Metabolomics-assisted proteomics identifies succinylation and SIRT5 as important regulators of cardiac function

Protein succinylation mechanisms and potential targeted therapies in urinary disease

Succinylation is a relatively common post-translational modification. It occurs in the cytoplasm, mitochondria, and the nucleus, where its essential precursor, succinyl-CoA, is present, allowing for the modification of non-histone and histone proteins. In normal cells, succinylation levels are carefully regulated to sustain a dynamic balance, necessitating the involvement of various regulatory mechanisms, including non-enzymatic reactions, succinyltransferases, and desuccinylases. Among these regulatory factors, sirtuin 5, the first identified desuccinylase, plays a significant role and has been extensively researched. The level of succinylation has a significant effect on multiple metabolic pathways, including the tricarboxylic acid cycle, redox balance, and fatty acid metabolism. Dysregulated succinylation can contribute to the progression or exacerbation of various urinary diseases. Succinylation predominantly affects disease progression by altering the expression of key genes and modulating the activity of enzymes involved in vital metabolic processes. Desuccinylases primarily affect enzymes associated with Warburg's effect, thereby affecting the energy supply of tumor cells, while succinyltransferases can regulate gene transcription to alter cell phenotype, thereby involving the development of urinary diseases. Considering these effects, targeting succinylation-related enzymes to regulate metabolic pathways or gene expression may offer a promising therapeutic strategy for treating urinary diseases.

The two faces of coenzyme A in cellular biology

Coenzyme A (CoA) is an essential cofactor present in all living cells, which plays critical roles in diverse biochemical processes, including cellular metabolism, signal transduction, regulation of gene expression, and the antioxidant response. This review summarizes current knowledge on the role of CoA and its metabolically active thioesters in promoting cellular growth and proliferation (pro-growth) and discusses emerging research on CoA's antioxidant properties that enhance cell survival (pro-survival).

Palmitoylation in cardiovascular diseases: Molecular mechanism and therapeutic potential

Cardiovascular disease is one of the leading causes of mortality worldwide, and involves complex pathophysiological mechanisms that encompass various biological processes and molecular pathways. Post-translational modifications of proteins play crucial roles in the occurrence and progression of cardiovascular diseases, among which palmitoylation is particularly important. Various proteins associated with cardiovascular diseases can be palmitoylated to enhance the hydrophobicity of their molecular subdomains. This lipidation can significantly affect some pathophysiological processes, such as metabolism, inflammation by altering protein stability, localization, and signal transduction. In this review, we narratively summarize recent advances in the palmitoylation of proteins related to cardiovascular diseases and discuss its potential as a therapeutic target.

SIRT5: a potential target for discovering bioactive natural products

Silent information regulator 5 (SIRT5) is the fifth member of the sirtuin family, which is mainly expressed in mitochondrial matrix. SIRT5 plays a key role in metabolism and antioxidant responses, and is an important regulator for maintaining intracellular homeostasis. Given its involvement in multiple cellular processes, dysregulation of SIRT5 activity is associated with a variety of diseases. This review explores the structural characteristics of SIRT5 that influence its substrate specificity, highlights recent research advances, and summarizes its four key enzymatic activities along with their corresponding substrates in disease contexts. We also discuss the natural products that modulate SIRT5 activity and identify potential targets of SIRT5 through virtual docking, which may provide new therapeutic avenues. Although the mechanism of SIRT5 in diseases needs to be further elucidated and deglutathionylation activities are still at an early stage, targeting SIRT5 and its substrates holds significant promise for the development of novel therapeutics.

Post-translational acylation of proteins in cardiac hypertrophy

Acylations are post-translational modifications in which functional groups are attached to amino acids on proteins. Most acylations (acetylation, butyrylation, crotonylation, lactylation, malonylation, propionylation and succinylation) involve lysine but cysteine (palmitoylation) and glycine (myristoylation) residues can also be altered. Acylations have important roles in physiological and pathophysiological processes, including cardiac hypertrophy and related cardiovascular diseases. These post-translational modifications influence chromatin architecture, transcriptional regulation and metabolic pathways, thereby affecting cardiomyocyte function and pathology. The dynamic interaction between these acylations and their regulatory enzymes, such as histone acetyltransferases, histone deacetylases and sirtuins, underscores the complexity of cellular homeostasis and pathological processes. Emerging evidence highlights the therapeutic potential of targeting acylations to modulate enzyme activity and metabolite levels, offering promising avenues for novel treatments. In this Review, we explore the diverse mechanisms through which acylations contribute to cardiac hypertrophy, highlighting the complexity and potential therapeutic targets in this regulatory network.

De-succinylation-induced accumulation of TRMT10C in the nucleus plays a detrimental role in coronary microembolization via its m1A modification function

Coronary microembolization (CME) refers to embolism in the coronary microcirculation. This study showed a reduction in succinyl transferase (CPT1A) and the succinylation substrate (succinyl-CoA) in cardiomyocytes in CME models, suppressing the succinylation of the mitochondrially localized protein TRMT10C. Suppression of succinylation promotes KPNA4 recognition of two nuclear localization signals (NLSs), KAKR and KKK(X)10KVKK, in TRMT10C, which induces the transport of TRMT10C from the cytoplasm to the nucleus rather than to the mitochondria. Nuclear TRMT10C induces YTHDF2-mediated decay of TAFAZZIN and NLRX1 through m1A modifications. The reduction in TAFAZZIN and NLRX1 is associated with multiple detrimental effects, such as inflammation mediated by NF-κB and NLRP3, reactive oxygen species (ROS) production, and suppression of mitophagy. TRMT10C knockdown suppressed the accumulation of TRMT10C in the nucleus. It restored NLRX1 and TAFAZZIN protein levels in cardiomyocytes under hypoxia. However, the deficiency of TRMT10C in the mitochondria did not improve-or even worsened-with TRMT10C knockdown. Inducing TRMT10C succinylation via CPT1A overexpression led to the redistribution of TRMT10C to the mitochondria rather than the nucleus, which is likely a better approach for improving cardiomyocyte function under hypoxia than direct TRMT10C knockdown. This study reveals a novel pathological mechanism underlying CME and suggests potential therapeutic targets for this disease.

Epigenetics and Mitochondrial Biogenesis: The Role of Sirtuins in HIV Neuropathogenesis

Mitochondrial energy deficits play a central role in HIV-associated neurocognitive disorder (HAND). HIV disrupts cellular functions, including epigenetic modifications such as class III histone deacetylation mediated by sirtuins (SIRTs). However, the role of SIRTs in HAND pathogenesis remains unclear. We hypothesize that HIV alters mitochondrial biogenesis and energy homeostasis by modifying SIRT family members 1-7, contributing to HAND progression. To test this hypothesis, we examined postmortem frontal lobe brain tissue from people with HIV (PWH) and HIV-negative controls, focusing on epigenetic alterations in SIRTs 1-7, the energy sensor adenosine monophosphate-activated protein kinase (AMPK), the mitochondrial master regulator peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and transcription factors such as mitochondrial transcription factor A (TFAM), nuclear respiratory factors 1 and 2 (NRF-1/2), and factors associated with oxidative phosphorylation (OXPHOS). Our analysis revealed a significant increase in AMPK, OXPHOS, and PGC-1α levels, alongside a decrease in TFAM levels in PWH brains compared to uninfected controls. NRF-1 was upregulated in mitochondria but downregulated in the cytoplasm, while NRF-2 exhibited the opposite trend in PWH compared to HIV-negative controls. The epigenetic signatures of SIRTs 1, 2, 3, 4, 6, and 7 were upregulated in PWH, while SIRT5 was downregulated compared to uninfected brain tissues. We exposed primary human astrocyte and microglial cultures to the HIV-1 transactivator of transcription (Tat) protein to identify the cell types involved. These studies confirmed that HIV-induced epigenetic modifications of SIRTs and mitochondrial impairments occurred in both astrocytes and microglia, highlighting the crucial role of SIRTs in HAND pathogenesis.

