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Iron-sulfur cluster synthesis and delivery to Sdh2. The tan box depicts the de novo synthesis of 2Fe-2S clusters within the ISU complex. Clusters are formed on the Isu1 scaffold protein with sulfide ions provided by the Nfs1 cysteine desulfurase and Yah1 ferredoxin. It is not clear how ferrous ions are delivered to the ISU complex. The preformed 2Fe-2S cluster is released from the scaffold complex through the actions of Hsp70 (Ssq1) and DnaJ (Jac1) to a transfer complex consisting of GSH-bound Grx5. The GSH-Grx5 delivers 2Fe-2S clusters to the ISA complex for the subsequent 4Fe-4S cluster synthesis depicted in the blue box. However, it is elusive whether the GSH-Grx5 is also required for 2Fe-2S cluster delivery to recipient proteins, in this case, Sdh2. It is also unknown whether the preformed 4Fe-4S clusters are directly delivered to Sdh2 or another factor is in need for this delivery step. All arrows with solid lines indicate transfer of components of Fe-S clusters or pre-formed Fe-S clusters.
Source publication
Succinate dehydrogenase (or complex II; SDH) is a heterotetrameric protein complex that links the tribarboxylic acid cycle with the electron transport chain. SDH is composed of four nuclear-encoded subunits that must translocate independently to the mitochondria and assemble into a mature protein complex embedded in the inner mitochondrial membrane...
Context in source publication
Context 1
... depleted of ISU components or the Fe-S targeting factors Grx5, ISA components and Nfu1 are impaired in SDH activity (Jensen & Culotta, 2000;Muhlenhoff et al., 2011;Rodriguez-Manzaneque et al., 2002). Mutations in human orthologs of Isd11, Isu1, Iba57 or Nfu1 (Ajit Bolar et al., 2013;Cameron et al., 2011;Crooks et al., 2012;FerrerCortes et al., 2013;Hall et al., 1993;Lim et al., 2013;Navarro-Sastre et al., 2011) or RNAi depletion of Isa1, or Isa2 lead to compromised SDH function ( Sheftel et al., 2012; Figure 2). ...
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Citations
... On the contrary, the accumulation of L-2-hydroxyglutarate is a result of the nonspecific activity of malate dehydrogenase that catalyzes the reduction of α-ketoglutarate to L-2-hydroxyglutarate [39]. Similarly the accumulation of succinate and fumarate results from mutations in succinate dehydrogenase and fumarase hydratase enzymes, respectively [40,41]. ...
Cancer due to its heterogeneous nature and large prevalence has tremendous socioeconomic impacts on populations across the world. Therefore, it is crucial to discover effective panels of biomarkers for diagnosing cancer at an early stage. Cancer leads to alterations in cell growth and differentiation at the molecular level, some of which are very unique. Therefore, comprehending these alterations can aid in a better understanding of the disease pathology and identification of the biomolecules that can serve as effective biomarkers for cancer diagnosis. Metabolites, among other biomolecules of interest, play a key role in the pathophysiology of cancer whose levels are significantly altered while ‘reprogramming the energy metabolism’, a cellular condition favored in cancer cells which is one of the hallmarks of cancer. Metabolomics, an emerging omics technology has tremendous potential to contribute towards the goal of investigating cancer metabolites or the metabolic alterations during the development of cancer. Diverse metabolites can be screened in a variety of biofluids, and tumor tissues sampled from cancer patients against healthy controls to capture the altered metabolism. In this review, we provide an overview of different metabolomics approaches employed in cancer research and the potential of metabolites as biomarkers for cancer diagnosis. In addition, we discuss the challenges associated with metabolomics-driven cancer research and gaze upon the prospects of this emerging field.
... In addition, the reactive oxidative metabolite NAPQI reduced succinate-driven ATP generation and specifically inhibited mitochondrial complex II in mouse model [22]. Succinate dehydrogenase (SDH) is crucial as it intimately involved in both carbon metabolism and cellular respiration [23]. It is recognized as complex II within the mitochondrial respiratory chain and plays a pivotal role in the oxidation of succinate to fumarate, thereby fueling mitochondrial respiration [24,25]. ...
