loss in muscle mass. We reported that intramuscular injection of a pentapeptide, DGpYMP, which acts as a mimic of the phosphorylation site in IRS-1, significantly inhibited denervation-induced skeletal muscle loss. In order to explore the possibility of the prevention of muscle atrophy by diet therapy, we examined the effects of oral administration of transgenic rice containing Cblin (Cbl-b inhibitor) peptide (DGYMP) on denervation-induced muscle mass loss in frogs. We generated transgenic rice seeds in which 15 repeats of Cblin peptides with a WQ spacer were inserted into the rice storage protein glutelin. A diet of the transgenic rice seeds had significant inhibitory effects on denervation-induced atrophy of the leg skeletal muscles in frogs, compared with those receiving a diet of wild-type rice.

The diagnostic criteria for juvenile myelomonocytic leukemia have recently been revised to include clinical findings and RAS-pathway gene mutations per the 2016 World Health Organization Classification of Tumors of Hematopoietic and Lymphoid Tissues. Differing clinical behaviors have been observed in cases with CBL versus other RAS-pathway gene (RAS-p) mutations, notably the patients with CBL mutations can be self-limiting with spontaneous resolution. Additional clinical characteristics and histopathologic findings between these subsets are less well-described. We performed a retrospective search and identified cases with either CBL or RAS-p mutations, as per targeted and/or massively parallel sequencing. Eight patients had sufficient material for review, including cytogenetic studies and peripheral blood, bone marrow aspirate, and/or biopsy with flow cytometry analyses. Three patients showed CBL mutations and lower percentages of hemoglobin F and peripheral blood absolute monocyte counts, lesser degrees of leukocytosis compared with the RAS-p cohort, and normal megakaryocyte morphology and myeloblast immunophenotypes. Two of these patients were managed with observation only and experienced resolution of their disease. The patients with RAS-p mutations had severe thrombocytopenia, moderate to severe anemia, and experienced variable clinical outcomes. Abnormal megakaryocyte morphology and decreased numbers of megakaryocytes were seen in cases with RAS-p mutations. In addition, 3 of 4 cases with flow cytometry data demonstrated aberrant CD7 expression in myeloblasts. Our study is the first to identify morphologic and immunophenotypic differences between juvenile myelomonocytic leukemia cases with CBL or RAS-p mutations, and further supports previous reports of significantly different clinical behaviors between these subsets of patients.

Bone-resorbing osteoclasts (OCLs) are multinucleated phagocytes, whose central roles in regulating bone formation and homeostasis are critical for normal health and development. OCLs are produced from precursor monocytes in a multistage process that includes initial differentiation, cell-cell fusion, and subsequent functional and morphological maturation; the molecular regulation of osteoclastogenesis is not fully understood. Here, we identify the receptor-type protein tyrosine phosphatase PTPRJ as an essential regulator specifically of OCL maturation. Monocytes from PTPRJ-deficient (JKO) mice differentiate and fuse normally, but their maturation into functional OCLs and their ability to degrade bone are severely inhibited. In agreement, mice lacking PTPRJ throughout their bodies or only in OCLs exhibit increased bone mass due to reduced OCL-mediated bone resorption. We further show that PTPRJ promotes OCL maturation by dephosphorylating the M-CSF receptor (M-CSFR) and Cbl, thus reducing the ubiquitination and degradation of the key osteoclastogenic transcription factor NFATc1. Loss of PTPRJ increases ubiquitination of NFATc1 and reduces its amounts at later stages of osteoclastogenesis, thereby inhibiting OCL maturation. PTPRJ thus fulfills an essential and cell-autonomous role in promoting OCL maturation by balancing between the pro- and anti-osteoclastogenic activities of the M-CSFR and maintaining NFATc1 expression during late osteoclastogenesis.

Casitas B-lineage lymphoma (CBL) is a ubiquitin ligase (E3) that becomes activated upon Tyr371-phosphorylation and targets receptor protein tyrosine kinases for ubiquitin-mediated degradation. Deregulation of CBL and its E3 activity is observed in myeloproliferative neoplasms and other cancers, including breast, colon, and prostate cancer. Here, we explore the oncogenic mechanism of E3-inactive CBL mutants identified in myeloproliferative neoplasms. We show that these mutants bind strongly to CIN85 under normal growth conditions and alter the CBL interactome. Lack of E3 activity deregulates CIN85 endosomal trafficking, leading to an altered transcriptome that amplifies signaling events to promote oncogenesis. Disruption of CBL mutant interactions with EGFR or CIN85 reduces oncogenic transformation. Given the importance of the CBL–CIN85 interaction in breast cancers, we examined the expression levels of CIN85, CBL, and the status of Tyr371-phosphorylated CBL (pCBL) in human breast cancer tissue microarrays. Interestingly, pCBL shows an inverse correlation with both CIN85 and CBL, suggesting that high expression of inactivated CBL could coordinate with CIN85 for breast cancer progression. Inhibition of the CBL–CIN85 interaction with a proline-rich peptide of CBL that binds CIN85 reduced the proliferation of MDA-MB-231 cells. Together, these results provide a rationale for exploring the potential of targeting the EGFR–CBL–CIN85 axis in CBL-inactivated mutant cancers.