SIRT5 Regulates Lipid Deposition in Goat Preadipocytes via PI3K-Akt and MAPK Signaling Pathways

Silent Information Regulator 5 (SIRT5) has been established as a crucial regulator of cellular alanylation modification. Furthermore, accumulating evidence suggests that SIRT5 plays a significant regulatory role in key metabolic pathways, including glycolysis, the tricarboxylic acid (TCA) cycle, and fatty acid oxidation, all of which are closely associated with cellular lipid metabolism. Despite these advancements, the specific role of SIRT5 in regulating intramuscular fat (IMF) deposition in goats, as well as the underlying molecular mechanisms, remains largely unexplored. In this study, we cloned the complete coding sequence of the goat SIRT5 gene and, through amino acid sequence alignment, demonstrated its closest phylogenetic relationship with sheep. Additionally, we characterized the higher expression of SIRT5 during the differentiation of goat intramuscular precursor adipocytes. The silencing of SIRT5 by siRNA-mediated knockdown significantly upregulated the expression of lipogenesis-related genes and enhanced lipid deposition in goat intramuscular preadipocytes. Concurrently, SIRT5 deficiency led to the inhibition of cell proliferation and a marked reduction in apoptosis. Interestingly, although overexpression of SIRT5 promoted cell proliferation, it did not significantly alter lipid deposition in goat intramuscular precursor adipocytes. RNA sequencing (RNA-seq) analysis identified a total of 106 differentially expressed genes (DEGs) following SIRT5 silencing in goat preadipocytes, predominantly involved in the Focal adhesion, HIF-1, PI3K-Akt, and MAPK signaling pathways by KEGG pathway enrichment analysis. Notably, we successfully reversed the phenotypic effects observed in SIRT5 knockdown goat precursor adipocytes by inhibiting the PI3K-Akt and MAPK signaling pathways using the AKT inhibitor LY294002 and the p38 MAPK pathway inhibitor PD169316, respectively. In conclusion, our findings demonstrated that SIRT5 may modulate intramuscular fat deposition in goats through PI3k-Akt and MAPK signaling pathways. These results expand the gene regulatory network associated with IMF formation and provide a theoretical foundation for improving meat quality by targeting IMF deposition.

ACAT1 regulates tertiary lymphoid structures and correlates with immunotherapy response in non-small cell lung cancer

Tertiary lymphoid structures (TLS) in the tumor microenvironment (TME) are emerging solid-tumor indicators of prognosis and response to immunotherapy. Considering that tumorigenesis requires metabolic reprogramming and subsequent TME remodeling, the discovery of TLS metabolic regulators is expected to produce immunotherapeutic targets. To identify such metabolic regulators, we constructed a metabolism-focused sgRNA library and performed an in vivo CRISPR screening in an orthotopic lung tumor mouse model. Combined with The Cancer Genome Atlas database analysis of TLS-related metabolic hub genes, we found that the loss of Acat1 in tumor cells sensitized tumors to anti-PD1 treatment, accompanied by increased TLS in the TME. Mechanistic studies revealed that ACAT1 resulted in mitochondrial protein hypersuccinylation in lung tumor cells and subsequently enhanced mitochondrial oxidative metabolism, which impeded TLS formation. Elimination of ROS by NAC or Acat1 knockdown promoted B cell aggregation and TLS construction. Consistently, data from tissue microassays of 305 patients with lung cancer showed that TLS were more abundant in non-small cell lung cancer (NSCLC) tissues with lower ACAT1 expression. Intratumoral ACAT1 expression was associated with poor immunotherapy outcomes in patients with NSCLC. In conclusion, our results identified ACAT1 as a metabolic regulator of TLS and a promising immunotherapeutic target in NSCLC.

Metabolites-mediated posttranslational modifications in cardiac metabolic remodeling: Implications for disease pathology and therapeutic potential

The nonenergy - producing functions of metabolism are attracting increasing attention, as metabolic changes are involved in discrete pathways modulating enzyme activity and gene expression. Substantial evidence suggests that myocardial metabolic remodeling occurring during diabetic cardiomyopathy, heart failure, and cardiac pathological stress (e.g., myocardial ischemia, pressure overload) contributes to the progression of pathology. Within the rewired metabolic network, metabolic intermediates and end-products can directly alter protein function and/or regulate epigenetic modifications by providing acyl groups for posttranslational modifications, thereby affecting the overall cardiac stress response and providing a direct link between cellular metabolism and cardiac pathology. This review provides a comprehensive overview of the functional diversity and mechanistic roles of several types of metabolite-mediated histone and nonhistone acylation, namely O-GlcNAcylation, lactylation, crotonylation, β-hydroxybutyrylation, and succinylation, as well as fatty acid-mediated modifications, in regulating physiological processes and contributing to the progression of heart disease. Furthermore, it explores the potential of these modifications as therapeutic targets for disease intervention.

Crosstalk between metabolism and epigenetics during macrophage polarization

Macrophage polarization is a dynamic process driven by a complex interplay of cytokine signaling, metabolism, and epigenetic modifications mediated by pathogens. Upon encountering specific environmental cues, monocytes differentiate into macrophages, adopting either a pro-inflammatory (M1) or anti-inflammatory (M2) phenotype, depending on the cytokines present. M1 macrophages are induced by interferon-gamma (IFN-γ) and are characterized by their reliance on glycolysis and their role in host defense. In contrast, M2 macrophages, stimulated by interleukin-4 (IL-4) and interleukin-13 (IL-13), favor oxidative phosphorylation and participate in tissue repair and anti-inflammatory responses. Metabolism is tightly linked to epigenetic regulation, because key metabolic intermediates such as acetyl-coenzyme A (CoA), α-ketoglutarate (α-KG), S-adenosylmethionine (SAM), and nicotinamide adenine dinucleotide (NAD+) serve as cofactors for chromatin-modifying enzymes, which in turn, directly influences histone acetylation, methylation, RNA/DNA methylation, and protein arginine methylation. These epigenetic modifications control gene expression by regulating chromatin accessibility, thereby modulating macrophage function and polarization. Histone acetylation generally promotes a more open chromatin structure conducive to gene activation, while histone methylation can either activate or repress gene expression depending on the specific residue and its methylation state. Crosstalk between histone modifications, such as acetylation and methylation, further fine-tunes macrophage phenotypes by regulating transcriptional networks in response to metabolic cues. While arginine methylation primarily functions in epigenetics by regulating gene expression through protein modifications, the degradation of methylated proteins releases arginine derivatives like asymmetric dimethylarginine (ADMA), which contribute directly to arginine metabolism-a key factor in macrophage polarization. This review explores the intricate relationships between metabolism and epigenetic regulation during macrophage polarization. A better understanding of this crosstalk will likely generate novel therapeutic insights for manipulating macrophage phenotypes during infections like tuberculosis and inflammatory diseases such as diabetes.

Metformin hydrochloride improves hepatic glucolipid metabolism in diabetes progression through SIRT5-mediated ECHA desuccinylation

The management of hyperglycemia and lipid metabolism is pivotal for the treatment of type 2 diabetes mellitus (T2DM). Metformin hydrochloride (DMBG) remains the most widely prescribed medication for this condition. This study aimed to elucidate the effects and underlying mechanisms by which DMBG enhances glucolipid metabolism using both in vivo and in vitro experimental models. Animal models were established using high-fat diet (HFD)-fed mice, while cellular models utilized palmitic acid (PA)-induced HepG2 cells. In vivo, the impact of DMBG on glucolipid metabolism was evaluated through measurements of insulin and HbA1c levels, intraperitoneal glucose tolerance tests (ipGTT), intraperitoneal insulin tolerance tests (ipITT), as well as histological assessments with hematoxylin-eosin (HE) and Oil-red O staining. Mitochondrial function was assessed via biochemical assays of TBARS, SOD, ATP, and H2O2 levels in liver tissue, alongside determinations of mitochondrial membrane potential, ROS production, mtDNA content, and SIRT5 mRNA expression. For in vitro analysis, glucose consumption, mitochondrial membrane potential, ROS levels, and protein expressions of AMPK and PGC-1α were quantified in HepG2 cells. Western blotting and co-immunoprecipitation (co-IP) techniques were employed to investigate the mechanistic pathways involved. Treatment with DMBG resulted in reduced levels of free fatty acids, body weight, and fat mass, while also alleviating hyperglycemia and hepatic lipid accumulation in HFD-fed mice. Furthermore, DMBG restored impaired mitochondrial function in these animals and increased SIRT5 expression via AMPK activation. In vitro, DMBG mitigated PA-induced alterations in glucose consumption and mitochondrial dysfunction in HepG2 cells, an effect that was abrogated upon SIRT5 knockdown. Overexpression of SIRT5 led to enhanced trifunctional enzyme subunit-alpha (ECHA) desuccinylation at the K540 site, thereby increasing its activity. Collectively, our findings indicate that DMBG improves hepatic glucolipid metabolism through a mechanism involving SIRT5-mediated ECHA desuccinylation, potentially offering a new therapeutic avenue for T2DM.