Background and aim
N-acetyl-p-benzoquinoneimine (NAPQI), a toxic byproduct of paracetamol (Acetaminophen, APAP), can accumulate and cause liver damage by depleting glutathione and forming protein adducts in the mitochondria. These adducts disrupt the respiratory chain, increasing superoxide production and reducing ATP. The goal of this study was to provide computational proof that succinate dehydrogenase (SDH), a subunit of complex II in the mitochondrial respiratory chain, is a favorable binding partner for NAPQI in this regard.
Method
Molecular docking, molecular dynamics simulation, protein-protein interaction networks (PPI), and KEGG metabolic pathway analysis were employed to identify binding characteristics, interaction partners, and their associations with metabolic pathways. A lipid membrane was added to the experimental apparatus to mimic the natural cellular environment of SDH. This modification made it possible to develop a context for investigating the role and interactions of SDH within a cellular ecosystem that was more realistic and biologically relevant.
Result
The molecular binding affinity score for APAP and NAPQI with SDH was predicted −6.5 and −6.7 kcal/mol, respectively. Furthermore, RMSD, RMSF, and Rog from the molecular dynamics simulations study revealed that NAPQI has slightly higher stability and compactness compared to APAP at 100 ns timeframe with mitochondrial SDH.
Conclusion
This study serves to predict the mechanistic process of paracetamol toxicity by using different computational approaches. In addition, this study will provide information about the drug target against APAP hepatotoxicity.
... Although data are limited [16][17][18] , the synthesis of a number of findings suggests that CII activity is regulated at the level of assembly in some biological situations. This may be a relatively complex process as mature CII contains four protein subunits (SDHA, SDHB, SDHC, and SDHD) and houses five permanently-associated cofactors (covalent FAD, [2Fe-2S], [4Fe-4S], and [3Fe-4S] clusters, and integral-membrane b heme) 19 . ...
Complex II (CII) activity controls phenomena that require crosstalk between metabolism and signaling, including neurodegeneration, cancer metabolism, immune activation, and ischemia-reperfusion injury. CII activity can be regulated at the level of assembly, a process that leverages metastable assembly intermediates. The nature of these intermediates and how CII subunits transfer between metastable complexes remains unclear. In this work, we identify metastable species containing the SDHA subunit and its assembly factors, and we assign a preferred temporal sequence of appearance of these species during CII assembly. Structures of two species show that the assembly factors undergo disordered-to-ordered transitions without the appearance of significant secondary structure. The findings identify that intrinsically disordered regions are critical in regulating CII assembly, an observation that has implications for the control of assembly in other biomolecular complexes.
... SDH catalyzes the oxidation of succinate to fumaric acid and FADH2. Therefore, it connects the TCA cycle with the respiratory chain, and the generated FADH2 does not dissociate from the enzyme, which directly uses the electrons to reduce the coenzyme Q, and then passes it to the complex III [38]. MDH (Malate dehydrogenase) can catalyze the reversible conversion between malic acid and oxaloacetate, and is also an important enzyme in mitochondrial function, which is mainly involved in some metabolic pathways such as photosynthesis, TCA cycle, and C4 cycle. ...
... Mar. Drugs 2024,22,38 ...
Mangrove-derived actinomycetes represent a rich source of novel bioactive natural products in drug discovery. In this study, four new polyene macrolide antibiotics antifungalmycin B-E (1–4), along with seven known analogs (5–11), were isolated from the fermentation broth of the mangrove strain Streptomyces hiroshimensis GXIMD 06359. All compounds from this strain were purified using semi-preparative HPLC and Sephadex LH-20 gel filtration while following an antifungal activity-guided fractionation. Their structures were elucidated through spectroscopic techniques including UV, HR-ESI-MS, and NMR. These compounds exhibited broad-spectrum antifungal activity against Talaromyces marneffei with minimum inhibitory concentration (MIC) values being in the range of 2–128 μg/mL except compound 2. This is the first report of polyene derivatives produced by S. hiroshimensis as bioactive compounds against T. marneffei. In vitro studies showed that compound 1 exerted a significantly stronger antifungal activity against T. marneffei than other new compounds, and the antifungal mechanism of compound 1 may be related to the disrupted cell membrane, which causes mitochondrial dysfunction, resulting in leakage of intracellular biological components, and subsequently, cell death. Taken together, this study provides a basis for compound 1 preventing and controlling talaromycosis.