Summary The distinction of self from non-self is crucial to prevent autoreactivity and ensure protection from infectious agents and tumors. Maintaining the balance between immunity and tolerance of immune cells is strongly controlled by several sophisticated regulatory mechanisms of the immune system. Among these, the E3 ligase ubiquitin Casitas B cell lymphoma-b (Cbl-b) is a newly identified component in the ubiquitin-dependent protein degradation system, which is thought to be an important negative regulator of immune cells. An update on the current knowledge and new concepts of the relevant immune homeostasis program co-ordinated by Cbl-b in different cell populations could pave the way for future immunomodulatory therapies of various diseases, such as autoimmune and allergic diseases, infections, cancers and other immunopathological conditions. In the present review, the latest findings are comprehensively summarized on the molecular structural basis of Cbl-b and the suppressive signaling mechanisms of Cbl-b in physiological and pathological immune responses, as well as its emerging potential therapeutic implications for immunotherapy in animal models and human diseases.

Excess bone loss due to increased osteoclastogenesis is a significant clinical problem. Intraflagellar transport (IFT) proteins have been reported to regulate cell growth and differentiation. The role of IFT80, an IFT complex B protein, in osteoclasts (OCs) is completely unknown. Here, we demonstrate that deletion of IFT80 in the myeloid lineage led to increased OC formation and activity accompanied by severe bone loss in mice. IFT80 regulated OC formation by associating with Casitas B-lineage lymphoma proto-oncogene-b (Cbl-b) to promote protein stabilization and proteasomal degradation of tumor necrosis factor (TNF) receptor–associated factor 6 (TRAF6). IFT80 knockdown resulted in increased ubiquitination of Cbl-b and higher TRAF6 levels, thereby hyperactivating the receptor activator of nuclear factor-κβ (NF-κβ) ligand (RANKL) signaling axis and increased OC formation. Ectopic overexpression of IFT80 rescued osteolysis in a calvarial model of bone loss. We have thus identified a negative function of IFT80 in OCs.

In this issue, Han and colleagues demonstrate in preclinical cancer models that genetic deletion of the E3 ubiquitin ligase Cbl proto-oncogene B (CBLB) in adoptively transferred CD8+ T cells induces resistance to regulatory T cells. CBLB deletion induces IFNγ and downmodulates TGFβ/SMAD signaling. This ultimately enforces these cells to be way more effective against various cancers. See related article by Han et al., p. 437 (4).

Thrombocyte formation from megakaryocyte and their progenitor cells is tightly regulated by thrombopoietin (TPO) and its receptor c‐MPL, thereby maintaining physiological functionality and numbers of circulating platelets. In patients, dysfunction of this regulation could cause thrombocytopenia or myeloproliferative syndromes. Since regulation of this pathway is still not completely understood, we investigated the role of the ubiquitin ligase c‐Cbl which was previously shown to negatively regulated c‐MPL signalling. We developed a new conditional mouse model using c‐Cblfl/flPf4Cre mice and demonstrated that platelet‐specific knockout of c‐Cbl led to severe microthrombocytosis and impaired uptake of TPO and c‐MPL receptor internalization. Furthermore, we characterized a constitutive STAT5 activation c‐Cbl KO platelets. This study identified c‐Cbl as a potential player in causing megakaryocytic and thrombocytic disorders.

There are eight human Src-family tyrosine kinases (SFKs). SFK members c-Src, c-Yes, Fyn, and Lyn are expressed in various cancer cells. SFK kinase activity is negatively regulated by Csk tyrosine kinase. Reduced activity of Csk causes aberrant activation of SFKs, which can be degraded by a compensatory mechanism depending on Cbl-family ubiquitin ligases. We herein investigated whether all SFK members are similarly downregulated by Cbl-family ubiquitin ligases in cancer cells lacking Csk activity. We performed Western blotting of multiple cancer cells knocked down for Csk and found that the protein levels of the 56 kDa isoform of Lyn (LynA), 53 kDa isoform of Lyn (LynB), c-Src, and Fyn, but not of c-Yes, were reduced by Csk depletion. Induction of c-Cbl protein levels was also observed in Csk-depleted cells. The reduction of LynA accompanying the depletion of Csk was significantly reversed by the knockdown for Cbls, whereas such significant recovery of LynB, c-Src, and Fyn was not observed. These results suggested that LynA is selectively downregulated by Cbls in cancer cells lacking Csk activity.