New Types of Post-Translational Modification of Proteins in Cardiovascular Diseases

Post-translational modifications (PTMs), which are covalent alterations of proteins after their synthesis, are critical for their proper function and the maintenance of cellular physiology. The significance of PTMs in the context of cardiovascular diseases (CVDs) has been increasingly recognized due to their potential to influence protein stability, activity, and localization, thereby affecting the progression of CVDs. The identification and understanding of PTMs in CVDs at the molecular level are vital for the discovery of new biomarkers and new targets for clinical interventions. This article provides a comprehensive overview of the role and mechanisms of new types of PTMs, such as acetylation, crotonylation, succinylation, S-nitrosylation, malonylation, S-palmitonylation, β-hydroxybutyrylation and lactylation, in CVDs, highlighting their importance in advancing diagnostic and therapeutic approaches for CVDs.

Microbiota-derived succinate promotes enterohaemorrhagic Escherichia coli virulence via lysine succinylation

Succinate upregulates enterohaemorrhagic Escherichia coli (EHEC) virulence. Lysine succinylation, a post-translational modification, regulates cellular function in eukaryotes but is less characterized in bacteria. We hypothesized that lysine succinylation regulates EHEC virulence. Here we used SILAC-based proteomics and characterized the EHEC succinylome to show that the transcription factor, PurR, is succinylated at K24 and K55. Succinylation of PurR inhibited its ability to directly bind DNA and repress expression of a major virulence factor, the Type 3 Secretion System (T3SS), thus increasing T3SS expression. Deletion of purR, or K24E or K55E mutation, increased EHEC adherence to cells and colonization of infant rabbits. Using mice treated with streptomycin to deplete succinate, or colonized with succinate-producing Prevotella copri to increase succinate levels, we showed that microbiota-derived succinate increased succinylation of PurR to promote virulence of Citrobacter rodentium, a model for EHEC, in mice. Lastly, we identified CitC as the succinyltransferase required for PurR modification.

Roles of Sirtuins in Cardiovascular Diseases: Mechanisms and Therapeutics

Cardiovascular diseases (CVDs) are experiencing a rapid surge and are widely recognized as the leading cause of mortality in the current aging society. Given the multifactorial etiology of CVDs, understanding the intricate molecular and cellular mechanisms is imperative. Over the past 2 decades, many scientists have focused on Sirtuins, a family of nicotinamide adenine dinucleotide-dependent deacylases. Sirtuins are highly conserved across species, from yeasts to primates, and play a crucial role in linking aging and diseases. Sirtuins participate in nearly all key physiological and pathological processes, ranging from embryogenic development to stress response and aging. Abnormal expression and activity of Sirtuins exist in many aging-related diseases, while their activation has shown efficacy in mitigating these diseases (eg, CVDs). In terms of research, this field has maintained fast, sustained growth in recent years, from fundamental studies to clinical trials. In this review, we present a comprehensive, up-to-date discussion on the biological functions of Sirtuins and their roles in regulating cardiovascular biology and CVDs. Furthermore, we highlight the latest advancements in utilizing Sirtuin-activating compounds and nicotinamide adenine dinucleotide boosters as potential pharmacological targets for preventing and treating CVDs. The key unresolved issues in the field-from the chemicobiological regulation of Sirtuins to Sirtuin-targeted CVD investigations-are also discussed. This timely review could be critical in understanding the updated knowledge of Sirtuin biology in CVDs and facilitating the clinical accessibility of Sirtuin-targeting interventions.

Succinylation enables IDE to act as a hub of larval tissue destruction and adult tissue reconstruction during insect metamorphosis

Metamorphosis is an important way for insects to adapt to the environment. In this process, larval tissue destruction regulated by 20-hydroxyecdysone (20E) and adult tissue reconstruction regulated by insulin-like peptides (ILPs) occur simultaneously, but the detailed mechanism is still unclear. Here, the results of succinylome, subcellular localization, and protein interaction analysis show that non-succinylated insulin-degrading enzyme (IDE) localizes in the cytoplasm, binds to insulin-like growth factor 2 (IGF-2-like), and degrades it. When the metamorphosis is initiated, 20E up-regulated carnitine palmitoyltransferase 1A (Cpt1a) through transcription factor Krüppel-like factor 15 (KLF15), thus increasing the level of IDE succinylation on K179. Succinylated IDE translocated from cytoplasm to nucleus, combined with ecdysone receptor to promote 20E signaling pathway, causing larval tissue destruction, while IGF-2-like was released to promote adult tissue proliferation. That is, succinylation alters subcellular localization of IDE so that it can bind to different target proteins and act as a hub of metamorphosis.

Lysine succinylation precisely controls normal erythropoiesis

Lysine succinylation (Ksu) has recently emerged as a protein modification that regulates diverse functions in various biological processes. However, the systemic, precise role of lysine succinylation in erythropoiesis remains to be fully elucidated. In this study, we noted a prominent increase of succinyl-CoA and lysine succinylation during human erythroid differentiation. To explore the functional significance of succinylation, we inhibited succinylation by either knocking down key succinyltransferases or overexpressing desuccinylases. Succinylation inhibition led to suppressed cell proliferation, increased apoptosis, and disrupted erythroid differentiation. In vivo overexpression of the desuccinylase SIRT5 delayed erythroid differentiation. Furthermore, integrative proteome and succinylome analysis identified 939 succinylated proteins with 3,562 Ksu sites, distributed across various cellular compartments and involved in multiple cellular processes. Significantly, inconsistencies were observed between protein expression levels and succinylation levels, indicating that the succinylation of certain proteins may function independently of expression. Mechanistically, we implicated KAT2A-mediated succinylation of histone H3 K79, leading to chromatin remodeling and, subsequently, regulation of erythropoiesis. Specifically, we identified CYCS as a key regulator of erythropoiesis, a function that depends on its succinylation sites K28/K40. Taken together, our comprehensive investigation of the succinylation landscape during erythropoiesis provides valuable insights into its regulatory role and offers potential implications for erythroid-related diseases.

Emerging interactions between mitochondria and NAD+ metabolism in cardiometabolic diseases

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme for redox reactions and regulates cellular catabolic pathways. An intertwined relationship exists between NAD+ and mitochondria, with consequences for mitochondrial function. Dysregulation in NAD+ homeostasis can lead to impaired energetics and increased oxidative stress, contributing to the pathogenesis of cardiometabolic diseases. In this review, we explore how disruptions in NAD+ homeostasis impact mitochondrial function in various cardiometabolic diseases. We discuss emerging studies demonstrating that enhancing NAD+ synthesis or inhibiting its consumption can ameliorate complications of this family of pathological conditions. Additionally, we highlight the potential role and therapeutic promise of mitochondrial NAD+ transporters in regulating cellular and mitochondrial NAD+ homeostasis.

Electro-acupuncture Suppresses Ferroptosis to Alleviate Cerebral Ischemia-Reperfusion Injury Through KAT3B-Mediated Succinylation of ACSL4

Electro-acupuncture (EA) is identified as an effective therapeutic method for cerebral ischemia/reperfusion injury (CIRI), which is a combination of Chinese traditional acupuncture and modern electro-therapy. However, the downstream molecular mechanisms of EA in CIRI process remains largely unknown. The purpose of the present study is to unveil the therapeutic effect of EA on CIRI rat and its regulatory mechanisms. At first, we constructed middle cerebral artery occlusion (MCAO) rat models and then treated them with EA to observe the pathological changes. The results indicated that EA decreased the infarct volume (43.81 ± 3.34 vs 15.96 ± 2.22) and the neurological scores (3.33 ± 0.52 vs 1.67 ± 0.52) and suppressed the apoptosis in MCAO model rats. For ferroptosis analysis, EA decreased the Fe2 + (0.08 ± 0.01 vs 0.06 ± 0.01), MDA (36.61 ± 4.29 vs 21.72 ± 2.79), and LPS (5.25 ± 0.69 vs 2.89 ± 0.42) contents and increased the GSH (4.94 ± 1.04 vs 11.69 ± 1.88) content in MCAO model rats. We next detected whether succinylation mediated EA-treated I/R injury. According to immunoprecipitation and western blot analysis, EA treatment could lower both levels of succinylation and KAT3B in MCAO rats. Moreover, mechanism experiments unveiled that KAT3B promoted the succinylation of the ferroptosis-related protein ACSL4 at K661 site and thus stabilizing ACSL4. Finally, EA-treated MCAO rats were further injected with KAT3B expression vector. The results showed that KAT3B overexpression increased the infarct volume (31.44 ± 3.92 vs 7.94 ± 2.84) and the neurological scores (2.67 ± 0.51 vs 1.33 ± 0.51) and promoted the apoptosis in EA treated MCAO model rats. For ferroptosis analysis, KAT3B overexpression increased the Fe2 + (0.08 ± 0.01 vs 0.05 ± 0.01), MDA (29.24 ± 4.30 vs 22.06 ± 1.89), and LPO (5.07 ± 0.45 vs 2.88 ± 0.49) contents and decreased the GSH (7.86 ± 1.09 vs 11.06 ± 1.76) content in EA treated MCAO model rats. Collectively, our study demonstrates that EA plays a therapeutic role in CIRI through suppressing KAT3B-induced stabilization of ACSL4 to inhibit ferroptosis. These findings contribute to our understanding of the molecular mechanisms underlying the neuroprotective effects of EA and open new avenues for the development of innovative therapeutic strategies for CIRI.

