SUMOylation as a Therapeutic Target for Myocardial Infarction

The Janus face of HIF-1α in ischemic stroke and the possible associated pathways

Stroke is the most devastating disease, causing paralysis and eventually death. Many clinical and experimental trials have been done in search of a new safe and efficient medicine; nevertheless, scientists have yet to discover successful remedies that are also free of adverse effects. This is owing to the variability in intensity, localization, medication routes, and each patient's immune system reaction. HIF-1α represents the modern tool employed to treat stroke diseases due to its functions: downstream genes such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Its role can be achieved via two downstream EPO and VEGF strongly related to apoptosis and antioxidant processes. Recently, scientists paid more attention to drugs dealing with the HIF-1 pathway. This review focuses on medicines used for ischemia treatment and their potential HIF-1α pathways. Furthermore, we discussed the interaction between HIF-1α and other biological pathways such as oxidative stress; however, a spotlight has been focused on certain potential signalling contributed to the HIF-1α pathway. HIF-1α is an essential regulator of oxygen balance within cells which affects and controls the expression of thousands of genes related to sustaining homeostasis as oxygen levels fluctuate. HIF-1α's role in ischemic stroke strongly depends on the duration and severity of brain damage after onset. HIF-1α remains difficult to investigate, particularly in ischemic stroke, due to alterations in the acute and chronic phases of the disease, as well as discrepancies between the penumbra and ischemic core. This review emphasizes these contrasts and analyzes the future of this intriguing and demanding field.

SUMOylation inhibitors activate anti-tumor immunity by reshaping the immune microenvironment in a preclinical model of hepatocellular carcinoma

PURPOSE

High levels of heterogeneity and immunosuppression characterize the HCC immune microenvironment (TME). Unfortunately, the majority of hepatocellular carcinoma (HCC) patients do not benefit from immune checkpoint inhibitors (ICIs) therapy. New small molecule therapies for the treatment of HCC are the goal of our research.

METHODS

SUMOylation inhibitors (TAK-981 and ML-792) were evaluated for the treatment of preclinical mouse HCC models (including subcutaneous and orthotopic HCC models). We profile immune cell subsets from tumor samples after SUMOylation inhibitors treatment using single-cell RNA sequencing (scRNA-seq), mass cytometry (CyTOF), flow cytometry, and multiple immunofluorescences (mIF).

RESULTS

We discover that SUMOylation is higher in HCC patient samples compared to normal liver tissue. TAK-981 and ML-792 decrease SUMOylation at nanomolar levels in HCC cells and also successfully reduced the tumor burden. Analysis combining scRNA-seq and CyTOF demonstrate that treatment with SUMOylation inhibitors reduces the exhausted CD8+T (Tex) cells while enhancing the cytotoxic NK cells, M1 macrophages and cytotoxic T lymphocytes (CTL) in preclinical mouse HCC model. Furthermore, SUMOylation inhibitors have the potential to activate innate immune signals from CD8+T, NK and macrophages while promoting TNFα and IL-17 secretion. Most notably, SUMOylation inhibitors can directly alter the TME by adjusting the abundance of intestinal microbiota, thereby restoring anti-tumor immunity in HCC models.

CONCLUSIONS

This preclinical study suggests that SUMO signaling inhibitors may be beneficial for the treatment of HCC.

Post-translational modifications of proteins in cardiovascular diseases examined by proteomic approaches

Over 400 different types of post-translational modifications (PTMs) have been reported and over 200 various types of PTMs have been discovered using mass spectrometry (MS)-based proteomics. MS-based proteomics has proven to be a powerful method capable of global PTM mapping with the identification of modified proteins/peptides, the localization of PTM sites and PTM quantitation. PTMs play regulatory roles in protein functions, activities and interactions in various heart related diseases, such as ischemia/reperfusion injury, cardiomyopathy and heart failure. The recognition of PTMs that are specific to cardiovascular pathology and the clarification of the mechanisms underlying these PTMs at molecular levels are crucial for discovery of novel biomarkers and application in a clinical setting. With sensitive MS instrumentation and novel biostatistical methods for precise processing of the data, low-abundance PTMs can be successfully detected and the beneficial or unfavorable effects of specific PTMs on cardiac function can be determined. Moreover, computational proteomic strategies that can predict PTM sites based on MS data have gained an increasing interest and can contribute to characterization of PTM profiles in cardiovascular disorders. More recently, machine learning- and deep learning-based methods have been employed to predict the locations of PTMs and explore PTM crosstalk. In this review article, the types of PTMs are briefly overviewed, approaches for PTM identification/quantitation in MS-based proteomics are discussed and recently published proteomic studies on PTMs associated with cardiovascular diseases are included.

