FAT10 protects against ischemia-induced ventricular arrhythmia by decreasing Nedd4-2/Nav1.5 complex formation

CKIP-1 mediates CK2 translocation to regulate Nav1.5 and Kir2.1 channel complexes in cardiomyocytes

Sodium and potassium channels, especially Nav1.5 and Kir2.1, play key roles in the formation of action potentials in cardiomyocytes. These channels interact with, and are regulated by, synapse-associated protein 97 (SAP97). However, the regulatory role of SAP97 in myocyte remains incompletely understood. Here, we investigate the function of SAP97 phosphorylation in the regulation of Nav1.5 and Kir2.1 channel complexes and the upstream regulation of SAP97. We found that SAP97 is phosphorylated by casein kinase II (CK2) in vitro. In addition, transfection of casein kinase 2 interacting protein-1 (CKIP-1) into cardiomyocytes to drive CK2 from the nucleus to the cytoplasm, increased SAP97 phosphorylation and Nav1.5 and Kir2.1 current activity. These findings demonstrated that CKIP-1 modulates the subcellular translocation of CK2, which regulates Nav1.5 and Kir2.1 channel complex formation and activity in cardiomyocytes.

The E3 ubiquitin ligases regulate inflammation in cardiovascular diseases

Accumulating evidence has illustrated that the E3 ubiquitin ligases critically participate in the development and progression of cardiovascular diseases. Dysregulation of E3 ubiquitin ligases exacerbates cardiovascular diseases. Blockade or activation of E3 ubiquitin ligases mitigates cardiovascular performance. Therefore, in this review, we mainly introduced the critical role and underlying molecular mechanisms of E3 ubiquitin ligase NEDD4 family in governing the initiation and progression of cardiovascular diseases, including ITCH, WWP1, WWP2, Smurf1, Smurf2, Nedd4-1 and Nedd4-2. Moreover, the functions and molecular insights of other E3 ubiquitin ligases, such as F-box proteins, in cardiovascular disease development and malignant progression are described. Furthermore, we illustrate several compounds that alter the expression of E3 ubiquitin ligases to alleviate cardiovascular diseases. Therefore, modulation of E3 ubiquitin ligases could be a novel and promising strategy for improvement of therapeutic efficacy of deteriorative cardiovascular diseases.

TRPV2 inhibitor tranilast prevents atrial fibrillation in rat models of pulmonary hypertension

Atrial fibrillation (AF) is common in pulmonary hypertension (PH), whereas the mechanisms and treatments remain to be explored. TRPV2 regulates the structure and function of the cardiovascular system; however, little attention has been given to its role in AF. This study was to determine whether TRPV2 was involved in PH-induced AF and the effects of TRPV2 inhibitor tranilast on AF in rat models of PH. Monocrotaline (MCT) and SU5416/hypoxia (SuHx)-induced PH models were performed to detect atrial electrophysiological parameters. Daily tranilast (a TRPV2 inhibitor) or saline was given starting 1 day before PH establishment. PH increased the susceptibility to AF, with TRPV2 up-regulated in the right atria. Compared to PH rats, tranilast reduced AF inducibility and the prolongations of ERP and APD; mitigated cardiopulmonary remodeling and the increases in P-wave duration and P-R interval; partially reversed the down-regulation of ion channels such as Cav1.2, Nav1.5, Kv4.3, Kv4.2, Kv1.5, Kir2.1, Kir3.1, Kir3.4 as well as connexin (Cx) 40 and Cx43; improved right atrial (RA) fibrosis, enlargement, and myocardial hypertrophy; decreased the accumulation of inflammatory cells; down-regulated inflammatory indicators such as TNF-α, IL-1β, CXCL1, and CXCL2; and inhibited the activation of the PI3K-AKT-NF-κB signaling pathway. Our results reveal that TRPV2 participates in PH-induced AF, and TRPV2 inhibitor tranilast prevents PH-induced RA remodeling. TRPV2 might be a promising target for PH-induced AF.