Emerging roles of mitochondrial sirtuin SIRT5 in succinylation modification and cancer development

Succinylation represents an emerging class of post-translational modifications (PTMs), characterized by the enzymatic or non-enzymatic transfer of a negatively charged four-carbon succinyl group to the ϵ-amino group of lysine residues, mediated by succinyl-coenzyme A. Recent studies have highlighted the involvement of succinylation in various diseases, particularly cancer progression. Sirtuin 5 (SIRT5), a member of the sirtuin family, has been extensively studied for its robust desuccinylase activity, alongside its deacetylase function. To date, only a limited number of SIRT5 substrates have been identified. These substrates mediate diverse physiological processes such as glucose oxidation, fatty acid oxidation, ammonia detoxification, reactive oxygen species scavenging, anti-apoptosis, and inflammatory responses. The regulation of these activities can occur through either the same enzymatic activity acting on different substrates or distinct enzymatic activities targeting the same substrate. Aberrant expression of SIRT5 has been closely linked to tumorigenesis and disease progression; however, its role remains controversial. SIRT5 exhibits dual functionalities: it can promote tumor proliferation, metastasis, drug resistance, and metabolic reprogramming, thereby acting as an oncogene; conversely, it can also inhibit tumor cell growth and induce apoptosis, functioning as a tumor suppressor gene. This review aims to provide a comprehensive overview of the current research status of SIRT5. We discuss its structural characteristics and regulatory mechanisms, compare its functions with other sirtuin family members, and elucidate the mechanisms regulating SIRT5 activity. Specifically, we focus on the role of succinylation modification mediated by SIRT5 in tumor progression, highlighting how desuccinylation by SIRT5 modulates tumor development and delineating the underlying mechanisms involved.

The role of myocardial energy metabolism perturbations in diabetic cardiomyopathy: from the perspective of novel protein post-translational modifications

Diabetic cardiomyopathy (DbCM), a significant chronic complication of diabetes, manifests as myocardial hypertrophy, fibrosis, and other pathological alterations that substantially impact cardiac function and elevate the risk of cardiovascular diseases and patient mortality. Myocardial energy metabolism disturbances in DbCM, encompassing glucose, fatty acid, ketone body and lactate metabolism, are crucial factors that contribute to the progression of DbCM. In recent years, novel protein post-translational modifications (PTMs) such as lactylation, β-hydroxybutyrylation, and succinylation have been demonstrated to be intimately associated with the myocardial energy metabolism process, and in conjunction with acetylation, they participate in the regulation of protein activity and gene expression activity in cardiomyocytes. This review examines the epigenetic pathogenesis of DbCM, primarily focusing on myocardial energy metabolism perturbations and novel PTMs associated with them. It provides a detailed analysis of the mechanisms of these novel PTMs in DbCM to enhance the understanding of DbCM pathophysiology and establish a theoretical foundation for the development of new treatment strategies for DbCM.

Global alignment and local curvature of microtubules in mouse fibroblasts are robust against perturbations of vimentin and actin

The eukaryotic cytoskeleton is an intricate network of three types of mechanically distinct biopolymers - actin filaments, microtubules and intermediate filaments (IFs). These filamentous networks determine essential cellular functions and properties. Among them, microtubules are important for intracellular transport and establishing cell polarity during migration. Despite their intrinsic stiffness, they exhibit characteristic bending and buckling in cells due to nonthermal forces acting on them. Interactions between cytoskeletal filaments have been found but are complex and diverse with respect to their effect on the mechanical behavior of the filaments and the architecture of networks. We systematically study how actin and vimentin IFs influence the network structure and local bending of microtubules by analyzing fluorescence microscopy images of mouse fibroblasts on protein micropatterns. Our automated analysis averages over large amounts of data to mitigate the effect of the considerable natural variance in biological cell data. We find that the radial orientation of microtubules in circular cells is robust and is established independently of vimentin and actin networks. Observing the local curvature of microtubules, we find highly similar average bending of microtubules in the entire cell regardless of the cytoskeletal surrounding. Small systematic differences cannot be attributed directly to vimentin and actin densities. Our results suggest that, on average, microtubules in unpolarized mouse fibroblasts are unexpectedly independent of the rest of the cytoskeleton in their global network structure and their local curvature.

SIRT5 prevents mitochondrial dysfunction and cardiac hypertrophy induced by RIP140

Objectives

To investigate the effect and mechanism of sirtuin5 (SIRT5) on mitochondrial dysfunction and cardiac hypertrophy induced by receptor-interacting protein 140 (RIP140).

Materials and Methods

The neonatal rat cardiomyocytes (NRCMs) and SD rats were treated with Angiotensin II (Ang II) to induce in vitro and in vivo model of cardiac hypertrophy. RIP140 was overexpressed by adenovirus infection, and SIRT5 was overexpressed by plasmid transfection. RIP140 and SIRT5 were knocked down by siRNA interference. The expression of RIP140, SIRT5, and biomarkers of cardiac hypertrophy were measured by qRT-PCR and western blot. The transcription levels of mitochondrial DNA-encoded genes were detected by qRT-PCR. Cell surface area and mitochondrial membrane potential were respectively detected by rhodamine-phalloidin and tetramethylrhodamine ethyl ester (TMRE) fluorescence analysis. Cellular oxygen consumption and ATP production were investigated using assay kits. All data are from at least three independent experiments.

Results

The expression of SIRT5 was down-regulated in NRCMs and hearts treated with Ang II. Overexpression of SIRT5 protected cardiomyocytes from AngII-induced hypertrophy, whereas knockdown of SIRT5 resulted in cardiac hypertrophy. Moreover, since SIRT5 was regulated by the transcriptional coactivator, we also found that SIRT5 could be negatively regulated by the transcriptional corepressor RIP140 in cardiomyocytes. Furthermore, SIRT5 significantly attenuated energy metabolic dysregulation and mitochondrial dysfunction and exerted its protective role on myocardial hypertrophy under the regulation of RIP140.

Conclusion

SIRT5 exerts a protective role in mitochondrial dysfunction and cardiac hypertrophy induced by RIP140.

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.

SIRT5-mediated PRKAA2 succinylation ameliorates apoptosis of human placental trophoblasts in hypertensive disorder complicating pregnancy

PURPOSE

Hypertensive disorder complicating pregnancy (HDCP) is a serious clinical disorder syndrome during pregnancy. This study aims at finding novel targets for HDCP therapy.

METHODS

HDCP-related mRNAs were firstly screened out and subjected to gene enrichment analysis. We chose protein kinase AMP-activated catalytic subunit alpha 2 (PRKAA2) as the research object. Thirty-nine HDCP patients at 32 to 40 weeks of gestation were selected as the HDCP group, and 39 normal controls who received cesarean section delivery at 37-42 weeks of pregnancy were enrolled in this study. Chorionic villi samples were collected within 30 min of delivery. The apoptosis of isolated placental trophoblasts was monitored to investigate the regulatory role of PRKAA2.

RESULTS

PRKAA2 expression was further proven to be enhanced in the placental tissues of HDCP patients compared with that of normal puerpera. Subsequently, the results of flow cytometry analysis and western blot indicated that PRKAA2 overexpression accelerated primary placental cell apoptosis, while its knockdown attenuated cell apoptosis. Mechanistically, we determined that the level of PRKAA2 succinylation was elevated in the placental tissue of HDCP patients. Through in vitro succinylation assay and mutagenesis, we confirmed that sirtuin 5 (SIRT5) interacts with PRKAA2 at K69 and K260 to induce PRKAA2 desuccinylation. SIRT5 regulated primary HDCP cell apoptosis through PRKAA2. Finally, the animal study revealed that PRKAA2 elevates the systolic blood pressure of HDCP rat model.

