Triphenylphosphonium-Derived Protein Sulfenic Acid Trapping Agents: Synthesis, Reactivity, and Effect on Mitochondrial Function

S-Sulfenylation Driven Antigen Capture Boosted by Radiation for Enhanced Cancer Immunotherapy

Radiotherapy (RT)-induced in situ vaccination greatly promotes the development of personalized cancer vaccines owing to the massive release of antigens initiated by tumor-localized RT eliciting the tumor-specific immune response. However, its broad application in cancer treatment is seriously impeded by poor antigen cross-presentation, low response rate, and short duration of efficacy. Herein, the tumor-antigen-capturing nanosystem dAuNPs@CpG consisting of gold nanoparticles, 3,5-cyclohexanedione (CHD), and immunoadjuvant CpG were fabricated to enhance RT-induced vaccination. Taking advantage of the specific covalent binding between CHD and sulfenic acids of antigen proteins, we show that this nanoplatform has an unexpected potential to capture the sulfenylated tumor-derived protein antigens (TDPAs) induced by RT to in situ generate a vaccination effect, achieving significant growth suppression of both primary and distant tumors in combination with PD-1 blockade. We thus believe that our work presents a powerful and effective means to improve the synergistic tumor radioimmunotherapy.

Key role of cycloalkyne nature in alkyne-dye reagents for enhanced specificity of intracellular imaging by bioorthogonal bioconjugation

Conjugates of benzothiophene-fused azacyclononyne BT9N-NH2 with fluorescent dyes were developed to visualise azidoglycans intracellularly. The significance of the cycloalkyne core was demonstrated by comparing new reagents with DBCO- and BCN-dye conjugates. To reduce non-specificity during intracellular bioconjugation using SPAAC, less reactive BT9N-dye reagents are preferred over highly reactive DBCO- and BCN-dye conjugates.

Sepsis, pyruvate, and mitochondria energy supply chain shortage

Balancing high energy-consuming danger resistance and low energy supply of disease tolerance is a universal survival principle that often fails during sepsis. Our research supports the concept that sepsis phosphorylates and deactivates mitochondrial pyruvate dehydrogenase complex control over the tricarboxylic cycle and the electron transport chain. StimulatIng mitochondrial energetics in septic mice and human sepsis cell models can be achieved by inhibiting pyruvate dehydrogenase kinases with the pyruvate structural analog dichloroacetate. Stimulating the pyruvate dehydrogenase complex by dichloroacetate reverses a disruption in the tricarboxylic cycle that induces itaconate, a key mediator of the disease tolerance pathway. Dichloroacetate treatment increases mitochondrial respiration and ATP synthesis, decreases oxidant stress, overcomes metabolic paralysis, regenerates tissue, organ, and innate and adaptive immune cells, and doubles the survival rate in a murine model of sepsis.

Oxidative Cysteine Modification of Thiol Isomerases in Thrombotic Disease: A Hypothesis

Significance: Oxidative stress is a characteristic of many systemic diseases associated with thrombosis. Thiol isomerases are a family of oxidoreductases important in protein folding and are exquisitely sensitive to the redox environment. They are essential for thrombus formation and represent a previously unrecognized layer of control of the thrombotic process. Yet, the mechanisms by which thiol isomerases function in thrombus formation are unknown. Recent Advances: The oxidoreductase activity of thiol isomerases in thrombus formation is controlled by the redox environment via oxidative changes to active site cysteines. Specific alterations can now be detected owing to advances in the chemical biology of oxidative cysteine modifications. Critical Issues: Understanding of the role of thiol isomerases in thrombus formation has focused largely on identifying single disulfide bond modifications in isolated proteins (e.g., α_IIbβ₃, tissue factor, vitronectin, or glycoprotein Ibα [GPIbα]). An alternative approach is to conceptualize thiol isomerases as effectors in redox signaling pathways that control thrombotic potential by modifying substrate networks. Future Directions: Cysteine-based chemical biology will be employed to study thiol-dependent dynamics mediated by the redox state of thiol isomerases at the systems level. This approach could identify thiol isomerase-dependent modifications of the disulfide landscape that are prothrombotic.

Contemporary proteomic strategies for cysteine redoxome profiling

Protein cysteine residues are susceptible to oxidative modifications that can affect protein functions. Proteomic techniques that comprehensively profile the cysteine redoxome, the repertoire of oxidized cysteine residues, are pivotal towards a better understanding of the protein redox signaling. Recent technical advances in chemical tools and redox proteomic strategies have greatly improved selectivity, in vivo applicability, and quantification of the cysteine redoxome. Despite this substantial progress, still many challenges remain. Here, we provide an update on the recent advances in proteomic strategies for cysteine redoxome profiling, compare the advantages and disadvantages of current methods and discuss the outstanding challenges and future perspectives for plant redoxome research.