Activated epidermal growth factor receptors (EGFRs) are crucial for inducing metastasis in cancer cells by promoting matrix metalloproteinase (MMP) expression. The present study was designed to investigate the effects of 1‑palmitoyl‑2‑linoleoyl‑3‑acetyl‑rac‑glycerol (PLAG) on MMP expression in epidermal growth factor (EGF)‑stimulated breast cancer cells in vitro. EGF stimulation induced internalization of its cognate receptor, EGFR, for stimulus‑desensitization. These internalized receptors, complexed with the ubiquitin ligase c‑Cbl and EGFR pathway substrate 15 (EPS15) (for degradation), were evaluated by confocal microscopy at 5‑90 min time intervals. During intracellular trafficking of EGFRs, EGF‑induced signaling cascades were analyzed by examining EGFR and SHC phosphorylation. Modulation of MMP expression was assessed by evaluating the activity of transcription factor AP‑1 using a luciferase assay. PLAG accelerated the assembly of EGFRs with c‑Cbl and EPS15 and promoted receptor degradation. This faster intracellular EGFR degradation reduced AP‑1‑mediated MMP expression. PLAG stimulation upregulated thioredoxin‑interacting protein (TXNIP) expression, and this mediated the accelerated receptor internalization. This PLAG‑induced increase in EGFR trafficking was blocked in TXNIP‑silenced cells. By downregulating MMP expression, PLAG effectively attenuated EGF‑induced mobility and invasiveness in these cancer cells. These data suggest that PLAG may be a potential therapeutic agent for blocking metastasis.

Genetic variation in the enzymes that catalyze posttranslational modification of proteins is a potentially important source of phenotypic variation during evolution. Ubiquitination is one such modification that affects turnover of virtually all of the proteins in the cell in addition to roles in signaling and epigenetic regulation. UBE2D3 is a promiscuous E2 enzyme, which acts as an ubiquitin donor for E3 ligases that catalyze ubiquitination of developmentally important proteins. We have used protein sequence comparison of UBE2D3 orthologs to identify a position in the C-terminal α-helical region of UBE2D3 that is occupied by a conserved serine in amniotes and by alanine in anamniote vertebrate and invertebrate lineages. Acquisition of the serine (S138) in the common ancestor to modern amniotes created a phosphorylation site for Aurora B. Phosphorylation of S138 disrupts the structure of UBE2D3 and reduces the level of the protein in mouse embryonic stem cells (ESCs). Substitution of S138 with the anamniote alanine (S138A) increases the level of UBE2D3 in ESCs as well as being a gain of function early embryonic lethal mutation in mice. When mutant S138A ESCs were differentiated into extraembryonic primitive endoderm, levels of the PDGFRα and FGFR1 receptor tyrosine kinases were reduced and primitive endoderm differentiation was compromised. Proximity ligation analysis showed increased interaction between UBE2D3 and the E3 ligase CBL and between CBL and the receptor tyrosine kinases. Our results identify a sequence change that altered the ubiquitination landscape at the base of the amniote lineage with potential effects on amniote biology and evolution.

Long non-coding RNAs (lncRNAs) have been unveiled to play crucial parts in tumorigenesis and chemo-resistance of multiple cancers. Herein, we explored the role of NCK1-AS1 in ovarian cancer (OC). As indicated by TCGA, NCK1-AS1 was markedly upregulated in OC tissues. Besides, we found a dramatic upregulation of NCK1-AS1 in OC cell lines relative to the normal IOSE cells. Interestingly, silencing NCK1-AS1 confined cell proliferation, induced apoptosis and suppressed migration and invasion as well as enhanced DDP sensitivity in OC cells. As for mechanistic investigation, starBase (http://starbase.sysu.edu.cn/) suggested that NCK1-AS1 expression in OC tissues was significantly positively correlated with its adjacent gene, NCK adaptor protein 1 (NCK1). Furtherly, we demonstrated that the cytoplasmic NCK1-AS1 competed with NCK1 mRNA for miR-137 binding to boost NCK1 mRNA expression. Importantly, miR-137 inhibition could only offset the suppression of NCK1-AS1 depletion on NCK1 mRNA level but not the protein level. Moreover, NCK1-AS1 stabilized NCK1 protein by hindering c-Cbl-induced degradation via directly interacting with c-Cbl. Furthermore, NCK1 upregulation reversed the influences of NCK1-AS1 inhibition on the biological behaviors and DDP resistance of OC cells. This study disclosed a NCK1-AS1/NCK1 axis in regulating OC progression and chemo-resistance, opening a new path for treatment and chemo-resistance overcoming in OC.