Mechanisms and functions of SUMOylation in health and disease: a review focusing on immune cells

SUMOylation, which is a type of post-translational modification that involves covalent conjugation of small ubiquitin-like modifier (SUMO) proteins to target substrates, regulates various important molecular and cellular processes, including transcription, the cell cycle, cell signaling, and DNA synthesis and repair. Newly synthesized SUMO is immature and cleaved by the SUMO-specific protease family, resulting in exposure of the C-terminal Gly-Gly motif to become the mature form. In the presence of ATP, mature SUMO is conjugated with the activating enzyme E1 through the cysteine residue of E1, followed by transfer to the cysteine residue of E2-conjugating enzyme Ubc9 in humans that recognizes and modifies the lysine residue of a substrate protein. E3 SUMO ligases promote SUMOylation. SUMOylation is a reversible modification and mediated by SUMO-specific proteases. Cumulative studies have indicated that SUMOylation affects the functions of protein substrates in various manners, including cellular localization and protein stability. Gene knockout studies in mice have revealed that several SUMO cycling machinery proteins are crucial for the development and differentiation of various cell lineages, including immune cells. Aberrant SUMOylation has been implicated in several types of diseases, including cancers, cardiovascular diseases, and autoimmune diseases. This review summarizes the biochemistry of SUMO modification and the general biological functions of proteins involved in SUMOylation. In particular, this review focuses on the molecular mechanisms by which SUMOylation regulates the development, maturation, and functions of immune cells, including T, B, dendritic, and myeloid cells. This review also discusses the underlying relevance of disruption of SUMO cycling and site-specific interruption of SUMOylation on target proteins in immune cells in diseases, including cancers and infectious diseases.

SUMOtherapeutics for Ischemic Stroke

The small, ubiquitin-like modifier (SUMO) is a post-translational modifier with a profound influence on several key biological processes, including the mammalian stress response. Of particular interest are its neuroprotective effects, first recognized in the 13-lined ground squirrel (Ictidomys tridecemlineatus), in the context of hibernation torpor. Although the full scope of the SUMO pathway is yet to be elucidated, observations of its importance in managing neuronal responses to ischemia, maintaining ion gradients, and the preconditioning of neural stem cells make it a promising therapeutic target for acute cerebral ischemia. Recent advances in high-throughput screening have enabled the identification of small molecules that can upregulate SUMOylation, some of which have been validated in pertinent preclinical models of cerebral ischemia. Accordingly, the present review aims to summarize current knowledge and highlight the translational potential of the SUMOylation pathway in brain ischemia.

SUMOylation of RNF146 results in Axin degradation and activation of Wnt/β-catenin signaling to promote the progression of hepatocellular carcinoma

Aberrant SUMOylation contributes to the progression of hepatocellular carcinoma (HCC), yet the molecular mechanisms have not been well elucidated. RING-type E3 ubiquitin ligase RNF146 is a key regulator of the Wnt/β-catenin signaling pathway, which is frequently hyperactivated in HCC. Here, it is identified that RNF146 can be modified by SUMO3. By mutating all lysines in RNF146, we found that K19, K61, K174 and K175 are the major sites for SUMOylation. UBC9/PIAS3/MMS21 and SENP1/2/6 mediated the conjugation and deconjugation of SUMO3, respectively. Furthermore, SUMOylation of RNF146 promoted its nuclear localization, while deSUMOylation induced its cytoplasmic localization. Importantly, SUMOylation promotes the association of RNF146 with Axin to accelerate the ubiquitination and degradation of Axin. Intriguingly, only UBC9/PIAS3 and SENP1 can act at K19/K175 in RNF146 and affect its role in regulating the stability of Axin. In addition, inhibiting RNF146 SUMOylation suppressed the progression of HCC both in vitro and in vivo. And, patients with higher expression of RNF146 and UBC9 have the worst prognosis. Taken together, we conclude that RNF146 SUMOylation at K19/K175 promotes its association with Axin and accelerates Axin degradation, thereby enhancing β-catenin signaling and contributing to cancer progression. Our findings reveal that RNF146 SUMOylation is a potential therapeutic target in HCC.