USP38 exacerbates atrial inflammation, fibrosis, and susceptibility to atrial fibrillation after myocardial infarction in mice

BACKGROUND

Inflammation plays an important role in the pathogenesis of atrial fibrillation (AF) after myocardial infarction (MI). The role of USP38, a member of the ubiquitin-specific protease family, on MI-induced atrial inflammation, fibrosis, and associated AF is unclear.

METHODS

In this study, we surgically constructed a mouse MI model using USP38 cardiac conditional knockout (USP38-CKO) and cardiac-specific overexpression (USP38-TG) mice and applied biochemical, histological, electrophysiological characterization and molecular biology to investigate the effects of USP38 on atrial inflammation, fibrosis, and AF and its mechanisms.

RESULTS

Our results revealed that USP38-CKO attenuates atrial inflammation, thereby ameliorating fibrosis, and abnormal electrophysiologic properties, and reducing susceptibility to AF on day 7 after MI. USP38-TG showed the opposite effect. Mechanistically, The TAK1/NF-κB signaling pathway in the atria was significantly activated after MI, and phosphorylated TAK1, P65, and IκBα protein expression was significantly upregulated. USP38-CKO inhibited the activation of the TAK1/NF-κB signaling pathway, whereas USP38-TG overactivated the TAK1/NF-κB signaling pathway after MI. USP38 is dependent on the TAK1/NF-κB signaling pathway and regulates atrial inflammation, fibrosis, and arrhythmias after MI to some extent.

CONCLUSIONS

USP38 plays an important role in atrial inflammation, fibrosis, and AF susceptibility after MI, providing a promising target for the treatment of AF after MI.

Human leukocyte antigen F-associated transcript 10 regulates the IKs potassium channel by competing for Kv7.1 ubiquitination

The protein expression and function changes from the slow-delayed rectifying K+ current, IKs, are tightly associated with ventricular cardiac arrhythmias. Human leukocyte antigen F-associated transcript 10 (FAT10), a member of the ubiquitin-like-modifier family, exerts a protective effect against myocardial ischaemia. However, whether or how FAT10 influences the function of IKs remains unclear. Here, human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and Fat10 knockout HEK293 (Fat10-/-) cells through CRISPR-Cas9 technology were used to evaluate the novel modulation of FAT10 in IKs function. Patch-clamp studies showed that the overexpression of FAT10 significantly enhanced the current density of IKs both in hiPSC-CMs and HEK293-Fat10-/- cells. In addition, a shortened action potential duration (APD) was seen from hiPSC-CMs transfected with the ad-Fat10 virus. Then, a series of molecular approaches from neonatal rat cardiomyocytes, H9C2 cells and HEK293 cells were used to determine the regulatory mechanism of FAT10 in IKs. First, western blot assays indicated that the expression of Kv7.1, the alpha-subunit of IKs, was increased when FAT10 was overexpressed. Furthermore, immunofluorescence and co-immunoprecipitation assays demonstrated that FAT10 could interact with Kv7.1. Notably, FAT10 impedes Kv7.1 ubiquitination and degradation, thereby stabilizing its expression. Finally, a hypoxia model of hiPSC-CMs was established, and the overexpression of FAT10 showed a protective effect against hypoxia-induced decreases in the current density of IKs. Taken together, these findings revealed a novel role of FAT10 in the regulation of the IKs potassium channel by competing for Kv7.1 ubiquitination, which provides a new electrophysiological insight that FAT10 could modulate Kv7.1. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

Ubiquitin like protein FAT10 repressed cardiac fibrosis after myocardial ischemic via mediating degradation of Smad3 dependent on FAT10-proteasome system

