Cbl-mediated K63-linked ubiquitination of JAK2 enhances JAK2 phosphorylation and signal transduction

miR-206 alleviates LPS-induced inflammatory injury in cardiomyocytes via directly targeting USP33 to inhibit the JAK2/STAT3 signaling pathway

Previous reports have confirmed that miR-206 participates in inflammatory cardiomyopathy, but its definite mechanism remains elusive. This study aims to elucidate the potential mechanism of miR-206 in septic cardiomyopathy (SCM). The primary mouse cardiomyocytes were isolated and exposed to lipopolysaccharides (LPS) to construct a septic injury model in vitro. Then, the gene transcripts and protein levels were detected by RT-qPCR and/or Western blot assay. Cell proliferation, apoptosis, and inflammatory responses were evaluated by CCK-8/EdU, flow cytometry, and ELISA assays, respectively. Dual luciferase assay, Co-IP, and ubiquitination experiments were carried out to validate the molecular interactions among miR-206, USP33, and JAK2/STAT3 signaling. miR-206 was significantly downregulated, but USP33 was upregulated in LPS-induced cardiomyocytes. Gain-of-function of miR-206 elevated the proliferation but suppressed the inflammatory responses and apoptosis in LPS-induced cardiomyocytes. USP33, as a member of the USP protein family, was confirmed to be a direct target of miR-206 and could catalyze deubiquitination of JAK2 to activate JAK2/STAT3 signaling. Rescue experiments presented that neither upregulation of USP33 nor JAK2/STAT3 signaling activation considerably reversed the protective effects of miR-206 upregulation in LPS-induced cardiomyocytes. The above data showed that miR-206 protected cardiomyocytes from LPS-induced inflammatory injuries by targeting the USP33/JAK2/STAT3 signaling pathway, which might be a novel target for SCM treatment.

Understanding triple negative myeloproliferative neoplasms: pathogenesis, clinical features, and management

ABSTRACTMyeloproliferative neoplasms (MPNs) that lack the classical "driver mutations," termed triple negative MPNs, remain a poorly understood entity. Despite considerable progress toward understanding MPN pathobiology, the mechanisms leading to the development of these MPNs remains inadequately elucidated. While triple negative primary myelofibrosis (TN-PMF) portends a poor prognosis, triple negative essential thrombocythemia (TN-ET) is more favorable as compared with JAK2 mutated ET. In this review, we summarize the clinical features and prognosis of TN-PMF and -ET as well as diagnostic challenges including identification of non-canonical driver mutations. We also discuss additional molecular drivers to better understand possible pathogenic mechanisms underlying triple negative MPNs. Finally, we highlight current therapeutic approaches as well as novel targets, particularly in the difficult to treat TN-PMF population.

Intercellular adhesion molecule 2 as a novel prospective tumor suppressor induced by ERG promotes ubiquitination-mediated radixin degradation to inhibit gastric cancer tumorigenicity and metastasis

BACKGROUND

Gastric cancer (GC) is a fatal cancer with unclear pathogenesis. In this study, we explored the function and potential mechanisms of intercellular adhesion molecule 2 (ICAM2) in the development and advancement of GC.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were performed to quantify ICAM2 expression in harvested GC tissues and cultured cell lines. Immunohistochemical analyses were conducted on a GC tissue microarray to quantify ICAM2 expression and explore its implication on the prognosis of GC patients. In vitro experiments were carried out to reveal the biological functions of ICAM2 in GC cell lines. Further, in vivo experiments were conducted using xenograft models to assess the impact of ICAM2 on GC development and metastasis. Western blot, immunofluorescence, immunoprecipitation, luciferase assay, chromatin immunoprecipitation, and ubiquitination analysis were employed to investigate the underlying mechanisms.

RESULTS

ICAM2 expression was downregulated in GC, positively correlating with advanced T stage, distant metastasis, advanced clinical stage, vessel invasion, and shorter patient survival time. ICAM2 overexpression suppressed the proliferation, migration, invasion, metastasis of GC cells as well as their ability to form tumors, whereas ICAM2 knockdown yielded opposite results. Erythroblast transformation-specific-related gene (ERG) as a transcription factor promoted the transcription of ICAM2 by binding to the crucial response element localized within its promoter region. Further analysis revealed that ICAM2 reduced radixin (RDX) protein stability and expression. In these cells, ICAM2 bound to the RDX protein to promote the ubiquitination and degradation of RDX via NEDD4 Like E3 Ubiquitin Protein Ligase (NEDD4L), and this post-translational modification resulted in the inhibition of GC.

CONCLUSIONS

In summary, this study demonstrates that ICAM2, which is induced by ERG, suppresses GC progression by enhancing the ubiquitination and degradation of RDX in a NEDD4L-dependent manner. Therefore, these results suggest that ICAM2 is a potential prognostic marker and a therapeutic target for GC.