... Oxidative phosphorylation and mitochondrial energy homeostasis were the most perturbed biological processes associated with sarcopenia in all ethnicities, with bioenergetic alterations spanning across all mitochondrial respiratory complexes both at the level of expression and activity, also the activity of the two mitochondrial TCA cycle enzymes citrate synthase and SDH were strongly reduced in sarcopenia muscle, con rming that a global alteration of oxidative metabolism and energy production was perturbed in human sarcopenia muscle [40]. The unique property of SDH was that it participates in the oxidative phosphorylation pathway and the TCA cycle and thus has dual functions in carbon metabolism and mitochondrial respiration [41,42]. To understand the consequences of SDHB de ciency on gene expression, a whole genome expression analysis was performed, notably, genes involved in glycolysis, hypoxia, cell proliferation, and cell differentiation were up regulated in this analysis, whereas genes involved in oxidative phosphorylation were down regulated [43]. ...
We aim to investigate the roles of succinate dehydrogenase complex subunit B (SDHB) in the pathogenesis of sarcopenia. We identified 1554 differentially expressed genes from 33824 background genes in sarcopenia versus non-sarcopenia control as well as SDHB-low group versus high group. The 1365 genes of the turquoise module were most strongly associated with sarcopenia and those with low SDHB expression, which were enriched in oxidative phosphorylation, thermogenesis, ribosome and tricarboxylic acid (TCA) cycle. The cross-talking pathways of SHDB in sarcopenia were determined, including oxidative phosphorylation, TCA cycle and thermogenesis. Low expressions of SDHB may be a potential pathogenic factor of sarcopenia, and may be related to oxidative phosphorylation, TCA cycle and thermogenesis.
... ACN9 also plays a critical role in succinate dehydrogenase (SDH) assembly, an enzyme complex involved in the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain (4). This enzyme complex couples the oxidation of succinate to fumarate with the reduction of ubiquinone to ubiquinol. ...
Introduction: The tumor microenvironment plays a critical role in cancer progression, with immune cell infiltration being a key determinant of patient outcomes. The ACN9 gene has been of interest due to its potential involvement in immune regulation within the tumor microenvironment. To explore its significance, we conducted a comprehensive analysis across multiple cancer types. Method: We utilized the TIMER2.0 platform to assess ACN9 gene expression and its correlation with patient survival in a pan-cancer context. ACN9 expression data were obtained from various cancer types, and its impact on overall survival was analyzed. Kaplan-Meier curves were employed to visualize survival outcomes, and log-rank tests were conducted to determine statistical significance. Results: Our analysis revealed intriguing findings regarding ACN9 gene expression and its association with patient survival. In colorectal adenocarcinoma (COAD), head and neck squamous cell carcinoma associated with human papillomavirus (HSNC-HPV), and thyroid carcinoma (THCA), high ACN9 expression was strongly and significantly correlated with improved overall survival. Conversely, in breast invasive carcinoma (BRCA) and lung squamous cell carcinoma (LUSC), high ACN9 expression was strongly and negatively correlated with survival outcomes. Conclusion: The study sheds light on the complex and context-dependent nature of ACN9's role within the tumor microenvironment. The positive and negative correlations with survival in specific cancer types underscore the gene's multifaceted impact. These findings have implications for further research into the mechanisms underlying ACN9's influence on immune responses in cancer. It also highlights the potential utility of 18 th UBAK, 16-17 Aralık 2023, Ankara ACN9 as a prognostic biomarker and a target for immunotherapeutic interventions. In summary, this study provides valuable insights into the diverse relationships between ACN9 gene expression and patient survival across various cancer types, emphasizing the need for tailored approaches to cancer immunotherapy and personalized treatment strategies.