Aberrant activation of Notch1 signaling frequently occurs in T-cell acute lymphoblastic leukemia (T-ALL). Notch1 activation causes release of intracellular Notch1 (ICN1, the activated form of Notch1) from cell membrane to cytoplasm. As a transcription factor, ICN1 must be transferred into nucleus and bind to the promoters of its downstream target genes. E3 ubiquitin ligase induces ICN1 degradation in cytoplasm, which blocks ICN1 transfer into the nucleus. Flavone is a natural plant polyphenol, demonstrated to have anti-cancer effects in vitro and in vivo in breast and colon cancers. However, the effects of flavone on leukemia have not been reported. In this study, we demonstrated that flavone inhibited cell proliferation by down-regulating Notch1 signal pathway in CCRF-CEM and Molt-4 T-ALL cells. Flavone-mediated upregulation of c-Cbl level results in the increase in its interaction with ICN1, further caused ICN1 ubiquitinylation and degradation. Knockdown of c-Cbl reversed flavone-induced down-regulation of ICN1 and inhibition of cell proliferation in T-ALL cells. In short, this study indicated that flavone exerted resistance to T-ALL by promoting c-Cbl-induced ubiquitinylation and degradation of ICN1.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a chronic inflammatory disease with relatively easy recurrence. However, the precise molecular mechanisms of this disease are poorly known. Based on gene sequencing data obtained from the Gene Expression Omnibus (GEO) database, we constructed coexpression networks by weighted gene coexpression network analysis (WGCNA). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed by the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The core gene of pathogenesis, CRSwNP, was screened by protein-protein interaction data (PPI) from the HPRD database. Unsupervised clustering was applied to screen hub genes related to the phenotype of CRSwNP. Blue and turquoise modules were found to be most significantly related to the pathogenicity of CRSwNP. Functional enrichment analysis showed that cell proliferation in the blue modules, the apoptotic process in the turquoise module, and the cancer pathway in both modules were mostly significantly correlated with the development of CRSwNP. The noncoding RNAs (long noncoding RNA and microRNA) and the top 10 core genes in each module were found to be associated with the pathogenesis of CRSwNP. A total of nine hub genes were identified to be related to the CRSwNP phenotype. By qRT-PCR analysis, AKT1, CDH1, PIK3R1, CBL, LRP1, MALAT1, and XIST were proven to be associated with the pathogenesis of CRSwNP. AGR2, FAM3D, PIP, DSE, and TMC were identified to be related to the CRSwNP phenotype. Further exploration of these genes will reveal more important information about the mechanisms of CRSwNP.

Mutations in the E3 ubiquitin ligase CBL, found in several myeloid neoplasms, lead to decreased ubiquitin ligase activity. In murine systems, these mutations are associated with cytokine‐independent proliferation, thought to result from the activation of hematopoietic growth receptors, including FLT3 and KIT. Using cell lines and primary patient cells, we compared the activity of a panel of FLT3 inhibitors currently being used or tested in AML patients and also evaluated the effects of inhibition of the non‐receptor tyrosine kinase, SYK. We show that FLT3 inhibitors ranging from promiscuous to highly targeted are potent inhibitors of growth of leukaemia cells expressing mutant CBL in vitro, and we demonstrate in vivo efficacy of midostaurin using mouse models of mutant CBL. Potentiation of effects of targeted FLT3 inhibition by SYK inhibition has been demonstrated in models of mutant FLT3‐positive AML and AML characterized by hyperactivated SYK. Here, we show that targeted SYK inhibition similarly enhances the effects of midostaurin and other FLT3 inhibitors against mutant CBL‐positive leukaemia. Taken together, our results support the notion that mutant CBL‐expressing myeloid leukaemias are highly sensitive to available FLT3 inhibitors and that this effect can be significantly augmented by optimum inhibition of SYK kinase.

Objectives MET c-Cbl binding site mutations constitute about 2 % of MET exon 14 alterations in lung cancer. Preclinical data suggests regarding these mutations as functional analogs of MET exon 14 skipping mutations, but clinical validation is lacking. Results We report the case of a patient with metastastic lung adenocarcinoma harboring a c-Cbl binding site alteration and demonstrate clinical, radiological and metabolic response to crizotinib with a PFS of 10.6 months. As escape mechanism, a typical MET resistance mutation could be identified. Conclusion MET c-Cbl binding site mutations should be regarded as a distinct subtype of MET exon 14 alterations. Patients with lung cancer harboring such mutations should be offered targeted therapy.