CONCLUSION

Our findings indicated that SIRT5-mediated PRKAA2 succinylation modulates placental cell apoptosis in HDCP, suggesting that PRKAA2 is a potential therapeutic target for HDCP treatment.

Sirtuin Proteins and Memory: A Promising Target in Alzheimer's Disease Therapy?

Sirtuins (SIRTs), nicotine adenine dinucleotide (+)-dependent histone deacetylases, have emerged as critical regulators in many signalling pathways involved in a wide range of biological processes. Currently, seven mammalian SIRTs have been characterized and are found across a number of cellular compartments. There has been considerable interest in the role of SIRTs in the brain due to their role in a plethora of metabolic- and age-related diseases, including their involvement in learning and memory function in physiological and pathophysiological conditions. Although cognitive function declines over the course of healthy ageing, neurological disorders including Alzheimer's disease (AD) can be associated with progressive cognitive impairments. This review aimed to report and integrate recent advances in the understanding of the role of SIRTs in cognitive function and dysfunction in the context of AD. We have also reviewed the use of selective and/or natural SIRT activators as potential therapeutic agents and/or adjuvants for AD.

Catalpol improved energy metabolism and inflammation through the SIRT5-mediated signaling pathway to ameliorate myocardial injury

BACKGROUND AND PURPOSE

Catalpol (CAT) has diverse pharmacological functions, including cellular homeostasis maintenance and anti-inflammatory effects. Sirtuin 5 (SIRT5) plays a considerable role in regulating cellular homeostasis in cardiac diseases. Our research explores the therapeutic potential of CAT against myocardial injury and its underlying mechanism.

METHODS

The H9c2 cells were pretreated with different CAT concentrations for 24 h, or CAT for 24 h followed by CoCl2 stimulation. Cell viability was determined with MTT assay. Biochemical assays, western blotting, and quantitative real-time PCR (qRT-PCR), combined with bioinformatic analysis, were used to examine the impact of CAT on CoCl2-induced myocardial injury in H9c2 cells and further explore its molecular mechanisms.

RESULTS

CAT ameliorated levels of myocardial enzymes, increased nicotinamide adenine dinucleotide (NAD+/NADH) ratio and adenosine triphosphate (ATP), while inhibited lactic acid (LD), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and IL-6 in CoCl2-induced H9c2 cells. Mechanistically, SIRT5 knockdown inhibited Lin28a expression and negated the effects of CAT on ATP level, LD content, and the expression of inflammatory factors in cells. CAT likely exerted its protective effects on myocardial function through the SIRT5-mediated signaling pathway.

CONCLUSIONS

CAT regulates energy metabolism and inflammation via the SIRT5-mediated signaling pathway, exerting a protective effect in myocardial injury.

Up-regulated succinylation modifications induce a senescence phenotype in microglia by altering mitochondrial energy metabolism

The aging of the central nervous system(CNS) is a primary contributor to neurodegenerative diseases in older individuals and significantly impacts their quality of life. Neuroinflammation, characterized by activation of microglia(MG) and release of cytokines, is closely associated with the onset of these neurodegenerative diseases. The activated status of MG is modulated by specifically programmed metabolic changes under various conditions. Succinylation, a novel post-translational modification(PTM) mainly involved in regulating mitochondrial energy metabolism pathways, remains unknown in its role in MG activation and aging. In the present study, we found that succinylation levels were significantly increased both during aging and upon lipopolysaccharide-induced(LPS-induced) MG activation undergoing metabolic reprogramming. Up-regulated succinylation induced by sirtuin 5 knockdown(Sirt5 KD) in microglial cell line BV2 resulted in significant up-regulation of aging-related genes, accompanied by impaired mitochondrial adaptability and a shift towards glycolysis as a major metabolic pathway. Furthermore, after LPS treatment, Sirt5 KD BV2 cells exhibited increased generation of reactive oxygen species(ROS), accumulation of lipid droplets, and elevated levels of lipid peroxidation. By employing immunoprecipitation, introducing point mutation to critical succinylation sites, and conducting enzyme activity assays for succinate dehydrogenase(SDH) and trifunctional enzyme subunit alpha(ECHA), we demonstrated that succinylation plays a regulatory role in modulating the activities of these mitochondrial enzymes. Finally, down-regulation the succinylation levels achieved through administration of succinyl phosphonate(SP) led to amelioration of MG senescence in vitro and neuroinflammation in vivo. To our knowledge, our data provide preliminary evidence indicating that up-regulated succinylation modifications elicit a senescence phenotype in MG through alterations in energy metabolism. Moreover, these findings suggest that manipulation of succinylation levels may offer valuable insights into the treatment of aging-related neuroinflammation.

Lidocaine inhibits the lung cancer progression through decreasing the HIST1H2BL levels via SIRT5 mediated succinylation

Lung cancer is a malignant tumor originating from the bronchial mucosa or gland of the lung. Recently, lidocaine, a widely used amide local anesthetic, was demonstrated to inhibit many cancer progression. This research was performed to explore the specific mechanism of lidocaine in the lung cancer progression. The human normal lung epithelial cells (BEAS-2B), and NSCLC cell lines (A549 and H1299) were used and treated with lidocaine in this study. The cell biological behaviors were detected by CCK-8, wound healing and transwell assay. Besides, the mRNA and protein levels of related genes were detected by western blot. The results showed that lidocaine treatment significantly decreased the cell viability and migration of the A549 and H1299 cells. Furthermore, the lidocaine treatment significantly decreased the succinylation and protein levels of HIST1H2BL, which was reversed after SIRT5 knockdown. Additionally, HIST1H2BL knockdown decreased the cell viability and migration of the A549 and H1299 cells, while HIST1H2BL overexpression reversed the effects of lidocaine on the cell viability and migration of the A549 and H1299 cells. In conclusion, lidocaine treatment might inhibited the lung cancer progression through decreasing the SIRT5 mediated succinylation of HIST1H2BL.

Inhibition of Sirtuin Deacylase Activity by Peroxynitrite

Sirtuins are a class of enzymes that deacylate protein lysine residues using NAD+ as a cosubstrate. Sirtuin deacylase activity has been historically regarded as protective; loss of sirtuin deacylase activity potentially increases susceptibility to aging-related disease development. However, which factors may inhibit sirtuins during aging or disease is largely unknown. Increased oxidant and inflammatory byproduct production damages cellular proteins. Previously, we and others found that sirtuin deacylase activity is inhibited by the nitric oxide (NO)-derived cysteine post-translational modification S-nitrosation. However, the comparative ability of the NO-derived oxidant peroxynitrite (ONOO-) to affect human sirtuin activity had not yet been assessed under uniform conditions. Here, we compare the ability of ONOO- (donated from SIN-1) to post-translationally modify and inhibit SIRT1, SIRT2, SIRT3, SIRT5, and SIRT6 deacylase activity. In response to SIN-1 treatment, inhibition of SIRT1, SIRT2, SIRT3, SIRT5, and SIRT6 deacylase activity correlated with increased tyrosine nitration. Mass spectrometry identified multiple novel tyrosine nitration sites in SIRT1, SIRT3, SIRT5, and SIRT6. As each sirtuin isoform has at least one tyrosine nitration site within the catalytic core, nitration may result in sirtuin inhibition. ONOO- can also react with cysteine residues, resulting in sulfenylation; however, only SIRT1 showed detectable peroxynitrite-mediated cysteine sulfenylation. While SIRT2, SIRT3, SIRT5, and SIRT6 showed no detectable sulfenylation, SIRT6 likely undergoes transient sulfenylation, quickly resolving into an intermolecular disulfide bond. These results suggest that the aging-related oxidant peroxynitrite can post-translationally modify and inhibit sirtuins, contributing to susceptibility to aging-related disease.

Cellular and molecular biology of posttranslational modifications in cardiovascular disease

Cardiovascular disease (CVD) has now become the leading cause of death worldwide, and its high morbidity and mortality rates pose a great threat to society. Although numerous studies have reported the pathophysiology of CVD, the exact pathogenesis of all types of CVD is not fully understood. Therefore, much more research is still needed to explore the pathogenesis of CVD. With the development of proteomics, many studies have successfully identified the role of posttranslational modifications in the pathogenesis of CVD, including key processes such as apoptosis, cell metabolism, and oxidative stress. In this review, we summarize the progress in the understanding of posttranslational modifications in cardiovascular diseases, including novel protein posttranslational modifications such as succinylation and nitrosylation. Furthermore, we summarize the currently identified histone deacetylase (HDAC) inhibitors used to treat CVD, providing new perspectives on CVD treatment modalities. We critically analyze the roles of posttranslational modifications in the pathogenesis of CVD-related diseases and explore future research directions related to posttranslational modifications in cardiovascular diseases.