... Given the absence of typical client proteins from the mitochondrial ISC pathway, such as proteins involved in the electron transport chain, the TCA cycle and cofactor biosynthesis [43][44][45][46], we performed an unbiased search for Fe-S proteins within the conceptual G. intestinalis cellular proteome using MetalPredator [47]. Upon manual checking with available literature and structural information, 40 proteins were identified that bind [4Fe-4S] clusters (Fig 3D and S2 Table). ...
Mitochondrial metabolism is entirely dependent on the biosynthesis of the [4Fe-4S] clusters, which are part of the subunits of the respiratory chain. The mitochondrial late ISC pathway mediates the formation of these clusters from simpler [2Fe-2S] molecules and transfers them to client proteins. Here, we characterized the late ISC pathway in one of the simplest mitochondria, mitosomes, of the anaerobic protist Giardia intestinalis that lost the respiratory chain and other hallmarks of mitochondria. In addition to IscA2, Nfu1 and Grx5 we identified a novel BolA1 homologue in G . intestinalis mitosomes. It specifically interacts with Grx5 and according to the high-affinity pulldown also with other core mitosomal components. Using CRISPR/Cas9 we were able to establish full bolA1 knock out, the first cell line lacking a mitosomal protein. Despite the ISC pathway being the only metabolic role of the mitosome no significant changes in the mitosome biology could be observed as neither the number of the mitosomes or their capability to form [2Fe-2S] clusters in vitro was affected. We failed to identify natural client proteins that would require the [2Fe-2S] or [4Fe-4S] cluster within the mitosomes, with the exception of [2Fe-2S] ferredoxin, which is itself part of the ISC pathway. The overall uptake of iron into the cellular proteins remained unchanged as also observed for the grx5 knock out cell line. The pull-downs of all late ISC components were used to build the interactome of the pathway showing specific position of IscA2 due to its interaction with the outer mitosomal membrane proteins. Finally, the comparative analysis across Metamonada species suggested that the adaptation of the late ISC pathway identified in G . intestinalis occurred early in the evolution this of supergroup of eukaryotes.
... In the Krebs cycle, the SDH complex in the mitochondria is responsible for catalyzing the oxidation of succinate to fumarate and providing electrons to the ubiquinone (UQ) pool in the respiratory chain 9 . SDH comprises four nuclear-encoded subunits, and its structure and gene makeup have remained primarily unchanged over evolution 9,10 . The catalytic domain is formed by SDHA and SDHB, while SDHC and SDHD are accountable for tethering the complex to the inner mitochondrial membrane and allowing the complex to participate in the respiratory chain as complex II 10 . ...
... SDH comprises four nuclear-encoded subunits, and its structure and gene makeup have remained primarily unchanged over evolution 9,10 . The catalytic domain is formed by SDHA and SDHB, while SDHC and SDHD are accountable for tethering the complex to the inner mitochondrial membrane and allowing the complex to participate in the respiratory chain as complex II 10 . Among these subunits, tumor cells that overexpress SDHA have a highly active metabolism and get their energy from glycolysis and oxidative phosphorylation in the mitochondria 11 . ...
Background
High throughput metabolic viability-based colorimetric MTT assay is widely used for cytotoxicity screening of various chemical compounds, anti-neoplastic drugs, and other chemotherapeutic agents. The yellow MTT tetrazolium salt reduces to purple formazan crystals, predominantly by mitochondrial dehydrogenases. The assay assumes all cells have a similar number of mitochondria with equivalent enzymatic activity, resulting in a linear relationship between colorimetric absorbance and cell number.
Method
Our present study involved the Cisplatin, Etoposide, and Doxorubicin-induced cytotoxicity evaluation using MTT and cell number enumeration in two widely used cancer cell lines, namely human lung epithelial adenocarcinoma cells (A549) and cervix carcinoma (HeLa). Further, Mitochondrial mass was examined to comment on the treatment-induced change in metabolic viability-based MTT assay.
Results
Drug-induced cell death determined by enumeration of the cell number did not correlate with growth inhibition observed by the MTT assay. Increased protein levels of majorly MTT converting enzyme SDH in both the cell lines following drug treatment were observed. The mitochondrial protein content of the cells was also found to be elevated in response to drug-induced cytotoxic stress.