Cardiomyopathy is a known complication of organic acidemias but generally thought to be secondary to poor metabolic control.Our patient was found through biochemical testing and Sanger sequencing to harbor an Icelandic founder mutation: NM_052845.4(MMAB):c.571C T(p.Arg191Trp), leading to an early presentation (4 h after birth) of cblB-type methylmalonic acidemia (MMA). Biochemical testing of this patient suggested B-12-responsiveness and thus the patient was treated with cyanocobalamin throughout life. Informed parental consent was obtained for this report.Our patient had three metabolic decompensations in her life (at birth, at 1 month, and at 5 months). The first decompensation was probably linked to stress of delivery, second to rhinovirus infection, and third by co-infection of norovirus and enterovirus. At 3 months, the patient was noted to be tachypneic, although this was attributed to her underlying metabolic acidosis. At 5 months and 10 days, the patient was admitted with minor flu-like symptoms but developed severe diarrhea in hospital and upon rehydration had cardiac decompensation and was found to have undiagnosed dilated cardiomyopathy. Although, patient was treated aggressively with dextrose, hemodialysis, levocarnitine, and vasoactive agents, there was limited response to medications to treat cardiac failure, and eventually the patient passed away before turning 6 months old.Other than these three mild decompensations, patient had very good metabolic control, thus demonstrating that even without frequent metabolic decompensation, cardiomyopathy can be an observed phenotype in cblB-type MMA even very early in life, suggesting that this phenotype may be independent of metabolic control.

As it is well known, muscle atrophy is a process in which protein degradation increases and protein synthesis decreases. This process is regulated by a variety of links. Among them, microRNAs play an essential role in this process, which has attracted widespread attention. In this paper, we find that miR-27b-3p and Cbl-b genes are significantly differentially expressed in the induced atrophy model. The dual-luciferase experiment and Western blot analysis confirmed that miR-27b-3p could regulate the expression of Cbl-b. In C2C12-differentiated myotubes, the overexpression of the Cbl-b gene showed that Cbl-b could upregulate the expression of MuRF-1 and Atrogin-1, which are related marker genes of muscle atrophy, at both the mRNA and protein levels, indicating that the Cbl-b gene can specifically affect muscle atrophy. The knockdown of the Cbl-b gene after C2C12-differentiated myotubes induced atrophy treatment can downregulate the expression of muscle-atrophy-related genes, indicating that manual intervention to downregulate the expression of Cbl-b has a certain alleviating effect on muscle atrophy. These data suggest that miR-27b-3p can regulate the expression of the Cbl-b gene and then exert a particular influence on muscle atrophy through the Cbl-b gene.

Pathogenic variants in MMAB cause cblB-type methylmalonic aciduria, an autosomal-recessive disorder of propionate metabolism. MMAB encodes ATP:cobalamin adenosyltransferase, using ATP and cob(I)alamin to create 5’-deoxyadenosylcobalamin (AdoCbl), the cofactor of methylmalonyl-CoA mutase (MMUT). We identified bi-allelic disease-causing variants in MMAB in 97 individuals with cblB-type methylmalonic aciduria, including 33 different and 16 novel variants. Missense changes accounted for the most frequent pathogenic alleles (p.(Arg186Trp), N = 57; p.(Arg191Trp), N = 19); while c.700C > T (p.(Arg234*)) was the most frequently identified truncating variant (N = 14). In fibroblasts from 76 affected individuals, the ratio of propionate incorporation in the presence and absence of hydroxocobalamin (PI ratio) was associated to clinical cobalamin responsiveness and later disease onset. We found p.(Arg234*) to be associated with cobalamin responsiveness in vitro, and clinically with later onset; p.(Arg186Trp) and p.(Arg191Trp) showed no clear cobalamin responsiveness and early onset. Mapping these and novel variants onto the MMAB structure revealed their potential to affect ATP and AdoCbl binding. Follow-up biochemical characterization of recombinant MMAB identified its three active sites to be equivalent for ATP binding, determined by fluorescence spectroscopy (Kd = 21 µM) and isothermal calorimetry (Kd = 14 µM), but function as two non-equivalent AdoCbl binding sites (Kd1 = 0.55 μM; Kd2 = 8.4 μM). Ejection of AdoCbl was activated by ATP (Ka = 24 µM), which was sensitized by the presence of MMUT (Ka = 13 µM). This study expands the landscape of pathogenic MMAB variants, provides association of in vitro and clinical responsiveness, and facilitates insight into MMAB function, enabling better disease understanding.

