Protein succinylation: regulating metabolism and beyond

Identification of Mitochondrial and Succinylation Modification-Related Gene Signature in Ischemic Stroke

Ischemic stroke (IS) is a leading cause of death and disability worldwide, often associated with immune dysregulation, mitochondrial dysfunction, and altered protein succinylation. This study aimed to identify mitochondrial and succinylation-related gene signatures with diagnostic potential in IS. Differentially expressed genes (DEGs) associated with IS were identified using transcriptome expression profiles from merged GSE16561 and GSE58294 GEO datasets. Functional enrichment and WGCNA identified hub genes. Mitochondrial and succinylation-related gene expression was assessed via ssGSEA. Feature genes were selected using machine learning. A prognostic nomogram was constructed. PPI networks were generated using GeneMANIA. Immune infiltration was assessed through ssGSEA. Drug-gene interactions were explored using DGIdb. qRT-PCR validation was performed on blood samples from IS patients and controls. We identified 317 DEGs enriched in immune response and inflammation pathways in 108 IS patients and 47 healthy controls using data from the merged datasets. WGCNA identified 101 hub genes in the yellow module and 65 in the brown module. Seven overlapping genes related to mitochondrial and succinylation processes were identified. Feature gene analysis revealed six key genes (MRPL41, NGRN, SLC25A42, SPTLC2, TUBB, and TXN) with robust diagnostic potential across both the merged and individual datasets (all AUCs > 0.7). Nomogram integration demonstrated predictive reliability. Feature genes exhibited significant correlations with immune cell infiltration. qRT-PCR validation confirmed the differential expression of four feature genes. TUBB and TXN showed interactions with various drugs. Mitochondrial and succinylation-related genes have diagnostic significance in IS, providing insights into disease pathogenesis and clinical applications.

Succinate predisposes mice to atrial fibrillation by impairing mitochondrial function via SUCNR1/AMPK axis

Atrial fibrillation (AF), a major public health concern, is associated with high rates of death and disability. Mitochondrial dysfunction has emerged as a key contributor to the pathophysiology of AF. Succinate, an essential Krebs cycle metabolite, is often elevated in the circulation of patients at risk for AF. However, its exact role in AF pathogenesis is still not well understood. To explore the association linking succinate overload and AF, we first established AF-susceptible mouse models of obesity and diabetes, confirming that circulating succinate levels were significantly elevated in these AF-prone mice. Next, we assessed AF vulnerability and atrial remodeling in succinate-treated mice (2 %/5 % for 7 weeks) or isolated primary atrial cells (0.5 mM for 24 h). Our results demonstrated that succinate overload increased AF susceptibility in mice and triggered adverse atrial remodeling, characterized by left atrial dilation, connexins lateralization, ion channel disturbances, and fibrosis. Moreover, succinate compromised atrial mitochondrial structure, leading to increased oxidative stress. Mechanistically, succinate overload upregulated the expression of its cognate receptor SUCNR1 (succinate receptor 1) and decreased AMPK (AMP-activated protein kinase) phosphorylation both in vitro and in vivo. AICAR (AMPK activator) maintained mitochondrial health to mitigate remodeling in succinate-exposed cells and prevented succinate-induced AF in obese and diabetic mice. In conclusion, succinate overload enhances AF vulnerability and atrial remodeling by impairing AMPK signaling and mitochondrial function. Succinate, therefore, represents an underappreciated contributor to AF pathogenesis and a potential biomarker.

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.

Lysine succinylome analysis of MRSA reveals critical roles in energy metabolism and virulence

Methicillin-resistant Staphylococcus aureus's (MRSA) resistance poses a global health challenge. This study investigates lysine succinylation in MRSA using proteomics and bioinformatics approaches to uncover metabolic and virulence mechanisms, with the goal of identifying novel therapeutic targets. Mass spectrometry and bioinformatics analyses mapped the MRSA succinylome, identifying 8048 succinylation sites on 1210 proteins. These analyses included Gene Ontology annotation, Kyoto Encyclopedia of Genes and Genomes pathway enrichment, and protein-protein interaction (PPI) network construction (e.g. using the STRING database, a widely used online tool for analyzing protein-protein interactions), providing a comprehensive functional and interactive landscape of succinylated proteins. The succinylated proteins were predominantly involved in cytoplasmic metabolic processes, with enrichment in glycolysis/gluconeogenesis and the tricarboxylic acid cycle. Both of these pathways are critical for MRSA's energy production, growth, and virulence, supplying the necessary metabolic intermediates and energy to support bacterial survival and pathogenicity. Motif analysis revealed 13 conserved motifs, while PPI analysis highlighted fibronectin-binding protein A (FnbA) as a central virulence factor. Succinylation significantly influences MRSA's metabolism and virulence, potentially impacting biofilm by modifying key proteins such as FnbA, bifunctional autolysin, and S-ribosylhomocysteine lyase(LuxS). These findings provide new avenues for developing antibiofilm strategies and therapeutic interventions against MRSA.