Circulating miRNAs are associated with frailty and ST-elevation myocardial infarction pathways

BACKGROUND

Frailty and ST-Elevation Myocardial Infarction (STEMI) share similar molecular pathways. Specific biomarkers, such as microRNAs (miRNAs), may provide insights into the molecular mechanisms that cause the relationship between frailty and STEMI.

OBJECTIVE

Our aim was to identify and compare circulating miRNA levels between frail and non-frail older adults following STEMI and comprehend the regulatory miRNA-gene networks and pathways involved in this condition.

METHODS

This exploratory study is a subanalysis of a larger observational study. In this study, we selected patients ≥ 65 years old, following STEMI, with pre-frail/frail (n=5) and non-frail (n=4) phenotype evaluated using the Clinical Frailty Scale and serum circulating miRNA levels were analyzed.

RESULTS

Pre-frail/frail patients had greater serum levels of 53 miRNAs, compared with non-frail patients. Notably, miR-103a-3p, miR-598-3p, and miR-130a-3p were the top three significantly deregulated miRNAs predicted to modulate gene expression associated with aging. Additional computational analyses showed 7,420 predicted miRNA gene targets, which were regulated by at least two of the 53 identified miRNAs. Pathway enrichment analysis showed that axon guidance and MAPK signaling were among pathways regulated by miRNA target genes.

CONCLUSIONS

These novel findings suggest a correlation between the identified miRNAs, target genes, and pathways in pre-frail and frail patients with myocardial infarction.

The Value of Myocardium and Kidney Histopathological and Immunohistochemical Findings in Accidental Hypothermia-Related Fatalities

Background and Objectives: The post-mortem diagnosis of hypothermia is challenging in forensics. The aim of our study was to detect the kidney and heart histopathological changes that occurred in a group of hypothermia-related fatalities. Materials and Methods: The cohort included 107 cases identified in the database of our department between 2007 and 2021, which have been associated with extreme cold stress. Demographic and clinicopathological data were collected from the medico-legal reports. Archived tissue samples were evaluated to identify the histopathological features, in routine haematoxylin-eosin (H&E), Periodic acid-Schiff (PAS), and Masson's trichrome stainings, while cardiac sirtuin1 (SIRT1) and renal ubiquitin (Ub) immunostaining have been performed. Results: The majority of cases exposed to low temperatures were males (76%) from rural regions (68.2%) during the cold season. Paradoxical undressing was documented in 9.3% of cases. The common comorbidities included alcoholism (50.5%), neuropsychiatric diseases (10.3%), diabetes mellitus (3.7%), and lung tuberculosis (4.7%). The microscopic heart exam revealed areas of myocardial degeneration (100%), contraction bands (95.3%), fatty change (13.1%) and focal wavy contractile myocardial cells. Basal vacuolisation of renal tubular epithelial cells (Armanni-Ebstein lesions) (21.5%), focal tubular necrosis (7.5%), tubular renal cysts (7.5%), interstitial haemorrhages (5.6%), diabetic kidney disease (3.7%), background benign nephroangiosclerosis (42.1%), variable thickening of tubules and corpuscles basement membranes, capsular space amorphous material, and intratubular casts were identified in kidney tissue samples. Myocardial cells displayed SIRT1 weak expression, with a loss of immunopositivity correlated with areas with contraction bands, while a variable Ub expression was observed in renal corpuscles capsules, proximal, distal, and collecting renal tubules, Henle's loops, urothelium, and intratubular casts. Conclusions: In the context of the current concept that death associated with hypothermia is still a diagnosis of exclusion, our findings suggest that the microscopic exam provides relevant data that support the diagnosis of hypothermia-related fatalities in appropriate circumstances of death. A deeper insight into the histopathologic findings in hypothermic patients may lead to new therapeutic approaches in these cases.