SIRT5 induces autophagy and alleviates myocardial infarction via desuccinylation of TOM1

Myocardial infarction (MI) is a prevalent form of ischemic heart disease, significantly contributing to heart disease-related deaths worldwide. This condition is primarily caused by myocardial ischemic-reperfusion injury (MIRI). Sirtuin 5 (SIRT5) is a desuccinylase known for its ability to reduce protein succinylation. Recent studies have highlighted the potential role of SIRT5 in various human diseases, including MIRI. This study aims to investigate the specific role of SIRT5 in modulating autophagy and cardiomyocyte death in a MIRI model, as well as to identify the downstream protein targets of SIRT5. Initially, we established a hypoxia/reoxygenation (H/R)-induced MIRI cell model to measure SIRT5 expression and assess its functions. Our results indicated that H/R induction led to a downregulation of SIRT5 expression, decreased autophagy, and increased cell death. Notably, overexpression of SIRT5 effectively promoted autophagy and inhibited cell death in the MIRI cell model. Mechanistically, SIRT5 was found to directly interact with the target of myb1 membrane trafficking protein (TOM1) at the K48 site, inducing its desuccinylation and stabilization. Further rescue assays revealed that TOM1 knockdown reversed the changes in autophagy and apoptosis caused by SIRT5 overexpression in the MIRI cell model. In vivo experiments demonstrated that SIRT5 alleviated myocardial injury in MI models. In conclusion, this study uncovers the role of SIRT5-mediated desuccinylation of TOM1 in regulating autophagy-related cell death in MIRI, providing new insights into potential therapeutic strategies for MI.

Histone deacetylases and inhibitors in diabetes mellitus and its complications

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia, with its prevalence linked to both genetic predisposition and environmental factors. Epigenetic modifications, particularly through histone deacetylases (HDACs), have been recognized for their significant influence on DM pathogenesis. This review focuses on the classification of HDACs, their role in DM and its complications, and the potential therapeutic applications of HDAC inhibitors. HDACs, which modulate gene expression without altering DNA sequences, are categorized into four classes with distinct functions and tissue specificity. HDAC inhibitors (HDACi) have shown efficacy in various diseases, including DM, by targeting these enzymes. The review highlights how HDACs regulate β-cell function, insulin sensitivity, and hepatic gluconeogenesis in DM, as well as their impact on diabetic cardiomyopathy, nephropathy, and retinopathy. Finally, we suggest that targeted histone modification is expected to become a key method for the treatment of diabetes and its complications. The study of HDACi offers insights into new treatment strategies for DM and its associated complications.

SIRTUIN 5 ALLEVIATES EXCESSIVE MITOCHONDRIAL FISSION VIA DESUCCINYLATION OF ATPASE INHIBITORY FACTOR 1 IN SEPSIS-INDUCED ACUTE KIDNEY INJURY

ABSTRACT

Sepsis-induced acute kidney injury (SAKI) poses a significant clinical challenge with high morbidity and mortality. Excessive mitochondrial fission has been identified as the central pathogenesis of sepsis-associated organ damage, which is also implicated in the early stages of SAKI. Sirtuin 5 (SIRT5) has emerged as a central regulator of cellular mitochondrial function; however, its role in the regulation of sepsis-induced excessive mitochondrial fission in kidney and the underlying mechanism remains unclear. In this study, SAKI was modeled in mice through cecal ligation and puncture, and in human renal tubular epithelial (HK-2) cells stimulated with lipopolysaccharide (LPS), to mimic the cell SAKI model. Our findings revealed that septic mice with a SIRT5 knockout exhibited shortened survival times and elevated levels of renal injury compared to wild-type mice, suggesting the significant involvement of SIRT5 in SAKI pathophysiology. Additionally, we observed that SIRT5 depletion led to increased renal mitochondrial fission, while the use of a mitochondrial fission inhibitor (Mdivi-1) reversed the detrimental effects caused by SIRT5 depletion, emphasizing the pivotal role of SIRT5 in preventing excessive mitochondrial fission. In vitro experiments demonstrated that the overexpression of SIRT5 effectively mitigated the adverse effects of LPS on HK-2 cells viability and mitochondrial fission. Conversely, downregulation of SIRT5 decreased HK-2 cells viability and exacerbated LPS-induced mitochondrial fission. Mechanistically, the protective function of SIRT5 may be in part, ascribed to its desuccinylating action on ATPase inhibitory factor 1. In conclusion, this study provides novel insights into the underlying mechanisms of SAKI, suggesting the possibility of identifying future drug targets in terms of improved mitochondrial dynamics by SIRT5.

The influence of estrogen on myocardial post-translational modifications and cardiac function in women

The lifetime risk of heart failure (HF) is comparable in men and women; nevertheless, disparities exist in our understanding of how HF differs between sexes. Several differences in cardiac physiology exist between men and women including the propensity to develop specific HF phenotypes. Men are more likely to be diagnosed with HF failure with reduced ejection fraction, while women have a greater propensity to develop HF with preserved ejection fraction. The mechanisms responsible for these differences remain unclear. Post-translational modifications (PTMs) of myofilament proteins likely contribute to these sex-specific propensities. The role of PTMs in heart disease is an expanding field with immense potential therapeutic targets. However, numerous PTMs remain underexplored, particularly in the context of the female heart. Estrogen, a key gonadal hormone, cardioprotective in pre-menopausal women and its loss with menopause likely contributes to disease in aging women. However, how estrogen regulates PTMs to contribute to HF development is not fully clear. This review outlines key sex differences in HF along with characterizing the contributions of novel myocardial PTMs in cardiac physiology and their regulation by estrogen. Collectively, we highlight the necessity for further investigation into women's heart health and the distinctive mechanisms distinguishing women from men.

Conjoint analysis of succinylome and phosphorylome reveals imbalanced HDAC phosphorylation-driven succinylayion dynamic contibutes to lung cancer

Cancerous genetic mutations result in a complex and comprehensive post-translational modification (PTM) dynamics, in which protein succinylation is well known for its ability to reprogram cell metabolism and is involved in the malignant evolution. Little is known about the regulatory interactions between succinylation and other PTMs in the PTM network. Here, we developed a conjoint analysis and systematic clustering method to explore the intermodification communications between succinylome and phosphorylome from eight lung cancer patients. We found that the intermodification coorperation in both parallel and series. Besides directly participating in metabolism pathways, some phosphosites out of mitochondria were identified as an upstream regulatory modification directing succinylome dynamics in cancer metabolism reprogramming. Phosphorylated activation of histone deacetylase (HDAC) in lung cancer resulted in the removal of acetylation and favored the occurrence of succinylation modification of mitochondrial proteins. These results suggest a tandem regulation between succinylation and phosphorylation in the PTM network and provide HDAC-related targets for intervening mitochondrial succinylation and cancer metabolism reprogramming.

Sirt5 improves cardiomyocytes fatty acid metabolism and ameliorates cardiac lipotoxicity in diabetic cardiomyopathy via CPT2 de-succinylation

RATIONALE

The disruption of the balance between fatty acid (FA) uptake and oxidation (FAO) leads to cardiac lipotoxicity, serving as the driving force behind diabetic cardiomyopathy (DbCM). Sirtuin 5 (Sirt5), a lysine de-succinylase, could impact diverse metabolic pathways, including FA metabolism. Nevertheless, the precise roles of Sirt5 in cardiac lipotoxicity and DbCM remain unknown.

OBJECTIVE

This study aims to elucidate the role and underlying mechanism of Sirt5 in the context of cardiac lipotoxicity and DbCM.

METHODS AND RESULTS

The expression of myocardial Sirt5 was found to be modestly elevated in diabetic heart failure patients and mice. Cardiac dysfunction, hypertrophy and lipotoxicity were exacerbated by ablation of Sirt5 but improved by forced expression of Sirt5 in diabetic mice. Notably, Sirt5 deficiency impaired FAO without affecting the capacity of FA uptake in the diabetic heart, leading to accumulation of FA intermediate metabolites, which mainly included medium- and long-chain fatty acyl-carnitines. Mechanistically, succinylomics analyses identified carnitine palmitoyltransferase 2 (CPT2), a crucial enzyme involved in the reconversion of fatty acyl-carnitines to fatty acyl-CoA and facilitating FAO, as the functional succinylated substrate mediator of Sirt5. Succinylation of Lys424 in CPT2 was significantly increased by Sirt5 deficiency, leading to the inactivation of its enzymatic activity and the subsequent accumulation of fatty acyl-carnitines. CPT2 K424R mutation, which mitigated succinylation modification, counteracted the reduction of enzymatic activity in CPT2 mediated by Sirt5 deficiency, thereby attenuating Sirt5 knockout-induced FAO impairment and lipid deposition.