It is well known that oxidative stress induces muscle atrophy, which decreases with the activation of Nrf2/HO-1. Fermented oyster extracts (FO), rich in γ-aminobutyric acid (GABA) and lactate, have shown antioxidative effects. We evaluated whether FO decreased oxidative stress by upregulating Nrf2/HO-1 and whether it decreased NF-κB, leading to decreased IL-6 and TNF-α. Decreased oxidative stress led to the downregulation of Cbl-b ubiquitin ligase, which increased IGF-1 and decreased FoxO3, atrogin1, and Murf1, and eventually decreased muscle atrophy in dexamethasone (Dexa)-induced muscle atrophy animal model. For four weeks, mice were orally administered with FO, GABA, lactate, or GABA+Lactate, and then Dexa was subcutaneously injected for ten days. During Dexa injection period, FO, GABA, lactate, or GABA+Lactate were also administered, and grip strength test and muscle harvesting were performed on the day of the last Dexa injection. We compared the attenuation effect of FO with GABA, lactate, and GABA+lactate treatment. Nrf2 and HO-1 expressions were increased by Dexa but decreased by FO; SOD activity and glutathione levels were decreased by Dexa but increased by FO; NADPH oxidase activity was increased by Dexa but decreased by FO; NF-κB, IL-6, and TNF-α activities were increased by Dexa were decreased by FO; Cbl-b expression was increased by Dexa but restored by FO; IGF-1 expression was decreased by Dexa but increased by FO; FoxO3, Atrogin-1, and MuRF1 expressions were increased by Dexa but decreased by FO. The gastrocnemius thickness and weight were decreased by Dexa but increased by FO. The cross-sectional area of muscle fiber and grip strength were decreased by Dexa but increased by FO. In conclusion, FO decreased Dexa-induced oxidative stress through the upregulation of Nrf2/HO-1. Decreased oxidative stress led to decreased Cbl-b, FoxO3, atrogin1, and MuRF1, which attenuated muscle atrophy.

Methylmalonic aciduria cblB type (MMA cblB type, MMAB OMIM #251110), caused by a deficiency in the enzyme ATP:cob(I)alamin adenosyltransferase (ATR, E.C_2. 5.1.17), is a severe metabolic disorder with a poor prognosis despite treatment. We recently described the potential therapeutic use of pharmacological chaperones (PCs) after increasing the residual activity of ATR in patient-derived fibroblasts. The present work reports the successful generation of hepatocyte-like cells (HLCs) differentiated from two healthy and two MMAB induced pluripotent stem cell (iPSC) lines, and the use of this platform for testing the effects of PCs. The MMAB cells produced little ATR, showed reduced residual ATR activity, and had higher concentrations of methylmalonic acid compared to healthy HLCs. Differential proteome analysis revealed the two MMAB HCLs to show reproducible differentiation, but this was not so for the healthy HLCs. Interestingly, PC treatment in combination with vitamin B12 increased the amount of ATR available, and subsequently ATR activity, in both MMAB HLCs. More importantly, the treatment significantly reduced the methylmalonic acid content of both. In summary, the HLC model would appear to be an excellent candidate for the pharmacological testing of the described PCs, for analyzing the effects of new drugs, and investigating the repurposing of older drugs, before testing in animal models, This work was funded by the Fundacion ´ Isabel Gemio-Fundaci´ on La Caixa [LCF/PR/PR16/11110018], the Instituto de Salud Carlos III (ISCIII),-European Regional Development Fund [PI19/01155] and the Consejería de Educaci´ on, Juventud y Deporte, Comunidad de Madrid [B2017/BMD3721]

Arginine kinase-binding protein 2 (ArgBP2) is an adapter protein that belongs to the sorbin homology (SoHo) family. The SoHo family also includes c-Cbl-associated protein (CAP) and vinexin, both of which share structural and functional similarities to ArgBP2. However, the role of SoHo family proteins in cell signaling, drug resistance, metabolism, and diseases, especially cancer, is not fully understood. Herein, we summarize the structure of SoHo family proteins, their post-translational modifications and the comprehensive network of cellular pathways regulated by these proteins, with an emphasis on ArgBP2. We also discuss the relevance of the SoHo family proteins in lipid raft distribution, extracellular matrix-associated microenvironments, and drug discovery. This review provides insights into the possibility of targeting ArgBP2 and other SoHo family proteins as drugs for use in preclinical trials.