SUMOylation of Nuclear γ-Actin by SUMO2 supports DNA Damage Repair against Myocardial Ischemia-Reperfusion Injury

Myocardial infarction triggers oxidative DNA damage, apoptosis and adverse cardiac remodeling in the heart. Small ubiquitin-like modifier (SUMO) proteins mediate post-translational SUMOylation of the cardiac proteins in response to oxidative stress signals. Upregulation of isoform SUMO2 could attenuate myocardial injury via increasing protein SUMOylation. The present study aimed to discover the identity and cardioprotective activities of SUMOylated proteins. A plasmid vector for expressing N-Strep-SUMO2 protein was generated and introduced into H9c2 rat cardiomyocytes. The SUMOylated proteins were isolated with Strep-Tactin^® agarose beads and identified by MALDI-TOF-MS technology. As a result, γ-actin was identified from a predominant protein band of ~42 kDa and verified by Western blotting. The roles of SUMO2 and γ-actin SUMOylation were subsequently determined in a mouse model of myocardial infarction induced by ligating left anterior descending coronary artery and H9c2 cells challenged by hypoxia-reoxygenation. In vitro lentiviral-mediated SUMO2 expression in H9c2 cells were used to explore the role of SUMOylation of γ-actin. SUMOylation of γ-actin by SUMO2 was proven to be a new cardioprotective mechanism from the following aspects: 1) SUMO2 overexpression reduced the number of TUNEL positive cells, the levels of 8-OHdG and p-γ-H2ax while promoted the nuclear deposition of γ-actin in mouse model and H9c2 cell model of myocardial infarction; 2) SUMO-2 silencing decreased the levels of nuclear γ-actin and SUMOylation while exacerbated DNA damage; 3) Mutated γ-actin (K⁶⁸R/K²⁸⁴R) void of SUMOylation sites failed to protect cardiomyocytes against hypoxia-reoxygenation challenge. The present study suggested that SUMO2 upregulation promoted DNA damage repair and attenuated myocardial injury via increasing SUMOylation of γ-actin in the cell nucleus.

Ubiquitin and Ubiquitin-like Proteins in Cancer, Neurodegenerative Disorders, and Heart Diseases

Post-translational modification (PTM) is an essential mechanism for enhancing the functional diversity of proteins and adjusting their signaling networks. The reversible conjugation of ubiquitin (Ub) and ubiquitin-like proteins (Ubls) to cellular proteins is among the most prevalent PTM, which modulates various cellular and physiological processes by altering the activity, stability, localization, trafficking, or interaction networks of its target molecules. The Ub/Ubl modification is tightly regulated as a multi-step enzymatic process by enzymes specific to this family. There is growing evidence that the dysregulation of Ub/Ubl modifications is associated with various diseases, providing new targets for drug development. In this review, we summarize the recent progress in understanding the roles and therapeutic targets of the Ub and Ubl systems in the onset and progression of human diseases, including cancer, neurodegenerative disorders, and heart diseases.

Natural Products Against Renal Fibrosis via Modulation of SUMOylation

Renal fibrosis is the common and final pathological process of kidney diseases. As a dynamic and reversible post-translational modification, SUMOylation and deSUMOylation of transcriptional factors and key mediators significantly affect the development of renal fibrosis. Recent advances suggest that SUMOylation functions as the promising intervening target against renal fibrosis, and natural products prevent renal fibrosis via modulating SUMOylation. Here, we introduce the mechanism of SUMOylation in renal fibrosis and therapeutic effects of natural products. This process starts by summarizing the key mediators and enzymes during SUMOylation and deSUMOylation and its regulation role in transcriptional factors and key mediators in renal fibrosis, then linking the mechanism findings of SUMOylation and natural products to develop novel therapeutic candidates for treating renal fibrosis, and concludes by commenting on promising therapeutic targets and candidate natural products in renal fibrosis via modulating SUMOylation, which highlights modulating SUMOylation as a promising strategy for natural products against renal fibrosis.