CONCLUSIONS

Sirt5 deficiency impairs FAO, leading to cardiac lipotoxicity in the diabetic heart through the succinylation of Lys424 in CPT2. This underscores the potential roles of Sirt5 and CPT2 as therapeutic targets for addressing DbCM.

Acylspermidines are conserved mitochondrial sirtuin-dependent metabolites

Sirtuins are nicotinamide adenine dinucleotide (NAD+)-dependent protein lysine deacylases regulating metabolism and stress responses; however, characterization of the removed acyl groups and their downstream metabolic fates remains incomplete. Here we employed untargeted comparative metabolomics to reinvestigate mitochondrial sirtuin biochemistry. First, we identified N-glutarylspermidines as metabolites downstream of the mitochondrial sirtuin SIR-2.3 in Caenorhabditis elegans and demonstrated that SIR-2.3 functions as a lysine deglutarylase and that N-glutarylspermidines can be derived from O-glutaryl-ADP-ribose. Subsequent targeted analysis of C. elegans, mouse and human metabolomes revealed a chemically diverse range of N-acylspermidines, and formation of N-succinylspermidines and/or N-glutarylspermidines was observed downstream of mammalian mitochondrial sirtuin SIRT5 in two cell lines, consistent with annotated functions of SIRT5. Finally, N-glutarylspermidines were found to adversely affect C. elegans lifespan and mammalian cell proliferation. Our results indicate that N-acylspermidines are conserved metabolites downstream of mitochondrial sirtuins that facilitate annotation of sirtuin enzymatic activities in vivo and may contribute to sirtuin-dependent phenotypes.

Mitochondrial glycerol 3-phosphate dehydrogenase deficiency exacerbates lipotoxic cardiomyopathy

Metabolic diseases such as obesity and diabetes induce lipotoxic cardiomyopathy, which is characterized by myocardial lipid accumulation, dysfunction, hypertrophy, fibrosis and mitochondrial dysfunction. Here, we identify that mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) is a pivotal regulator of cardiac fatty acid metabolism and function in the setting of lipotoxic cardiomyopathy. Cardiomyocyte-specific deletion of mGPDH promotes high-fat diet induced cardiac dysfunction, pathological hypertrophy, myocardial fibrosis, and lipid accumulation. Mechanically, mGPDH deficiency inhibits the expression of desuccinylase SIRT5, and in turn, the hypersuccinylates majority of enzymes in the fatty acid oxidation (FAO) cycle and promotes the degradation of these enzymes. Moreover, manipulating SIRT5 abolishes the effects of mGPDH ablation or overexpression on cardiac function. Finally, restoration of mGPDH improves lipid accumulation and cardiomyopathy in both diet-induced and genetic obese mouse models. Thus, our study indicates that targeting mGPDH could be a promising strategy for lipotoxic cardiomyopathy in the context of obesity and diabetes.

Human SIRT5 variants with reduced stability and activity do not cause neuropathology in mice

SIRT5 is a sirtuin deacylase that removes negatively charged lysine modifications, in the mitochondrial matrix and elsewhere in the cell. In benign cells and mouse models, under basal conditions, the phenotypes of SIRT5 deficiency are quite subtle. Here, we identify two homozygous SIRT5 variants in patients suspected to have mitochondrial disease. Both variants, P114T and L128V, are associated with reduced SIRT5 protein stability and impaired biochemical activity, with no evidence of neomorphic or dominant negative properties. The crystal structure of the P114T enzyme was solved and shows only subtle deviations from wild-type. Via CRISPR-Cas9, we generated a mouse model that recapitulates the human P114T mutation; homozygotes show reduced SIRT5 levels and activity, but no obvious metabolic abnormalities, neuropathology, or other gross phenotypes. We conclude that these human SIRT5 variants most likely represent severe hypomorphs, but are likely not by themselves the primary pathogenic cause of the neuropathology observed in the patients.

Dysregulation of protein succinylation and disease development

As a novel post-translational modification of proteins, succinylation is widely present in both prokaryotes and eukaryotes. By regulating protein translocation and activity, particularly involved in regulation of gene expression, succinylation actively participates in diverse biological processes such as cell proliferation, differentiation and metabolism. Dysregulation of succinylation is closely related to many diseases. Consequently, it has increasingly attracted attention from basic and clinical researchers. For a thorough understanding of succinylation dysregulation and its implications for disease development, such as inflammation, tumors, cardiovascular and neurological diseases, this paper provides a comprehensive review of the research progress on abnormal succinylation. This understanding of association of dysregulation of succinylation with pathological processes will provide valuable directions for disease prevention/treatment strategies as well as drug development.

Epigenetic determinants and non-myocardial signaling pathways contributing to heart growth and regeneration

Congenital heart disease is the most common birth defect worldwide. Defective cardiac myogenesis is either a major presentation or associated with many types of congenital heart disease. Non-myocardial tissues, including endocardium and epicardium, function as a supporting hub for myocardial growth and maturation during heart development. Recent research findings suggest an emerging role of epigenetics in nonmyocytes supporting myocardial development. Understanding how growth signaling pathways in non-myocardial tissues are regulated by epigenetic factors will likely identify new disease mechanisms for congenital heart diseases and shed lights for novel therapeutic strategies for heart regeneration.

12,13-diHOME attenuates high glucose-induced calcification of vascular smooth muscle cells through repressing CPT1A-mediated HMGB1 succinylation

Diabetes is closely associated with vascular calcification (VC). Exorbitant glucose concentration activates pro-calcific effects in vascular smooth muscle cells (VSMCs). This study enrolled 159 elderly patients with type 2 diabetes and divided them into three groups, T1, T2 and T3, according to brachial-ankle pulse wave velocity(BaPWV). There were statistically significant differences in the waist circumference, waist hip ratio, systolic blood pressure, 12,13-diHOME (a lipokin) concentration among T1, T2 and T3. 12,13-diHOME levels were positively correlated to high density lipoprotein cholesterol and total cholesterol, but negatively correlated to with waist circumference, waist hip ratio, systolic blood pressure and baPWV. Studies in vitro showed that 12,13-diHOME effectively inhibits calcification in VSMCs under high glucose conditions. Notably, 12,13-diHOME suppressed the up-regulation of carnitine O-palmitoyltransferase 1 (CPT1A) and CPT1A-induced succinylation of HMGB1. The succinylation of HMGB1 at the K90 promoted the protein stability and induced the enrichment of HMGB1 in cytoplasm, which induced the calcification in VSMCs. Together, 12,13-diHOME attenuates high glucose-induced calcification in VSMCs through repressing CPT1A-mediated HMGB1 succinylation.

Sirt5-mediated lysine desuccinylation regulates oxidative stress adaptation in Magnaporthe oryzae during host intracellular infection

Plant pathogenic fungi elaborate numerous detoxification strategies to suppress host reactive oxygen species (ROS), but their coordination is not well-understood. Here, we show that Sirt5-mediated protein desuccinylation in Magnaporthe oryzae is central to host ROS detoxification. SIRT5 encodes a desuccinylase important for virulence via adaptation to host oxidative stress. Quantitative proteomics analysis identified a large number of succinylated proteins targeted by Sirt5, most of which were mitochondrial proteins involved in oxidative phosphorylation, TCA cycle, and fatty acid oxidation. Deletion of SIRT5 resulted in hypersuccinylation of detoxification-related enzymes, and significant reduction in NADPH : NADP+ and GSH : GSSG ratios, disrupting redox balance and impeding invasive growth. Sirt5 desuccinylated thioredoxin Trx2 and glutathione peroxidase Hyr1 to activate their enzyme activity, likely by affecting proper folding. Altogether, this work demonstrates the importance of Sirt5-mediated desuccinylation in controlling fungal process required for detoxifying host ROS during M. oryzae infection.

Yiqigubiao pill treatment regulates Sirtuin 5 expression and mitochondrial function in chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a heterogeneous group of pathophysiological bases of airway inflammation and its anti-inflammatory response. Aberrant mitochondrial signaling and mitochondrial dysfunction underlie the pathomechanisms leading to COPD. This study aims to investigate the effects of the Yiqigubiao (YQGB) pill, a traditional Chinese medicine (TCM), on Sirtuin 5 (SIRT5) and mitochondrial function in patients with COPD.