ARID2 mitigates hepatic steatosis via promoting the ubiquitination of JAK2

Non-alcoholic fatty liver disease (NAFLD) has become a growing public health problem. However, the complicated pathogenesis of NAFLD contributes to the deficiency of effective clinical treatment. Here, we demonstrated that liver-specific loss of Arid2 induced hepatic steatosis and this progression could be exacerbated by HFD. Mechanistic study revealed that ARID2 repressed JAK2-STAT5-PPARγ signaling pathway by promoting the ubiquitination of JAK2, which was mediated by NEDD4L, a novel E3 ligase for JAK2. ChIP assay revealed that ARID2 recruited CARM1 to increase H3R17me2a level at the NEDD4L promoter and activated the transcription of NEDD4L. Moreover, inhibition of Jak2 by Fedratinib in liver-specific Arid2 knockout mice alleviated HFD-induced hepatic steatosis. Downregulation of ARID2 and the reverse correlation between ARID2 and JAK2 were also observed in clinical samples. Therefore, our study has revealed an important role of ARID2 in the development of NAFLD and provided a potential therapeutic strategy for NAFLD.

JAK2-CHK2 signaling safeguards the integrity of the mitotic spindle assembly checkpoint and genome stability

Checkpoint kinase 2 (CHK2) plays an important role in safeguarding the mitotic progression, specifically the spindle assembly, though the mechanism of regulation remains poorly understood. Here, we identified a novel mitotic phosphorylation site on CHK2 Tyr156, and its responsible kinase JAK2. Expression of a phospho-deficient mutant CHK2 Y156F or treatment with JAK2 inhibitor IV compromised mitotic spindle assembly, leading to genome instability. In contrast, a phospho-mimicking mutant CHK2 Y156E restored mitotic normalcy in JAK2-inhibited cells. Mechanistically, we show that this phosphorylation is required for CHK2 interaction with and phosphorylation of the spindle assembly checkpoint (SAC) kinase Mps1, and failure of which results in impaired Mps1 kinetochore localization and defective SAC. Concordantly, analysis of clinical cancer datasets revealed that deletion of JAK2 is associated with increased genome alteration; and alteration in CHEK2 and JAK2 is linked to preferential deletion or amplification of cancer-related genes. Thus, our findings not only reveal a novel JAK2-CHK2 signaling axis that maintains genome integrity through SAC but also highlight the potential impact on genomic stability with clinical JAK2 inhibition.

Role of CBL Mutations in Cancer and Non-Malignant Phenotype

Simple Summary

CBL mutations are progressively being described as involved in different clinical manifestations. Somatic CBL mutations can be found in different type of cancer. The clinical spectrum of germline mutations configures the so-called CBL syndrome, a cancer-predisposing condition that includes multisystemic involvement characterized by variable phenotypic expression and expressivity. In this review we provide an up-to-date review of the clinical manifestation of CBL mutations and of the molecular mechanisms in which CBL exerts its pathogenic role.

Abstract

CBL plays a key role in different cell pathways, mainly related to cancer onset and progression, hematopoietic development and T cell receptor regulation. Somatic CBL mutations have been reported in a variety of malignancies, ranging from acute myeloid leukemia to lung cancer. Growing evidence have defined the clinical spectrum of germline CBL mutations configuring the so-called CBL syndrome; a cancer-predisposing condition that also includes multisystemic involvement characterized by variable phenotypic expression and expressivity. This review provides a comprehensive overview of the molecular mechanisms in which CBL exerts its function and describes the clinical manifestation of CBL mutations in humans.

Overexpression of E3 ubiquitin ligase Cbl attenuates endothelial dysfunction in diabetes mellitus by inhibiting the JAK2/STAT4 signaling and Runx3-mediated H3K4me3

BACKGROUND

Diabetes mellitus (DM), a most common chronic disease, is featured with impaired endothelial function and bioavailability of nitric oxide (NO), while E3 ubiquitin ligase appears to alleviate endothelial dysfunction as a promising option for DM treatment. Herein, we aimed to determine whether E3 ubiquitin ligase casitas B-lineage lymphoma (Cbl) alleviates endothelial dysfunction in DM rats by JAK2/STAT4 pathway.

METHODS

A rat model of DM was developed through intraperitoneal injection of streptozotocin, followed by collection of aortic tissues to determine the expression of Cbl, JAK2, runt-related transcription factor 3 (Runx3) and STAT4. Human umbilical vein endothelial cells (HUVECs) were cultured in high glucose (HG) condition to induce DM as an in vitro model. With gain- and loss-function method, we assessed the aberrantly expressed Cb1 on endothelial dysfunction, NO production and apoptosis of HUVECs.

RESULTS

Cbl was reduced in DM rat tissues and HG-induced HUVECs, where JAK2, Runx3 and STAT4 were elevated. It was found that overexpression of Cbl alleviated endothelial dysfunction by increasing NO production and restoring vasodilation and suppressing apoptosis of HUVECs. Mechanistically, Cb1 enhanced JAK2 ubiquitination and decreased JAK2 and STAT4 expression, where STAT4 improved Runx3 expression by regulating histone H3 lysine 4 trimethylation level. Overexpression of JAK2 and STAT4, or Runx3 increased apoptosis of HUVECs, abrogating the effect of Cb1 on endothelial function.