Cardiac fibrosis after myocardial ischemic (MI) injury is a key factor in heart function deterioration. We recently showed that ubiquitin-like protein human HLA-F adjacent transcript (FAT10) plays a novel role in ischemic cardiovascular diseases, but its function in cardiac fibrosis remains unknown. The present study aims to detail the pathophysiological function of FAT10 in MI injury-induced cardiac fibrosis and its underlying mechanism. In vivo, a systemic FAT10 deficiency mouse (Fat10 ^-/-) model was established which exhibited excessive cardiac fibrosis and deleterious cardiac function after MI when compared to wild-type mice. Cardiac fibrotic-related proteins (α-SMA, collagen I and collagen III) content were increased in MI-Fat10 ^-/- mice. Similarly, cardiac FAT10 restoration in Fat10^-/- mice suppressed fibrosis and improved cardiac function. In vitro, FAT10 overexpression exert a protective effect against the transforming growth β1 (TGF-β1)-induced proliferation, migration and differentiation in cardiac fibroblast (CFs), primary CFs from Fat10^-/- mice and human induced pluripotent stem cell-derived CFs (hiPSC-CFs). Furthermore, immunoprecipitation-mass spectrometry (IP-MS) data demonstrated that FAT10 might mediate Smad3, a critical factor in cardiac fibrosis. Combined with rescue assays both in vivo and vitro, the protective effects of FAT10 against cardiac fibrosis was detected to be dependent on Smad3. In depth, Smad3 as a FAT10 specific substrate, FAT10 specifically bind to the K378 site of Smad3 directly via its C-terminal glycine residues and mediated the degradation of Smad3 through the FAT10-proteasome system instead of ubiquitin. In conclusion, we here show that FAT10 is a novel regulator against cardiac fibrosis after MI by mediating Smad3 degradation through FAT10-mediated proteasome system. Our study confirms the cardioprotective role of FAT10 in the heart, and providing a new prospective insight into the regulation of cardiac fibrosis after MI.

Stress - Regulation of SUMO conjugation and of other Ubiquitin-Like Modifiers

Stress is unavoidable and essential to cellular and organismal evolution and failure to adapt or restore homeostasis can lead to severe diseases or even death. At the cellular level, stress drives a plethora of molecular changes, of which variations in the profile of protein post-translational modifications plays a key role in mediating the adaptative response of the genome and proteome to stress. In this context, post-translational modification of proteins by ubiquitin-like modifiers, (Ubl), notably SUMO, is an essential stress response mechanism. In this review, aiming to draw universal concepts of the Ubls stress response, we will decipher how stress alters the expression level, activity, specificity and/or localization of the proteins involved in the conjugation pathways of the various type-I Ubls, and how this result in the modification of particular Ubl targets that will translate an adaptive physiological stress response and allow cells to restore homeostasis.

FAT10 Combined with Miltefosine Inhibits Mitochondrial Apoptosis and Energy Metabolism in Hypoxia-Induced H9C2 Cells by Regulating the PI3K/AKT Signaling Pathway

Hypoxia-induced cardiomyocyte apoptosis is the main contributor to heart diseases. Human leukocyte antigen F-associated transcript 10 (FAT10), the small ubiquitin-like protein family subtype involved in apoptosis, is expressed in the heart and exhibits cardioprotective functions. This study explored the impact of FAT10 on hypoxia-induced cardiomyocyte apoptosis and the involved mechanisms. The cardiomyocyte cell line H9C2 was cultivated in hypoxia-inducing conditions (94% N₂, 5% CO_2, and 1% O₂) and the expression of FAT10 in hypoxia-stimulated H9C2 cells was identified. For this, FAT10 overexpression/interference vectors were exposed to transfection into H9C2 cells with/without the PI3K/AKT inhibitor, miltefosine. The results indicated that hypoxia exposure decreased the FAT10 expression, suppressed H9C2 cell growth, disrupted mitochondrial metabolism, and promoted H9C2 cell apoptosis and oxidative stress. However, these impacts were reversed by the FAT10 overexpression. In addition, the inhibition of PI3K/AKT in FAT10-overexpressing cells suppressed cell proliferation, impaired mitochondrial metabolism, and promoted apoptosis and oxidative stress response. The findings demonstrated that FAT10 inhibited mitochondrial apoptosis and energy metabolism in hypoxia-stimulated H9C2 cells through the PI3K/AKT pathway. This finding can be utilized for developing therapeutic targets for treating heart disorders associated with hypoxia-induced apoptosis.