The family of Abelson interactor (Abi) proteins is a component of WAVE regulatory complex (WRC) and a downstream target of Abelson (Abl) tyrosine kinase. The fact that Abi proteins also interact with diverse membrane proteins and intracellular signaling molecules places these proteins at a central position in the network that controls cytoskeletal functions and cancer cell metastasis. Here, we identified a motif in Abi proteins that conforms to consensus sequences found in a cohort of receptor and non-receptor tyrosine kinases that bind to Cbl-tyrosine kinase binding domain. The phosphorylation of tyrosine 213 in this motif is essential for Abi degradation. Double knockout of c-Cbl and Cbl B in Bcr-Abl-transformed leukemic cells abolishes Abi1, Abi2, and WAVE2 degradation. Moreover, knockout of Abi1 reduces Src family kinase Lyn activation in Bcr-Abl-positive leukemic cells and promotes EGF-induced EGF receptor downregulation in breast cancer cells. Importantly, Abi1 depletion impeded breast cancer cell invasion in vitro and metastasis in mouse xenografts. Together, these studies uncover a novel mechanism by which the WRC and receptor/non-receptor tyrosine kinases are regulated and identify Abi1 as a potential therapeutic target for metastatic breast cancer.

Dendritic cells (DCs) are composed of multiple lineages of hematopoietic cells and orchestrate immune responses upon detecting the danger and inflammatory signals associated with pathogen and damaged tissues. Under steady-state, DCs are maintained at limited numbers and the functionally quiescent status. While it is known that a fine balance in the DC homeostasis and activation status is also important to prevent autoimmune diseases and hyperinflammation, mechanisms that control DC development and activation under stead-state remain not fully understood. Here we show that DC-specific ablation of CBL and CBL-B (CBL-/-CBL-B-/-) leads to spontaneous liver inflammation and fibrosis and early death of the mice. The mutant mice have a marked expansion of classic CD8α+/CD103+ DCs (cDC1s) in peripheral lymphoid organs and the liver. These DCs exhibit atypical activation phenotypes characterized by an increased production of inflammatory cytokines and chemokines but not the cell surface MHC-II and costimulatory ligands. While the mutant mice also have massive T cell activation, lymphocytes are not required for the disease development. The CBL-/-CBL-B-/- mutation enhances FLT3-mTOR signaling, due to defective FLT3 ubiquitination and degradation. Blockade of FLT3-mTOR signaling normalizes the homeostasis of cDC1s and attenuates liver inflammation. Our result thus reveals a critical role of CBLs in the maintenance of DC homeostasis and immune quiescence. This regulation could be relevant to liver inflammatory diseases and fibrosis in humans.

CBL family proteins (CBL, CBLB and CBLC in mammals) are E3 ubiquitin ligases of protein tyrosine kinases. CBL mediates the lysosomal degradation of activated EGFR through K63-linked ubiquitination, while CBLC has an oncogenic function by positively regulating EGFR activation through K6 and K11-linked ubiquitination in EGFR mutant lung adenocarcinoma (LAD). Here, we used immunoprecipitation and mass spectrometry to study the CBLC interactome, and found that CBLC is also involved in cell cycle regulation by stabilizing Aurora kinase A (AURKA). CBLC interacted with the kinase domain of AURKA and positively regulated the stability of AURKA by conjugating monoubiquitination and K11/K63-linked polyubiquitination, which are protective from degrading K11/K48 polyubiquitination. CBLC depletion markedly decreased the half-life of AURKA in cycloheximide-treated LAD cells. When LAD cells were synchronized with double thymidine block at the G1/S boundary and then released into mitotic arrest, CBLC depletion delayed the accumulation and activation of AURKA and prevented cancer cells from entering mitosis. CBLC deficiency significantly delayed cell cycle progression, reduced the mitotic population, and increased apoptosis of LAD cells. Targeting CBLC inhibited tumor growth of LAD cells and enhanced their sensitivity to paclitaxel in xenograft models. Immunohistochemical staining of the tissue microarray also revealed a positive correlation between the expression of CBLC and AURKA in normal and LAD tissues, further supporting the positive regulation of AURKA expression by CBLC. In summary, these findings indicate that the oncogenic E3 ligase CBLC plays a role in mitotic entry by stabilizing AURKA via ubiquitination in LAD. This work demonstrates that targeting CBLC combined with paclitaxel might be a potential option for the treatment of LAD patients who have no available targeted therapies.