CONCLUSION

In conclusion, Cbl alleviates endothelial dysfunction by inactivation of the JAK2/STAT4 pathway and inhibition of Runx3 expression in DM. These evidence might underlie novel Cbl-based treatment against DM in the future.

SENP1-mediated deSUMOylation of JAK2 regulates its kinase activity and platinum drug resistance

The JAK2/STAT pathway is hyperactivated in many cancers, and such hyperactivation is associated with a poor clinical prognosis and drug resistance. The mechanism regulating JAK2 activity is complex. Although translocation of JAK2 between nucleus and cytoplasm is an important regulatory mechanism, how JAK2 translocation is regulated and what is the physiological function of this translocation remain largely unknown. Here, we found that protease SENP1 directly interacts with and deSUMOylates JAK2, and the deSUMOylation of JAK2 leads to its accumulation at cytoplasm, where JAK2 is activated. Significantly, this novel SENP1/JAK2 axis is activated in platinum-resistant ovarian cancer in a manner dependent on a transcription factor RUNX2 and activated RUNX2/SENP1/JAK2 is critical for platinum-resistance in ovarian cancer. To explore the application of anti-SENP1/JAK2 for treatment of platinum-resistant ovarian cancer, we found SENP1 deficiency or treatment by SENP1 inhibitor Momordin Ic significantly overcomes platinum-resistance of ovarian cancer. Thus, this study not only identifies a novel mechanism regulating JAK2 activity, but also provides with a potential approach to treat platinum-resistant ovarian cancer by targeting SENP1/JAK2 pathway.

Inhibition of USP9X Downregulates JAK2-V617F and Induces Apoptosis Synergistically with BH3 Mimetics Preferentially in Ruxolitinib-Persistent JAK2-V617F-Positive Leukemic Cells

JAK2-V617F plays a key role in the pathogenesis of myeloproliferative neoplasm. However, its inhibitor ruxolitinib has shown limited clinical efficacies because of the ruxolitinib-persistent proliferation of JAK2-V617F-positive cells. We here demonstrate that the USP9X inhibitor WP1130 or EOAI3402143 (G9) inhibited proliferation and induced apoptosis more efficiently in cells dependent on JAK2-V617F than on cytokine-activated JAK2. WP1130 preferentially downregulated activated and autophosphorylated JAK2-V617F by enhancing its K63-linked polyubiquitination and inducing its aggresomal translocation to block downstream signaling. Furthermore, JAK2-V617F associated physically with USP9X in leukemic HEL cells. Induction of apoptosis by inhibition of USP9X was mediated through the intrinsic mitochondria-mediated pathway, synergistically enhanced by BH3 mimetics, prevented by overexpression of Bcl-xL, and required oxidative stress to activate stress-related MAP kinases p38 and JNK as well as DNA damage responses in HEL cells. Although autophosphorylated JAK2-V617F was resistant to WP1130 in the ruxolitinib-persistent HEL-R cells, these cells expressed Bcl-2 and Bcl-xL at lower levels and showed an increased sensitivity to WP1130 as well as BH3 mimetics as compared with ruxolitinib-naive HEL cells. Thus, USP9X represents a promising target along with anti-apoptotic Bcl-2 family members for novel therapeutic strategies against JAK2-V617F-positive myeloproliferative neoplasms, particularly under the ruxolitinib persistence conditions.

Receptor Tyrosine Kinase Ubiquitination and De-Ubiquitination in Signal Transduction and Receptor Trafficking

Receptor tyrosine kinases (RTKs) are membrane-based sensors that enable rapid communication between cells and their environment. Evidence is now emerging that interdependent regulatory mechanisms, such as membrane trafficking, ubiquitination, proteolysis and gene expression, have substantial effects on RTK signal transduction and cellular responses. Different RTKs exhibit both basal and ligand-stimulated ubiquitination, linked to trafficking through different intracellular compartments including the secretory pathway, plasma membrane, endosomes and lysosomes. The ubiquitin ligase superfamily comprising the E1, E2 and E3 enzymes are increasingly implicated in this post-translational modification by adding mono- and polyubiquitin tags to RTKs. Conversely, removal of these ubiquitin tags by proteases called de-ubiquitinases (DUBs) enables RTK recycling for another round of ligand sensing and signal transduction. The endocytosis of basal and activated RTKs from the plasma membrane is closely linked to controlled proteolysis after trafficking and delivery to late endosomes and lysosomes. Proteolytic RTK fragments can also have the capacity to move to compartments such as the nucleus and regulate gene expression. Such mechanistic diversity now provides new opportunities for modulating RTK-regulated cellular responses in health and disease states.