Conclusion
In line with our earlier observation about the limitation of MTT assay in estimating radiation-induced cytotoxicity, it was found that certain anti-neoplastic drugs also modulate mitochondrial biogenesis and SDH expression level and enzymatic activity. Therefore, caution should be taken in applying the MTT assay to analyze drug-induced growth inhibition.
General significance
Our findings reveal the MTT assay's limitations, which should be considered when determining anti-cancer and chemotherapeutic drugs' pre-clinical cytotoxicity and IC-50.
... As the smallest multisubunit OXPHOS enzyme, SDH must be sequentially assembled and be equipped with several cofactors to form a functional complex located in the inner mitochondrial membrane (IMM) [7]. To date, four assembly factors that facilitate the assembly and maturation of the SDH complex in mammalian cells [8,9] as well as in yeast [9] and Drosophila [9] have been identified. ...
... Although the SDH complex is composed of only four subunits, SDH biogenesis, similar to that of other OXPHOS complexes, clearly requires specific assembly factors. As recently attributed to recently identified assembly factors by Dr. Jared Rutter's team [9], four assembly factors named SDHAF1, SDHAF2, SDHAF3, and SDHAF4 in humans (Sdh6, Sdh5, Sdh7, and Sdh8 in Saccharomyces cerevisiae) fully coordinate major steps of SDH biogenesis, including the maturation of individual subunits and assembly of the whole complex [2,7,17]. SDHAF2 mediates the flavin acylation of SDHA, while SDHAF4 prevents the oxidative stress injury to the FAD-SDHA dimer, contributing to SDHA maturation and driving SDHA bonding with SDHB [9,22]. ...
... Following the maturation of SDHA and SDHB, SDHC and SDHD dimerize in the IMM [1,23,24]. After the assembly factors are liberated from subunits via an unknown mechanism, SDHA-SDHB binds to SDHC-SDHD to form a complete complex [7,12,[24][25][26] (Fig. 3). ...
Mitochondrial succinate dehydrogenase (SDH), also known as electron transport chain (ETC) Complex II, is the only enzyme complex engaged in both oxidative phosphorylation and the tricarboxylic acid (TCA) cycle. SDH has received increasing attention due to its crucial role in regulating mitochondrial metabolism and human health. Despite having the fewest subunits among the four ETC complexes, functional SDH is formed via a sequential and well-coordinated assembly of subunits. Along with the discovery of subunit-specific assembly factors, the dynamic involvement of the SDH assembly process in a broad range of diseases has been revealed. Recently, we reported that perturbation of SDH assembly in different tissues leads to interesting and distinct pathophysiological changes in mice, indicating a need to understand the intricate SDH assembly process in human health and diseases. Thus, in this review, we summarize recent findings on SDH pathogenesis with respect to disease and a focus on SDH assembly.
... and FADH2 and the reduction of oxygen to water. ETC is composed of four complexes and two mobile electron carriers (coenzyme Q and cytochrome c) (Van Vranken et al. 2015). Three cellular processes are involved in aerobic respiration: glycolysis, the TCA, and OXPHOS (Moosavi et al. 2020). ...
... Electrons derived from the oxidation of NADH by complex I or TCA succinate by the enzyme succinate dehydrogenase, also known as complex II (CII) of ETC or succinate: ubiquinone oxidoreductase (SQR) (Moosavi et al. 2020), are passed along the ETC, along with pumping protons and establishing the proton gradient across the inner mitochondrial membrane. Ultimately, the controlled flow of protons in this electrochemical gradient is utilized by complex V (ATP synthase) to catalyze ATP synthesis (Van Vranken et al. 2015). The normal enzyme activity of SDH serves to suppress tumors in humans (Van Vranken et al. 2015). ...
... Ultimately, the controlled flow of protons in this electrochemical gradient is utilized by complex V (ATP synthase) to catalyze ATP synthesis (Van Vranken et al. 2015). The normal enzyme activity of SDH serves to suppress tumors in humans (Van Vranken et al. 2015). However, mutation that results in loss of function in any of the four subunits (SDHA, SDHB, SDHC, and SDHD), destabilizes the SDH protein complex and eliminates its enzymatic activity (Zhao et al. 2020). ...