Casitas B-lineage lymphoma b (Cbl-b) is one of the E3 ubiquitin ligases that ubiquitinate Tropomyosin-related kinase A (TrkA), a key nerve growth factor receptor involved in the pathological pain. Here we found that Cbl-b was abundant in dorsal root ganglion (DRG) neurons of mice and co-localized with TrkA. Ubiquitination of TrkA by Cbl-b exerted a tonic negative control over the protein level of TrkA. Knockdown of Cbl-b caused TrkA accumulation in DRGs and evoked mechanical and heat hypersensitivity in intact mice. Our data showed that knee osteoarthritis induced by destabilization of the medial meniscus (DMM) led to the dissociation of Cbl-b with TrkA in DRG neurons, which impaired the ability of Cbl-b to ubiquitinate TrkA and served as an important mechanism to cause TrkA-dependent pain sensitization. Viral expression of constitutively active Cbl-b in DRGs of osteoarthritic mice effectively repressed TrkA protein level and more importantly, alleviated mechanical allodynia and heat hyperalgesia. Viral delivery of Cbl-b through intra-articular route generated a similar analgesic action. These data suggested that ubiquitination of TrkA by Cbl-b might represent an effective way to treat the osteoarthritic pain.

Juvenile myelomonocytic leukemia (JMML) typically requires allogeneic hematopoietic cell transplantation with full donor chimerism for cure. Certain genetic subtypes, including JMML due to germline mutations in CBL, can have a more indolent course. We describe a young male patient with CBL-related JMML who experienced primary graft failure after allogeneic hematopoietic cell transplantation. Despite autologous recovery, the resulting hematopoietic tissue did not harbor the original homozygous CBL mutations, due to reversion of prior loss of heterozygosity of the 11q chromosomal region. The patient remains disease free without further leukemia-directed therapy.

The spatiotemporal mitotic processes are controlled qualitatively by phosphorylation and qualitatively by ubiquitination. Although the SKP1-CUL1-F-box protein (SCF) complex and the anaphase-promoting complex/cyclosome (APC/C) mainly mediate ubiquitin-dependent proteolysis of mitotic regulators, the E3 ligase for a large portion of mitotic proteins has yet to be identified. Here, we report c-Cbl as an E3 ligase that degrades DDA3, a protein involved in spindle dynamics. Depletion of c-Cbl led to increased DDA3 protein levels, resulting in increased recruitment of Kif2a to the mitotic spindle, a concomitant reduction in spindle formation, and chromosome alignment defects. Furthermore, c-Cbl depletion induced centrosome over-duplication and centriole amplification. Therefore, we concluded that c-Cbl controls spindle dynamics and centriole duplication through its E3 ligase activity against DDA3.

Spinal cord injury (SCI) is a devastating disease. Strategies that enhance the intrinsic regenerative ability are very important for the recovery of SCI to radically prevent the occurrence of sensory disorders. Epidermal growth factor (EGF) showed a limited effect on the growth of primary sensory neuron neurites due to the degradation of phosphorylated-epidermal growth factor receptor (p-EGFR) in a manner dependent on Casitas B-lineage lymphoma (CBL) (an E3 ubiquitin-protein ligase). MiR-22-3p predicted from four databases could target CBL to inhibit the expression of CBL, increase p-EGFR levels and neurites length via STAT3/GAP43 pathway rather than Erk1/2 axis. EGF, EGFR, and miR-22-3p were downregulated sharply after injury. In vivo miR-22-3p Agomir application could regulate CBL/p-EGFR/p-STAT3/GAP43/p-GAP43 axis, and restore spinal cord sensory conductive function. This study clarified the mechanism of the limited promotion effect of EGF on adult primary sensory neuron neurite and targeting miR-22-3p could be a novel strategy to treat sensory dysfunction after SCI.

Effective bone resorption by osteoclasts is critical for balanced bone remodeling. We have previously reported that mice harboring a substitution mutation of tyrosine 737 to phenylalanine in the adapter protein Cbl (Cbl Y737F , YF) have increased bone volume partly due to decreased osteoclast-mediated bone resorption. The Cbl Y737F mutation abrogates interaction between Cbl and the p85 subunit of PI3K. Here, we studied the mechanism for defective resorptive function of YF mutant osteoclasts. The YF osteoclasts had intact actin cytoskeletons and sealing zones. Expression and localization of proteins needed for acidification of the resorptive lacunae were also comparable between the WT and YF osteoclasts. In contrast, secretion of Cathepsin K, a major protease needed to degrade collagen, was diminished in the conditioned media derived from YF osteoclasts. The targeting of Cathepsin K into LAMP2-positive vesicles was also compromised due to decreased number of LAMP2-positive vesicles in YF osteoclasts. Further, we found that in contrast to WT, conditioned media derived from YF osteoclasts promoted increased numbers of alkaline phosphatase positive colonies, and increased expression of osteogenic markers in WT calvarial cultures. Cumulatively, our results suggest that the Cbl-PI3K interaction regulates Cathepsin K secretion required for proper bone resorption, and secretion of factors which promote osteogenesis.