Comprehensive Analyses of miRNAs Revealed miR-92b-3p, miR-182-5p and miR-183-5p as Potential Novel Biomarkers in Melanoma-Derived Extracellular Vesicles

Extracellular vesicles (EVs) are important mediators in the intercellular communication, influencing the function and phenotype of different cell types within the tumor micro-milieu and thus promote tumor progression. Since EVs safely transport packages of proteins, lipids and also nucleic acids such as miRNAs, EVs and their cargo can serve as diagnostic and prognostic markers. Therefore, the aim of this study was to investigate EV embedded miRNAs specific for melanoma, which could serve as potential biomarkers. In contrast to previous studies, we not only analysed miRNAs from EVs, but also included the miRNA profiles from the EV-secreting cells to identify candidates as suitable biomarkers. While the characterization of EVs derived from normal melanocytes and melanoma cells showed largely comparable properties with regard to size distribution and expression of protein markers, the NGS analyses yielded marked differences for several miRNAs. While miRNA load of EVs derived from normal human epidermal melanocytes (NHEMs) and melanoma cells were very similar, they were highly different from their secreting cells. By comprehensive analyses, six miRNAs were identified to be enriched in both melanoma cells and melanoma cell-derived EVs. Of those, the accumulation of miR-92b-3p, miR-182-5p and miR-183-5p in EVs could be validated in vitro. By functional network generation and pathway enrichment analysis we revealed an association with different tumor entities and signaling pathways contributing melanoma progression. Furthermore, we found that miR-92b-3p, miR-182-5p and miR-183-5p were also enriched in EVs derived from serum of melanoma patients. Our results support the hypothesis that miRNAs derived from EVs can serve as prognostic or diagnostic liquid biopsy markers in melanoma. We identified EV-derived miRNAs and showed that those miRNAs, which were enriched in melanoma cells and EVs, are also found elevated in serum-derived EVs of patients with metastatic melanoma, but not in healthy subjects.

Autologous Bone Marrow Mononuclear Cells (BMMC)-Associated Anti-Inflammatory Nanoparticles for Cardiac Repair after Myocardial Infarction

To investigate the effect of transplantation of stem cells from the bone marrow mononuclear cells (BMMC) associated with 15d-PGJ2-loaded nanoparticles in a rat model of chronic MI. Chronic myocardial infarction (MI) was induced by the ligation of the left anterior descending artery in 40 male Wistar rats. After surgery, we transplanted bone marrow associated with 15d-PGJ2-loaded nanoparticle by intramyocardial injection (10⁶ cells/per injection) seven days post-MI. Myocardial infarction was confirmed by echocardiography, and histological analyses of infarct morphology, gap junctions, and angiogenesis were obtained. Our results from immunohistochemical analyses demonstrated the presence of angiogenesis identified in the transplanted region and that there was significant expression of connexin-43 gap junctions, showing a more effective electrical and mechanical integration of the host myocardium. This study suggests that the application of nanoparticle technology in the prevention and treatment of MI is an emerging field and can be a strategy for cardiac repair.

Ubiquitin D Promotes Progression of Oral Squamous Cell Carcinoma via NF-Kappa B Signaling

Ubiquitin D (UBD) is highly upregulated in many cancers, and plays a pivotal role in the pathophysiological processes of cancers. However, its roles and underlying mechanisms in oral squamous cell carcinoma (OSCC) are still unclear. In the present study, we investigated the role of UBD in patients with OSCC. Quantitative real-time polymerase chain reaction and Western blot were used to measure the expression of UBD in OSCC tissues. Immunohistochemistry assay was used to detect the differential expressions of UBD in 244 OSCC patients and 32 cases of normal oral mucosae. In addition, CCK-8, colony formation, wound healing and Transwell assays were performed to evaluate the effect of UBD on the cell proliferation, migration, and invasion in OSCC. Furthermore, a xenograft tumor model was established to verify the role of UBD on tumor formation in vivo. We found that UBD was upregulated in human OSCC tissues and cell lines and was associated with clinical and pathological features of patients. Moreover, the overexpression of UBD promoted the proliferation, migration and invasion of OSCC cells; however, the knockdown of UBD exerted the opposite effects. In this study, our results also suggested that UBD promoted OSCC progression through NF-κB signaling. Our findings indicated that UBD played a critical role in OSCC and may serve as a prognostic biomarker and potential therapeutic target for OSCC treatment.