Electroacupuncture inhibits neuronal pyroptosis in ischemic brain injury through modulating SIRT5-mediated NEK7 succinylation

Ischemic stroke is a leading cause of global death. The treatment of this disease can inevitably result in reperfusion, thereby triggering cerebral ischemia-reperfusion injury (IRI) and neuronal pyroptosis. Electroacupuncture derived from traditional acupuncture has been proven to have favorable effects on ameliorating brain IRI and pyroptosis. Hence, the goal of the current research was to elucidate the mechanism governing electroacupuncture in cerebral IRI. We employed middle cerebral artery occlusion (MCAO) model to induce brain IRI. Our results revealed that electroacupuncture attenuated IRI in MCAO mice by minishing brain damage and hindering neuronal pyroptosis. Strikingly, it was discovered that electroacupuncture provoked the decrease of succinylation level and enhanced expression of SIRT5. Then, we demonstrated that knockdown of SIRT5 reversed the role of electroacupuncture in cerebral infarct injury and pyroptosis. In terms of mechanism, SIRT5 impeded the succinylation modification of NEK7 at K81 site to downregulate its expression level. Eventually, overexpression of NEK7 abrogated the impacts of electroacupuncture on MCAO mice. In conclusion, electroacupuncture restrained neuronal pyroptosis after cerebral ischemia via desuccinylating NEK7 in a SIRT5-dependent way.

Total glucosides of paeony ameliorates chemotherapy-induced neuropathic pain by suppressing microglia pyroptosis through the inhibition of KAT2A-mediated p38 pathway activation and succinylation

Chemotherapy-induced neuropathic pain (CINP) is a prevalent side effect of chemotherapy. Total glucosides of paeony (TGP) have been shown to be effective in pain management. This study aimed to investigate the efficacy and mechanism of TGP in alleviating CINP. Sprague-Dawley rats were treated with oxaliplatin to establish CINP models, and BV2 microglia were exposed to lipopolysaccharides (LPS) to induce pyroptosis. The impact of TGP on CINP was assessed by measuring mechanical withdrawal threshold (MWT), cold pain threshold (CPT), and thermal pain threshold (TPT), as well as inflammatory factor levels. Pyroptosis was evaluated using flow cytometry, lactate dehydrogenase (LDH) release, and pyroptosis marker levels. Quantitative real-time PCR and molecular docking were employed to identify TGP targets, while phospho-kinase arrays, western blotting, and co-immunoprecipitation were used to elucidate the mechanism. Results indicated that TGP increased MWT, CPT, and TPT and inhibited inflammatory factor release in CINP rats. Furthermore, TGP suppressed LPS-induced pyroptosis and downregulated KAT2A expression in BV2 cells; this suppression was reversed by KAT2A overexpression. Mechanistically, KAT2A overexpression activated the p38 pathway and promoted p38 succinylation at K295. KAT2A knockdown inhibited pyroptosis in LPS-induced BV2 cells, an effect that was reversed by the p38 activator metformin. Additionally, the improvements in MWT, CPT, TPT, and inflammatory factor levels observed in CINP rats treated with TGP were negated by KAT2A overexpression. In conclusion, TGP alleviated CINP by suppressing microglial pyroptosis through inhibition of the KAT2A-mediated p38 pathway activation and succinylation. This study provides insights into a potential new therapeutic approach for CINP.

The emerging importance of the α-keto acid dehydrogenase complexes in serving as intracellular and intercellular signaling platforms for the regulation of metabolism

The α-keto acid dehydrogenase complex (KDHc) class of mitochondrial enzymes is composed of four members: pyruvate dehydrogenase (PDHc), α-ketoglutarate dehydrogenase (KGDHc), branched-chain keto acid dehydrogenase (BCKDHc), and 2-oxoadipate dehydrogenase (OADHc). These enzyme complexes occupy critical metabolic intersections that connect monosaccharide, amino acid, and fatty acid metabolism to Krebs cycle flux and oxidative phosphorylation (OxPhos). This feature also imbues KDHc enzymes with the heightened capacity to serve as platforms for propagation of intracellular and intercellular signaling. KDHc enzymes serve as a source and sink for mitochondrial hydrogen peroxide (mtH2O2), a vital second messenger used to trigger oxidative eustress pathways. Notably, deactivation of KDHc enzymes through reversible oxidation by mtH2O2 and other electrophiles modulates the availability of several Krebs cycle intermediates and related metabolites which serve as powerful intracellular and intercellular messengers. The KDHc enzymes also play important roles in the modulation of mitochondrial metabolism and epigenetic programming in the nucleus through the provision of various acyl-CoAs, which are used to acylate proteinaceous lysine residues. Intriguingly, nucleosomal control by acylation is also achieved through PDHc and KGDHc localization to the nuclear lumen. In this review, I discuss emerging concepts in the signaling roles fulfilled by the KDHc complexes. I highlight their vital function in serving as mitochondrial redox sensors and how this function can be used by cells to regulate the availability of critical metabolites required in cell signaling. Coupled with this, I describe in detail how defects in KDHc function can cause disease states through the disruption of cell redox homeodynamics and the deregulation of metabolic signaling. Finally, I propose that the intracellular and intercellular signaling functions of the KDHc enzymes are controlled through the reversible redox modification of the vicinal lipoic acid thiols in the E2 subunit of the complexes.