Methods

Thirty-four patients with COPD were randomized into oral YQGB or placebo groups concurrent with a 24-week routine treatment. The pulmonary function was assessed by examining the levels of forced expiratory volume in one second (FEV1)/forced vital capacity (FVC), FEV1, and FVC. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were used to detect SIRT5 expression in mitochondria isolated from peripheral blood. Flow cytometry was used to detect changes in mitochondrial membrane potential and reactive oxygen species (ROS) in peripheral blood lymphocytes. Human bronchial epithelial (HBE) cells stimulated by cigarette smoke extract (CSE) were treated with YQGB. After SIRT5 was knocked down in cells, the changes in mitochondrial membrane potential, levels of adenosine triphosphate (ATP), and ROS were detected.

Results

YQGB treatment significantly improved lung function in patients with COPD. The expression of SIRT5 and the mitochondrial membrane potential significantly increased and ROS decreased in patients with COPD after YQGB treatment. The CSE decreased cell proliferation and SIRT5 expression, which was alleviated after YQGB treatment. Furthermore, SIRT5 was knocked down in CSE-stimulated HBE cells, and its expression was elevated upon YQGB treatment. The knockdown of SIRT5 significantly altered the CSE-stimulation-induced dysregulation of mitochondrial membrane potential, ATP levels, and ROS. This was also restored after YQGB treatment.

Conclusions

YQGB treatment can elevate SIRT5 expression, restore mitochondrial function in COPD, and exert protective effects.

TMT-labeled quantitative malonylome analysis on the longissimus dorsi muscle of Laiwu pigs reveals the role of ACOT7 in fat deposition

The Laiwu pig is an indigenous fatty pig breed distributed in North China, characterized by an extremely high level of intramuscular fat (IMF) content (9% ∼ 12%), but the regulatory mechanism underlying intramuscular fat deposition in skeletal muscle is still unknown. In this study, the TMT-labeled quantitative malonylome of the longissimus dorsi muscle in Laiwu pigs at the fastest IMF deposition stage (240 d vs 120 d) was compared to analyze the molecular mechanism of IMF variation in pigs. In Laiwu pigs aged 240 days/120 days, we identified 291 malonylated lysine sites across 188 proteins in the longissimus dorsi muscle. Among these, 38 sites across 31 proteins exhibited differential malonylation. Annotation analysis and enrichment analysis were performed for differentially malonylated proteins (DMPs). These DMPs were mainly clustered into 12 GO functional categories accounting for 5 biological processes, 4 cellular components and 3 molecular functions, and 2 signaling pathways by KEGG enrichment analysis. The function of differentially malonylated protein ACOT7 in the process of fat deposition was further investigated during the differentiation of 3 T3-L1 cells. The results showed that the protein level of ACOT7 in 3 T3-L1 cells decreased but the malonylated level of ACOT7 increased significantly. The malonyl-CoA that is synthesized by ACSF3 affected the malonylation level of ACOT7 in 3 T3-L1 cells. SIGNIFICANCE: The intramuscular fat (IMF) content, by affecting sensory quality traits of meat, such as tenderness, flavor and juiciness, plays an important role in meat quality. Using TMT-based quantitative malonylated proteome analysis, we identified malonylated proteins in LD muscle samples in two stages (120 d and 240 d) of development and further identified differentially malonylated proteins, such as SLC25A4, ANXA5, TPM3 and ACOT7, that are associated with intramuscular fat deposition and fat metabolism in pigs. These differentially malonylated proteins could serve as candidates for elucidating the molecular mechanism of IMF deposition in pigs. In addition, we found that the malonyl-CoA in 3 T3-L1 cells is mainly synthesized by ACSF3, affecting the malonylated level of ACOT7. The study provides some data concerning the role of protein malonylation in regulating the variation in porcine IMF content.

Set7/9 aggravates ischemic brain injury via enhancing glutamine metabolism in a blocking Sirt5 manner

The aberrant expression of methyltransferase Set7/9 plays a role in various diseases. However, the contribution of Set7/9 in ischemic stroke remains unclear. Here, we show ischemic injury results in a rapid elevation of Set7/9, which is accompanied by the downregulation of Sirt5, a deacetylase reported to protect against injury. Proteomic analysis identifies the decrease of chromobox homolog 1 (Cbx1) in knockdown Set7/9 neurons. Mechanistically, Set7/9 promotes the binding of Cbx1 to H3K9me2/3 and forms a transcription repressor complex at the Sirt5 promoter, ultimately repressing Sirt5 transcription. Thus, the deacetylation of Sirt5 substrate, glutaminase, which catalyzes the hydrolysis of glutamine to glutamate and ammonia, is decreased, promoting glutaminase expression and triggering excitotoxicity. Blocking Set7/9 eliminates H3K9me2/3 from the Sirt5 promoter and normalizes Sirt5 expression and Set7/9 knockout efficiently ameliorates brain ischemic injury by reducing the accumulation of ammonia and glutamate in a Sirt5-dependent manner. Collectively, the Set7/9-Sirt5 axis may be a promising epigenetic therapeutic target.

Protein succinylation, hepatic metabolism, and liver diseases

Succinylation is a highly conserved post-translational modification that is processed via enzymatic and non-enzymatic mechanisms. Succinylation exhibits strong effects on protein stability, enzyme activity, and transcriptional regulation. Protein succinylation is extensively present in the liver, and increasing evidence has demonstrated that succinylation is closely related to hepatic metabolism. For instance, histone acetyltransferase 1 promotes liver glycolysis, and the sirtuin 5-induced desuccinylation is involved in the regulation of the hepatic urea cycle and lipid metabolism. Therefore, the effects of succinylation on hepatic glucose, amino acid, and lipid metabolism under the action of various enzymes will be discussed in this work. In addition, how succinylases regulate the progression of different liver diseases will be reviewed, including the desuccinylation activity of sirtuin 7, which is closely associated with fatty liver disease and hepatitis, and the actions of lysine acetyltransferase 2A and histone acetyltransferase 1 that act as succinyltransferases to regulate the succinylation of target genes that influence the development of hepatocellular carcinoma. In view of the diversity and significance of protein succinylation, targeting the succinylation pathway may serve as an attractive direction for the treatment of liver diseases.

SIRT5 promote malignant advancement of chordoma by regulating the desuccinylation of c-myc

Chordoma is a relatively rare and locally aggressive malignant tumor. Sirtuin (SIRT)5 plays pivotal roles in various tumors, but the role of SIRT5 in chordoma has not been found. This study was performed to investigate the regulatory effects of SIRT5 on cell proliferation, migration, and invasion and the underlying mechanism in chordoma. A xenograft tumor mouse model was established to assess tumor growth. Reverse transcription-quantitative polymerase chain reaction was used to analyze the mRNA levels of SIRT5 and c-myc. The effects of SIRT5 and c-myc on cell proliferation, migration, and invasion of chordoma cells were detected by cell counting kit-8, colony formation, and Transwell assays. The interaction between SIRT5 and c-myc was evaluated by co-immunoprecipitation (IP) assay. The succinylation of c-myc was analyzed by IP and Western blot. The results showed that SIRT5 expression was upregulated in chordoma tissues and cells. SIRT5 interacted with c-myc to inhibit the succinylation of c-myc at K369 site in human embryonic kidney (HEK)-293T cells. Silencing of SIRT5 suppressed the cell proliferation, migration, and invasion of chordoma cells, while the results were reversed after c-myc overexpression. Moreover, silencing SIRT5 suppressed tumor growth in mice. These findings suggested that SIRT5 promoted the malignant advancement of chordoma by regulating the desuccinylation of c-myc.

Role of succinylation modification in central nervous system diseases

Diseases of the central nervous system (CNS), including stroke, brain tumors, and neurodegenerative diseases, have a serious impact on human health worldwide, especially in elderly patients. The brain, which is one of the body's most metabolically dynamic organs, lacks fuel stores and therefore requires a continuous supply of energy substrates. Metabolic abnormalities are closely associated with the pathogenesis of CNS disorders. Post-translational modifications (PTMs) are essential regulatory mechanisms that affect the functions of almost all proteins. Succinylation, a broad-spectrum dynamic PTM, primarily occurs in mitochondria and plays a crucial regulatory role in various diseases. In addition to directly affecting various metabolic cycle pathways, succinylation serves as an efficient and rapid biological regulatory mechanism that establishes a connection between metabolism and proteins, thereby influencing cellular functions in CNS diseases. This review offers a comprehensive analysis of succinylation and its implications in the pathological mechanisms of CNS diseases. The objective is to outline novel strategies and targets for the prevention and treatment of CNS conditions.