Sulfenic Acid-Mediated on-Site-Specific Immobilization of Mitochondrial-Targeted NIR Fluorescent Probe for Prolonged Tumor Imaging

Mitochondria plays pivotal roles in energy production and apoptotic pathways. Mitochondria-targeting strategy has been recognized as a promising way for cancer theranostics. Thus, spatiotemporally manipulating the prolonged retention of theranostic agents within mitochondria is considerably significant in cancer diagnosis and therapy. Herein, as a proof-of concept, we for the first time report a sulfenic acid-responsive platform on controlled immobilization of probes within mitochondria for prolonged tumor imaging. A novel near-infrared (NIR) probe DATC constructed with a NIR dye (Cy5) as signal unit, a cationic triphenylphosphonium (TPP) for mitochondria targeting, and a sulfenic acid-reactive group (1,3-cyclohexanedione) for mitochondrial fixation was rationally designed and synthesized. This probe displayed good target ability to mitochondria and could act as a promising fluorescent probe for specific visualization of endogenous protein sulfenic acids expressed in the mitochondria. Moreover, the probe could be spontaneously fixed on site through the specific reaction and covalent binding to the sulfenic acids of oxidized proteins under oxidative stress, resulting in enhanced intracellular uptake and prolonged retention. We thus believe that this mitochondria-targeted and locational immobilization strategy may offer a new insight for long-term tumor imaging and effective therapy.

Activity-Based Sensing for Site-Specific Proteomic Analysis of Cysteine Oxidation

Oxidative post-translational modifications (OxiPTMs) of cysteine residues are the molecular foundation of thiol-based redox regulation that modulates physiological events such as cell proliferation, differentiation, and migration and, when dysregulated, can lead to biomolecule damage and cell death. Common OxiPTMs of cysteine thiols (-SH) include reversible modifications such as S-sulfenylation (-SOH), S-glutathionylation (-SSG), disulfide formation (-SSR), S-nitrosylation (-SNO), and S-sulfhydration (-SSH) as well as more biologically stable modifications like S-sulfinylation (-SO₂H) and S-sulfonylation (-SO₃H). In the past decade, our laboratory has developed first-in-class chemistry-based tools and proteomic methods to advance the field of thiol-based redox biology and oxidative stress. In this Account, we take the reader through the historical aspects of probe development and application in our laboratory, highlighting key advances in our understanding of sulfur chemistry, in the test tube and in living systems. Offering superior resolution, throughput, accuracy, and reproducibility, mass spectrometry (MS)-based proteomics coupled to chemoselective "activity-based" small-molecule probes is the most rigorous technique for global mapping of cysteine OxiPTMs. Herein, we describe the evolution of this field from indirect detection to state-of-the-art site-centric quantitative chemoproteomic approaches that enable mapping of physiological and pathological changes in cysteine oxidation. These methods enable protein and site-level identification, mechanistic studies, mapping fold-changes, and modification stoichiometry. In particular, this Account focuses on activity-based methods for profiling S-sulfenylation, S-sulfinylation, and S-sulfhydration with an eye toward new reactions and methodologies developed in our group as well as their applications that have shed new light on fundamental processes of redox biology. Among several classes of sulfenic acid probes, dimedone-based C-nucleophiles possess superior chemical selectivity and compatibility with tandem MS. Cell-permeable dimedone derivatives with a bioconjugation handle are capable of detecting of S-sulfenylation in living cells. In-depth screening of a C-nucleophile library has yielded several entities with significantly enhanced reactivity over dimedone while maintaining selectivity, and reversible linear C-nucleophiles that enable controlled target release. C-Nucleophiles have also been implemented in tag-switch methods to detect S-sulfhydration. Most recently, activity-based detection of protein S-sulfinylation with electrophilic nitrogen species (ENS), such as C-nitroso compounds and electron deficient diazines, offers significant advantages in simplicity-of-use and target specificity compared to label-free methods. When feasible, the rich information provided by site-centric quantitative proteomics should not be tainted by oxidation artifacts from cell lysis. Therefore, chemoselective probes that function in a native environment with low cytotoxicity, good cell-permeability, and competitive kinetics are desired in modern redox chemoproteomics approaches. As our understanding of sulfur chemistry and redox signaling evolves, newly discovered cysteine OxiPTMs in microorganisms, plants, cells, tissues, and disease models should innovatively promote mechanistic and therapeutic research.